A new animal model of hyperoxaluria and nephrolithiasis in rats with small bowel resection.

An association between small bowel resection and stone disease has been noted, which is primarily due to increased gut oxalate absorption and resulting excretion by the kidney. In order to better understand the factors affecting both oxalate absorption and renal excretion, and the resulting renal lesions, we have developed a rodent model of small bowel resection and hyperoxaluria. Using this model, we have studied the renal histology in animals with hyperoxaluria over time spans from 2 weeks to 7 months. The initial lesion appears to be crystal formation along the brush border of the proximal tubule, with eventual crystal deposition in collecting ducts and papillary interstitium, and eventual tubule obstruction, interstitial inflammation and fibrosis. Crystal formation appears to dissociate from urinary supersaturation. We hypothesize that oxalate transporters in the proximal tubule may increase local saturations, leading to crystal formation at this site initially. Further studies are required to better characterize the causes and consequences of hyperoxaluria in this animal model.

Defining maximal renal tolerance to warm ischemia in porcine laparoscopic and open surgery model.

OBJECTIVES: To establish the upper limit for warm ischemia time (WIT) beyond which irreversible renal failure will occur in a single-kidney porcine model. The maximal renal tolerance during WIT is currently under revision. Traditionally, 30 minutes was defined as the safe limit for renal WIT. However, accumulating data have suggested that a WIT of up to 90 minutes may not result in permanent damage. METHODS: Twenty female pigs weighing 60 to 80 lb at arrival underwent initial right laparoscopic nephrectomy to create a single-kidney model. Twelve days later, the animals were randomized into four groups of 5 animals each: 120 minutes of open WIT, 120 minutes of laparoscopic WIT, 5 open controls, and 5 laparoscopic controls. Renal function was assessed with serial glomerular filtration rate and serum creatinine measurements, which were assessed preoperatively and on postoperative days (PODs) 1, 3, 8, and 15. RESULTS: No significant difference existed between the laparoscopic and open groups. The glomerular filtration rate reached the lowest value and the serum creatinine levels peaked on POD 3 and were significantly different from baseline at PODs 1, 3, 8, and 15. Renal function did not return to baseline by POD 15, and 66% of the animals showed significant renal insufficiency (more than 25% decline in glomerular filtration rate) in the study group. CONCLUSIONS: After 120 minutes of WIT, no difference in renal function recovery was observed between the laparoscopic and open techniques. A WIT of 120 minutes produced significant renal failure and mortality. Thus, 120 minutes of WIT in the single kidney porcine model exceeds the kidney's tolerance to ischemia.

Use of suspension traction system for renal positioning during laparoscopic partial nephrectomy.

BACKGROUND AND PURPOSE: The technical difficulty of laparoscopic partial nephrectomy (LPN) lies mainly in the steps required during warm ischemia time (WIT), which includes tumor excision and renal reconstruction. We present a renal-suspension traction system to place the tumor in stable optimal view during the critical steps of LPN. PATIENTS AND METHODS: Thirty-three patients underwent LPN from October 2002 through December 2003. Eight had a renal sling placed intraoperatively because of difficult access to the tumor. Perioperative parameters were assessed. The renal hilum was dissected and the tumor exposed. To keep the tumor oriented perfectly toward the camera and the working ports, a 2-0 braided polyglactin (Vicryl) traction suture was passed through Gerota's fascia, catching the renal capsule; brought out through the abdominal wall; and secured to the skin with a clamp. RESULTS: All surgical margins were negative. For the traction and nontraction groups, the mean sizes of the tumor were 2.5 cm and 2.2 cm, respectively (P = 0.426). The estimated blood loss was 125 mL and 246 mL respectively (P = 0.041). The WIT average 27.4 minutes and 30.12 minutes (P = 0.470). The surgical time was 192 minutes and 235 minutes respectively, (P = 0.062). Based on our findings, we have devised a renal suspension traction algorithm for specific tumor locations during LPN. CONCLUSIONS: The renal suspension traction system allows precision in tumor excision and renal reconstruction during the critical steps of LPN. With the renal suspension system we devised, we are able to simplify LPN for tumors located away from optimal port access.

Comparison of external catheters with subcutaneous vascular access ports for chronic vascular access in a porcine model.

We sought to compare the outcomes of two chronic vascular access techniques, the externalized catheter and the subcutaneous vascular access port, in pigs. Female farm pigs (n = 30) underwent placement of a chronic vascular access device in the jugular vein for a research protocol: 18 of the animals underwent placement of a tunneled Hickman catheter (THC), and the remaining 12 animals underwent placement of a subcutaneous vascular access port (VAP) without external components. After placement of the devices, animals underwent serial blood sampling. All animals were given identical antibiotic prophylaxis. VAP access required the use of a restraint sling for Huber needle insertion, whereas THC access required no additional equipment. Animals were euthanatized 1 month after placement of the device. In the VAP group, the port was retrieved, cleaned, and steam-autoclaved for reuse. In the THC group, 13 (72%) animals developed infectious complications, and blood and wound cultures were often polymicrobial. One animal was euthanatized secondary to overwhelming sepsis. In addition, three (17%) animals developed thromboembolic complications. In contrast, no thromboembolic complications were noted in the VAP group, and only one animal developed a transient fever which resolved spontaneously; no septic complications or abscesses developed. Blood draws with no anesthesia were successful in both groups. We conclude that subcutaneous vascular access ports are a safe and efficient method for obtaining reliable chronic vascular access for a 1-month period in pigs. The subcutaneous devices were associated with low morbidity. In contrast, externalized catheters can be associated with considerable morbidity.

Early release of the neurovascular bundles and optical loupe magnification lead to improved and earlier return of potency following radical retropubic prostatectomy.

PURPOSE: Since 1999 we have made 2 modifications in the nerve sparing approach to radical retropubic prostatectomy (RRP), namely early release of the neurovascular bundles (NVBs) before division of the posterior membranous urethra and the use of 2.5x optical loupe magnification during NVB preservation. We retrospectively reviewed our results. MATERIALS AND METHODS: Between January 1998 and August 2003, 507 men underwent RRP for prostate cancer. All surgeries were performed by a single surgeon (CBB). Bilateral nerve sparing procedures were performed in 313 men. Modifications were introduced sequentially to the surgical technique and potency rates were compared to those of patients operated on before these modifications. Patients were divided into groups based on the technique of nerve sparing as group 1 (standard release of the NVB), group 2 (early release of the NVB) and group 3 (early release with loupe magnification). All patients were followed for a minimum of 5 months. Postoperative potency rates were compared among the 3 groups. RESULTS: Mean followup was 15.9 months. Mean patient age was 56.2 years. The overall potency rate among groups 1, 2 and 3 was 40.5%, 54.8% and 66.1%, respectively. Mean time to potency was 10.7, 8.5 and 2.0 months, respectively. Significant differences were found in the overall potency rate among all groups (p <0.05). Mean time to potency was significantly improved between groups 1 and 3 (p <0.05) and between groups 2 and 3 (p <0.05). CONCLUSIONS: Minor modifications in nerve sparing technique lead to improved postoperative potency rates and decreased time to potency in men undergoing RRP.

Renal tolerance to prolonged warm ischemia time in a laparoscopic versus open surgery porcine model.

PURPOSE: To our knowledge the effects of renal warm ischemia (WI) during laparoscopic vs open surgery have not been investigated. Decreased renal blood flow during pneumoperitoneum may precondition the kidney to tolerate longer WI time. Traditionally 30 minutes has defined the limit of renal WI time in open surgery. However, recent reports show renal function recovery at WI times of 45 to 120 minutes. We assessed renal function recovery after prolonged WI during laparoscopic vs open surgery in a solitary kidney porcine model. MATERIALS AND METHODS: A total of 32 female farm pigs underwent right laparoscopic nephrectomy to create a single kidney model. At 12 days later the animals were randomized into open and laparoscopic groups, each with 4 subgroups, namely 30, 60 and 90 minutes of WI, and a 90-minute control. Serum creatinine and the glomerular filtration rate were assessed preoperatively and on postoperative days 1, 3, 8 and 15. RESULTS: There was no statistical difference in renal function between the laparoscopic and open groups. Although the early decrease in renal function (72 hours) was highest in the 60 and 90-minute WI groups, by postoperative day 15 this difference was not statistically significant. Postoperative day 15 glomerular filtration rate and serum creatinine values were not significantly different from baseline in any of the WI groups. CONCLUSIONS: We found no difference in renal function recovery when comparing laparoscopic and open WI. Although WI up to 90 minutes resulted in initial renal dysfunction, by 2 weeks postoperatively function normalized. Our results indicate that in a single kidney porcine model the renal unit can fully recover from WI times of up to 90 minutes.