Werner Draaisma - Academia.edu (original) (raw)

Papers by Werner Draaisma

Research paper thumbnail of Recurrent paraesophageal hernia due to diaphragm rupture: a case report

Hernia : the journal of hernias and abdominal wall surgery, 2006

A 58-year-old male patient was operated for complaints of dysphagia, anemia and retrosternal disc... more A 58-year-old male patient was operated for complaints of dysphagia, anemia and retrosternal discomfort due to a type II hiatal hernia. A complete hernia sac excision and posterior crural repair was performed laparoscopically with support of the da Vincitrade mark robotic system. An antireflux procedure was not performed because of the absence of gastroesophageal reflux disease. Nine months after surgery the patient presented with recurrent complaints of dysphagia and retrosternal pain. Barium esophagram series revealed a recurrent paraesophageal hernia which was confirmed on esophagogastroscopy. A robot-assisted re-laparoscopy was performed. Left to the still intact hiatoplasty of the original operation a tear in the diaphragm, through which part of the stomach covered with peritoneum had herniated, was encountered. The hernia sac was excised, the diaphragmatic defect closed and reinforced with an expanded polytetrafluoroethylene strip of 5 x 8 cm. After surgery the patient recover...

Research paper thumbnail of Cost-effectiveness of proton pump inhibitors versus laparoscopic Nissen fundoplication for patients with gastroesophageal reflux disease: a systematic review of the literature

Surgical Endoscopy, 2011

Gastroesophageal reflux disease is a common condition in Western countries. It is unknown whether... more Gastroesophageal reflux disease is a common condition in Western countries. It is unknown whether medical or surgical treatment is more cost-effective. This study was conducted to determine whether laparoscopic Nissen fundoplication or treatment by proton pump inhibitors is the most cost-effective for gastroesophageal reflux disease in the long term. Medline, EMBASE, and Cochrane databases were searched for articles published between January 1990 and 2010. The search results were screened by two independent reviewers for economic evaluations comparing costs and effects of laparoscopic Nissen fundoplication and proton pump inhibitors in adults eligible for both treatments. Cost and effectiveness or utility data were extracted for both treatment modalities. The quality of the economic evaluations was scored using a dedicated checklist, as were the levels of evidence. Four publications were included; all were based on decision analytic models. The economic evaluations were all of similar quality and all based on data with a variety of evidence levels. Surgery was more expensive than medical treatment in three publications. Two papers reported more quality-adjusted life-years for surgery. However, one of these reported more symptom-free months for medical treatment. In two publications surgery was considered to be the most cost-effective treatment, whereas the other two favored medical treatment. The results with regard to cost-effectiveness are inconclusive. All four economic models are based on high- and low-quality data. More reliable estimates of cost-effectiveness based on long-term trial data are needed.

Research paper thumbnail of Conventional and Laparoscopic Reversal of the Hartmann Procedure: a Review of Literature

Journal of Gastrointestinal Surgery, 2010

Purpose The aim of this study was to provide a systematic overview on both laparoscopic and conve... more Purpose The aim of this study was to provide a systematic overview on both laparoscopic and conventional Hartmann reversal. Furthermore, the Hartmann procedure is reevaluated in the light of new emerging alternatives. Methods Medline, Ovid, EMBASE, and Cochrane database were searched for studies reporting on outcomes after Hartmann reversal. Results Thirty-five studies were included in this review of which 30 were retrospective. A total of 6,249 patients with a mean age of 60 years underwent Hartmann reversal. Two thirds of patients were classified as American Society of Anesthesiologists (ASA) I-II. The mean reversal rate after a Hartmann procedure was 44%, and mean time interval between Hartmann procedure and Hartmann reversal was 7.5 months. The most frequent reported reasons for renouncing Hartmann reversal were high ASA classification and patients' refusal. The overall morbidity rate ranged from 3% to 50% (mean 16.3%) and mortality rate from 0% to 7.1% (mean 1%). Patients treated laparoscopically had a shorter hospital stay (6.9 vs. 10.7 days) and appeared to have lower mean morbidity rates compared to conventional surgery (12.2% vs. 20.3%). Conclusion Hartmann reversal carries a high risk on perioperative morbidity and mortality. The mean reversal rate is considerably low (44%). Laparoscopic reversal compares favorably to conventional; however, high level evidence is needed to determine whether it is superior.

Research paper thumbnail of Endoscopic evaluation of the colon after an episode of diverticulitis: a call for a more selective approach

International Journal of Colorectal Disease, 2012

Purpose Routine colonic evaluation is advised after an episode of diverticulitis to exclude color... more Purpose Routine colonic evaluation is advised after an episode of diverticulitis to exclude colorectal cancer. In the recent years, the possible relation between diverticulitis and colorectal cancer has been subject of debate. The aim of this study is to evaluate the benefit of routine colonic endoscopy after an episode of diverticulitis. Methods Records of all consecutive patients presenting with a radiologically confirmed episode of diverticulitis between 2007 and 2010 were retrieved from an in-hospital database. Patients who subsequently underwent colonic evaluation were included. The endoscopic detection rate of hyperplastic polyps, adenomas and advanced colonic neoplasia was assessed. Findings were categorized on the basis of the most advanced lesion identified. Results Three hundred and seven patients presented with a radiologically confirmed primary episode of diverticulitis. Two hundred and five patients underwent colonic evaluation. Hyperplastic polyps were found in15 (6.8%), adenomas in 18 (8.8%) and advanced neoplastic lesions in 7 (3.4%) patients. Only two patients had a colorectal malignancy. Conclusion There appears to be no benefit in performing routine colonic evaluation after an episode of diverticulitis as the incidence of colorectal cancer is almost equal to that of the general population. A more selective approach might therefore be justified. Potentially, only patients with persisting abdominal complaints after an episode of diverticulitis should be offered colonic evaluation to definitively exclude causal pathology.

Research paper thumbnail of DIRECT trial. Diverticulitis recurrences or continuing symptoms: Operative versus conservative Treatment. A MULTICENTER RANDOMISED CLINICAL TRIAL

Background: Persisting abdominal complaints are common after an episode of diverticulitis treated... more Background: Persisting abdominal complaints are common after an episode of diverticulitis treated conservatively. Furthermore, some patients develop frequent recurrences. These two groups of patients suffer greatly from their disease, as shown by impaired health related quality of life and increased costs due to multiple specialist consultations, pain medication and productivity losses. Both conservative and operative management of patients with persisting abdominal complaints after an episode of diverticulitis and/or frequently recurring diverticulitis are applied. However, direct comparison by a randomised controlled trial is necessary to determine which is superior in relieving symptoms, optimising health related quality of life, minimising costs and preventing diverticulitis recurrences against acceptable morbidity and mortality associated with surgery or the occurrence of a complicated recurrence after conservative management. We, therefore, constructed a randomised clinical trial comparing these two treatment strategies.

Research paper thumbnail of 901c Surgery Versus Conservative Treatment for Recurrent and Ongoing Diverticulitis; Results of a Multicenter Randomized Controlled Trial (DIRECT)

Research paper thumbnail of Mid-term results of robot-assisted laparoscopic repair of large hiatal hernia: a symptomatic and radiological prospective cohort study

Surgical technology international, 2008

Studies reporting on the recurrence rate after laparoscopic repair of large hiatal hernias (HH), ... more Studies reporting on the recurrence rate after laparoscopic repair of large hiatal hernias (HH), including anatomical asymptomatic recurrence, are scarce. This prospective cohort study evaluated the symptomatic and objective outcome of robot-assisted laparoscopic HH repair up to more than 1 year after surgery. A prospective cohort study was performed on 40 consecutive patients with emphasis on operating times, blood loss, intra- and postoperative complications, symptomatic outcome, and anatomical recurrence rate at a minimum of 1 year after surgery. Robot-assisted laparoscopic HH repair proved to be an effective technique with a relatively low mid-term recurrence rate in this prospective series. The operating team experienced the support of the robotic system as beneficial, especially in the dissection of the hernia sac and extensive crural repair.

Research paper thumbnail of Robot-assisted Laparoscopic Resection of a Large Paraganglioma: A Case Report

Surgical Laparoscopy, Endoscopy & Percutaneous Techniques, 2006

A 19-year-old female patient presented with headache, nausea, hypertension, visual impairment of ... more A 19-year-old female patient presented with headache, nausea, hypertension, visual impairment of the left eye and exertion-related complaints of palpitations since 1 year. Fundoscopy showed severe hypertensive retinopathy grade IV. A paraganglioma in the left para-aortic region was diagnosed by urinary screening and magnetic resonance imaging scanning. The tumor was resected by a robot-assisted laparoscopic procedure. The surgical operating time was 250 minutes and the blood loss was 150 mL. After surgery the blood pressure normalized and antihypertensive drugs were no longer required. Oral intake was resumed on the first postoperative day and the hospital stay was 3 days. Final pathology examination revealed a paraganglioma with pheochromocytomal features of 7x5.1x3.5 cm. Reports on laparoscopic resection of large paragangliomas are scarce. This case has demonstrated that the procedure is feasible and associated with rapid recovery from surgery. The surgical team experienced explicit support by the robot in the dissection of this highly vascularized tumor.

Research paper thumbnail of Transanal endoscopic operation for rectal lesions using two-dimensional visualization and standard endoscopic instruments: a prospective cohort study and comparison with the literature

Surgical Endoscopy, 2009

The transanal endoscopic operation (TEO) has proved to be an effective alternative to conventiona... more The transanal endoscopic operation (TEO) has proved to be an effective alternative to conventional surgery for the treatment of rectal lesions. The TEO procedure offers reduced morbidity, faster recovery and equivalent oncologic outcome. Currently, two instrument sets are available: one with three-dimensional (Wolf) and one with two-dimensional (Storz) optic capacities. The three-dimensional (3D) instrument set is considered the golden standard. Although the advantages of TEO are imposing, the procedure with the 3D armamentarium has certain technical and financial drawbacks. This study therefore aimed to compare results for the TEO 2D alternative with recently published results for 3D TEO. All consecutive patients with benign or malignant pT1 or pT2 rectal lesions undergoing TEO were prospectively followed. All procedures were performed with the 2D armamentarium using standard endoscopic instruments, a rectoscope (diameter, 4 cm; working length, 7.5-15 cm), and 5-mm Ligasure and Ultracision. Operating times, complications, hospital stay, and oncologic outcome were gathered and compared with published data. Between 2004 and 2006, 31 patients with a median age of 75 years (range, 33-87 years) underwent 31 TEOs for a total of 36 rectal lesions (29 tubulovillous adenomas and 7 adenocarcinomas). The median distance of the lesion from the anal verge was 7.5 cm (range, 5-15 cm). The median lesion diameter was 2.3 cm (range, 0.5-5.0 cm). The locations of the lesions were as follows: 18 on the dorsal, 5 on the ventral, and 5 on the lateral rectal wall. The median operating time was 55 min (range, 25-165 min), compared with 105 min reported in the literature. All the lesions except one could be radically excised. No intraoperative complications occurred. Postoperative complications occurred for three patients, all due to hemorrhage. The median hospital stay was 3 days (range, 1-21 days). During a median follow-up period of 15 months (range, 1-35 months), two recurrences took place. The study findings showed that for rectal tumors located up to 15 cm from the anal verge with a maximal diameter of 5 cm, TEO using standard laparoscopic instruments with a 2D view is feasible and provides results comparable with those associated with a 3D view and dedicated instruments. Furthermore, the 2D procedure can be performed with improved ergonomics due to movable monitors and is considerably less expensive.

Research paper thumbnail of First experience with robot-assisted thoracoscopic esophagolymphadenectomy for esophageal cancer

Surgical Endoscopy, 2006

No part of this thesis may be reproduced, stored in a database or retrieval system, or transmitte... more No part of this thesis may be reproduced, stored in a database or retrieval system, or transmitted in any form or by any means without prior written permission of the author, or when appropriate, the publishers of the published papers.

Research paper thumbnail of Robot-assisted laparoscopic rectovaginopexy for rectal prolapse: a prospective cohort study on feasibility and safety

Journal of Robotic Surgery, 2008

Robotic systems may be particularly supportive for procedures requiring careful pelvic dissection... more Robotic systems may be particularly supportive for procedures requiring careful pelvic dissection and suturing in the Douglas pouch, as in surgery for rectal prolapse. Studies reporting robot-assisted laparoscopic rectovaginopexy for rectal prolapse, however, are scarce. This prospective cohort study evaluated the outcome of this technique up to one year after surgery. From January 2005 to June 2006, 15 consecutive patients with a rectal prolapse, either with or without a concomitant rectocele or enterocele, underwent robot-assisted laparoscopic rectovaginopexy with support of the da Vinci robotic system. A prospective cohort study was performed on operating times, blood loss, intra-operative and post-operative complications, and outcome at a minimum of one year after surgery. Median age at time of operation was 62 years (33-72) and median body mass index 24.9 (20.9-33.9). Median robot set-up time was 10 min (3-15) and median skin-to-skin operating time was 160 min (120-180). No conversions to open surgery were necessary. No in-hospital complications occurred and there was no mortality. Median hospital stay was four days (2-9). During one year follow-up, two patients needed surgical reintervention. One patient was operated for recurrent enterocele and rectocele one week after surgery. In another patient an incisional hernia at the camera port occurred three months after surgery. At one year after surgery, 87% of patients claimed to be satisWed with their postoperative result. Robot-assisted laparoscopic rectovaginopexy proved to be an eVective technique with favourable outcomes in most patients in this prospective series. The operating team experienced the support of the robotic system as beneWcial, especially during the dissection of the rectovaginal plane and suturing in the Douglas pouch.

Research paper thumbnail of Conventional and Laparoscopic Reversal of the Hartmann Procedure: a Review of Literature

Journal of Gastrointestinal Surgery, 2010

Purpose The aim of this study was to provide a systematic overview on both laparoscopic and conve... more Purpose The aim of this study was to provide a systematic overview on both laparoscopic and conventional Hartmann reversal. Furthermore, the Hartmann procedure is reevaluated in the light of new emerging alternatives. Methods Medline, Ovid, EMBASE, and Cochrane database were searched for studies reporting on outcomes after Hartmann reversal. Results Thirty-five studies were included in this review of which 30 were retrospective. A total of 6,249 patients with a mean age of 60 years underwent Hartmann reversal. Two thirds of patients were classified as American Society of Anesthesiologists (ASA) I-II. The mean reversal rate after a Hartmann procedure was 44%, and mean time interval between Hartmann procedure and Hartmann reversal was 7.5 months. The most frequent reported reasons for renouncing Hartmann reversal were high ASA classification and patients' refusal. The overall morbidity rate ranged from 3% to 50% (mean 16.3%) and mortality rate from 0% to 7.1% (mean 1%). Patients treated laparoscopically had a shorter hospital stay (6.9 vs. 10.7 days) and appeared to have lower mean morbidity rates compared to conventional surgery (12.2% vs. 20.3%). Conclusion Hartmann reversal carries a high risk on perioperative morbidity and mortality. The mean reversal rate is considerably low (44%). Laparoscopic reversal compares favorably to conventional; however, high level evidence is needed to determine whether it is superior.

Research paper thumbnail of Surgical Reintervention After Failed Antireflux Surgery: A Systematic Review of the Literature

Journal of Gastrointestinal Surgery, 2009

Background Outcome and morbidity of redo antireflux surgery are suggested to be less satisfactory... more Background Outcome and morbidity of redo antireflux surgery are suggested to be less satisfactory than those of primary surgery. Studies reporting on redo surgery, however, are usually much smaller than those of primary surgery. The aim of this study was to summarize the currently available literature on redo antireflux surgery. Material and Methods A structured literature search was performed in the electronic databases of MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials. Results A total of 81 studies met the inclusion criteria. The study design was prospective in 29, retrospective in 15, and not reported in 37 studies. In these studies, 4,584 reoperations in 4,509 patients are reported. Recurrent reflux and dysphagia were the most frequent indications; intraoperative complications occurred in 21.4% and postoperative complications in 15.6%, with an overall mortality rate of 0.9%. The conversion rate in laparoscopic surgery was 8.7%. Mean(±SEM) duration of surgery was 177.4±10.3 min and mean hospital stay was 5.5±0.5 days. Symptomatic outcome was successful in 81.1% and was equal in the laparoscopic and conventional approach. Objective outcome was obtained in 24 studies (29.6%) and success was reported in 78.3%, with a slightly higher success rate in case of laparoscopy than with open surgery (85.8% vs. 78.0%). Conclusion This systematic review on redo antireflux surgery has confirmed that morbidity and mortality after redo surgery is higher than after primary surgery and symptomatic and objective outcome are less satisfactory. Data on objective results were scarce and consistency with regard to reporting outcome is necessary.

Research paper thumbnail of S1106 The Relevance of Symptom Association Analysis for the Outcome After Nissen Fundoplication

Research paper thumbnail of Lumbar discitis after laparoscopic ventral rectopexy for rectal prolapse

International Journal of Colorectal Disease, 2011

Research paper thumbnail of Endoscopic evaluation of the colon after an episode of diverticulitis: a call for a more selective approach

International Journal of Colorectal Disease, 2012

Routine colonic evaluation is advised after an episode of diverticulitis to exclude colorectal ca... more Routine colonic evaluation is advised after an episode of diverticulitis to exclude colorectal cancer. In the recent years, the possible relation between diverticulitis and colorectal cancer has been subject of debate. The aim of this study is to evaluate the benefit of routine colonic endoscopy after an episode of diverticulitis. Records of all consecutive patients presenting with a radiologically confirmed episode of diverticulitis between 2007 and 2010 were retrieved from an in-hospital database. Patients who subsequently underwent colonic evaluation were included. The endoscopic detection rate of hyperplastic polyps, adenomas and advanced colonic neoplasia was assessed. Findings were categorized on the basis of the most advanced lesion identified. Three hundred and seven patients presented with a radiologically confirmed primary episode of diverticulitis. Two hundred and five patients underwent colonic evaluation. Hyperplastic polyps were found in15 (6.8 %), adenomas in 18 (8.8 %) and advanced neoplastic lesions in 7 (3.4 %) patients. Only two patients had a colorectal malignancy. There appears to be no benefit in performing routine colonic evaluation after an episode of diverticulitis as the incidence of colorectal cancer is almost equal to that of the general population. A more selective approach might therefore be justified. Potentially, only patients with persisting abdominal complaints after an episode of diverticulitis should be offered colonic evaluation to definitively exclude causal pathology.

Research paper thumbnail of DIRECT trial. Diverticulitis recurrences or continuing symptoms: Operative versus conservative treatment. A multicenter randomised clinical trial

BMC surgery, 2010

Persisting abdominal complaints are common after an episode of diverticulitis treated conservativ... more Persisting abdominal complaints are common after an episode of diverticulitis treated conservatively. Furthermore, some patients develop frequent recurrences. These two groups of patients suffer greatly from their disease, as shown by impaired health related quality of life and increased costs due to multiple specialist consultations, pain medication and productivity losses.Both conservative and operative management of patients with persisting abdominal complaints after an episode of diverticulitis and/or frequently recurring diverticulitis are applied. However, direct comparison by a randomised controlled trial is necessary to determine which is superior in relieving symptoms, optimising health related quality of life, minimising costs and preventing diverticulitis recurrences against acceptable morbidity and mortality associated with surgery or the occurrence of a complicated recurrence after conservative management.We, therefore, constructed a randomised clinical trial comparing ...

Research paper thumbnail of S1105 Esophageal Hypersensitivity Is Not a Contraindication for Nissen Fundoplication

Gastroenterology, 2008

BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the ... more BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the serosa of the stomach to alter gastric electrical activity (GEA). GES has been shown to be a potent anti-emetic and safe way of treating intractable symptomatic gastroparesis and morbid obesity in reported cases (Abell, Van Cutsem et al. 2002 ; Favretti, De Luca et al. 2004). Simulations of GES can be used to optimize stimulation parameters such as the placement of electrodes and stimulation frequency. AIMS: i) To create a computer model that represents the electrical interactions between the smooth muscle cells (SMCs) and the interstitial cells of Cajal (ICCs) based on the current understanding of gastric physiology; ii) To simulate GEA under a) normal conditions, and b) with an artificial stimulus representing a single percutaneous electrode placed on the serosa of the pylorus; iii) To investigate the effects of a range of stimulating frequencies on GEA. METHODS and RESULTS: The computer model consisted of a block gastric tissue measuring 100x100 mm containing a layer of SMCs (represented by the model of Corrias and Buist 2007), and a rule-based layer of ICCs Propagation of slow waves was visualised as colour-coded potentials across the tissue in time. Electrical activities in both the SMC and ICC layers were computed for multiple slow waves. The results demonstrated the correct entrainment behaviors seen in a slice of normal stomach with electrical activity conducting at 11mms-1 in the longitudinal direction and 22mms-1 in the circumferential direction. Further investigations also revealed that complete retrograde GEA could be achieved by adding an extraneous stimulation of higher than the entrainment frequency (3 cycles per minute) at the pylorus of the stomach. In addition, the simulations illustrated that stimuli of equal frequency to the normal entrainment frequency could only produce retrograde activity in a limited region, and the size of the region was dependent on the timing of the onset of the stimuli relative to the normal GEA. CONCLU-SIONS: Both normal GEA and retrograde activity were successfully simulated in a tissue block. The model therefore provides a good initial platform for more detailed investigation of GEA and functional electrical stimulation of the stomach.

Research paper thumbnail of S1104 The Learning Curve in Laparoscopic Nissen Fundoplication Revisited

Gastroenterology, 2008

BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the ... more BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the serosa of the stomach to alter gastric electrical activity (GEA). GES has been shown to be a potent anti-emetic and safe way of treating intractable symptomatic gastroparesis and morbid obesity in reported cases (Abell, Van Cutsem et al. 2002 ; Favretti, De Luca et al. 2004). Simulations of GES can be used to optimize stimulation parameters such as the placement of electrodes and stimulation frequency. AIMS: i) To create a computer model that represents the electrical interactions between the smooth muscle cells (SMCs) and the interstitial cells of Cajal (ICCs) based on the current understanding of gastric physiology; ii) To simulate GEA under a) normal conditions, and b) with an artificial stimulus representing a single percutaneous electrode placed on the serosa of the pylorus; iii) To investigate the effects of a range of stimulating frequencies on GEA. METHODS and RESULTS: The computer model consisted of a block gastric tissue measuring 100x100 mm containing a layer of SMCs (represented by the model of Corrias and Buist 2007), and a rule-based layer of ICCs Propagation of slow waves was visualised as colour-coded potentials across the tissue in time. Electrical activities in both the SMC and ICC layers were computed for multiple slow waves. The results demonstrated the correct entrainment behaviors seen in a slice of normal stomach with electrical activity conducting at 11mms-1 in the longitudinal direction and 22mms-1 in the circumferential direction. Further investigations also revealed that complete retrograde GEA could be achieved by adding an extraneous stimulation of higher than the entrainment frequency (3 cycles per minute) at the pylorus of the stomach. In addition, the simulations illustrated that stimuli of equal frequency to the normal entrainment frequency could only produce retrograde activity in a limited region, and the size of the region was dependent on the timing of the onset of the stimuli relative to the normal GEA. CONCLU-SIONS: Both normal GEA and retrograde activity were successfully simulated in a tissue block. The model therefore provides a good initial platform for more detailed investigation of GEA and functional electrical stimulation of the stomach.

Research paper thumbnail of S1103 Long-Term Outcome of Nissen Fundoplication in Erosive and Non-Erosive Reflux Disease

Gastroenterology, 2008

BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the ... more BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the serosa of the stomach to alter gastric electrical activity (GEA). GES has been shown to be a potent anti-emetic and safe way of treating intractable symptomatic gastroparesis and morbid obesity in reported cases (Abell, Van Cutsem et al. 2002 ; Favretti, De Luca et al. 2004). Simulations of GES can be used to optimize stimulation parameters such as the placement of electrodes and stimulation frequency. AIMS: i) To create a computer model that represents the electrical interactions between the smooth muscle cells (SMCs) and the interstitial cells of Cajal (ICCs) based on the current understanding of gastric physiology; ii) To simulate GEA under a) normal conditions, and b) with an artificial stimulus representing a single percutaneous electrode placed on the serosa of the pylorus; iii) To investigate the effects of a range of stimulating frequencies on GEA. METHODS and RESULTS: The computer model consisted of a block gastric tissue measuring 100x100 mm containing a layer of SMCs (represented by the model of Corrias and Buist 2007), and a rule-based layer of ICCs Propagation of slow waves was visualised as colour-coded potentials across the tissue in time. Electrical activities in both the SMC and ICC layers were computed for multiple slow waves. The results demonstrated the correct entrainment behaviors seen in a slice of normal stomach with electrical activity conducting at 11mms-1 in the longitudinal direction and 22mms-1 in the circumferential direction. Further investigations also revealed that complete retrograde GEA could be achieved by adding an extraneous stimulation of higher than the entrainment frequency (3 cycles per minute) at the pylorus of the stomach. In addition, the simulations illustrated that stimuli of equal frequency to the normal entrainment frequency could only produce retrograde activity in a limited region, and the size of the region was dependent on the timing of the onset of the stimuli relative to the normal GEA. CONCLU-SIONS: Both normal GEA and retrograde activity were successfully simulated in a tissue block. The model therefore provides a good initial platform for more detailed investigation of GEA and functional electrical stimulation of the stomach.

Research paper thumbnail of Recurrent paraesophageal hernia due to diaphragm rupture: a case report

Hernia : the journal of hernias and abdominal wall surgery, 2006

A 58-year-old male patient was operated for complaints of dysphagia, anemia and retrosternal disc... more A 58-year-old male patient was operated for complaints of dysphagia, anemia and retrosternal discomfort due to a type II hiatal hernia. A complete hernia sac excision and posterior crural repair was performed laparoscopically with support of the da Vincitrade mark robotic system. An antireflux procedure was not performed because of the absence of gastroesophageal reflux disease. Nine months after surgery the patient presented with recurrent complaints of dysphagia and retrosternal pain. Barium esophagram series revealed a recurrent paraesophageal hernia which was confirmed on esophagogastroscopy. A robot-assisted re-laparoscopy was performed. Left to the still intact hiatoplasty of the original operation a tear in the diaphragm, through which part of the stomach covered with peritoneum had herniated, was encountered. The hernia sac was excised, the diaphragmatic defect closed and reinforced with an expanded polytetrafluoroethylene strip of 5 x 8 cm. After surgery the patient recover...

Research paper thumbnail of Cost-effectiveness of proton pump inhibitors versus laparoscopic Nissen fundoplication for patients with gastroesophageal reflux disease: a systematic review of the literature

Surgical Endoscopy, 2011

Gastroesophageal reflux disease is a common condition in Western countries. It is unknown whether... more Gastroesophageal reflux disease is a common condition in Western countries. It is unknown whether medical or surgical treatment is more cost-effective. This study was conducted to determine whether laparoscopic Nissen fundoplication or treatment by proton pump inhibitors is the most cost-effective for gastroesophageal reflux disease in the long term. Medline, EMBASE, and Cochrane databases were searched for articles published between January 1990 and 2010. The search results were screened by two independent reviewers for economic evaluations comparing costs and effects of laparoscopic Nissen fundoplication and proton pump inhibitors in adults eligible for both treatments. Cost and effectiveness or utility data were extracted for both treatment modalities. The quality of the economic evaluations was scored using a dedicated checklist, as were the levels of evidence. Four publications were included; all were based on decision analytic models. The economic evaluations were all of similar quality and all based on data with a variety of evidence levels. Surgery was more expensive than medical treatment in three publications. Two papers reported more quality-adjusted life-years for surgery. However, one of these reported more symptom-free months for medical treatment. In two publications surgery was considered to be the most cost-effective treatment, whereas the other two favored medical treatment. The results with regard to cost-effectiveness are inconclusive. All four economic models are based on high- and low-quality data. More reliable estimates of cost-effectiveness based on long-term trial data are needed.

Research paper thumbnail of Conventional and Laparoscopic Reversal of the Hartmann Procedure: a Review of Literature

Journal of Gastrointestinal Surgery, 2010

Purpose The aim of this study was to provide a systematic overview on both laparoscopic and conve... more Purpose The aim of this study was to provide a systematic overview on both laparoscopic and conventional Hartmann reversal. Furthermore, the Hartmann procedure is reevaluated in the light of new emerging alternatives. Methods Medline, Ovid, EMBASE, and Cochrane database were searched for studies reporting on outcomes after Hartmann reversal. Results Thirty-five studies were included in this review of which 30 were retrospective. A total of 6,249 patients with a mean age of 60 years underwent Hartmann reversal. Two thirds of patients were classified as American Society of Anesthesiologists (ASA) I-II. The mean reversal rate after a Hartmann procedure was 44%, and mean time interval between Hartmann procedure and Hartmann reversal was 7.5 months. The most frequent reported reasons for renouncing Hartmann reversal were high ASA classification and patients' refusal. The overall morbidity rate ranged from 3% to 50% (mean 16.3%) and mortality rate from 0% to 7.1% (mean 1%). Patients treated laparoscopically had a shorter hospital stay (6.9 vs. 10.7 days) and appeared to have lower mean morbidity rates compared to conventional surgery (12.2% vs. 20.3%). Conclusion Hartmann reversal carries a high risk on perioperative morbidity and mortality. The mean reversal rate is considerably low (44%). Laparoscopic reversal compares favorably to conventional; however, high level evidence is needed to determine whether it is superior.

Research paper thumbnail of Endoscopic evaluation of the colon after an episode of diverticulitis: a call for a more selective approach

International Journal of Colorectal Disease, 2012

Purpose Routine colonic evaluation is advised after an episode of diverticulitis to exclude color... more Purpose Routine colonic evaluation is advised after an episode of diverticulitis to exclude colorectal cancer. In the recent years, the possible relation between diverticulitis and colorectal cancer has been subject of debate. The aim of this study is to evaluate the benefit of routine colonic endoscopy after an episode of diverticulitis. Methods Records of all consecutive patients presenting with a radiologically confirmed episode of diverticulitis between 2007 and 2010 were retrieved from an in-hospital database. Patients who subsequently underwent colonic evaluation were included. The endoscopic detection rate of hyperplastic polyps, adenomas and advanced colonic neoplasia was assessed. Findings were categorized on the basis of the most advanced lesion identified. Results Three hundred and seven patients presented with a radiologically confirmed primary episode of diverticulitis. Two hundred and five patients underwent colonic evaluation. Hyperplastic polyps were found in15 (6.8%), adenomas in 18 (8.8%) and advanced neoplastic lesions in 7 (3.4%) patients. Only two patients had a colorectal malignancy. Conclusion There appears to be no benefit in performing routine colonic evaluation after an episode of diverticulitis as the incidence of colorectal cancer is almost equal to that of the general population. A more selective approach might therefore be justified. Potentially, only patients with persisting abdominal complaints after an episode of diverticulitis should be offered colonic evaluation to definitively exclude causal pathology.

Research paper thumbnail of DIRECT trial. Diverticulitis recurrences or continuing symptoms: Operative versus conservative Treatment. A MULTICENTER RANDOMISED CLINICAL TRIAL

Background: Persisting abdominal complaints are common after an episode of diverticulitis treated... more Background: Persisting abdominal complaints are common after an episode of diverticulitis treated conservatively. Furthermore, some patients develop frequent recurrences. These two groups of patients suffer greatly from their disease, as shown by impaired health related quality of life and increased costs due to multiple specialist consultations, pain medication and productivity losses. Both conservative and operative management of patients with persisting abdominal complaints after an episode of diverticulitis and/or frequently recurring diverticulitis are applied. However, direct comparison by a randomised controlled trial is necessary to determine which is superior in relieving symptoms, optimising health related quality of life, minimising costs and preventing diverticulitis recurrences against acceptable morbidity and mortality associated with surgery or the occurrence of a complicated recurrence after conservative management. We, therefore, constructed a randomised clinical trial comparing these two treatment strategies.

Research paper thumbnail of 901c Surgery Versus Conservative Treatment for Recurrent and Ongoing Diverticulitis; Results of a Multicenter Randomized Controlled Trial (DIRECT)

Research paper thumbnail of Mid-term results of robot-assisted laparoscopic repair of large hiatal hernia: a symptomatic and radiological prospective cohort study

Surgical technology international, 2008

Studies reporting on the recurrence rate after laparoscopic repair of large hiatal hernias (HH), ... more Studies reporting on the recurrence rate after laparoscopic repair of large hiatal hernias (HH), including anatomical asymptomatic recurrence, are scarce. This prospective cohort study evaluated the symptomatic and objective outcome of robot-assisted laparoscopic HH repair up to more than 1 year after surgery. A prospective cohort study was performed on 40 consecutive patients with emphasis on operating times, blood loss, intra- and postoperative complications, symptomatic outcome, and anatomical recurrence rate at a minimum of 1 year after surgery. Robot-assisted laparoscopic HH repair proved to be an effective technique with a relatively low mid-term recurrence rate in this prospective series. The operating team experienced the support of the robotic system as beneficial, especially in the dissection of the hernia sac and extensive crural repair.

Research paper thumbnail of Robot-assisted Laparoscopic Resection of a Large Paraganglioma: A Case Report

Surgical Laparoscopy, Endoscopy & Percutaneous Techniques, 2006

A 19-year-old female patient presented with headache, nausea, hypertension, visual impairment of ... more A 19-year-old female patient presented with headache, nausea, hypertension, visual impairment of the left eye and exertion-related complaints of palpitations since 1 year. Fundoscopy showed severe hypertensive retinopathy grade IV. A paraganglioma in the left para-aortic region was diagnosed by urinary screening and magnetic resonance imaging scanning. The tumor was resected by a robot-assisted laparoscopic procedure. The surgical operating time was 250 minutes and the blood loss was 150 mL. After surgery the blood pressure normalized and antihypertensive drugs were no longer required. Oral intake was resumed on the first postoperative day and the hospital stay was 3 days. Final pathology examination revealed a paraganglioma with pheochromocytomal features of 7x5.1x3.5 cm. Reports on laparoscopic resection of large paragangliomas are scarce. This case has demonstrated that the procedure is feasible and associated with rapid recovery from surgery. The surgical team experienced explicit support by the robot in the dissection of this highly vascularized tumor.

Research paper thumbnail of Transanal endoscopic operation for rectal lesions using two-dimensional visualization and standard endoscopic instruments: a prospective cohort study and comparison with the literature

Surgical Endoscopy, 2009

The transanal endoscopic operation (TEO) has proved to be an effective alternative to conventiona... more The transanal endoscopic operation (TEO) has proved to be an effective alternative to conventional surgery for the treatment of rectal lesions. The TEO procedure offers reduced morbidity, faster recovery and equivalent oncologic outcome. Currently, two instrument sets are available: one with three-dimensional (Wolf) and one with two-dimensional (Storz) optic capacities. The three-dimensional (3D) instrument set is considered the golden standard. Although the advantages of TEO are imposing, the procedure with the 3D armamentarium has certain technical and financial drawbacks. This study therefore aimed to compare results for the TEO 2D alternative with recently published results for 3D TEO. All consecutive patients with benign or malignant pT1 or pT2 rectal lesions undergoing TEO were prospectively followed. All procedures were performed with the 2D armamentarium using standard endoscopic instruments, a rectoscope (diameter, 4 cm; working length, 7.5-15 cm), and 5-mm Ligasure and Ultracision. Operating times, complications, hospital stay, and oncologic outcome were gathered and compared with published data. Between 2004 and 2006, 31 patients with a median age of 75 years (range, 33-87 years) underwent 31 TEOs for a total of 36 rectal lesions (29 tubulovillous adenomas and 7 adenocarcinomas). The median distance of the lesion from the anal verge was 7.5 cm (range, 5-15 cm). The median lesion diameter was 2.3 cm (range, 0.5-5.0 cm). The locations of the lesions were as follows: 18 on the dorsal, 5 on the ventral, and 5 on the lateral rectal wall. The median operating time was 55 min (range, 25-165 min), compared with 105 min reported in the literature. All the lesions except one could be radically excised. No intraoperative complications occurred. Postoperative complications occurred for three patients, all due to hemorrhage. The median hospital stay was 3 days (range, 1-21 days). During a median follow-up period of 15 months (range, 1-35 months), two recurrences took place. The study findings showed that for rectal tumors located up to 15 cm from the anal verge with a maximal diameter of 5 cm, TEO using standard laparoscopic instruments with a 2D view is feasible and provides results comparable with those associated with a 3D view and dedicated instruments. Furthermore, the 2D procedure can be performed with improved ergonomics due to movable monitors and is considerably less expensive.

Research paper thumbnail of First experience with robot-assisted thoracoscopic esophagolymphadenectomy for esophageal cancer

Surgical Endoscopy, 2006

No part of this thesis may be reproduced, stored in a database or retrieval system, or transmitte... more No part of this thesis may be reproduced, stored in a database or retrieval system, or transmitted in any form or by any means without prior written permission of the author, or when appropriate, the publishers of the published papers.

Research paper thumbnail of Robot-assisted laparoscopic rectovaginopexy for rectal prolapse: a prospective cohort study on feasibility and safety

Journal of Robotic Surgery, 2008

Robotic systems may be particularly supportive for procedures requiring careful pelvic dissection... more Robotic systems may be particularly supportive for procedures requiring careful pelvic dissection and suturing in the Douglas pouch, as in surgery for rectal prolapse. Studies reporting robot-assisted laparoscopic rectovaginopexy for rectal prolapse, however, are scarce. This prospective cohort study evaluated the outcome of this technique up to one year after surgery. From January 2005 to June 2006, 15 consecutive patients with a rectal prolapse, either with or without a concomitant rectocele or enterocele, underwent robot-assisted laparoscopic rectovaginopexy with support of the da Vinci robotic system. A prospective cohort study was performed on operating times, blood loss, intra-operative and post-operative complications, and outcome at a minimum of one year after surgery. Median age at time of operation was 62 years (33-72) and median body mass index 24.9 (20.9-33.9). Median robot set-up time was 10 min (3-15) and median skin-to-skin operating time was 160 min (120-180). No conversions to open surgery were necessary. No in-hospital complications occurred and there was no mortality. Median hospital stay was four days (2-9). During one year follow-up, two patients needed surgical reintervention. One patient was operated for recurrent enterocele and rectocele one week after surgery. In another patient an incisional hernia at the camera port occurred three months after surgery. At one year after surgery, 87% of patients claimed to be satisWed with their postoperative result. Robot-assisted laparoscopic rectovaginopexy proved to be an eVective technique with favourable outcomes in most patients in this prospective series. The operating team experienced the support of the robotic system as beneWcial, especially during the dissection of the rectovaginal plane and suturing in the Douglas pouch.

Research paper thumbnail of Conventional and Laparoscopic Reversal of the Hartmann Procedure: a Review of Literature

Journal of Gastrointestinal Surgery, 2010

Purpose The aim of this study was to provide a systematic overview on both laparoscopic and conve... more Purpose The aim of this study was to provide a systematic overview on both laparoscopic and conventional Hartmann reversal. Furthermore, the Hartmann procedure is reevaluated in the light of new emerging alternatives. Methods Medline, Ovid, EMBASE, and Cochrane database were searched for studies reporting on outcomes after Hartmann reversal. Results Thirty-five studies were included in this review of which 30 were retrospective. A total of 6,249 patients with a mean age of 60 years underwent Hartmann reversal. Two thirds of patients were classified as American Society of Anesthesiologists (ASA) I-II. The mean reversal rate after a Hartmann procedure was 44%, and mean time interval between Hartmann procedure and Hartmann reversal was 7.5 months. The most frequent reported reasons for renouncing Hartmann reversal were high ASA classification and patients' refusal. The overall morbidity rate ranged from 3% to 50% (mean 16.3%) and mortality rate from 0% to 7.1% (mean 1%). Patients treated laparoscopically had a shorter hospital stay (6.9 vs. 10.7 days) and appeared to have lower mean morbidity rates compared to conventional surgery (12.2% vs. 20.3%). Conclusion Hartmann reversal carries a high risk on perioperative morbidity and mortality. The mean reversal rate is considerably low (44%). Laparoscopic reversal compares favorably to conventional; however, high level evidence is needed to determine whether it is superior.

Research paper thumbnail of Surgical Reintervention After Failed Antireflux Surgery: A Systematic Review of the Literature

Journal of Gastrointestinal Surgery, 2009

Background Outcome and morbidity of redo antireflux surgery are suggested to be less satisfactory... more Background Outcome and morbidity of redo antireflux surgery are suggested to be less satisfactory than those of primary surgery. Studies reporting on redo surgery, however, are usually much smaller than those of primary surgery. The aim of this study was to summarize the currently available literature on redo antireflux surgery. Material and Methods A structured literature search was performed in the electronic databases of MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials. Results A total of 81 studies met the inclusion criteria. The study design was prospective in 29, retrospective in 15, and not reported in 37 studies. In these studies, 4,584 reoperations in 4,509 patients are reported. Recurrent reflux and dysphagia were the most frequent indications; intraoperative complications occurred in 21.4% and postoperative complications in 15.6%, with an overall mortality rate of 0.9%. The conversion rate in laparoscopic surgery was 8.7%. Mean(±SEM) duration of surgery was 177.4±10.3 min and mean hospital stay was 5.5±0.5 days. Symptomatic outcome was successful in 81.1% and was equal in the laparoscopic and conventional approach. Objective outcome was obtained in 24 studies (29.6%) and success was reported in 78.3%, with a slightly higher success rate in case of laparoscopy than with open surgery (85.8% vs. 78.0%). Conclusion This systematic review on redo antireflux surgery has confirmed that morbidity and mortality after redo surgery is higher than after primary surgery and symptomatic and objective outcome are less satisfactory. Data on objective results were scarce and consistency with regard to reporting outcome is necessary.

Research paper thumbnail of S1106 The Relevance of Symptom Association Analysis for the Outcome After Nissen Fundoplication

Research paper thumbnail of Lumbar discitis after laparoscopic ventral rectopexy for rectal prolapse

International Journal of Colorectal Disease, 2011

Research paper thumbnail of Endoscopic evaluation of the colon after an episode of diverticulitis: a call for a more selective approach

International Journal of Colorectal Disease, 2012

Routine colonic evaluation is advised after an episode of diverticulitis to exclude colorectal ca... more Routine colonic evaluation is advised after an episode of diverticulitis to exclude colorectal cancer. In the recent years, the possible relation between diverticulitis and colorectal cancer has been subject of debate. The aim of this study is to evaluate the benefit of routine colonic endoscopy after an episode of diverticulitis. Records of all consecutive patients presenting with a radiologically confirmed episode of diverticulitis between 2007 and 2010 were retrieved from an in-hospital database. Patients who subsequently underwent colonic evaluation were included. The endoscopic detection rate of hyperplastic polyps, adenomas and advanced colonic neoplasia was assessed. Findings were categorized on the basis of the most advanced lesion identified. Three hundred and seven patients presented with a radiologically confirmed primary episode of diverticulitis. Two hundred and five patients underwent colonic evaluation. Hyperplastic polyps were found in15 (6.8 %), adenomas in 18 (8.8 %) and advanced neoplastic lesions in 7 (3.4 %) patients. Only two patients had a colorectal malignancy. There appears to be no benefit in performing routine colonic evaluation after an episode of diverticulitis as the incidence of colorectal cancer is almost equal to that of the general population. A more selective approach might therefore be justified. Potentially, only patients with persisting abdominal complaints after an episode of diverticulitis should be offered colonic evaluation to definitively exclude causal pathology.

Research paper thumbnail of DIRECT trial. Diverticulitis recurrences or continuing symptoms: Operative versus conservative treatment. A multicenter randomised clinical trial

BMC surgery, 2010

Persisting abdominal complaints are common after an episode of diverticulitis treated conservativ... more Persisting abdominal complaints are common after an episode of diverticulitis treated conservatively. Furthermore, some patients develop frequent recurrences. These two groups of patients suffer greatly from their disease, as shown by impaired health related quality of life and increased costs due to multiple specialist consultations, pain medication and productivity losses.Both conservative and operative management of patients with persisting abdominal complaints after an episode of diverticulitis and/or frequently recurring diverticulitis are applied. However, direct comparison by a randomised controlled trial is necessary to determine which is superior in relieving symptoms, optimising health related quality of life, minimising costs and preventing diverticulitis recurrences against acceptable morbidity and mortality associated with surgery or the occurrence of a complicated recurrence after conservative management.We, therefore, constructed a randomised clinical trial comparing ...

Research paper thumbnail of S1105 Esophageal Hypersensitivity Is Not a Contraindication for Nissen Fundoplication

Gastroenterology, 2008

BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the ... more BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the serosa of the stomach to alter gastric electrical activity (GEA). GES has been shown to be a potent anti-emetic and safe way of treating intractable symptomatic gastroparesis and morbid obesity in reported cases (Abell, Van Cutsem et al. 2002 ; Favretti, De Luca et al. 2004). Simulations of GES can be used to optimize stimulation parameters such as the placement of electrodes and stimulation frequency. AIMS: i) To create a computer model that represents the electrical interactions between the smooth muscle cells (SMCs) and the interstitial cells of Cajal (ICCs) based on the current understanding of gastric physiology; ii) To simulate GEA under a) normal conditions, and b) with an artificial stimulus representing a single percutaneous electrode placed on the serosa of the pylorus; iii) To investigate the effects of a range of stimulating frequencies on GEA. METHODS and RESULTS: The computer model consisted of a block gastric tissue measuring 100x100 mm containing a layer of SMCs (represented by the model of Corrias and Buist 2007), and a rule-based layer of ICCs Propagation of slow waves was visualised as colour-coded potentials across the tissue in time. Electrical activities in both the SMC and ICC layers were computed for multiple slow waves. The results demonstrated the correct entrainment behaviors seen in a slice of normal stomach with electrical activity conducting at 11mms-1 in the longitudinal direction and 22mms-1 in the circumferential direction. Further investigations also revealed that complete retrograde GEA could be achieved by adding an extraneous stimulation of higher than the entrainment frequency (3 cycles per minute) at the pylorus of the stomach. In addition, the simulations illustrated that stimuli of equal frequency to the normal entrainment frequency could only produce retrograde activity in a limited region, and the size of the region was dependent on the timing of the onset of the stimuli relative to the normal GEA. CONCLU-SIONS: Both normal GEA and retrograde activity were successfully simulated in a tissue block. The model therefore provides a good initial platform for more detailed investigation of GEA and functional electrical stimulation of the stomach.

Research paper thumbnail of S1104 The Learning Curve in Laparoscopic Nissen Fundoplication Revisited

Gastroenterology, 2008

BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the ... more BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the serosa of the stomach to alter gastric electrical activity (GEA). GES has been shown to be a potent anti-emetic and safe way of treating intractable symptomatic gastroparesis and morbid obesity in reported cases (Abell, Van Cutsem et al. 2002 ; Favretti, De Luca et al. 2004). Simulations of GES can be used to optimize stimulation parameters such as the placement of electrodes and stimulation frequency. AIMS: i) To create a computer model that represents the electrical interactions between the smooth muscle cells (SMCs) and the interstitial cells of Cajal (ICCs) based on the current understanding of gastric physiology; ii) To simulate GEA under a) normal conditions, and b) with an artificial stimulus representing a single percutaneous electrode placed on the serosa of the pylorus; iii) To investigate the effects of a range of stimulating frequencies on GEA. METHODS and RESULTS: The computer model consisted of a block gastric tissue measuring 100x100 mm containing a layer of SMCs (represented by the model of Corrias and Buist 2007), and a rule-based layer of ICCs Propagation of slow waves was visualised as colour-coded potentials across the tissue in time. Electrical activities in both the SMC and ICC layers were computed for multiple slow waves. The results demonstrated the correct entrainment behaviors seen in a slice of normal stomach with electrical activity conducting at 11mms-1 in the longitudinal direction and 22mms-1 in the circumferential direction. Further investigations also revealed that complete retrograde GEA could be achieved by adding an extraneous stimulation of higher than the entrainment frequency (3 cycles per minute) at the pylorus of the stomach. In addition, the simulations illustrated that stimuli of equal frequency to the normal entrainment frequency could only produce retrograde activity in a limited region, and the size of the region was dependent on the timing of the onset of the stimuli relative to the normal GEA. CONCLU-SIONS: Both normal GEA and retrograde activity were successfully simulated in a tissue block. The model therefore provides a good initial platform for more detailed investigation of GEA and functional electrical stimulation of the stomach.

Research paper thumbnail of S1103 Long-Term Outcome of Nissen Fundoplication in Erosive and Non-Erosive Reflux Disease

Gastroenterology, 2008

BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the ... more BACKGROUND: Gastric electrical stimulation (GES) involves placing percutaneous electrodes on the serosa of the stomach to alter gastric electrical activity (GEA). GES has been shown to be a potent anti-emetic and safe way of treating intractable symptomatic gastroparesis and morbid obesity in reported cases (Abell, Van Cutsem et al. 2002 ; Favretti, De Luca et al. 2004). Simulations of GES can be used to optimize stimulation parameters such as the placement of electrodes and stimulation frequency. AIMS: i) To create a computer model that represents the electrical interactions between the smooth muscle cells (SMCs) and the interstitial cells of Cajal (ICCs) based on the current understanding of gastric physiology; ii) To simulate GEA under a) normal conditions, and b) with an artificial stimulus representing a single percutaneous electrode placed on the serosa of the pylorus; iii) To investigate the effects of a range of stimulating frequencies on GEA. METHODS and RESULTS: The computer model consisted of a block gastric tissue measuring 100x100 mm containing a layer of SMCs (represented by the model of Corrias and Buist 2007), and a rule-based layer of ICCs Propagation of slow waves was visualised as colour-coded potentials across the tissue in time. Electrical activities in both the SMC and ICC layers were computed for multiple slow waves. The results demonstrated the correct entrainment behaviors seen in a slice of normal stomach with electrical activity conducting at 11mms-1 in the longitudinal direction and 22mms-1 in the circumferential direction. Further investigations also revealed that complete retrograde GEA could be achieved by adding an extraneous stimulation of higher than the entrainment frequency (3 cycles per minute) at the pylorus of the stomach. In addition, the simulations illustrated that stimuli of equal frequency to the normal entrainment frequency could only produce retrograde activity in a limited region, and the size of the region was dependent on the timing of the onset of the stimuli relative to the normal GEA. CONCLU-SIONS: Both normal GEA and retrograde activity were successfully simulated in a tissue block. The model therefore provides a good initial platform for more detailed investigation of GEA and functional electrical stimulation of the stomach.