Spectral solution of delayed random walks.

We develop a spectral method for computing the probability density function for delayed random walks; for such problems, the method is exact to machine precision and faster than existing approaches. In conjunction with a step function approximation and the weak Euler-Maruyama discretization, the spectral method can be applied to nonlinear stochastic delay differential equations (SDDE). In essence, this means approximating the SDDE by a delayed random walk, which is then solved using the spectral method. We carry out tests for a particular nonlinear SDDE that show that this method captures the solution without the need for Monte Carlo sampling.

Page kidney following renal allograft biopsy - early recognition and treatment.

Ultrasound- guided percutaneous allograft renal biopsy is commonly done to evaluate graft dysfunction. Complications of renal biopsy are usually minor, and major complications occur only in less than 1% cases. We report a case of allograft renal biopsy which caused a subcapsular hematoma, Page kidney and deterioration of graft function. This was diagnosed by computed tomography (CT) scan, and early surgical intervention led to complete recovery.

Nonlinear constructive interference in electrical lattices.

We analyze the constructive interference of input signals in nonlinear, discrete, two-dimensional media. The media consist of inductor-capacitor lattices with saturating, voltage-dependent capacitors. We find that nonlinearity significantly boosts the ability of such media to generate large-amplitude output signals from small-amplitude inputs. To understand this boosting, we develop a general perturbative method suitable for finding the steady-state solution of a damped NxN nonlinear lattice that is driven at a single frequency. We verify our theory using extensive numerical simulations.

Initial experience with laparoscopic donor nephrectomies.

BACKGROUND: Laparoscopic donor nephrectomy (LDN) is being adopted rapidly by transplant centres around the world as it offers less postoperative pain, quicker convalescence, and better cosmetic result when compared with the open approach. There may, however, be a steep learning curve with this technique. METHOD: A retrospective review was performed to evaluate the donor morbidity and graft outcome of 21 consecutive LDN performed at one centre between May 2002 and August 2003. RESULTS: Eighteen LDN were performed on the left and three on the right side. All left and one right LDN were done transperitoneally while the remaining two right side kidneys were removed by a retroperitoneal approach. The mean (+/-SD) operating time and warm ischemic time were, respectively, 236 minutes (+/- 46) and 4 minutes (+/- 1). The mean time for resuming oral intake was 23 hours (SD +/- 22.7). The median length of hospital stay was 5 days (range 3 to 18). One patient was reoperated for bleeding and required four units of packed cell transfusion. One recipient displayed delayed graft function requiring dialysis for 14 days. There were no graft losses. The mean creatinine of the recipients at the time of discharge was 1.15 mg/dL (+/- 0.21). CONCLUSIONS: There is undoubtedly a learning curve with LDN. Nevertheless, with prior skills in similar procedures such as laparoscopic radical nephrectomies, it is feasible to diminish the learning curve and morbidity of LDN to yield results consistent with those in the published literature.

Terminal hand-assist for laparoscopic donor nephrectomy.

BACKGROUND: Laparoscopic donor nephrectomy (LDN) has become widely popular in developed countries but not so in developing countries. One explanation for this maybe the difficulty in getting access devices due to the prohibitive cost. We report our method of terminal hand-assisted LDN in which successful donor nephrectomy is feasible without expensive access devices. METHOD: The patient is placed in the corresponding classic renal surgery position. Three ports are placed for left-sided and four for right-sided LDN. After complete mobilization of the kidney laparoscopically, the assistant's right hand is introduced for left-sided LDN through a 7-cm left lower quadrant transverse muscle-splitting incision. For right-sided LDN, the surgeon's right hand is inserted through a corresponding ipsilateral incision (for right-handed surgeons). A simple method to prevent the leakage of pneumoperitoneum is described. The hand inside the abdomen aids in the final steps and completes the extraction of the kidney swiftly. Manual mopping, lavage, and hemostasis are also possible. RESULTS: Five cases of LDN at our centre were done in this fashion, four on the left side and one on the right. The mean kidney retrieval time after clamping the renal artery was 3:18 +/- 0:46 minutes (range 2:30 to 4:30). Postoperative stay was 4 to 5 days. Recipient serum creatinine normalized within 3 to 4 days. CONCLUSIONS: Short duration terminal hand-assist for LDN without any special access device is possible without the fear of excessive gas leakage. It is helpful to reduce prolonged warm ischemia and to relieve the surgeon's apprehension, at least in the initial learning phase of LDN.

Right-sided laparaoscopic donor nephrectomy is feasible: experience with three cases.

BACKGROUND: Laparoscopic donor nephrectomy (LDN) is more difficult on the right than the left and is typically not recommended for the right kidney. MATERIALS AND METHODS: Between November 2002 and May 2003, three patients underwent right-sided donor nephrectomy: one transperitoneally and two retroperitoneoscopically. All procedures were performed in the right kidney position. Three ports were placed for retroperitoneoscopic approach and four for transperitoneal, including one to retract the liver. Renal arteries were clipped thrice and divided, and renal veins divided using an endo-GIA30 stapler. Kidneys were retrieved in all cases by extending the lower port incision by 7 to 8 cm. The records of donors and recipients, including early graft outcomes were reviewed. RESULTS: Kidney retrieval time and total warm ischemic time were 3:30 minutes and 5 minutes, respectively, for transperitoneal LDN and 3:40 to 4:10 minutes and 5 to 7 minutes, respectively, for retroperitoneal LDN. The operating times were 176, 224, and 160 minutes, respectively. The first donor (transperitoneal) was discharged on the fourth postoperative day, and the other two (retroperitoneal) on the third day. The serum creatinine of all recipients normalized within 72 hours, with normal isotope renal scans on the fifth postoperative day. CONCLUSIONS: Right-sided LDN is feasible and safe without adversely affecting graft quality. The retroperitoneal approach is technically easier, gives a longer length of renal artery, and has a quicker convalescence.

Laparoscopic simultaneous bilateral pretransplant nephrectomy for uncontrolled hypertension.

Severe hypertension resistant to multiple antihypertensive drugs represents an indication for bilateral pretransplant renal ablation by surgery or angioembolization. Besides causing severe pain and renal postinfarction syndrome, angioembolization may be ineffective. We present our experience with simultaneous bilateral laparoscopic pretransplant nephrectomies in patients with end-stage renal disease and severe uncontrollable hypertension. Among the three patients considered for bilateral pretransplant laparoscopic nephrectomy between September 2002 and August 2003, the procedure was successfully performed in two patients. Left nephrectomy was performed transperitoneally and right nephrectomy retroperitoneoscopically. In one of the three patients, a prior attempt at angioembolization had produced a dense perirenal reaction, rendering laparoscopic surgery impossible. Total operating time for bilateral laparoscopic nephrectomies was 260 and 280 minutes. Within 1 month following the nephrectomies, all patients became normotensive with minimal or no antihypertensive medications. We conclude that simultaneous bilateral laparoscopic nephrectomy is feasible and less morbid in end-stage renal disease patients. Prior angioembolisation can make laparoscopic surgery difficult or impossible.

Paediatric ureteric calculi: efficacy of primary in situ extracorporeal shock wave lithotripsy.

OBJECTIVE: To evaluate the efficacy of primary in situ extracorporeal shockwave lithotripsy (ESWL) for the treatment of ureteric calculi in children. PATIENTS AND METHODS: The Wolf 2500 Piezolith was used to treat 63 children (aged 4 months to 12 years) with 76 ureteric calculi, including 10 children with impacted calculi. The calculi were located in 14 upper, 13 mid and 44 lower ureters, and the stone burden varied from 4 to 17.8 mm (mean 12.6). All children aged < or = 10 years were treated under general anaesthesia; lithotripsy was attempted under intravenous sedation in the older children. RESULTS: At the 3-month follow-up, there was an overall successful outcome in 55 children (87%), which included 12 of 13, eight of nine (89%) and 35 of 41 (85%) of the children with upper, mid and lower ureteric calculi, respectively, and nine of the 10 with impacted calculi. Re-treatment was required in 20 (36%) patients, while auxiliary procedures after ESWL were required in three (6%). The major complications encountered were ureteric obstruction with sepsis in two children, bacteraemia in another and urinary retention due to a urethral stone fragment in a fourth child. CONCLUSIONS: In situ ESWL was an effective treatment modality for ureteric calculi at all levels in children, even when impacted. In the short term, complications were minimal, but the long-term effects need further assessment.

'Gossypiboma': an unusual cause of perinephric abscess.

Retained surgical sponges, euphemistically called 'Gossypibomas', are rare occurrences which are infrequently reported in the literature because of legal implications. Their manifestations and complications are so variable that diagnosis is difficult and patient morbidity is significant. In this note, we discuss the classical ultrasound, computerized tomography (CT) scanning and magnetic resonance imaging (MRI) features, which, in the presence of a high index of suspicion in a patient who has previously been operated upon, will greatly aid in the pre-operative diagnosis of this unfortunate complication. The gossypiboma masquerading as a perinephric abscess has not been previously reported.

Vasovasostomy. A clinical study with 10 years' follow-up.

PIP: 36 cases of vas reconstruction after vasectomy are reported with 10 years of follow-up study. 83% of the vasectomies had been done for family planning purposes and the major reason for wanting vas reconstruction was the desire for more children. The majority of the patients were between 31 and 40 years of age and all were sexually active. After careful examination for active spermatogenesis and vas patency, end-to-end anastomosis was performed, usually using a splint. Bed rest for at least 5 days postoperatively was recommended. Semen samples were analyzed for motile sperm at 3-month intervals. 70% of the 30 patients undergoing vasovasostomy showed spermatozoa in their semen, usually within 1 year. Only 1 of the 6 epididymovasostomy patients showed spermatozoa and the poor results associated with this procedure may be due to previous postvasectomy inflammation. No correlation was found between the interval between vasectomy and anastomosis, age and splint use, and the success of the reconstruction. 5 of the 14 patients with normal sperm counts produced normal pregnancies.^ieng