Charles Tsang - Academia.edu (original) (raw)

Papers by Charles Tsang

Pelvic Floor Disorders, 2020

Surgery, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Khon Kaen Medical Journal ขอนแก่นเวชสาร, Feb 23, 2010

Background: Preoperative clinical staging of rectal tumors is very important to allow surgeons ma... more Background: Preoperative clinical staging of rectal tumors is very important to allow surgeons make informed decisions about the types of surgeries that should be performed. Endorectal ultrasonography (ERUS) is one of the tools that has been commonly used in clinical staging of rectal tumors. The aim of the present study was to evaluate the accuracy of endorectal ultrasonography in preoperative staging of rectal tumors and evaluate the factors that influence on the reliability of endorectal ultrasound staging such as experience of ultrasonographer, Characteristics of the tumor and tumor site (in terms of height) Methods: Fifty-three patients with rectal adenocarcinomas underwent an endorectal ultrasonography evaluation during a period of three years. The evaluation was performed by three surgeons. We compared the endorectal ultrasonography staging with the pathology findings based on the surgical specimens. Patients with preoperative chemoradiation were excluded from the study. Results: Overall accuracy in assessing the level of rectal wall invasion was 55%, with 19% of the tumours overstaged and 26% understaged. Accuracy in assessing nodal involvement in 44 patients treated with radical surgery was 45%, with 41% overstaged and 14% understaged. If focus on experience of ultrasonographer that show learning curve for good progression in accuracy of assessing tumor invasion from 42% in 2005 to 87% in 2007. Accuracy for Characteristics of the tumor that show better progression in accuracy for ulcerative tumor from 25% in 2005, 62% in 2006 and 100% in 2007 but for polypoid tumor that show poorer accuracy rate only 50% for all three years. Whether tumour site (in terms of height) found a significantly poorer accuracy rate for tumours of the distal third (2-6 cm from anal verge) that show accuracy only 48% ,on the other hand significantly better for tumours of the middle third (7-12 cm from anal verge) that show accuracy 62%. Accuracy depended on the tumor stage, ultrasonographer experience , characteristics of the tumor and tumor site (in terms of height). Conclusions: The accuracy of endorectal ultrasonography in assessing the depth of tumor invasion, particularly for early cancers, is lower than previously reported. Endorectal ultrasound is more operator dependent and accuracies improve with experience and characteristics of the tumor and tumor site (in terms of height) that influence on the reliability of accuracy.

Journal of Electronic Imaging, 2005

Extraction and reconstruction of rectal wall structures from an ultrasound image is helpful for s... more Extraction and reconstruction of rectal wall structures from an ultrasound image is helpful for surgeons in rectal clinical diagnosis and 3-D reconstruction of rectal structures from ultrasound images. The primary task is to extract the boundary of the muscular layers on the rectal wall. However, due to the low SNR from ultrasound imaging and the thin muscular layer structure of the rectum, this boundary detection task remains a challenge. An active contour model is an effective high-level model, which has been used successfully to aid the tasks of object representation and recognition in many image-processing applications. We present a novel multigradient field active contour algorithm with an extended ability for multiple-object detection, which overcomes some limitations of ordinary active contour models-"snakes." The core part in the algorithm is the proposal of multigradient vector fields, which are used to replace image forces in kinetic function for alternative constraints on the deformation of active contour, thereby partially solving the initialization limitation of active contour for rectal wall boundary detection. An adaptive expanding force is also added to the model to help the active contour go through the homogenous region in the image. The efficacy of the model is explained and tested on the boundary detection of a ring-shaped image, a synthetic image, and an ultrasound image. The experimental results show that the proposed multigradient field-active contour is feasible for multilayer boundary detection of rectal wall.

International Journal of Colorectal Disease, 2011

Purpose There is growing enthusiasm for robotic-assisted laparoscopic operations across many surg... more Purpose There is growing enthusiasm for robotic-assisted laparoscopic operations across many surgical specialities, including colorectal surgery, often not supported by robust clinical or cost-effectiveness data. A proper assessment of this new technology is required, prior to widespread recommendation or implementation. Methods/design The ROLARR trial is a pan-world, prospective, randomised, controlled, unblinded, superiority trial of robotic-assisted versus standard laparoscopic surgery for the F.

Diseases of the Colon & Rectum, 1992

Mm: To study the value of fecal occult blood testing for early detection of colorectal neoplasms ... more Mm: To study the value of fecal occult blood testing for early detection of colorectal neoplasms in a randomized study. Method: All inhabitants in G6teborg, 68,366 persons (between 60 and 64 years of age at the time of the start of the study) were randomly divided into a test and a control group, The 34,175 subjects in the test group were invited to perform fecal occult blood testing with Hemoccult II | and retesting 1 89 years later. Two tests were taken from three consecutive stools and the test rehydrated before development. Two letters of reminder were sent to those who did not answer. Results: 21,341 completed the test. 943 of these had a positive test and 812 came for a full work-up including rectosigmoidoscopy and double barium enema. 75 subjects with carcinoma and a positive test have so far been diagnosed and 368 subjects with an adenoma (207 subjects _> 1.0 centimeter). The distribution according to Dukes' was significantly better in the test group than in the control group (p<_0.05) and there was significantly more Dukes' A carcinomas among the screen detected carcinomas than in the control group (P<0.001).

Diseases of the Colon & Rectum, 2000

Diseases of the Colon & Rectum, 2009

The initial staging CT scan for patients with colorectal cancer may reveal small, &amp;am... more The initial staging CT scan for patients with colorectal cancer may reveal small, &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;indeterminate&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; hepatic lesions. The significance of these lesions is often unknown at the time of diagnosis. Surveillance of these lesions is often recommended because they may have an impact on the subsequent management of these patients. This study was designed to determine the prevalence and significance of small (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;1 cm on CT scan), indeterminate liver lesions detected preoperatively in patients with colorectal cancer and to determine whether further surveillance imaging of these patients is required. Data were collected retrospectively, from January 1, 2002, to December 31, 2005. All colorectal cancer patients with small, indeterminate liver lesions on their initial staging CT scan were included. These lesions were formally reported as being too small to be characterized. All subsequent surveillance images of the liver were reviewed to assess the natural history of these lesions. Four hundred nineteen patients with colorectal cancer had staging CT performed. Seventy patients (16.7%) had small liver lesions on their initial CT that could not be definitely characterized. Forty-six (65.7%) underwent subsequent imaging of their liver lesions. Forty-one (89.1%) of these were shown to be stable lesions that were likely benign. Only five patients (10.9%) showed progression on subsequent liver imaging, suggestive of early metastases and consistent with their clinical picture. Small, indeterminate liver lesions may occur in up to 16.7% of patients with colorectal cancer. Although most of these lesions remain quiescent, surveillance imaging is recommended because a small but not insignificant proportion of patients with such lesions actually harbor early metastases.

Colorectal Disease, 2009

There is a relative dearth of literature comparing hand-assisted (HALC) to standard (SLC) laparos... more There is a relative dearth of literature comparing hand-assisted (HALC) to standard (SLC) laparoscopic colectomies. HALC seems beneficial in terms of shorter operative times and lower conversion rates, but this is counterbalanced by a greater inflammatory response, larger incisions and higher direct costs. Nevertheless, these results are not consistent throughout existing studies and there are to date no detailed cost comparisons. Our hypothesis was that HALC would not incur significantly higher institutional costs compared with standard laparoscopic techniques. Patients undergoing either SLC or HALC between August 2004 and September 2006 were retrospectively reviewed. All patients were managed using a standard protocol. Outcomes assessed included operative times, conversion rates, pain scores, time to resolution of ileus, length of stay and complications. Total costs were calculated from the day of surgery. Statistical analyses included chi(2), Fisher's exact test, the Mann-Whitney U-test or nonparametric bootstrapping method. Seventy-three patients underwent SLC while 101 had HALC. Demographics and indications for surgery in both groups were similar; the majority were performed for colorectal cancers. Operative times were shorter (147.5 vs 172.5 min, P < 0.05) and complication rates lower (28.7%vs 45.2%, P < 0.025) for HALC. There was no significant difference in the other clinical outcomes. Operative costs and cost of consumables were higher for HALC (US$4024.2 vs US$3568.1, P = 0.01 and US$1724.7 vs US$1302.7, P < 0.001, respectively). However, total costs were not significantly different (HALC US$8999.8, SLC US$7910.7, P = 0.11). Institutional costs are not significantly higher for HALC compared with SLC.

Colorectal Disease, 2013

This study aimed to determine if successful seton placement at the initial drainage procedure imp... more This study aimed to determine if successful seton placement at the initial drainage procedure improves outcomes in the management of deep postanal space abscesses. A retrospective review was performed of all patients who underwent initial drainage of a DPA space abscess between December 2002 and August 2010. A seton was placed through the internal opening if it could be identified. Thirty-two patients of median age 41 (21-64) years formed the study group. Twenty-four (75.0%) had a seton inserted at the initial drainage procedure. The patients underwent a total of 56 operations. The median interval from the initial to the final operation was 5 (2-18) months with 17 (70.8%) patients having the final operation within 6 months. In the 8 (25.0%) patients whose internal opening could not be found, 26 operations were required with a median interval from the initial to the final surgery of 11 (3-24) months. Patients who had a seton successfully inserted at drainage underwent significantly earlier definitive surgery and required fewer operations (P < 0.038). Identification of an internal opening with placement of a seton at the initial drainage procedure is associated with earlier definitive surgery and fewer operations.

ANZ Journal of Surgery, 2009

Background: Laparoscopic colectomy has yet to gain widespread acceptance in costconscious health-... more Background: Laparoscopic colectomy has yet to gain widespread acceptance in costconscious health-care institutions. The aim of the present study was to define the costbenefit relationship of laparoscopic versus open colectomy. Methods: Thirty-two consecutive patients undergoing elective laparoscopic colectomy (LC) by a single colorectal surgeon between August 2004 and September 2005 were reviewed. Cases were matched with a historical cohort undergoing elective open colectomy (OC) between June 2003 and July 2004. Demography, perioperative data, histopathology and cost were compared. Results: Both groups had similar demographics. Most resections (90.6%) were for cancer. Operative time was significantly longer for LC compared to OC (180 min vs 110 min, P < 0.001). Four patients (12.5%) in the LC group required conversion. LC patients, however, had lower median pain scores (3, 2 and 1 vs 6, 4 and 2 at 24, 48 and 72 h postoperatively, P < 0.001), faster resolution of ileus (3 vs 4 days, P < 0.001) and earlier discharge (6 vs 9 days, P < 0.001) compared to the OC group. As a result, overall hospital cost for both procedures was not significantly different (US$7943 vs US$7253, P = 0.41). Conclusion: Laparoscopic colectomy is as cost-beneficial in the short term as open colectomy.

Annals of Surgery, 2002

To assess the efficacy of a novel coloplasty colonic pouch design in optimizing bowel function af... more To assess the efficacy of a novel coloplasty colonic pouch design in optimizing bowel function after ultralow anterior resection. Summary Background Data A colonic J-pouch may reduce excessive stool frequency and incontinence after anterior resection, but at the risk of evacuation problems. Experimental surgery on pigs has suggested that a coloplasty pouch (CP) may be a useful alternative. Although CP has recently been shown to be feasible in patients, there is no randomized controlled trial comparing bowel function with the J-pouch. Methods After anterior resection for cancer, patients were allocated to either J-pouch or CP-anal anastomoses. Continence scoring, anorectal manometry, and endoanal ultrasound assessments were made before surgery. All complications were recorded, and these preoperative assessments were repeated at 4 months. The assessments were repeated again at 1 year, and a quality of life questionnaire was added. Results Eighty-eight patients were recruited from October 1998 to April 2000. Both groups were well matched for age, gender, staging, adjuvant therapy, and mean follow-up. There were no differences in the intraoperative time and hospital stay. CP resulted in more anastomotic leaks. At 4 months, J-pouch patients had 10.3% less stool fragmentation but poorer stool deferment and more nocturnal leakage. However, there were no differences in the bowel function, continence score, and quality of life at 1 year. There were no differences in the anorectal manometry and endoanal ultrasound findings. Conclusions Coloplasty pouches resulted in more anastomotic leaks and minimal differences in bowel function. At present, the J-pouch remains the benchmark for routine clinical practice, and due care (including defunctioning stoma) should be exercised in situations requiring CP. Ultralow anterior resection is a well-recognized surgical technique for effective excision of mid-to low rectal cancer and also restoration of bowel continuity. However, poor bowel function may be expected with a straight coloanal anastomosis. 1,2 This includes excessive stool frequency, urgency, and incontinence. The reservoir function of the excised rectum is not adequately restored, 2,3 and there may be some damage to the anal sphincters. 2-5 In particular, the bowel function decompensates where the anastomosis is less than about 4 cm from the anal verge. 3 In such circumstances, restoration of the rectal reservoir by a colonic J-pouch results in significantly improved early function. 6 Randomized controlled trials have since confirmed the early advantages of the J-pouch, although adaptation may eventually equalize the function of straight coloanal anastomoses and J-pouches during a period of 2 years. 7-10 However, 10% to 30% of J-pouch patients may be afflicted with stool evacuation problems, such as constipation and stool

Diseases of the Colon & Rectum, 2012

The ideal surgery following seton insertion for high anal fistulas remains debatable. This study ... more The ideal surgery following seton insertion for high anal fistulas remains debatable. This study aimed to compare the success between the endorectal advancement flap and the ligation of intersphincteric fistula tract techniques as the definitive procedure following seton placement. This study is a retrospective review. This study was conducted at the Division of Colorectal Surgery, University Surgical Cluster, National University Health System, Singapore, between April 2006 and July 2011. After seton placement for high anal fistulas, 31 and 24 patients underwent the endorectal advancement flap and the ligation of intersphincteric fistula tract procedures. Failure was defined as the nonhealing of the surgical wounds or persistent discharge at the external opening. We identified 31 patients with a median age of 49 (range, 19-74) years in the endorectal advancement flap group. The median interval from the seton procedure to the flap procedure was 13 (range, 4-284) weeks. Over a median follow up of 6 (range, 2-26) months, 29 (93.5%) patients had successful outcomes. There were 24 patients, median age 41 (range, 16-75) years, in the ligation of intersphincteric fistula tract group. The median interval from the seton placement to the definitive surgery was 14 (range, 8-74) weeks. Over a median follow-up of 13 (range, 4-67) months, 15 (62.5%) patients had successful outcomes. Hence when performed as the initial definitive procedure after a seton, the endorectal advancement flap technique had a significantly higher success rate in comparison with the ligation of intersphincteric fistula tract approach (93.5% vs 62.5%) (p = 0.006). In patients who have had seton placement for high anal fistulas, the endorectal advancement flap technique is associated with better short-term outcomes in comparison with the ligation of intersphincteric fistula tract technique.

Seminars in Colon and Rectal Surgery

Diseases of the Colon and Rectum, Sep 1, 1998

Traumatic sphincter disruption frequently is associated with a rectovaginal fistula, but the effe... more Traumatic sphincter disruption frequently is associated with a rectovaginal fistula, but the effect of a persistent sphincter defect on the outcome of rectovaginal fistula repair is poorly documented. We analyzed the outcome of rectovaginal fistula repairs based on preoperative sphincter status. We identified 52 women who underwent 62 repairs of simple obstetrical rectovaginal fistulas between 1992 and 1995. Fourteen patients (27 percent) had preoperative endoanal ultrasound studies and 25 (48 percent) had anal manometry studies. Follow-up was by mailed questionnaire in 36 patients (69 percent) and by telephone interview in 12 (23 percent), for a total response rate of 92 percent. Median age was 30.5 (range, 18-70) years, and median follow-up was 15 (range, 0.5-123) months. Twenty-five patients (48 percent) complained of varying degrees of fecal incontinence before surgery. There were 27 endorectal advancement flaps and 35 sphincteroplasties (28 with and 8 without levatoroplasty). Success rates were 41 percent with endorectal advancement flaps and 80 percent with sphincteroplasties (96 percent success with and 33 percent without levatoroplasty; P = 0.0001). Endorectal advancement flap was successful in 50 percent of patients with normal sphincter function but in only 33 percent of patients with abnormal sphincter function (P = not significant). For sphincteroplasties, success rates were 73 vs. 84 percent for normal and abnormal sphincter function, respectively (P = not significant). Results were better after sphincteroplasties vs. endorectal advancement flaps in patients with sphincter defects identified by endoanal ultrasound (88 vs. 33 percent; P = not significant) and by manometry (86 vs. 33 percent; P = not significant). Poor results correlated with prior surgery in patients undergoing endorectal advancement flaps (45 percent vs. 25 percent; P = not significant) but not sphincteroplasties (80 vs. 75 percent; P = not significant). All patients with rectovaginal fistula should undergo preoperative evaluation for occult sphincter defects by endoanal ultrasound or anal manometry or both procedures. Local tissues are inadequate for endorectal advancement flap repairs in patients with sphincter defects and a history of previous repairs. Patients with clinical or anatomic sphincter defects should be treated by sphincteroplasty with levatoroplasty.

Seminars in Colon and Rectal Surgery, 2010

ABSTRACT Preoperative staging of rectal cancer is important in tailoring the most optimal treatme... more ABSTRACT Preoperative staging of rectal cancer is important in tailoring the most optimal treatment for the patient. Early tumors T0 to T1 may be suitable for local excision therapy. More advanced lesions, such as T3 to T4, should be treated with neoadjuvant chemoirradiation before surgery because it has been shown to reduce local recurrence and improve outcomes. Endorectal ultrasound has been shown to be reliably accurate in helping the physician to assess the depth of penetration of tumor (uT staging) and acceptable in evaluating nodal involvement (uN staging). It is superior to computed tomography scan but inferior to magnetic resonance imaging. Large stenotic tumors that preclude intubation and complete assessment of the tumor are more suitably staged by magnetic resonance imaging, which is superior in evaluating involvement of deeper structures such as the mesorectal fascia. Small early tumors are better evaluated by endorectal ultrasound, which demonstrates better clarity of the individual rectal wall layers. The advent of 3-dimensional imaging has enabled better spatial visualization and assessment of tumors. Tumor volume and distance between distal limit of tumor to upper border of anal canal can now be measured. Tumor response to neoadjuvant treatment and distal margin clearance for sphincter salvage can now be objectively assessed. Meticulous technique is important to reduce artifacts that may affect the accuracy of the scan. Technically demanding, there is a learning curve for this procedure.

2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2001

This paper presents a novel multigradient field active contour algorithm with an extended ability... more This paper presents a novel multigradient field active contour algorithm with an extended ability for multiple object delineation, which overcomes some limitations of ordinary active contour models. One of the aims is to apply this technique for multilayer boundary detection of ultrasound rectal wall image, which is important in colorectal clinical diagnosis for rectal tumor staging. The core part in