Biomedical subjects
Publications and source records attributed to B S Ooi.
We report the first demonstration to our knowledge of an ultrabroad emission laser using InGaAs/GaAs quantum dots by cycled monolayer deposition. The device exhibits a lasing wavelength coverage of approximately 40 nm at an approximately 1160 nm center wavelength at room temperature. The broadband signature results from the superposition of quantized lasing states from highly inhomogeneous dots.
Forearm-based Bier's block has been advocated as a useful anaesthesic technique in hand surgery. However, there is limited data comparing forearm blocks with the conventional Bier's block. We conducted a randomised controlled trial (n=30) comparing the two techniques of anaesthesia for manipulation and reduction of closed distal radius fractures in an emergency room setting. Pain scores measured using the Visual Analogue Scale during the procedure were used as the primary outcome assessment. There was no significant difference in pain scores between the forearm and conventional Bier's block (mean VAS 18.4 SD 22.10 versus 33.7 SD 29.6). No major complications were observed in either group. The forearm-based Bier block is an effective alternative to the conventional block.
BACKGROUND: Fibre is often recommended as the first-choice treatment but its effects can be uneven. The aim of the study was to compare the clinical efficacy and tolerability of fibre versus lactulose in outpatients with chronic constipation. METHODS: In a prospective randomized crossover trial, patients were randomized to receive fibre or lactulose for four weeks. Between treatments, patients had at least one week free of laxatives. RESULTS: 50 patients, of median age 50 years (range, 18-85) were recruited and 39 patients completed the trial. Compared to fibre, lactulose resulted in significantly higher mean bowel frequency (7.3, 95% CI 5.7 to 8.9 vs. 5.5, 95% CI 4.4 to 6.5; p=0.001) and stool consistency score (3.4, 95% CI 3.1 to 3.7 vs. 2.9, 95% CI 2.5 to 3.3; p=0.018). Scores for ease of evacuation were similar. The frequencies of adverse effects were not significantly different, but greater in the lactulose group. Mean patients' recorded improvement score was significantly higher after taking lactulose than fibre (6.2, 95% CI 5.5 to 7.0 vs. 4.8, 95% CI 4.0 to 5.9; p=0.017). Of the 39 patients who completed the trial, 24 (61.5%) preferred lactulose and 14 (35.9%) preferred fibre. CONCLUSIONS: Lactulose had better efficacy than fibre for chronic constipation in ambulant patients, although both treatments were equally well tolerated in terms of adverse effects.
BACKGROUND: Stapled hemorrhoidopexy is an established treatment for hemorrhoidal disease. We evaluated our experience with stapled hemorrhoidopexy using the new Procedure for Prolapse and Hemorrhoids (PPH03) Proximate HCS hemorrhoidal circular stapler (Ethicon Endo-Surgery). METHODS: We retrospectively reviewed clinical data for 238 patients who had undergone stapled hemorrhoidopexy in our department over a 2-month period. Patients were followed-up for a median of 3.5 weeks (range, 1-11 weeks) and were analyzed for complications and resolution of symptoms. RESULTS: The hemorrhoids treated were third- and fourth-degree, as well as second degree (after failure of other therapies). Mean duration of surgery was 12.7 minutes (range, 5-20 minutes) and the majority of patients was treated with an ambulatory procedure. Most patients were discharged within 6 hours after surgery. On follow-up, 3.7% of patients had minor complaints after surgery. Technically, the new PPH03 stapler device has a quickclose knob, which allows rapid opening and closing. The closed staple height of 0.75 mm increases staple line compression on tissue and key blood vessels, hence minimizing bleeding. Prior to this, stapled hemorrhoidopexy was done using the PPH01 device. CONCLUSIONS: Stapled hemorrhoidopexy using the new PPH03 stapler is a safe, short and effective procedure in the management of hemorrhoids. It can be done in the ambulatory setting and patients have few postoperative complications.
BACKGROUND: Midline laparotomies offer excellent exposure but are associated with increased postoperative pain and longer recovery. A minilaparotomy resection of leftsided colorectal cancers was studied as an alternative approach. PATIENTS AND METHODS: We performed a case-control retrospective review of 280 randomly selected patients (140 midline incisions; 140 left skin crease incisions) who underwent elective, curative resection of left-sided colorectal cancers. RESULTS: Patients in both groups were of comparable age and sex. The left skin crease incision was shorter (median length, 13.5 cm) than the midline incision (median length, 20.0 cm). Median operation time was less in the left skin crease group (75 min) than in the midline incision group (105 min). Similar types of operations were performed, including left hemicolectomies, sigmoid colectomies, anterior resections and ultra-low anterior resections. Adequacy of resection was confirmed by histological analysis, with no involvement of margins. The median numbers of lymph nodes removed were comparable: 10 for the skin crease incision group and 12 for the midline incision group. Postoperative parameters for the skin crease incision group showed that feeding, ambulation, narcotic use and hospital stay were significantly better than the parameters in the midline group. Complications of intestinal obstruction were also reduced in the skin crease incision group. CONCLUSIONS: The limited left skin crease incision provides adequate margins of clearance in colorectal cancers when compared to the midline incision, but has advantages of shorter operation time, earlier feeding and ambulation, and earlier discharge from hospital.
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We report the case of a 45-year-old man with rectal amebiasis, presenting with rectal bleeding and chronic diarrhea, confirmed on rectal biopsy. The endoscopic view was highly suggestive of a carcinoma and caused confusion about its etiology. The striking difference in the endoscopic view before and after medical therapy of the tumor-like lesion was remarkable. This case illustrates the importance of an accurate histologic diagnosis before definitive treatment and highlights the mimicry of rectal carcinoma by rectal amebiasis on endoscopy.
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The malignant potential and prognosis of rectal carcinoids are said to be related to tumor size. Our study assessed if size could predict the malignant potential and hence its management. All patients in the Department of Colorectal Surgery, Singapore General Hospital, who underwent surgery for rectal carcinoid tumors between February 1991 and September 2000 were analyzed. Twenty patients (11 men), median age 48 years (range, 33-77 years) were studied. Median follow-up was 40 months (range, 5-120 months). The median tumor diameter was 2.5 cm (range, 0.1-5.0 cm). Eleven patients underwent radical resection and 9 patients had local resection for a presumed benign tumor. Morbidity was 15% and postoperative death was 5%. Overall median survival was 24 months (range, 5-120 months). One patient had an anterior resection for rectal adenocarcinoma but had an incidental 0.1-cm carcinoid tumor near the resection margin which on histology was found to have carcinoid tumor metastasis to 2 out of 12 lymph nodes. In conclusion, tumor size cannot predict malignant potential as even small tumors (<1 cm) can be malignant. Accurate preoperative staging with radical surgery may be required.
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BACKGROUND: Primary colorectal signet-ring cell carcinoma is a rare but distinctive tumour of the colon and rectum. The clinicopathological features are still controversial. The aim of this study is to review the clinicopathological features and management of this type of tumour in our hospital. METHODS: The clinicopathological features and survival data of all cases of primary colorectal signet-ring cell carcinoma were reviewed retrospectively. RESULTS: There were nine cases of primary colorectal signet-ring cell carcinoma in 3000 consecutive colorectal carcinoma patients seen from 1989 to 1999. There were seven male and two female patients with a mean age of 54.7 years. Three patients were younger than 40 years. The common presenting symptoms were rectal bleeding (33%) and small bowel obstruction (33%). Two (22%) patients required emergency surgery due to acute small bowel obstruction. The most common tumour location was the right colon (44%) followed by the rectum (33%). All nine patients presented at a very late stage of disease. A majority (77%) had Dukes' C disease while two (22%) had Dukes' D disease with distant dissemination. Peritoneal spread (33%) was the most frequent way of dissemination. There was no patient with liver metastases at the time of diagnosis and initial presentation. The mean survival time was 30 (range 5-108) months. The 5-year survival rate was 12%. CONCLUSIONS: Primary colorectal signet-ring cell carcinoma is frequently diagnosed late with a very poor prognosis. A high incidence of peritoneal seeding and low incidence of liver metastases appears to be a characteristic of signet-ring cell carcinoma of the colon and rectum.
BACKGROUND: Troublesome faecal incontinence following a lateral internal sphincterotomy (LIS) is often attributed to faulty surgical techniques: division of excessive amount of internal sphincter or inadvertent injury to the external sphincter. The aim of the present paper was to assess the anatomic and physiological factors that may contribute to faecal incontinence following a technically satisfactory lateral internal sphincterotomy by a group of colorectal specialists. METHODS: Fourteen patients (nine women, five men; median age: 38 years; range: 23-52 years) who developed troublesome postoperative faecal incontinence were evaluated by clinical assessment, endoanal ultrasonography and anorectal physiological studies (manometry, pudendal nerve terminal motor latency) by two independent observers. The Cleveland Clinic continence score (0-20; 0, perfect continence; 20, complete incontinence) was used to quantify the severity of faecal incontinence. Fourteen continent subjects after a LIS (nine female patients, five male patients; median age: 36 years; range: 20-44 years) were also evaluated as 'continent' controls (continence score </= 4). RESULTS: In the incontinent group, the median postoperative Cleveland Clinic continence score was 9 (range: 6-13) compared with a preoperative score of 1 (range: 0-3). On assessment by endoanal ultrasonography the site of the internal sphincterotomy was clearly identified. There were additional coexisting defects, on endoanal ultrasonography, of the external anal sphincter in seven female patients, of the internal sphincter in two female and two male patients; and a defect of both the external and internal sphincters in a male patient who had had a prior fistulotomy. The pudendal nerve terminal motor latency (PNTML) was prolonged in two female patients on the side contralateral to the lateral internal sphincterotomy. In two of five male patients there was no evidence of any occult sphincter injuries. In the continent controls a defect of the distal portion of the external sphincter was noted in one female patient. None of the patients had a prolonged PNTML. The maximum voluntary contraction was significantly lower in the female subjects than in the female continent controls (92 mmHg vs 140 mmHg; P < 0.05), while the resting anal canal pressures and length of the high pressure zone were similar between the study subjects and the continent controls. CONCLUSION: Troublesome faecal incontinence after a satisfactorily performed lateral internal sphincterotomy is often associated with coexisting occult sphincter defects.
INTRODUCTION: Primary malignant melanoma arising from the anorectum is uncommon. The natural history of anorectal malignant melanoma is that of a very poor prognosis with early dissemination of disease. Successful surgical treatment has been rare. The present series reviews the clinical features and results of surgical management of patients with anorectal malignant melanoma treated in the Department of Colorectal Surgery, Singapore General Hospital. MATERIALS AND METHODS: Data for all patients treated for anorectal malignant melanoma during an 11-year period from 1989 to 1999 were reviewed. The age, sex, presenting symptoms, duration of symptoms prior to diagnosis, size of tumour, extent of disease, type of surgery and length of survival were analysed. RESULTS: Four men and 2 women, ranging in age from 31 to 81 years with histologically proven primary anorectal malignant melanoma, were included in the study. The most common (67%) presenting symptom was rectal bleeding. The mean tumour size was 2.5 cm (range 1 to 5 cm). All underwent abdomino-perineal resection. Three died of disseminated disease within 17 months while the other 3 were still alive at the time of this study; the longest up to 6.5 years from the time of diagnosis. CONCLUSION: The prognosis of primary anorectal malignant melanoma is poor. However, it is worthwhile treating aggressively as long-term survivor may be encountered in some.
PURPOSE: Bowel dysfunction is common in patients with spinal cord lesions. This study aims to determine whether there are any discriminatory findings at anorectal physiologic testing in patients with spinal cord lesions. METHODS: Twelve consecutive patients (6 females) with significant spinal cord lesions who had mixed symptoms of constipation, fecal impaction, and fecal incontinence were evaluated by perfusion manometry and pudendal nerve terminal motor latency. None of the patients had a sphincter defect as evaluated by endoanal ultrasonography. RESULTS: The median age was 54 (range, 40-87) years. Eight (67 percent) of them had had traumatic spinal cord injuries. Other spinal cord lesions included spina bifida, syringomyelia, arachnoid cyst, and spinal cord ischemia after abdominal aortic aneurysm repair. In patients with spinal cord lesions, the mean (range) resting anal canal pressure and maximum squeeze anal canal pressure were 46 (10-100) mmHg and 76 (30-120) mmHg respectively compared with 62 (50-70) mmHg, and 138 (100-180) mmHg, respectively, in healthy controls. Eleven (92 percent) patients had prolonged pudendal nerve terminal motor latency (9 bilateral and 2 unilateral) whereas rectoanal inhibitory reflex was abolished in all 9 patients tested. CONCLUSIONS: Spinal patients with severe bowel symptoms tended to have lower anal canal pressures than healthy controls. Pudendal netropathy and impaired rectoanal inhibitory reflex are common and may be important in the pathogenesis of bowel dysfunction in patients with spinal cord lesions.
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PURPOSE: Rectocele is often associated with anorectal symptoms. Various surgical techniques have been described to repair the rectocele. The surgical results are variable. This study evaluated the results of transanal repair of rectocele, with particular emphasis on the impact of concomitant anismus on postoperative functional outcome. METHODS: Fifty-nine consecutive females who underwent transanal repair of rectocele for obstructed defecation were prospectively reviewed. All 59 patients were parous with a median parity of 2 (range, 1-6) and a median age of 58 (range, 46-68) years. The median length of follow-up was 19 (range, 6-40) months. Anismus was detected by anorectal physiology and defecography. The functional outcome was assessed by a standard questionnaire, physical examination, anorectal manometry, neurophysiology, and defecography. The quality-of-life index was obtained using a visual analog scale (from 1-10, with 10 being the best). RESULTS: The functional outcome of transanal repair of rectocele was superior in patients without anismus. Forty (93 percent) of the 43 patients without anismus showed improved evacuation after repair compared with 6 (38 percent) of the 16 patients with anismus (P<0.05). The quality-of-life index improved (9 vs. 4) if anismus was not present (P<0.05). There were minimal complications. Hemorrhage requiring blood transfusion (2 units) occurred in one patient and urinary retention in another. CONCLUSION: Transanal repair of rectocele is safe and, in the absence of anismus, effectively corrects obstructed defecation.
PURPOSE: Although adjuvant chemoradiotherapy may improve outcomes after surgery for high-risk rectal cancer, its toxicities are not well documented. This is a review of complications associated with adjuvant therapy in randomized, controlled trials. METHODS: A MEDLINE and literature search was performed for randomized, controlled trials of adjuvant therapy for rectal cancer. Modalities of adjuvant therapy evaluated included preoperative radiotherapy, preoperative chemoradiotherapy, postoperative radiotherapy, and postoperative chemoradiotherapy. All documented complications were analyzed, including any effect on pelvic floor function and quality of life. RESULTS: Short-term (acute) complications of preoperative radiotherapy include lethargy, nausea, diarrhea, and skin erythema or desquamation. These acute effects develop to some degree in most patients during treatment but are usually self-limiting. With preoperative radiotherapy the incidence of perineal wound infection increases from 10 to 20 percent. The acute toxicities after postoperative radiotherapy for rectal cancer occur in 4 to 48 percent of cases, and serious toxicities, requiring hospitalization or surgical intervention, occur in 3 to 10 percent of cases. Postoperative radiotherapy is associated with more complications than preoperative radiotherapy. The main problems with postoperative radiotherapy are small-bowel obstruction (5-10 percent), delay in starting radiotherapy caused by delayed wound healing (6 percent) and postoperative fatigue (14 percent), and toxicities precluding completion of adjuvant therapy (49-97 percent). The morbidity and mortality of both preoperative and postoperative radiotherapy are higher in elderly patients and when two-portal rather than three-portal or four-portal radiation technique is used. Meticulous radiation technique is important, and multiple fields of irradiation are mandatory. After combined adjuvant chemotherapy and radiotherapy acute hematologic and gastrointestinal toxic effects are frequent (5-50 percent). Delayed radiation toxicities include radiation enteritis (4 percent), small-bowel obstruction (5 percent), and rectal stricture (5 percent). Pelvic floor function and quality of life have not been well evaluated in randomized, controlled trials. CONCLUSION: Adjuvant therapy for rectal cancer has considerable adverse effects. Adverse effects on bowel and sphincter function and quality of life have not been defined.
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