Jan Monkelbaan | Utrecht University (original) (raw)

Papers by Jan Monkelbaan

Journal of Gastroenterology and Hepatology, 2016

The implementation of polymerase chain reaction (PCR)-based diagnostics of intestinal protozoa ha... more The implementation of polymerase chain reaction (PCR)-based diagnostics of intestinal protozoa has led to higher sensitivity and (subtype) specificity, more convenient sampling, and the possibility for high-throughput screening. PCR for routine detection of human intestinal protozoa in fecal samples is used by an increasing number of clinical laboratories. This paper discusses the recent developments in the diagnosis of intestinal protozoa, with an emphasis on PCR-based diagnostics. Although many reviews have described the technical aspects of PCR-based diagnostics, this review focuses on the clinical consequences that result from the shift from microscopic toward PCR-based diagnostics. Despite its undisputed superiority, the use of PCR comes with challenges that clinicians should be aware of.

Annals of gastroenterology : quarterly publication of the Hellenic Society of Gastroenterology, 2012

We report a case of a 44-year-old male patient who presented with melena and hemodynamic instabil... more We report a case of a 44-year-old male patient who presented with melena and hemodynamic instability. The endoscopic investigation of the upper and lower gastrointestinal tract was initially negative, but a repeat gastroduodenoscopy revealed a submucosal mass in the lesser curvature of the stomach with central erosion, primarily perceived as ectopic pancreas, but it was later discovered that it pertained to a gastrointestinal stromal tumor.

Huisarts en wetenschap, 2014

The American Journal of Gastroenterology, 2016

Electromagnetic (EM)-guided bedside placement of nasoenteral feeding tubes by nurses may improve ... more Electromagnetic (EM)-guided bedside placement of nasoenteral feeding tubes by nurses may improve efficiency and reduce patient discomfort and costs compared with endoscopic placement by gastroenterologists. However, evidence supporting this task shift from gastroenterologists to nurses is limited. We aimed to compare the effectiveness of EM-guided and endoscopic nasoenteral feeding tube placement. We performed a multicenter randomized controlled non-inferiority trial in 154 adult patients who required nasoenteral feeding and were admitted to gastrointestinal surgical wards in five Dutch hospitals. Patients were randomly assigned (1:1) to undergo EM-guided or endoscopic nasoenteral feeding tube placement. The primary end point was the need for reinsertion of the feeding tube (e.g., after failed initial placement or owing to tube-related complications) with a prespecified non-inferiority margin of 10%. Reinsertion was required in 29 (36%) of the 80 patients in the EM-guided group and 31 (42%) of the 74 patients in the endoscopy group (absolute risk difference -6%, upper limit of one-sided 95% confidence interval 7%; P for non-inferiority=0.022). No differences were noted in success and complication rates. In the EM-guided group, there was a reduced time to start of feeding (424 vs. 535 min, P=0.001). Although the level of discomfort was higher in the EM-guided group (Visual Analog Scale (VAS) 3.9 vs. 2.0, P=0.009), EM-guided placement received higher recommendation scores (VAS 8.2 vs. 5.5, P=0.008). EM-guided bedside placement of nasoenteral feeding tubes by nurses was non-inferior to endoscopic placement by gastroenterologists in surgical patients and may be considered the preferred technique for nasoenteral feeding tube placement.Am J Gastroenterol advance online publication, 7 June 2016; doi:10.1038/ajg.2016.224.

Data Revues 00165107 V75i4ss S0016510712016586, May 17, 2012

Trials, Jan 26, 2015

Gastroparesis is common in surgical patients and frequently leads to the need for enteral tube fe... more Gastroparesis is common in surgical patients and frequently leads to the need for enteral tube feeding. Nasoenteral feeding tubes are usually placed endoscopically by gastroenterologists, but this procedure is relatively cumbersome for patients and labor-intensive for hospital staff. Electromagnetic (EM) guided bedside placement of nasoenteral feeding tubes by nurses may reduce patient discomfort, workload and costs, but randomized studies are lacking, especially in surgical patients. We hypothesize that EM guided bedside placement of nasoenteral feeding tubes is at least as effective as endoscopic placement in surgical patients, at lower costs. The CORE trial is an investigator-initiated, parallel-group, pragmatic, multicenter randomized controlled non-inferiority trial. A total of 154 patients admitted to gastrointestinal surgical wards in five hospitals, requiring nasoenteral feeding, will be randomly allocated to undergo EM guided or endoscopic nasoenteral feeding tube placement...

The Netherlands Journal of Medicine, 1995

Patients with phaeochromocytoma may present a broad spectrum of clinical manifestations as presen... more Patients with phaeochromocytoma may present a broad spectrum of clinical manifestations as presented here in 5 case reports. Pathophysiology, clinical management, pharmacotherapy and associated diseases are discussed. Although catecholamine measurements in both urine and blood as well as modern localisation techniques are valuable adjuncts to establishing the diagnosis, a high index of suspicion remains the key to this diagnosis.

The American Journal of Gastroenterology, 2013

The American journal of gastroenterology, 2012

To determine whether endoscopic clip-assisted nasoenteral feeding tube placement is more effectiv... more To determine whether endoscopic clip-assisted nasoenteral feeding tube placement is more effective than standard feeding tube placement with transnasal endoscopy. Between August 2009 and February 2011, 143 patients referred for endoscopic nasoenteral feeding tube placement were randomized between clip-assisted and standard nasoenteral tube placement. Endoscopies were performed in the endoscopy unit and intensive care unit in a tertiary referral center in the Netherlands. For the clip-assisted procedure, the feeding tube was introduced with a suture fixed to the tip, picked up in the stomach with an endoclip and attached (as distal as possible) to the duodenal wall. In the standard group, a guide wire was placed in the duodenum using a transnasal endoscope, followed by blind insertion of a feeding tube over the guide wire. Primary end point was a repeat endoscopy for incorrect tube placement or spontaneous retrograde tube migration. Secondary end points were incorrect tube placement,...

Gastroenterology, 2011

BACKGROUND: Radiofrequency ablation (RFA) is an endoscopic ablation modality that typically requi... more BACKGROUND: Radiofrequency ablation (RFA) is an endoscopic ablation modality that typically requires multiple treatment sessions to fully eliminate dysplastic tissue. It is unclear if increasing experience reduces complications or the necessary number of ablation sessions, and how many ablations are necessary to achieve competence. AIM: To assess the learning curve for physicians performing RFA. METHODS: This was a retrospective study of patients treated with RFA for BE at a tertiary care referral center between June 2006 and November 2010. Pertinent information was extracted from medical records, including: demographics, pre-ablation histology, indicators of GERD activity (symptoms, erosive esophagitis), upper endoscopy findings (Prague criteria, hiatus hernia), ablation outcomes (elimination of metaplasia and dysplasia), and complications (stricture, bleeding). Endoscopist experience was measured by the number of treatment sessions performed prior to initiation of therapy for each patient. Patients with incomplete treatment and those who initiated treatment in the last 6 months were excluded. Patient characteristics and treatment outcomes were examined among 4 quartiles of endoscopist experience by non-parametric tests (Fisher's exact test for categorical variables and Kruskal-Wallis one-way ANOVA for continuous variables). Linear regression and Pearson's correlation were performed to assess the strength of the association between endoscopist experience and number of sessions necessary for complete ablation. RESULTS: Among 305 RFA treatments by 3 physicians in 113 patients, 245 treatments were in 77 patients who completed therapy more than 6 months prior and were included in the analysis. Over time, there was a significant reduction in the number of RFA sessions and time required to complete therapy, from an average of 4.4 sessions and 226 days in the earliest quartile to 2.3 sessions and 111 days in the most recent quartile (p<0.05 for both). Operator experience and number of RFA sessions to complete treatment were significantly correlated(r=0.38, p<0.001). Linear regression identified operator experience (p<0.001) and Prague M length (p<0.001) as independent predictors of number of treatment sessions to complete eradication of BE. By this model, an endoscopist needs to perform 81 ablations to average 3.0 treatments per patient. Complication rates did not differ significantly dependent on operator experience (p=0.26). CONCLUSIONS: There was a clinically and statistically significant learning curve associated with endoscopic ablation of BE, with initial subjects requiring approximately 2.1 additional treatment sessions for complete ablation. After 81 ablations an endoscopist is projected to average 3.0 treatments per patient. For optimal delivery, this procedure should be performed in high volume centers.

Gastrointestinal Endoscopy, 2015

Adequate bowel preparation is important for optimal colonoscopy. It is important to identify pati... more Adequate bowel preparation is important for optimal colonoscopy. It is important to identify patients at risk for inadequate bowel preparation because this allows taking precautions in this specific group. To develop a prediction score to identify patients at risk for inadequate bowel preparation who may benefit from an intensified bowel cleansing regimen. Patient and colonoscopy data were prospectively collected, whereas clinical data were retrospectively collected for a total of 1996 colonoscopies in participants who received split-dose bowel preparation. Multivariate logistic regression analyses were conducted in a random two-thirds of the cohort to develop a prediction model. Validation and evaluation of the discriminative power of the prediction model were performed within the remaining one-third of the cohort. Four centers, including one academic and three medium-to-large size nonacademic centers. Consecutive colonoscopies in November and December 2012. Mean age was 57.3 ± 15.9 years, 45.8% were male and indications for colonoscopy were screening and/or surveillance (27%), abdominal symptoms and/or blood loss and/or anemia (60%), inflammatory bowel disease (9%), and others (4%). Colonoscopy. Inadequate bowel preparation defined as Boston Bowel Preparation Scale score &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;6. A total of 1331 colonoscopies were included in the development cohort, of which 172 (12.9%) had an inadequate bowel preparation. Independent factors included in the prediction model were American Society of Anesthesiologists Physical Status Classification System score ≥3, use of tricyclic antidepressants, use of opioids, diabetes, chronic constipation, history of abdominal and/or pelvic surgery, history of inadequate bowel preparation, and current hospitalization. The discriminative ability of the scale was good, with an area under the curve of 0.77 in the validation cohort. Study design partially retrospective, no data on patient compliance. We developed a validated, easy-to-use prediction scale that can be used to identify subjects with an increased risk of inadequate bowel preparation with good accuracy.

Gastrointestinal Endoscopy, 2012

European Journal of Gastroenterology & Hepatology, 2008

Beneficial effects of probiotics have been reported in liver disease. Inflammatory bowel disease ... more Beneficial effects of probiotics have been reported in liver disease. Inflammatory bowel disease concurs in 90% of primary sclerosing cholangitis (PSC) patients, suggesting that substances originating from the inflamed gut may damage the biliary tree. To assess potential beneficial effects of probiotics on serum liver tests, pruritus and fatigue in PSC. Fourteen patients (13 male/one female, mean age 45 years), with concurrent inflammatory bowel disease were randomized to treatment with probiotics (Ecologic 641, containing four Lactobacillus and two Bifidobacillus strains; Winclove Bio Industries, Amsterdam, The Netherlands) or placebo during 3 months in a double-blind fashion. After a 1-month washout period, crossover was made. No changes in pruritus, fatigue and stool frequency were noted during placebo or probiotics. No significant differences were observed between treatment with probiotics and placebo in bilirubin (at end of probiotic vs. placebo period: -13 vs. -15% change from baseline; P=0.89), alkaline phosphatase (-9 vs. -9%; P=0.99), gamma glutamyl transpeptidase (-11 vs. -5%; P=0.60), aspartate aminotransferase (-16 vs. -15%; P=0.99), alanine aminotransferase (-27 vs. -26%; P=0.97), prothrombin, albumin or bile salts. Our data do not support beneficial effects of probiotics on symptoms, liver biochemistry or liver function in PSC.

European Journal of Endocrinology, 1993

A patient with acromegaly and hyperthyroidism due to a growth hormone-, thyrotrophin- and alpha-s... more A patient with acromegaly and hyperthyroidism due to a growth hormone-, thyrotrophin- and alpha-subunit-secreting pituitary adenoma is described. His decreased father had suffered from a pituitary tumour, and was likely to have had acromegaly as well. Plasma growth hormone and insulin-like growth factor I concentrations were elevated, with levels between 10 and 20 micrograms/l and 4.4 and 7.3 kU/l, respectively. In spite of hyperthyroidism (free thyroxine, 45 pmol/l; free triiodothyronine, 24 pmol/l), plasma thyrotrophin remained at 2.8 mU/l without any response to thyrotrophin-releasing hormone and could not be suppressed with exogenous administration of triiodothyronine. Plasma alpha-subunits were raised to 3.3-3.7 U/l (normal 0.4-1.1 U/l). Pathological examination of the surgically removed tumour showed a pituitary adenoma with the immunohistochemical presence of growth hormone, thyrotrophin, prolactin and alpha-subunit. This is the first report of a growth hormone-, thyrotrophin- and alpha-subunit-producing pituitary adenoma, which occurred in a familial setting.

Digestive and Liver Disease, 2011

Maintaining the position of an endoscopically placed nasoenteral feeding tube beyond the pylorus ... more Maintaining the position of an endoscopically placed nasoenteral feeding tube beyond the pylorus is often problematic because of retrograde migration. Fixation of a feeding tube to the small intestinal wall with an endoclip may prevent this. This article reviews available literature on the feasibility, efficacy and safety of endoclips for fixation of nasoenteral feeding tubes. A systematic search of the English literature was performed using MEDLINE, EMBASE and Cochrane databases to identify articles assessing the use of endoclips for fixation of feeding tubes, as well as articles assessing duration of attachment of endoclips. Five cohort series were identified that evaluated the applicability of endoclips for fixation of feeding tubes to the small intestinal wall. In all patients, except one, a nasoenteral feeding tube could be successfully fixated to the small intestinal wall. During follow-up, no spontaneous migrations of feeding tubes were observed. No complications related to placement or removal of endoclips were observed. Three comparative studies evaluated duration of attachment of different types of endoclips to the gastrointestinal wall. Duration of attachment ranged from less than 1 week to more than 18 weeks, depending on the type of endoclip. Based on available literature the use of endoclips for fixation of nasoenteral feeding tubes is feasible, effective and safe. Data from randomized controlled trials are needed.

Annals of Nutrition and Metabolism, 1994

Oral calcium supplementation is thought to be a useful interventional agent to decrease colon can... more Oral calcium supplementation is thought to be a useful interventional agent to decrease colon cancer risk. This is supposedly due, at least in part, to the binding of bile acids and fatty acids by calcium in the colon, thus prohibiting the damaging effects of these substances to the epithelium. To determine the effects of calcium supplementation on fecal fat excretion, 24 subjects kept a fat and calcium constant diet for one week and were supplemented with either 0, 2 or 4 g elemental calcium as calcium carbonate in a double-blind fashion. At the end of the week 72-hour feces was collected, and total fat, neutral fat, fatty acids and the ratio of polyunsaturated and saturated fatty acids (P/S ratio) were measured. Calcium dose-dependently increased the percentual excretion of total fat as related to fat intake: 6.8 +/- 0.9% during 0 g, 7.4 +/- 1.0% during 2 g and 10.2 +/- 1.4% during 4 g, r = 0.44, p = 0.03. This was due to increased fatty acid excretion, excretion of neutral fat was not affected, nor was the P/S ratio. It is concluded that calcium supplementation modestly increases fecal fatty acid excretion. No adverse metabolic effects are to be expected from this in case of long-term calcium supplementation in subjects at increased risk for colon cancer.