Biomedical subjects
Publications and source records attributed to S K Yip.
We discuss the line shape for an internal state transition for bosonic atoms confined as a one-dimensional gas, using a method by Haldane. Typical line shape is an edge singularity due to the absence of Bose-Einstein condensation in such systems.
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We describe 4 cases of extramammary Paget's disease of the scrotum with underlying invasive carcinoma from 1997 to 1999. Three patients had metastatic inguinal lymphadenopathy. The delay in diagnosis was significant (mean 1 year). The diagnosis was made by skin biopsy in all patients. Histologically, intraepidermal cells with enlarged vesicular nuclei and vacuolated cytoplasm, which was mucin positive, were found. The mainstay of treatment is wide surgical excision, but positive margins remain a major problem. Other modes of treatment have been advocated but the efficacy for invasive disease is low. The key to successful control of the disease is therefore a high index of suspicion and early diagnosis.
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OBJECTIVES: To compare the outcome of outpatient ureteroscopic laser lithotripsy (URSL) for ureteral stone larger than 10 mm in longest diameter (group 1) with those less than or equal to 10 mm (group 2). METHODS: 134 patients with solitary ureteral stone were treated by outpatient URSL. No exclusion criteria with regards to stone size, level or composition were applied. Semirigid ureteroscopy and holmium-YAG laser lithotripsy was performed under general anaesthesia as outpatient procedure. Radiological follow-up by intravenous urogram was performed 3 months postoperatively. Patients' demographic data, stone parameters, operative details and treatment outcome were collected prospectively and compared between the two groups. RESULTS: Among the 134 ureteral stones, 41(31%) were larger than 10 mm. Group 1 contained more upper and middle ureteral stones than group 2 (68 vs. 40% p = 0.001). Operating time was significantly longer for group 1 (68.9 vs. 46.8 min, p<0.001) and postoperative stenting rate was higher (83 vs. 60%, p = 0.01). There was no difference between the groups in terms of 3 months stone clearance rate (92.7 vs. 91.4%, p = 0.8). Complication rate was higher in group 1 (22 vs. 5.4%, p = 0.004) especially for lower stones (46.2 vs. 5.4%, p = 0.001) but most of which were minor complications that were treated conservatively. One patient in group 1 (2.4%) developed ureteral stricture at the longstanding stone impaction site despite postoperative stenting. The stricture resolved subsequent to balloon dilatation. CONCLUSIONS: URSL can treat stones larger than 10 mm in longest diameter at all levels safely and effectively in an outpatient setting.
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A 46-year-old previously healthy man presented with urosepsis and lower urinary tract obstruction. Both urine and blood cultures grew Burkholderia pseudomallei. Intravenous Ceftazidime failed to control the infection. Prostatic abscess formation was first detected by transrectal ultrasonography, and the extent was subsequently delineated by computed tomography. The abscess was drained by transurethral resection, which served to eradicate a possible persistent focus of infection. The diagnosis and management of prostatic abscess, and Melioidosis infection, are discussed.
Megaureter is infrequently diagnosed in adulthood. A 27-year-old man who presented with recurrent left loin pain was found to have megaureter on intravenous urography. His symptoms did not resolve after balloon dilatation of the 3 cm stenotic aperistaltic segment of the lower ureter. He eventually underwent ureteric re-implantation with satisfactory symptomatic relief. The resolution of obstruction was demonstrated radiologically. The role of imaging in the diagnosis and surveillance of megaureter, as well as indications for intervention, are discussed.
INTRODUCTION: Renal oncocytoma is a rare benign tumour. CLINICAL PICTURE: A 73-year-old man presented with bilateral renal tumours, suggestive of renal cell carcinoma (RCC). Nephron-sparing surgery (NSS) and radical nephrectomy were performed. Both specimens revealed renal oncocytoma on final histology. A review of nephrectomy specimens showed 4 other solitary oncocytomas out of 250 RCCs over the period 1991 to 2000. Diagnosis of oncocytoma could only be firmly established by careful histological evaluation to exclude RCC. TREATMENT: Renal oncocytoma carries a good prognosis. The use of NSS for synchronous bilateral renal masses is highlighted. CONCLUSION: NSS is recommended for renal oncocytoma wherever possible.
Horseshoe kidney is the commonest congenital renal anomaly. Its inherently-poor drainage system renders the patient prone to stone formation. A 56-year-old man with bilateral renal stones in a horseshoe system associated with hydronephrosis is presented. He was treated successfully with bilateral CT-guided percutaneous nephrostomy and percutaneous nephrolithotripsy. Various treatment options, including ESWL, PCNL and open surgery, are discussed.
OBJECTIVE: To determine whether a single oral dose of misoprostol is associated with change in Doppler resistance indices (RIs) of the uterine artery in early pregnancy. METHODS: Forty pregnant women seeking legal termination of pregnancy at 7-15 completed gestational weeks were each given a single oral dose of 200 microg misoprostol. Resistance indices (A/B ratio) and pulsatility index (PI) of the uterine arteries (UA) and fetal heart rate (FHR) were assessed by Doppler ultrasound before and 1 hour after administration of misoprostol. RESULTS: Doppler RIs (UA-A/B and UA-PI) of the right and left uterine arteries increased significantly 1 hour after misoprostol administration. The right UA-A/B increased from 7.16 +/- 1.09 (mean +/- SEM) to 10.26 +/- 0.67 (P < .001), and the left UA-A/B increased from 7.40 +/- 0.72 to 9.21 +/- 0.82 (P = .04). The right UA-PI increased from 2.38 +/- 0.11 to 2.90 +/- 0.12 (P < .001), and the left UA-PI increased from 2.38 +/- 0.17 to 2.70 +/- 0.18 (P = .03). No significant changes in FHR were noted 1 hour after misoprostol administration. None of the fetuses died during that time. CONCLUSION: Doppler RIs of the uterine arteries increased significantly after single oral doses of misoprostol during the first trimester, implying a reduction in arterial blood flow. Those changes were not associated with fetal death, possibly explaining congenital abnormalities associated with misoprostol in early pregnancy.
Angiomyolipoma (AML) is a benign renal tumour that occasionally requires intervention. We evaluated the surgical management of symptomatic angiomyolipoma, with special attention to the feasibility of nephron-sparing surgery. A retrospective study was conducted enlisting 23 patients (including 3 patients with tuberous sclerosis) who had their AML treated surgically from 1991 to 1998. The study included 7 males and 16 females, with a mean age of 49 years (range 24-75). The mean tumour size was 12.3 cm (range 1.5-30.0) including 7 lesions < or = 4 cm and 16 lesions > 4 cm. The presenting features included abdominal/loin pain (9 patients), spontaneous rupture (5 patients), non-specific symptoms (7 patients) and incidental findings (2 patients). AML was diagnosed by computed tomography in 16 patients and malignancy was suspected in 7 patients. The latter group included 5 patients with lesions smaller than 4 cm, one of them having coexisting AML and renal cell carcinoma. All patients underwent elective surgery, with the exception of one, who required a semi-emergency operation. Nephron-sparing surgery using frozen section in 5 patients (all diagnostic) was carried out on 16 patients, including all 5 patients with previous haemorrhage and 2 patients with suspected lesions from preoperative studies. Total nephrectomy was performed in 7 patients, including the other 5 patients with lesions suspected to be malignant. There was no operative mortality. Two complications were encountered in the entire group. We conclude that elective nephron-sparing surgery is feasible, even for massive angiomyolipoma or after previous rupture, especially when the diagnosis is made by preoperative imaging and/or intraoperative frozen section.
PURPOSE: To evaluate a policy of selective, short-duration internal stenting after outpatient ureteroscopic laser lithotripsy. PATIENTS AND METHODS: From January 1997 to April 1998, 62 patients (34 male, 28 female) with a mean age of 50 (range 21-80) years underwent outpatient ureteroscopic lithotripsy using a holmium laser (365 microm; 0.5-1.4J/5-10 Hz) and 6F/7.5F semirigid ureteroscope. Internal stents were inserted selectively in patients with severe preoperative obstruction (intravenous urogram finding), tight stone impaction (endoscopic finding), or significant residual obstruction (on-table retrograde pyelogram finding) despite stone clearance. Patient demographics, stone measures, stone clearance rates, complications, postoperative pain scores, analgesic requirement, and follow-up imaging were compared for the stented and unstented patients. RESULTS: With the present criteria of selective internal stenting, stents were inserted in 56% of the patients for a mean duration of 3.6 weeks. Excluding those patients with residual stones requiring further interventions, the stenting rate was 39% with a mean duration of 1.9 weeks. There was no difference in patient characteristics, stone burden, and stone levels between the stented and unstented group. The mean operating time for the unstented group was shorter than for the stented group (45.6 minutes v 56.6 minutes; P = 0.03). The stone clearance rates were similar for the two groups (96% v 97%), but the complication rate of the stented group was higher (8.6% v 3.7%). The mean postoperative pain score and analgesic requirement were similar in the two groups on postoperative day 1 but significantly less in the unstented group on day 3. CONCLUSIONS: The criteria for selective internal stenting are useful in determining when a stent should be used. By omitting the stent insertion in the absence of these criteria, operating time, postoperative pain, and analgesic requirement were reduced without increasing the complication rate. Ureteral stricturing was absent despite the low stenting rate.
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Acquired cystic disease of the kidney and renal cell carcinoma are associated with chronic renal failure. In recent years, there has been increased incidental detection of renal tumours through the liberal use of ultrasonography (US) and computed tomography (CT). A 40-year-old man suffering from chronic renal failure and who was being treated with haemodialysis for six years, was found to have a complex cystic lesion on US and CT. Nephrectomy was performed and the lesion was confirmed to be renal cell carcinoma associated with acquired cystic kidney disease. The current role of imaging in the management of affected patients are discussed.