Effect of freeze time during renal cryoablation: a swine model.

BACKGROUND AND PURPOSE: Cryotherapy provides a minimally invasive treatment for small renal tumors via an open, percutaneous, or laparoscopic approach. We sought to determine the most appropriate duration of freezing and the number of probes necessary to produce cell death without concomitant morbidity. MATERIALS AND METHODS: Nine domestic female pigs were divided into three groups of three animals each. Each group underwent a single freeze cycle with a commercially available cryotherapy device with 3.4-mm probes: group 1 for 5 minutes, group 2 for 10 minutes, and group 3 for 15 minutes. The right kidney was treated with a single probe, the left with a double probe. Animals were permitted to survive for an average of 4.8 days (range 4-7 days), after which the kidneys were harvested. A single pathologist examined the kidneys for gross and histologic changes. Evidence of complications (fistula, bleeding, bowel injury) was documented at the time of necropsy. RESULTS: For group 1, the temperature obtained with a single probe 5, 10, 15, and 20 mm from the probe was -57 degrees C, 3 degrees C, 25 degrees C, and 33 degrees C, respectively; for group 2 -85 degrees C, -37 degrees C, -2 degrees C, and 25 degrees C; and for group 3 -10 degrees C, -45 degrees C, -20 degrees C, and 6 degrees C. For group 1, the temperature obtained with a double probe at 5, 10, 15, and 20 mm from each probe was -65 degrees C, 0 degrees C, 20 degrees C, and 30 degrees C, respectively; for group 2 -72 degrees C, -25 degrees C, 5 degrees C, 25 degrees C; and for Group 3 -82 degrees C, -30 degrees C, -12 degrees C, 13 degrees C. Complete necrosis was seen 5 mm from the cryoprobe within each group, but only in groups 2 and 3 did necrosis extend 10 mm or beyond the probes when utilizing either single or double probes. The maximum diameter of consistent necrosis was 35 to 40 mm in the animals in group 3 treated with a double probe. Bleeding and renal fracture were the two most common complications. CONCLUSIONS: A 5-minute freeze appears to be inadequate to cause tissue necrosis and is associated with excessive bleeding at the time of the procedure, whereas the 15-minute freeze produces consistent necrosis but is associated with renal fracture. In this animal model, the 10-minute freeze with the single or double probe configuration appears optimal to produce necrosis without complications.

Ureteral access sheath provides protection against elevated renal pressures during routine flexible ureteroscopic stone manipulation.

BACKGROUND AND PURPOSE: New-generation flexible ureteroscopes allow the management of proximal ureteral and intrarenal pathology with high success rates, including complete removal of ureteral and renal calculi. One problem is that the irrigation pressures generated within the collecting system can be significantly elevated, as evidenced by pyelovenous and pyelolymphatic backflow seen during retrograde pyelography. We sought to determine if the ureteral access sheath (UAS) can offer protection from high intrarenal pressures attained during routine ureteroscopic stone surgery. PATIENTS AND METHODS: Five patients (average age 72.6 years) evaluated in the emergency department for obstructing calculi underwent percutaneous nephrostomy (PCN) tube placement to decompress their collecting systems. The indications for PCN tube placement were obstructive renal failure (N=1), urosepsis (N=2), and obstruction with uncontrolled pain and elevated white blood cell counts (N=2). Flexible ureteroscopy was subsequently performed with and without the aid of the UAS while pressures were measured via the nephrostomy tube connected to a pressure transducer. Pressures were recorded at baseline and in the distal, mid, and proximal ureter and renal pelvis, first without the UAS, and then with the UAS in place. RESULTS: The average baseline pressure within the collecting system was 13.6 mm Hg. The mean intrarenal pressure with the ureteroscope in the distal ureter without the UAS was 60 mm Hg and with the UAS was 15 mm Hg. With the ureteroscope in the midureter, the pressures were 65.6 and 17.5 mm Hg, respectively; with the ureteroscope in the proximal ureter 79.2 and 24 mm Hg, and with the ureteroscope in the renal pelvis 94.4 and 40.6 mm Hg, respectively. All differences at each location were statistically significant (P<0.008). Compared with baseline, all pressures measured without the UAS were significantly greater, but only pressures recorded in the proximal ureter and renal pelvis after UAS insertion were significantly higher (P<0.03). CONCLUSIONS: The irrigation pressures transmitted to the renal pelvis and subsequently to the parenchyma are significantly greater during routine URS without the use of the UAS. The access sheath is potentially protective against pyelovenous and pyelolymphatic backflow, with clinical implications for the ureteroscopic management of upper-tract transitional cell carcinoma, struvite stones, or calculi associated with urinary tract infection.

Pain after percutaneous nephrolithotomy: impact of nephrostomy tube size.

BACKGROUND AND PURPOSE: Percutaneous nephrolithotomy (PCNL) is the procedure of choice for managing large renal calculi. Investigations have recently focused on reducing the morbidity of the procedure and improving postoperative patient comfort by using smaller endoscopic instruments. We sought to evaluate the effect of a smaller percutaneous drainage catheter on postoperative pain. PATIENTS AND METHODS: Thirty consecutive patients were randomized to receive either a 10F pigtail catheter or a 22F Councill-tip catheter for their percutaneous drainage after PCNL. The demographics were similar in the two groups, as was the rate of supracostal access (47% v 43%, respectively). Self-assessed analog pain scores were collected at 6 hours postoperatively as well as on the morning of the first and second postoperative days (POD). Total narcotic usage was tabulated using morphine equivalents. Complications, including the change from baseline hematocrit, were reviewed. RESULTS: There was no significant difference in the change in hematocrit (6.8 v 6.2 percentage points, respectively). Those patients with the smaller nephrostomy tube noted significantly lower pain scores at 6 hours (3.75 v 5.3; P=0.03). Although the pain scores were lower on POD 1 and 2 for the 10F catheter group, the difference was not statistically different (1.9 v 2.9 and 1.25 v 1.9, respectively; both P>0.05). The patients having the 10F catheter required fewer narcotics: 78 mg v 91 mg, although the difference was not statistically significant. CONCLUSION: The use of a small drainage catheter after PCNL is associated with lower pain scores in the immediate postoperative period, yet no statistically significant benefit to the patient with regard to comfort is demonstrated beyond 6 hours. In addition, there is a trend toward reduced narcotic requirements. Finally, there is no apparent increase in patient morbidity from the use of the smaller nephrostomy tubes.

Use of bipolar laparoscopic forceps to occlude and transect the retroperitoneal vasculature: a porcine model.

BACKGROUND AND PURPOSE: Surgical clips are commonly employed during laparoscopic radical nephrectomy to ligate perihilar vessels reliably, yet these clips can interfere with the application of a vascular stapler to major vessels, potentially leading to catastrophic hemorrhage. We assessed the efficacy of the PlasmaKinetic trade mark (PK) bipolar cutting forceps (Gyrus Medical, Minneapolis, MN) as a single modality in coagulating and dividing the retroperitoneal vessels in a swine model. MATERIALS AND METHODS: Three 40- to 50-kg domestic swine (six renal units) underwent celiotomy and retroperitoneal exposure. The inferior vena cava (IVC) and the renal, gonadal, and iliac vessels were isolated, and, using 5- and 10-mm forceps, coagulated and divided. The mean diameter of the renal vein was 8.7 mm, the renal artery 6.5 mm, and the IVC 14 mm. RESULTS: Hemostasis was achieved consistently using the 5-mm and 10-mm PK Cutting Forceps on the renal artery, renal vein, and gonadal vein. The 10-mm forceps coagulated the iliac veins and IVC 83% of the time with only a single application. Larger vessels or vessels with higher inherent vascular pressure required additional applications of the device to achieve hemostasis. All animals were hemodynamically stable through division of the IVC, as measured by heart rate and pulse oximetry. No complications were noted with the device or using the cutting element. CONCLUSIONS: The PK bipolar cutting forceps appear to be effective in controlling and dividing the renal hilar vessels and larger low-pressure vessels of the porcine retroperitoneum, with no gross damage to adjacent structures. Although further studies are necessary before use during laparoscopic nephrectomy in humans, these results are promising. Bipolar cutting forceps may prove to be a safe, cost-effective, and time-saving device with numerous applications during urologic laparoscopy.