David A. Lifshitz

Stone Fragmentation During Shock Wave Lithotripsy is Improved by Slowing the Shock Wave Rate: Studies With a New Animal Model

PURPOSE The current trend toward ungated shock wave lithotripsy means that more patients are being treated with shock waves delivered at a rapid rate (120 shock waves per minute or greater). However, no benefit of an increased shock wave rate has been shown and in vitro studies indicate that slowing the shock wave rate actually improves stone fragmentation. We tested the effect of the shock wave rate on stone comminution in a new animal model. MATERIALS AND METHODS Gypsum model stones were inserted via upper pole percutaneous access into the lower pole calix of the kidneys of female pigs weighing approximately 100 pounds. Shock wave lithotripsy was performed (400 shock waves uninterrupted at 20 kV. and 30 or 120 shock waves per minute) 2 hours later using an unmodified HM3 lithotriptor (Dornier Medical Systems, Marietta, Georgia). After en bloc excision of the urinary tract stone fragments were collected and sieved through 2 mm. mesh. The particles were weighed and surface area was determined. RESULTS Stones treated at 30 shock waves per minute broke more completely than stones treated at 120 shock waves per minute. The percent of fragments greater than 2 mm. was significantly higher for stones treated at the fast rate of 120 versus the slow rate of 30 shock waves per minute (mean +/- SEM 81% +/- 14% versus 45% +/- 12%, p <0.005). When stone fragmentation was expressed as the percent increase in fragment surface area, significantly greater fragmentation occurred at the slower than at the more rapid rate (327% +/- 63% versus 135% +/- 136%, p <0.02). CONCLUSIONS Slowing the rate of shock wave administration during shock wave lithotripsy significantly improves the efficiency of stone fragmentation in vivo.

PREDICTING THE SUCCESS OF RETROGRADE STENTING FOR MANAGING URETERAL OBSTRUCTION

PURPOSE Retrograde ureteral stenting is often considered the first line option for relieving ureteral obstruction when temporary drainage is indicated. Several retrospective studies have implied that in cases of extrinsic obstruction retrograde ureteral stenting may fail and, therefore, percutaneous nephrostomy drainage is required. We examined the efficacy of retrograde ureteral stenting for resolving ureteral obstruction and identified clinical and radiological parameters predicting failure. MATERIALS AND METHODS Enrolled in our prospective study were 92 consecutive patients with ureteral obstruction, which was bilateral in 8. Retrograde ureteral stenting was attempted in all cases by the urologist on call. When stent insertion failed, drainage was achieved by percutaneous nephrostomy. Patients were followed at 3-week intervals for 3 months. Each followup visit included a medical interview, blood evaluation, urine culture and ultrasound. Stent malfunction was defined as continuous flank pain manifesting as recurrent episodes of acute renal colic, 1 or more episodes of pyelonephritis, persistent hydronephrosis or elevated creatinine. Preoperative data and outcomes were compared in cases of intrinsic and extrinsic obstruction. Univariate and multivariate analysis was done to identify predictors of the failure of ureteral stent insertion and long-term function. RESULTS The etiology of obstruction was intrinsic in 61% of patients and extrinsic in 39%. Extrinsic obstruction, which was associated with a greater degree of hydronephrosis, was located more distal. Retrograde ureteral stenting was successful in 94% and 73% of patients with intrinsic and extrinsic obstruction, respectively. At the 3-month followup stent function was maintained in all patients with intrinsic obstruction but in only 56.4% with extrinsic obstruction. On multivariate logistic regression the type of obstruction, level of obstruction and degree of hydronephrosis were the only predictors of stent function at 3 months. Stent diameter and preoperative creatinine had no predictive value. CONCLUSIONS Retrograde ureteral stenting is a good solution for most acutely obstructed ureters. In patients with extrinsic ureteral obstruction a more distal level of obstruction and higher degree of hydronephrosis are associated with a greater likelihood of stent failure. These patients may be better served by percutaneous drainage.

Ureteroscopy as a first-line intervention for ureteral calculi in pregnancy

BACKGROUND AND PURPOSE Renal colic in pregnancy presents a diagnostic and therapeutic challenge. When conservative therapy fails or is not indicated, temporary measures such as ureteral stenting are often chosen as a first-line intervention, postponing definitive management until after delivery. We propose that advances in endoscopic equipment and anesthesia techniques dictate a more definitive strategy. PATIENTS AND METHODS A retrospective analysis was performed on 10 consecutive pregnant patients presenting with renal colic necessitating intervention between April 1998 and April 2000. The mean patient age was 23 (range 17-31) years. One patient presented during the first trimester, six in the second, and three in the third. Four of the patients had a history of stone disease. All patients had flank pain at presentation, six on the left side and four on the right. Hematuria, fever, and nausea were present in eight, one and two patients, respectively. RESULTS Ultrasound scanning was performed in all patients and showed a low sensitivity (28.5%) when compared with intraoperative findings. Ureteroscopy (rigid and/or flexible) was performed as a first-line intervention in six patients, in two of whom no stone was found. Percutaneous nephrolithotomy was carried out in one patient presenting with a nephrostomy tube. Double-J stents were placed in only three patients with specific indications, namely urinary infection, late gestational phase, and difficult ureteroscopy secondary to a narrow ureter. No obstetric or urologic complications were noted. The mean size of the stones retrieved in seven patients was 7 mm. CONCLUSIONS Ureteroscopy may be considered a safe and effective first-line definitive therapeutic option in pregnant patients requiring intervention for stone disease.

In Vivo Pressure Measurements of Lithotripsy Shock Waves in Pigs

Stone comminution and tissue damage in lithotripsy are sensitive to the acoustic field within the kidney, yet knowledge of shock waves in vivo is limited. We have made measurements of lithotripsy shock waves inside pigs with small hydrophones constructed of a 25-microm PVDF membrane stretched over a 21-mm diameter ring. A thin layer of silicone rubber was used to isolate the membrane electrically from pig fluid. A hydrophone was positioned around the pig kidney following a flank incision. Hydrophones were placed on either the anterior (shock wave entrance) or the posterior (shock wave exit) surface of the left kidney. Fluoroscopic imaging was used to orient the hydrophone perpendicular to the shock wave. For each pig, the voltage settings (12-24 kV) and the position of the shock wave focus within the kidney were varied. Waveforms measured within the pig had a shape very similar to those measured in water, but the peak pressure was about 70% of that in water. The focal region in vivo was 82 mm x 20 mm, larger than that measured in vitro (57 mm x 12 mm). It appeared that a combination of nonlinear effects and inhomogeneities in the tissue broadened the focus of the lithotripter. The shock rise time was on the order of 100 ns, substantially more than the rise time measured in water, and was attributed to higher absorption in tissue.

Impact of ischemia on renal function after laparoscopic partial nephrectomy: a multicenter study.

PURPOSE We assessed the influence of renal ischemia on long-term global renal function after laparoscopic partial nephrectomy in patients with 2 functioning kidneys in a large, multicenter cohort. MATERIALS AND METHODS Collected data included demographic, clinical and surgical characteristics, tumor parameters and renal function outcomes at 4 institutions in a total of 401 patients with 2 functioning kidneys who underwent laparoscopic partial nephrectomy. Renal function was assessed in the immediate postoperative period (days 1 to 3) and at last followup (greater than 1 month) using the estimated glomerular filtration rate calculated by the 4-variable Modification of Diet in Renal Disease equation. Ischemia time and covariates were modeled on the percent change in the estimated glomerular filtration rate using linear regression. RESULTS Median ischemia time was 29 minutes (IQR 22, 34). The postoperative change and the last (long-term) change in the estimated glomerular filtration rate were -16% and -11%, respectively. Median time to the last estimated glomerular filtration rate measurement was 13 months (IQR 6, 24). On multivariate analysis shorter ischemia and operative times, external or ureteral irrigation with cold saline and female gender were associated with less postoperative percent change in the estimated glomerular filtration rate. Smaller tumor size and absent diabetes were associated with less of a final percent change in the estimated glomerular filtration rate. Ischemia time was not associated with a percent change in the estimated glomerular filtration rate at last followup. CONCLUSIONS Within the range of times in these series renal ischemia did not have a clinically significant impact on global renal function in patients with 2 functioning kidneys who underwent laparoscopic partial nephrectomy, as measured by the estimated glomerular filtration rate.

Knotless closure of the collecting system and renal parenchyma with a novel barbed suture during laparoscopic porcine partial nephrectomy

INTRODUCTION Closure of the urinary collecting system and renal parenchyma is a technically challenging aspect of laparoscopic nephron-sparing surgery and an obstacle to its more widespread use. A novel barbed polydioxanone suture material Quill self-retaining suture (SRS) (Angiotech Pharmaceuticals) has been introduced for knot-free tissue approximation. We compared the outcomes of Quill SRS versus a conventional technique for kidney and collecting system closure during laparoscopic porcine partial nephrectomy. METHODS After approval of the Institutional Animal Care and Use Committee, 10 female pigs underwent bilateral transperitoneal laparoscopic lower pole heminephrectomy. Closure of the collecting system and approximation of the renal parenchyma was performed in two layers using continuous knotless barbed suture for one kidney (Quill SRS) and polyglactin (Vicryl) with absorbable polydioxanone clips (LapraTy; Ethicon) on the contralateral kidney. For both techniques, the collecting system was closed with 2-0 suture and renal parenchyma with #1 suture. Warm ischemia and suturing time were recorded, and resected tissue was weighed. All animals were sacrificed 1 week after surgery. Serum hemoglobin and visual inspection at necropsy were used to assess for bleeding; visual inspection of the peritoneum and bilateral retrograde pyelography were used to assess for urinary fistula. RESULTS Mean (+/-standard deviation [SD]) weight of resected tissue (barbed, 34 +/- 13 g; clips, 34 +/- 11 g; p = 0.6), mean (+/-SD) ischemia time (barbed, 34 +/- 8 minutes; clips, 34 +/- 10 minutes; p = 0.7), and mean (+/-SD) suturing time (barbed, 21 +/- 4 minutes; clips, 22 +/- 7 minutes; p = 0.7) were similar between groups. No animal had a visible hematoma or urinoma at necropsy. On retrograde pyelography, a small urinary leak was found in two kidneys in each group (p = 0.6). CONCLUSIONS In a porcine laparoscopic partial nephrectomy model, it appears that knotless barbed suture is as effective, efficient, and safe as a conventional technique. Further evaluation in humans is warranted and required.

MULTILAYERED SMALL INTESTINAL SUBMUCOSA IS INFERIOR TO AUTOLOGOUS BOWEL FOR LAPAROSCOPIC BLADDER AUGMENTATION

PURPOSE Bladder augmentation is most commonly performed with ileum. However, porcine small intestinal submucosa has been reported as a substitute for bowel for incorporation into the urinary tract. We assessed the feasibility and long-term 12-month results of laparoscopic bladder augmentation with ileum or multilayered small intestinal submucosa (Cook Biotech, Spencer, Indiana) in a porcine model. MATERIALS AND METHODS We performed laparoscopically assisted hemicystectomy and bladder augmentation in 24 female Yucatan mini-pigs using an ileal segment (12) or multilayered small intestinal submucosa (12). The followup protocol included anesthetic bladder capacity, renal ultrasonography and serum chemistry. At 3, 6 and 12 months, respectively, 4 animals per group were scheduled for sacrifice and pathological analysis. RESULTS Despite longer anastomotic time in the multilayered small intestinal submucosa group (120 versus 91 minutes, p = 0.026) total operative time was similar in the 2 groups. In each group bladder capacity increased with time but by 12 months bladder capacity was significantly better in the bowel than in the small intestinal submucosa group (825 versus 431 cc, p = 0.016). At 3 months pathological evaluation revealed that the multilayered regenerated bladder patch had shrunken and by 6 months it was replaced by dense calcified scar tissue. Long-term 6 and 12-month bladder capacity in the small intestinal submucosa group was the result of the regeneration of native bladder with exclusion of the whole multilayered patch in the majority of cases. CONCLUSIONS Laparoscopic bladder augmentation using multilayered small intestinal submucosa produced functional and pathological results inferior to those of bowel at 12-month followup in a porcine model.

Transperitoneal laparoscopic renal surgery using blunt 12-mm trocar without fascial closure.

BACKGROUND AND PURPOSE Conical blunt trocar insertion may eliminate the need for fascial closure (FC) in transperitoneal laparoscopic renal surgery. This concept applies to 12-mm blunt trocar placement through muscular parts of the abdominal wall, relying on muscle splitting and eventual muscle retraction when the trocar is removed. We retrospectively assessed the safety of fascial nonclosure (FNC) after 12-mm blunt port insertion. PATIENTS AND METHODS Ninety transperitoneal laparoscopic renal procedures were performed between August 1999 and May 2000. Four ports (two 12 mm and two 5 mm) were usually used except for 30 donor nephrectomies, where an additional 5-mm port was used. The 12-mm trocars were inserted at the lateral border of the rectus muscle 5 cm below the costal margin and in the anterior axillary line 8 cm below the costal margin. Fascial closure was performed in 62 patients and nonclosure in 28 patients. Exclusion criteria for FNC included midline location, malnutrition, renal failure, and chronic use of steroids. Postoperative outcomes were compared in 20 patients with FNC matched with 20 patients with FC. RESULTS At an average of 4.8 months of follow-up, none of the patients developed a trocar site hernia. No significant statistical differences were observed between the groups with regard to intraoperative and postoperative data. CONCLUSIONS These two approaches appear to be equivalent in terms of patient morbidity and postoperative hospital stay. Fascial nonclosure after transperitoneal 12-mm blunt trocar insertion, through muscular parts of the abdominal wall may be safe and efficacious and eliminates the last step in transperitoneal laparoscopic renal surgery.

Holmium Laser Endoureterotomy for Benign Ureteral Stricture: A Single Center Experience

PURPOSE We assessed the long-term outcome of laser endoureterotomy for benign ureteral stricture. MATERIALS AND METHODS From a database of 69 patients who underwent retrograde laser endoureterotomy from October 2001 to June 2007 we identified 35 with a benign ureteral stricture. Clinical characteristics, operative results and functional outcomes were investigated. Success was defined as symptomatic improvement and radiographic resolution of obstruction. RESULTS Median followup was 27 months (range 10 to 72). All except 1 patient were followed at least 16 months. All patients completed clinical followup and 33 completed imaging. Of 35 patients 29 (82%) were symptom-free during followup and 26 of 33 (78.7%) were free of radiographic evidence of obstruction. All except 1 failure occurred within less than 9 months postoperatively. The success rate was higher for nonischemic strictures (100% vs 64.7%, p = 0.027) and tended to be higher for strictures 1 cm or less (89.4% vs 64.2%, p = 0.109). CONCLUSIONS Holmium laser endoureterotomy is effective for benign ureteral stricture in well selected patients. Most failures occur within less than 9 months after surgery, which may indicate a need for closer followup during postoperative year 1. Factors that might may outcome are ischemia and stricture length.

Renal Nerves Mediate Changes in Contralateral Renal Blood Flow after Extracorporeal Shockwave Lithotripsy

Renal blood flow falls in both kidneys following delivery of a clinical dose of shockwaves (SW) (2000 SW, 24 kV, Dornier HM3) to only one kidney. The role of renal nerves in this response was examined in a porcine model of renal denervation. Six-week-old pigs underwent unilateral renal denervation. Nerves along the renal artery of one kidney were identified, sectioned and painted with 10% phenol. Two weeks later the pigs were anesthetized and baseline renal function was determined using inulin and PAH clearances. Animals then had either sham-shockwave lithotripsy (SWL) (group 1), SWL to the innervated kidney (group 2) or SWL to the denervated kidney (group 3). Bilateral renal function was again measured 1 and 4 h after SWL. Both kidneys were then removed for analysis of norepinephrine content to validate the denervation. Renal plasma (RPF) flow was significantly reduced in shocked innervated kidneys (group 2) and shocked denervated kidneys (group 3). RPF was not reduced in the unshocked denervated kidneys of group 2. These observations suggest that renal nerves play a pivotal role in modulating the vascular response of the contralateral unshocked kidney to SWL, but only a partial role, if any, in modulating that response in the shocked kidney.