Effect of mineral oil on porcine urothelium.

Mineral oil has been used to facilitate ureteral stone extraction and to treat selected patients with infected residual urine. The purpose of this study was to evaluate the effect of mineral oil on the urothelium. Twelve adult female farm pigs underwent bilateral ureteral catheter placement under general endotracheal anesthesia. Retrograde pyelograms were performed and the ureteral diameters measured. Using a randomization protocol, six animals underwent injection of 10 mL of normal saline into one ureteral catheter and 50 mL of normal saline instillation into the bladder. In the remaining six animals, 10 mL of mineral oil was injected into one ureteral catheter and 50 mL of mineral oil into the bladder. The instillation was maintained for 30 minutes, and then the catheters were removed. One week later, under general endotracheal anesthesia, cystoscopy and retrograde pyelography were performed to measure the diameter of the ureters, and the animals were euthanized. The bladder, ureters, and kidneys were harvested for macroscopic and histopathologic evaluation. There was no significant difference in the diameter of the ureters injected with normal saline, the uninjected ureters, or the mineral oil-injected ureters. The bladders, ureters, and kidneys were grossly normal in all animals. No significant histopathologic changes were noted in the ureteral or bladder urothelium or the renal parenchyma in the animals injected with mineral oil. In conclusion, the instillation of mineral oil within the urinary tract does not have any significant long-term functional or histopathologic effect on the urothelium.

Comparison of fibrin glue, laser weld, and mechanical suturing device for the laparoscopic closure of ureterotomy in a porcine model.

PURPOSE: We evaluated fibrin glue, laser welding, and a mechanical suturing device (Endo-Stitch) as alternatives to standard laparoscopic suturing with a free needle. METHODS: In 14 pigs, 22 linear proximal ureterotomies were closed laparoscopically with one of 4 different methods: fibrin glue, laser welding, Endo-Stitch suture placement (4-0 polyglactin), and free-needle suture placement (4-0 polyglactin). The ureterotomy was left open in 6 ureters. Acute leakage was tested by instillation of methylene blue. After 12 weeks, the ureters were assessed with radiography, ex-vivo pressure-flow studies, bursting pressures, and histology. RESULTS: All alternative closure techniques were more rapid than free-needle suturing, and less frequently allowed acute leakage. Closure with fibrin glue yielded significantly higher flow rates than control, whereas the other closure techniques yielded flow rates similar to that of unclosed ureters. All alternative closure methods demonstrated histological evidence of healing that were superior to free-needle suturing. In multifactorial analysis, leakage at the ureterotomy site was the factor most significantly associated with subsequent poor ex-vivo flow characteristics. CONCLUSIONS: All of the alternative laparoscopic ureteral closure methods compared favorably with standard free-needle suturing. Fibrin glue produced better radiographic findings, flow characteristics, and histology, suggesting that it currently has the most promise as an alternative or adjunct to laparoscopic suturing. Development of alternative laparoscopic techniques is ongoing, however, and thus the current state-of-the-art techniques used in this study may well be supplanted by other technologies in the future.

Laparoscopic pyeloplasty in the animal model.

PURPOSE: Laparoscopic pyeloplasty has been associated with long operative times. This study proposed to evaluate the feasibility of two different laparoscopic techniques for the performance of pyeloplasty repair of secondary ureteropelvic junction (UPJ) obstruction. MATERIALS AND METHODS: Sixteen female Yucatan minipigs underwent general anesthesia for cystoscopy, retrograde pyelography, urine culture and a baseline renal scan. Unilateral UPJ obstruction was created by ligating the UPJ over a 5F catheter. Six weeks later a laparoscopic pyeloplasty was performed utilizing an intracorporeal suturing technique and the Lapra-Ty suture clip or the Endostitch device with intracorporeal knot typing. Four control animals underwent only cystoscopy and in/out ureteral catheterization. In the study animals the ureteral stent was maintained for six weeks and at six weeks, three months and six months post-pyeloplasty the animals underwent the previously mentioned studies. At six months post-pyeloplasty the animals were euthanized and the UPJ was calibrated. Histopathology was obtained on the ureter below the anastomosis, at the anastomosis, above the anastomosis and on a renal biopsy. RESULTS: All planned laparoscopic pyeloplasties were completed. However, the stricture model was too severe in that most animals developed 40-45% decrease in renal function in the kidney following ipsilateral UPJ ligation. There was no significant difference between the two pyeloplasty techniques with respect to operative time to perform the pyeloplasty (mean of 40 minutes), post-pyeloplasty ureteral caliber (7.5-8.0 F), serum creatinine or healing scores at, above or below the anastomosis. CONCLUSION: Laparoscopic pyeloplasty can be performed equally successfully with the Endostitch device and intracorporeal knot tying or with the intracorporeal suturing technique and Lapra-Ty clips. The resultant pyeloplasty is also equivalent for the two techniques.

Recent advances in laparoscopic partial nephrectomy: comparative study of electrosurgical snare electrode and ultrasound dissection.

Although technically feasible, laparoscopic partial nephrectomy (LPN) using conventional instrumentation presents the intraoperative challenge of hemostasis, creating a flush (i.e., precise guillotine) incision, and closure of the collecting system. In an effort to resolve these technical problems, we used a unique electrosurgical snare electrode (ESE) in combination with an ERBE electrosurgical generator and compared its effectiveness with that of two ultrasonic dissectors (Cavitron Ultrasonic Surgical Aspirator [CUSA] and harmonic scalpel [HS]) in performing LPN. Twelve female minipigs underwent right lower-pole LPN using one of the aforementioned modalities. Six weeks later, in the same animals, a left lower-pole LPN was performed using the same device, thereby providing an acute and chronic renal remnant to examine. The animals were harvested, and transverse and perpendicular histologic sections were prepared of the cut surface of each specimen. The weights of the LPN specimens and the remaining kidney were also recorded. The time required for partial nephrectomy, degree of hemostasis (i.e., blood loss), ease of excising the targeted tissue, changes in renal function, tissue reactivity, and depth of damage to the surface of the remaining renal parenchyma were measured for each device. All 12 procedures were successful using the ultrasonic dissection, and 11 procedures were successful using the ESE. The ESE was significantly faster than the two forms of ultrasonic dissection (p < 0.0001) and produced less intraoperative bleeding (P = 0.002). Both forms of ultrasonic energy produced significantly deeper parenchymal injury in the acute surgical specimen (P = 0.03) and more parenchymal fibrosis and chronic inflammation in the chronic surgical specimens (P = 0.007) than the ESE. None of the animals exhibited any extravasation from the incised collecting system when studied by retrograde pyelography 6 weeks postoperatively at the time of left LPN and harvest. The function of the renal remnant was consistent with the size of the partial nephrectomy specimen. No hypertension developed in any of the study animals. Our results using a unique electrosurgical snare probe show it to have potential advantages as a rapid, hemostatic method for performing a partial nephrectomy. We believe that this instrument may represent an important tool for performing nephron-sparing surgery via an open or laparoscopic approach. Clinical trials are in progress.

In vivo comparison of electrosurgical vaporization electrodes.

To determine the acute tissue effects of endoscopic electrosurgery using different electrodes, smooth ball, smooth bar, vertically grooved bar, and horizontally fluted bar electrodes were applied to the epithelial surface of porcine bladders in vivo with electrosurgical cutting current supplied at 100, 150, and 200 W. A single pass was made on the surface of the tissue under endoscopic control with sorbitol irrigation using an excursion rate of 5 mm/sec. Each electrode was tested five times at each setting. The depths of electrosurgical vaporization and coagulation were measured by a pathologist blinded to the electrode and power setting. Depth of vaporization increased with the power setting of the generator and was greater with the non-smooth electrodes than the smooth electrodes. The depth of coagulation likewise was greater using the non-smooth electrodes but increased only minimally with increasing power settings. There were no differences in vaporization or coagulation depth between the small ball and smooth bar electrodes. The differences between the vertically grooved bar and horizontally fluted bar also were insignificant, except that in one-third of cases, the horizontally fluted bar created clefts undermining otherwise-undamaged areas of tissue. Non-smooth electrosurgical electrodes produce more vaporization and coagulation than smooth electrodes at a given power setting and therefore may be preferred for endoscopic applications. For use in tissues where precise control is required, the vertically grooved bar may be superior to the horizontally fluted bar because it provides similar vaporization and coagulation with a more uniform tissue effect.

Functional MR imaging of the porcine kidney: physiologic changes of prolonged pneumoperitoneum.

BACKGROUND: Increased intraabdominal pressure (IPA) during laparoscopy has been associated with decreased urine output. The purpose of this study was to use a noninvasive MRI technique to measure renal vessel flow velocity and change in differential renal medulla and cortex perfusion during pneumoperitoneum. STUDY DESIGN: Six female farm pigs underwent general endotracheal anesthesia and dynamic imaging following left ventricular (LV) injection of Gd-DTPA, utilizing a dual echo gradient echo sequence. MRI was repeated after three hours of continuous 15 mm Hg pneumoperitoneum in three study pigs and after three hours of monitored general anesthesia without pneumoperitoneum in three control pigs. Renal artery and renal vein flow velocities were calculated using cine phase-contrast technique. Renal perfusion was independently measured by LV injection of radiolabelled microspheres. RESULTS: There was a decrease in mean renal vein flow velocity in the pneumoperitoneum group as compared to the control group. During pneumoperitoneum there was a similar percentage reduction in the perfusion of the cortex (-28%) and medulla (-31%); this corresponded with a decreased urine output. In addition, radiolabelled microspheres corroborated the similar decrease in both cortical and medullary perfusion rates during pneumoperitoneum. CONCLUSIONS: Prolonged IAP is associated with a decrease in renal vein flow velocity and urine output. There is a similar decrease in the renal medulla and cortex perfusion rates during pneumoperitoneum of 15 mm Hg.

Comparative ureteral microanatomy.

Several animals have been used as models for experimental upper urinary tract surgery. Although minipigs have recently gained favor because their upper urinary tract is grossly similar to that of humans, the ureteral microanatomic features of the two species have not been compared. We evaluated the histologic features of human and animal ureters in order to provide addition information regarding experimental models for upper urinary tract surgery. Cross-sections of upper, middle, and lower ureteral segments from human autopsy specimens and animals (farm pig, minipig, dog, sheep, rabbit, and rat) were evaluated after preparation with Masson's trichrome stain. Morphology, computer-assisted morphometry, linear micrometry, and point-count estimation of smooth muscle/connective tissue ratios were assessed. The epithelium was remarkably consistent across all species, both morphologically and in terms of absolute size. The lamina propria was highly vascularized in all species, but the compactness varied with the overall ureteral dimensions. In the muscularis, the relative size and the percentage composed of smooth muscle differed widely among species, as did the ratio of muscularis to lamina propria cross-sectional surface area. Among the species evaluated, the sheep, farm pig, and minipig ureters were the best histologic approximations of the human ureter. Given the difficulties with manipulation of the small sheep ureter, the minipig and farm pig models appear to be optimal for experimental research on upper urinary tract surgery by an endourologic approach.

The iso1 gene of Chlamydomonas is involved in sex determination.

Sexual differentiation in the heterothallic alga Chlamydomonas reinhardtii is controlled by two mating-type loci, mt+ and mt-, which behave as a pair of alleles but contain different DNA sequences. A mutation in the mt minus-linked imp11 gene has been shown previously to convert a minus gamete into a pseudo-plus gamete that expresses all the plus gametic traits except the few encoded by the mt+ locus. Here we describe the iso1 mutation which is unlinked to the mt- locus but is expressed only in minus gametes (sex-limited expression). A population of minus gametes carrying the iso1 mutation behaves as a mixture of minus and pseudo-plus gametes: the gametes isoagglutinate but they do not fuse to form zygotes. Further analysis reveals that individual gametes express either plus or minus traits: a given cell displays one type of agglutinin (flagellar glycoprotein used for sexual adhesion) and one type of mating structure. The iso1 mutation identifies a gene unlinked to the mating-type locus that is involved in sex determination and the repression of plus-specific genes.