Clinical implication of routine stone culture in percutaneous nephrolithotomy--a prospective study.

OBJECTIVES: To evaluate the correlation between preoperative urine culture (UC) and intraoperative stone culture (SC) and the impact of SC findings on clinical decisions. METHODS: UC and intraoperative fragmented SC were prospectively obtained in all patients undergoing percutaneous nephrolithotomy between January 2004 and March 2005. Patients with a positive UC received a full course of antibiotics before surgery. All postoperative systemic inflammatory response syndrome (SIRS) events were recorded, as was the antibiotic regimen used and any changes in antibiotic treatment secondary to the SC results. RESULTS: The study group consisted of 75 consecutive patients. Of these 75 patients, 33 (49%) had sterile UC and SC results. Both urine and renal stones were colonized in 17 patients (24%); in 6 of them, the UC and SC showed different pathogens. A colonized SC associated with a sterile UC was found in 19 patients (25%). The calculated UC sensitivity, specificity, and positive and negative predictive value for the detection of stone colonization was 30%, 94%, and 84% and 58%, respectively. Seventeen patients (22%) had postoperative SIRS. In 13 of them, a change in antibiotic treatment was made according to the SC findings. On univariate analysis, the incidence of SIRS was not related to the length of the operation, stone-free rate, or supracostal or infracostal access. The relative risk of SIRS when the SC was positive was 3.6. CONCLUSIONS: Renal calculi pathogens are one of the predisposing factors for infectious events; however, preoperative UC often fails to grow stone-colonizing bacteria. Intraoperative SC may be essential in directing the antibiotic regimen postoperatively and should be routinely used.

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.

Laparoscopic transverse hemicystectomy with ileocystoplasty in a porcine model.

BACKGROUND AND PURPOSE: The ideal replacement for bladder tissue is yet to be described, although multiple alternatives have been studied. Currently, enterocystoplasty, despite its limitations, is considered the gold standard for bladder augmentation. This study evaluated the feasibility, safety, and morbidity of laparoscopic ileocystoplasty in a large-animal model. MATERIALS AND METHODS: In eight minipigs, laparoscopy was performed using four ports. A segment of ileum was delivered through a 3-cm umbilical incision and detubularized and refashioned using standard open surgical technique. Laparoscopic hemicystectomy was then performed, followed by laparoscopic suturing of the ileal patch to the bladder. The bladder was drained with a Foley catheter, but no pelvic drain was placed. All animals were followed for for a minimum of 3 months. Preoperative and postoperative evaluation included measurement of bladder capacity, ultrasound imaging of the kidneys, blood counts, and serum electrolyte and creatinine measurements. Two of the animals were sacrificed at 3 months and one at 6 months, and the bladders were harvested. RESULTS: Eight animals underwent ileocystoplasty without intraoperative or postoperative complications. The average operating and anastomosis time was 250 minutes and 96 minutes, respectively. All animals had normal preoperative blood values that remained normal during follow-up. Bladder capacity decreased initially to 71% of the baseline volume and then increased to 83% and 117% at 3 and 6 months. One of three animals sacrificed was noted to have a right midureteral stricture. CONCLUSIONS: We developed a reliable laparoscopic technique for ileocystoplasty that may extend the advantages of laparoscopy, including better cosmesis and reduced risk of postoperative adhesions, to bladder augmentation.

Metabolic evaluation of stone disease patients: a practical approach.

In the last three decades, minimally invasive techniques have progressed significantly, replacing traditional open surgery as the mainstay of stone disease surgical treatment. The challenge for the next millennium remains medical prevention of calcium urolithiasis, a field where less dramatic progress has been achieved during the same period of time. The purpose of this article is to provide the practicing urologist with current practical guidelines for the assessment and management of calcium urolithiasis patients. The recommendations are based on the latest available information regarding the pathogenesis, medical treatment options, and decision-making rationale when managing these challenging patients. Every urolithiasis patient should undergo a basic evaluation, which is considered the minimal essential diagnostic work-up, in order to rule out obvious, treatable systemic causes of urinary stone disease. All patients should be advised about conservative nonspecific preventive measures. High-risk stone patients should have a more extensive metabolic evaluation based on two 24-hour urine samples. Treatment protocols for each patient are tailored individually according to the metabolic evaluation findings.

Predictive value of urinary cultures in assessment of microbial colonization of ureteral stents.

BACKGROUND AND PURPOSE: Bacterial colonization of indwelling ureteral stents may serve as a nidus for bacteriuria in operations where stents are manipulated. The predictive value of urine cultures in the assessment of stent colonization was examined in 65 patients with indwelling ureteral stents. PATIENTS AND METHODS: Prophylactic antibiotic treatment was administered prior to stent insertion. All patients were ambulatory at the time of investigation and were examined in the outpatient clinic. Urine cultures were taken prior to stent removal after 8 to 150 (mean 64) days. The stents were removed under aseptic conditions, and the proximal and distal ends were cut off and placed in a culture medium for evaluation. None of the patients was treated for urinary tract infection prior to stent removal. RESULTS: Bacteriuria was found in 15% of the patients. In 35 patients (54%), urine and stent cultures were sterile. In 20 patients (31%), the urine culture was sterile but the stent was colonized (Enterococcus 9, E. coli 5, Staphylococcus aureus 2, S. epidermidis 2, Candida 1, Citrobacter diversus 1). One patient had a sterile stent culture with bacteriuria. In 9 patients (13.5%), urine and stent cultures were identical (E. coli 4, Pseudomonas 4, Candida 1). The incidence of stent colonization did not correlate with stent dwelling time. The sensitivity of urine cultures for the detection of stent colonization was poor, being 31% only. In a specific patient with negative urine culture, the probability of stent colonization was 36%. CONCLUSION: A sterile urine culture does not rule out the stent itself being colonized. Therefore, patients with indwelling ureteral stents and a sterile urine culture may benefit from prophylactic antibiotic treatment prior to endourologic procedures. The prophylactic regimen must provide coverage for common gram-negative uropathogens as well as gram-positive bacteria, including enterococci.

Alterations in predicted growth rates of pediatric kidneys treated with extracorporeal shockwave lithotripsy.

The long-term effects of extracorporeal shockwave lithotripsy (SWL) on the kidneys of children treated for renal calculi are unclear. In order to determine if SWL has any negative effects on renal growth rates, we reviewed long-term (mean 9-year) follow-up data on 29 pediatric patients treated between 1984 and 1988 with an unmodified Dornier HM3 lithotripter. Changes in renal length, serum creatinine, and blood pressure were analyzed. Predicted renal growth was calculated using a formula for age-adjusted renal length. Treated kidneys were stratified into normal and abnormal groups based on a history of renal surgery, evidence of recurrent infection, and obvious anatomic abnormalities. Fifty-six upper urinary tract calculi were treated in 34 renal units. Twenty-two renal units (68%) were rendered stone free, and 65% of the patients continue to be stone free. At follow-up, one patient was classified as having new-onset hypertension, and the mean serum creatinine was 0.93 +/- 0.08 mg/dL. Both at treatment and at follow-up, no significant differences were found in the sizes of the treated and untreated kidneys. However, at treatment, the abnormal group of kidneys seemed to be smaller than expected (mean Z -1.30 +/- 1.10), whereas the group of normal kidneys was very close (mean Z 0.18 +/- 0.54) to the predicted length. At follow-up, the deviations between actual and predicted renal length were significantly more negative. Treated kidneys were an additional 1.26 +/- 0.49 SD units below their expected length (p = 0.02). Untreated kidneys were further below normal as well but possibly to a lesser degree (-0.82 +/- 0.36; p <0.04). Although there was a trend for the abnormal group to have smaller kidneys than the normal group, both groups showed the same trend toward an age-adjusted reduction in renal growth at follow-up. The alterations in renal growth patterns observed in this population are unsettling and could be secondary to either treatment effect (SWL) or, more likely, to some underlying pathology intrinsic to pediatric kidneys with urolithiasis. Until further data are available, SWL in the pediatric population should be applied with caution and at the lowest dosage sufficient to achieve stone comminution.

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.

Quantitation of shock wave cavitation damage in vitro.

Acoustic cavitation damage was quantitated using aluminum foil targets placed within 2-mL polypropylene cryovials. The vials contained various media tested for their potential to support cavitation and were exposed to shock waves using an unmodified Dornier HM3 lithotripter. Foil damage, expressed in terms of a "damage index," was measured from digitized light microscopy images by quantitating the spread of gray-scale histograms. Target sensitivity was demonstrated by reproducible dose-response curves over the range (1-200 shock waves) commonly used for in vitro cell injury studies. Increased shock wave repetition rate reduced the damage index. Untreated foils showed a very low damage index (0.001% +/- 0.001%), while treated foils submerged in Ringer buffer yielded significant damage (2.2% +/- 0.3%, p < 0.001). Degassing the buffer reduced damage to 0.3% +/- 0.1% (p < 0.001). Foils submerged in castor oil showed virtually no damage. These results implicate acoustic cavitation in target damage. Targets immersed in biological fluids (blood and urine) had significantly less damage than in Ringer. The effect of degassing was also evaluated in a red blood cell lysis assay. Hemoglobin release in degassed preparations was significantly reduced compared to nondegassed controls (p < 0.001) and correlated with reduced foil damage index in cell-free vials. These findings characterize a sensitive method to quantitate acoustic cavitation and implicate a role for cavitation in shock wave lithotripsy-induced cell lysis.