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A P Leong

Publications and source records attributed to A P Leong.

12 recordsLinked to original sources
PubMed1998

Dynamic decision analysis in medicine: a data-driven approach.

Dynamic decision analysis concerns decision problems in which both time and uncertainty are explicitly considered. Two major challenges in dynamic decision analysis are on proper formulation of a model for the problem and effective elicitation of the numerous time-dependent conditional probabilities for the model. Based on a new, general dynamic decision modeling framework called DynaMoL (Dynamic decision Modeling Language), we propose a data-driven approach to addressing these issues. Our approach uses available problem data from large medical databases, guides the decision modeling at a proper level of abstraction and establishes a Bayesian learning method for automatic extraction of the probabilistic parameters. We demonstrate the theoretical implications and practical promises of this new approach to dynamic decision analysis in medicine through a comprehensive case study in the optimal follow-up of patients after curative colorectal cancer surgery.

Bayes Theorem↗
PubMed1997

Clinical behavior of complicated right-sided and left-sided diverticulosis.

PURPOSE: The aim of the study was to characterize the clinical entity of multiple right-sided (RS) diverticular disease, which is uniquely common in Asians. METHODS: Patients hospitalized with proven diverticular disease from June 1989 to January 1996 were reviewed. Data were retrieved from a prospectively collected computerized database. RESULTS: One hundred eighty consecutive patients were admitted to the Department of Colorectal Surgery, Singapore General Hospital, with multiple diverticular disease. Average age was 65.1 (standard error of the mean, 13.9) years. There were 96 men and 84 women. Women presented, on average, 8.4 years later than men (P < 0.005). Eighty-five patients (47 percent) had massive rectal bleeding, 65 (36 percent) had diverticulitis, 21 (12 percent) had obstructive symptoms, and 9 (15 percent) had enteric fistulas. The diverticula were RS in 76 patients(42 percent), left-sided (LS) in 62 patients (34 percent), and on both sides in 42 patients (24 percent). RS diverticulosis tended to present with massive rectal bleeding (42/76; 55 percent) more often than LS disease (14/62; 23 percent; P < 0.005). Surgery for bleeding was also required more often for RS (17/42; 41 percent) than for LS disease (1/14; 7 percent; P < 0.05); however, diverticulitis was more common on the left (RS, 25/76, 33 percent; LS, 32/62, 52 percent; P < 0.05). Seventy-eight patients (43 percent) required surgery for these complications of diverticular disease. At a mean follow-up of 15.2 (standard error of the mean, 2) months, mortality was 2 in 78 patients who underwent surgery (3 percent), and morbidity was 15 percent. CONCLUSIONS: In comparison with LS, RS diverticular disease tended to present more often with massive bleeding than with diverticulitis and fistulation. This bleeding was often more severe and required surgical intervention.

Aged↗
PubMed1997

Lymph node involvement and tumor depth in rectal cancers: an analysis of 805 patients.

BACKGROUND: Superficial rectal tumors are said to involve regional lymph nodes rarely. This presumption must be proven beyond any doubt if less radical surgery is to be offered for such patients. PATIENTS AND METHODS: Eight hundred five cases (467 males; median age, 64 (range, 19-97) years) of rectal cancer were reviewed. RESULTS: Lymph node positivity, number of lymph nodes involved, lymphatic vessel, and venous and perineural invasion were significantly increased with increasing depth of invasion of tumor through the bowel wall in univariate analysis. The percentage of lymph node involvement at each tumor depth was as follows: T1, 5.7 percent; T2, 19.6 percent; T3, 65.7 percent; T4, 78.8 percent. Overall lymph node involvement was 59 percent. For patients younger than 45 years of age, the percentage of lymph node involvement was 33.3, 30, 69.3, and 83.3 percent compared with 3.1, 8.4, 64.2, and 78.8 percent for patients aged 45 years or above for T1, T2, T3, and T4, respectively. CONCLUSION: Increased depths of tumor penetration beyond T1 and age less than 45 years have an excessive incidence of lymph node positivity. The finding of lymphatic vessel invasion on biopsy is highly indicative of lymph node metastasis.

Adenocarcinoma↗
PubMed1997

Randomized controlled trial of trimebutine (anal sphincter relaxant) for pain after haemorrhoidectomy.

BACKGROUND: Anal sphincter spasm may aggravate pain after haemorrhoidectomy. The aims of this study were to investigate whether a trimebutine suppository (Proctolog) reduced anal resting pressure and, subsequently, to test its efficacy in relieving pain after haemorrhoidectomy. METHODS: Ten patients underwent anal manometry before and 4 h after Proctolog application. A controlled randomized trial was then conducted on 160 consecutive patients. A standard haemorrhoidectomy was performed. Eighty patients were then randomized to receive an application of Proctolog immediately after the procedure (group 1). The remaining 80 did not receive a suppository (controls, group 2). An independent, blinded observer determined the pain scores. RESULTS: Proctolog resulted in a mean 35 per cent reduction in resting anal pressure (P < 0.001). However, there were no differences in the pain score at 4 h after haemorrhoidectomy, maximum pain during the first 24 h, maximum pain during the second postoperative day, ketoprofen requirement or need for intramuscular pethidine injections between groups 1 and 2. CONCLUSION: Although Proctolog reduced mean resting anal pressure at 4 h after application, this did not affect pain after haemorrhoidectomy.

Female↗
PubMed1996

Surgery for inflammatory bowel disease in Singapore.

Inflammatory bowel disease is uncommon in Asians and reports of surgery in these populations are rare. Eighty-two patients with inflammatory bowel disease were seen in the Department of Colorectal Surgery over a five-year period (1989-1994). Twenty-three patients underwent surgery for their disease. There were 12 males and 11 females with 16 Chinese, 4 Indians and 3 Malays. Twelve had Crohn's disease and 11, ulcerative colitis. The majority of patients with Crohn's disease had emergency surgery for bleeding, perforation, abdominal masses and intestinal fistulae. Fifty percent of these had the diagnosis made intraoperatively or post-operatively. Surgery for ulcerative colitis was indicated because of multiple relapses, non-response to medical treatment, side effects of therapy or malignant change. The median age at surgery of patients with Crohn's disease and ulcerative colitis was 39 years (range 24-84) and 40 (range 18-60) respectively. The median follow-up was 22.4 months (range 9-50). The results of surgical therapy in these patients show that surgery when indicated can be done with minimum morbidity and mortality.

Adult↗
PubMed1994

Life-table analysis of stomal complications following ileostomy.

Stomal complications of ileostomy may occur many years after construction. An actuarial analysis of complications of 150 permanent end ileostomies constructed over a 10-year period is reported. By 20 years the incidence of stomal complications approached 76 per cent in patients operated on for ulcerative colitis and 59 per cent in those with Crohn's disease (P < 0.05). Revisional surgery rates were higher in patients with ulcerative colitis than in those with Crohn's disease (28 versus 16 per cent), albeit not significantly. The four commonest complications were skin problems (cumulative probability 34 per cent), intestinal obstruction (23 per cent), retraction (17 per cent) and parastomal herniation (16 per cent). Closure of the lateral space did not reduce the probability of developing intestinal obstruction (18 per cent at 20 years in those with closure versus 3 per cent in those without, P > 0.1). Fixation of the mesentery did not reduce the probability of developing prolapse of the ileostomy (11 per cent in those with fixation versus none in those without, P < 0.1). The incidence of parastomal herniation was not reduced by sitting through the rectus abdominis (21 per cent in those sited through the body of the rectus abdominis versus 7 per cent in those sited through the oblique muscles, P < 0.1). Some of the surgical dogmas relating to ileostomy construction are not supported by the results of this study.

Adolescent↗
PubMed1994

Life table analysis of stomal complications following colostomy.

PURPOSE: This study was designed to evaluate the long-term complication rate of left iliac fossa end sigmoid colostomies and to determine etiologic factors. METHODS: A retrospective chart review and actuarial analysis were performed. RESULTS: The crude and actuarial risks of paracolostomy complications in 203 patients were 51.2 percent and 58.1 percent at 13 years, respectively. Paracolostomy hernia was the most common complication (36.7 percent at 10 years). Siting the stoma through the belly of the rectus abdominis muscle did not reduce the risk of hernia, but an extraperitoneal course had a significantly lower risk of herniation when compared with a transperitoneal course and intestinal obstruction was marginally less frequent. Paracolostomy hernias were otherwise more likely in the elderly, and in those with other abdominal wall hernias. Mesenteric fixation did not reduce the subsequent chance of prolapse. The reduction in the risk of intestinal obstruction when lateral space closure was employed was not statistically significant (4 percent vs. 10 percent, P < 0.1), and all three patients with stomal retraction had had lateral space closure. CONCLUSION: The evidence in this study that spans a 22-year period questions much surgical technical dogma and raises the possibility that parastomal hernias may, like inguinal hernias, represent a failure in the transversalis fascia that might technically be avoidable.

Adult↗