Percutaneous nephrolithotomy in the spinal cord injury population

Percutaneous Nephrolithotomy for De Novo Urolithiasis After Kidney Transplantation: A Systematic Review of the Literature

Introduction and Objective: Renal transplantation is the treatment for end-stage renal disease that offers better quality of life and survival. Among the possible complications that might affect allografts, urolithiasis might have severe consequences, causing acute kidney injury (AKI) or septic events in immunocompromised patients. Allograft stones might be treated with percutaneous nephrolithotomy (PCNL). The aim of this Cochrane style review was to assess the safety and efficacy of PCNL in patients with renal transplant. Methods: A comprehensive search in the literature was performed including articles between July 1982 and June 2023, with only English original articles selected for this review. Results: The final review encompassed nine articles (108 patients). The mean age was 46.4 ± 8.7 years, with a male:female ratio of 54:44. The average time from transplantation to urolithiasis onset was 47.54 ± 23.9 months. Predominant symptoms upon presentation were AKI (32.3%), followed by urinary tract infection and fever (24.2%), and oliguria (12.9%). The mean stone size was 20.1 ± 7.3 mm, with stones located in the calices or pelvis (41%), ureteropelvic junction (23.1%), or proximal ureter (28.2%). PCNL (22F-30F) was more frequently performed than mini-PCNLs (16F-20F) (52.4% vs 47.6%). Puncture was guided by ultrasound (42.9%), fluoroscopy (14.3%), or both (42.9%). The stone-free rate (SFR) and complication rates were 92.95% (range: 77%-100%) and 5.5%, respectively, with only one major complication reported. Postoperatively, a ureteral stent and nephrostomy were commonly placed in 47%, with four patients needing a second look PCNL. During an average follow-up of 32.5 months, the recurrence rate was 3.7% (4/108), and the mean creatinine level was 1.37 ± 0.28 mg/dL. Conclusions: PCNL remains a safe and effective option in de novo allograft urolithiasis, allowing to treat large stones in one-step surgery. A good SFR is achieved with a low risk of minor complications. These patients should be treated in an endourology center in conjunction with the renal or transplant team.

[Flexible ureterorenoscopy and laser lithotripsy for upper urinary tract stones in neurologic patients with severe motor disability]

OBJECTIVE

The study's objective was to evaluate the effectiveness and morbidity of flexible ureterorenoscopy and laser lithotripsy for upper urinary tract stones in patients with a nervous system pathology including severe motor disability.

METHODS

Between 2006 and 2013, we retrospectively analyzed 83 flexible ureterorenoscopy to treat 63 kidneys in 42 patients. Stone free (SF) kidneys defined as an absence of stones on computerized tomography, renal ultrasound, X-ray or direct ureterorenoscopy, were considered a surgical success. Complications were classified according to the Clavien-Dindo system.

RESULTS

Success rates were 49.2 %, 57.1 % and 58.7 %, respectively after first, second and third flexible ureterorenoscopy procedure. Clearance after one procedure was achieved in 64.3 % of cases involving less than 20mm stones. No major complication (Clavien-Dindo>2) was described (0 %). Complication rates were 44.7 %, with 31.6 % Clavien-Dindo 2. The main complication was urosepsis, which occurred in 27.6 % of cases.

CONCLUSION

Flexible ureteroscopy and laser lithotripsies for upper urinary tract stones in neurologic patients with severe motor disability are associated with a lower success rate and some frequent low grade complications compared to overall population. In clinical practice, the indications of flexible ureterorenoscopy for these patients seem restricted.

LEVEL OF EVIDENCE

5.

Percutaneous Nephrolithotomy in Immunocompromised Patients: Outcomes from a Matched Case-Control Study

OBJECTIVE

To compare the outcomes of percutaneous nephrolithotomy (PCNL) in immunocompromised patients with those of PCNL in healthy population.

PATIENTS AND METHODS

A matched case-control study was performed from January 2009 through December 2014 using our prospectively collected kidney stone database. Patients with positive serology to human immunodeficiency virus (HIV), hepatitis C (cellular immune dysfunction), and patients on high dose of immunosuppressive drugs for treatment of autoimmune diseases composed the case group. Control group included patients with kidney stones and no other comorbidity. Patients were randomly matched based on Guy's score as a surrogate of case complexity.

RESULTS

Sixty-two patients were enrolled in this study, 21 cases and 42 controls. There were no significant differences in age, gender, and body mass index between groups. Regarding PCNL technique, there were no differences in patient positioning, number of accesses, and operative time. Complication rate was higher in the case group (38.1% vs 14.3%; p = 0.032); however, major complications, defined by Clavien score ≥3, were not statistically different (4.8% vs 2.4%; p = 0.611). There was a tendency of more postoperative urinary tract infection in the case group (19% vs 4.8%; p = 0.069). Mean decrease in hemoglobin level (3.3 vs 2.4 mg/dL; p = 0.037) and blood transfusion rate (23.8% vs 4.8%; p = 0.036) was significantly higher in the case group. Immunocompromised patients had a 2.8-fold increased risk of complications (odds ratio [OR] = 2.0, 95% confidence interval [CI] 1.01, 7.74) and a 5.8-fold increased risk of blood transfusion (OR = 5.8, 95% CI 1.29, 26.55). There were no differences in stone-free rate, nephrostomy tube time, and length of hospital stay.

CONCLUSION

Immunocompromised patients are at higher risk for complications such as bleeding after PCNL.

Flexible ureteroscopic laser lithotripsy for upper urinary tract stone disease in patients with spinal cord injury

The objective of this study is to present the outcomes of flexible ureteroscopic laser lithotripsy (URS) for upper urinary tract stone disease in spinal cord injury (SCI) patients performed by a single surgeon. A retrospective analysis was performed for SCI patients treated with flexible URS for proximal ureter and kidney stone disease by a single surgeon between 2003 and 2013. Patient characteristics, operative outcomes, metabolic evaluation, and stone analyses were assessed in detail. A total of 27 URS procedures were performed for urolithiasis in 21 renal units of 19 patients. The mean age was 52.1 ± 15.6 years (16-72) and mean BMI was 29.2 ± 7.3 kg/m(2) (20-45.7). Etiology of SCI was trauma (n: 10), multiple sclerosis (n: 6), cerebrovascular accident (n: 1), or undetermined (n: 2). The mean stone size was 15.9 ± 8.6 (6-40) mm. In the 27 URS procedures, stones were located in the ureter (n: 5), the kidney (n: 14), and both areas (n: 8). Mean hospitalization time was 2.0 ± 2.4 (0-10) days. Postoperative complications were observed in 6 cases (22.2%). Three major complications included urosepsis (n: 1) and respiratory failure (n: 2), that were observed postoperatively and required admission to the intensive care unit. The 2 minor complications were hypotension, fever and UTI, and required medical treatment. Fourteen (66.6%) of the 21 renal units were stone free. Calcium phosphate carbonate (n: 9) and struvite (n: 5) were the primary stone compositions detected. Hypocitraturia (n: 6), hypercalciuria (n: 5), hypernaturia (n: 5), hyperoxaluria (n: 4), and hyperuricosuria (n: 1) were common abnormalities in 24-h urine analysis. Ureteroscopic laser lithotripsy can be an effective treatment modality for SCI patients with upper urinary tract calculi.

Surgical management of urolithiasis in spinal cord injury patients

Urolithiasis is a common condition in patients with spinal cord injury (SCI). Surgical management of stones in this population is more challenging and associated with lower clearance rates than the general population. The rate of complications - specifically infectious complications - is also high due to the chronic bacterial colonization. Shock wave lithotripsy (SWL) has a low clearance rate of 44-73 %. Percutaneous nephrolithotripsy is indicated for larger nephrolithiasis, but multiple procedures may be required to clear the stones. Ureteroscopy has been associated with low success rates because of difficulty in obtaining ureteral access. Historically, bladder stones were managed with open surgery or SWL. Recently, good results have been reported with the combination of endoscopic and laparoscopic techniques. Surgical management of urolithiasis in patients with SCI should be performed in high-volume centers in light of the technical challenges and higher rate of perioperative complications.

Postoperative Complications Leading to Death after Coagulum Pyelolithotomy in a Tetraplegic Patient: Can We Prevent Prolonged Ileus, Recurrent Intestinal Obstruction due to Adhesions Requiring Laparotomies, Chest Infection Warranting Tracheostomy, and Mechanical Ventilation?

A 22-year-old male sustained C-6 tetraplegia in 1992. In 1993, intravenous pyelography revealed normal kidneys. Suprapubic cystostomy was performed. He underwent open cystolithotomy in 2004 and 2008. In 2009, computed tomography revealed bilateral renal calculi. Coagulum pyelolithotomy of left kidney was performed. Pleura and peritoneum were opened. Peritoneum could not be closed. Following surgery, he developed pulmonary atelectasis; he required tracheostomy and mechanical ventilation. He did not tolerate nasogastric feeding. CT of abdomen revealed bilateral renal calculi and features of proximal small bowel obstruction. Laparotomy revealed small bowel obstruction due to dense inflammatory adhesions involving multiple small bowel loops which protruded through the defect in sigmoid mesocolon and fixed posteriorly over the area of previous intervention. All adhesions were divided. The wide defect in mesocolon was not closed. In 2010, this patient again developed vomiting and distension of abdomen. Laparotomy revealed multiple adhesions. He developed chest infection and required ventilatory support again. He developed pressure sores and depression. Later abdominal symptoms recurred. This patient's general condition deteriorated and he expired in 2011. Conclusion. Risk of postoperative complications could have been reduced if minimally invasive surgery had been performed instead of open surgery to remove stones from left kidney. Suprapubic cystostomy predisposed to repeated occurrence of stones in urinary bladder and kidneys. Spinal cord physicians should try to establish intermittent catheterisation regime in tetraplegic patients.

A new scoring system for predicting stone-free rate after retrograde intrarenal surgery: the "resorlu-unsal stone score"

OBJECTIVE

To investigate the prognostic factors associated with the treatment efficacy of retrograde intrarenal surgery (RIRS) and develop a scoring system for predicting the stone-free rate after this surgery.

METHODS

We performed a retrospective analysis of 207 patients who underwent RIRS for renal stones between January 2009 and September 2011. Patient age, gender, body mass index, stone size, stone side, stone location, stone composition, number of stones, lower pole infundibulopelvic angle, using anticoagulant therapy, abnormal skeletal anatomy, and abnormal renal anatomy were investigated as potential preoperative predictive factors.

RESULTS

The present study included 111 (53.6%) men and 96 (46.4%) women. Mean patient age was 32.9 ± 18.8 years (range 1-74) and mean stone size was 16.2 ± 4.1 mm (range 8-40). Overall, 178 of the 207 (86%) patients were stone free after the initial treatment. Univariate analysis showed that stone size (P <.001), stone location (P = .025), stone composition (P = .01), stone number (P = .049), renal malformations (P = .042), and lower pole infundibulopelvic angle (P = .003) had significant influence on the stone-free rate after RIRS. Multivariate analysis excluded stone location from the logistic regression model, whereas other factors maintained their statistically significant effect on success rate, indicating that they were independent predictors.

CONCLUSION

Our study demonstrated that stone size, stone number, stone composition, infundibulopelvic angle, and renal malformations are significant predictors of RIRS outcome. A scoring system based on these factors helps separate patients into outcome groups and facilitates treatment planning.

Ureteroscopy with laser lithotripsy for urolithiasis in the spinal cord injury population

STUDY DESIGN

Retrospective study.

OBJECTIVES

The purpose of this investigation was to review the outcomes and safety of retrograde ureteroscopic laser lithotripsy (URS) for the treatment of urolithiasis in the spinal cord injury (SCI) population.

SETTING

Virginia, USA.

METHODS

All patients with SCI who underwent URS with holmium:YAG laser lithotripsy for urolithiasis over a 15-year period were identified. Stone size, location and number at presentation were recorded. Information regarding patient characteristics, intra-operative complications, surgical efficacy, stone clearance, peri-operative complications, and follow-up stone events was collected and analyzed.

RESULTS

A total of 67 URS procedures were performed on 29 SCI patients during the study period with an average follow-up of 3.4 years. Patients had an average of 2.3 ipsilateral ureteroscopies. The majority (85.1%) used indwelling catheters for long-term bladder management, and complete stone clearance after the first procedure was 34.3%. Of the 44 cases with residual stones >4 mm, 20 (45.5%) were secondary to technical or procedural limitations. The intra-operative complication rate was comparable to non-SCI studies at 1.5%, but peri-operative complications were significantly higher at 29.9% with the majority due to urosepsis. Factors associated with peri-operative complications include chronic obstructive pulmonary disease, motor incomplete injuries and lack of a pre-operative ureteral stent.

CONCLUSION

URS in the SCI population is an effective treatment for ureteral or renal stones but may be associated with greater risks and reduced efficacy.

Is percutaneous nephrolithotomy suitable for patients with scoliosis: single-center experience

OBJECTIVES

To present our experience with percutaneous nephrolithotomy (PCNL) for treating urolithiasis in patients with scoliosis.

METHODS

We retrospectively reviewed the records of 5 patients with congenital scoliosis who had undergone PCNL. The demographic data, number and location of access sites, hemoglobin values, stone analyses, and complications were studied. Of the 5 patients, 3 had a history of failed shock wave lithotripsy, and 2 had undergone stone intervention in same kidney. All procedures were performed with the patient in the prone position after retrograde ureteral catheterization. Tract dilation was accomplished using Amplatz dilators of ≤24F or 28F. PCNL was accomplished using a rigid nephroscope with ultrasound and/or pneumatic lithotriptor with the patient under general anesthesia.

RESULTS

Of the 5 patients, 2 were men and 3 were women, and the mean age was 36.8 years (range 32-44), and the mean stone burden was 475 mm2 (range 400-1350). The mean operative and fluoroscopic screening time was 62.2 minutes (range 50-90) and 3.1 minutes (range 2-5), respectively. Of the 5 patients, 3 were stone free after PCNL. Auxiliary procedures were required in 2 patients and included second-look PCNL in 1 and ureteroscopy in 1. Thus, all 5 patients were rendered completely stone free after the final procedure. No severe complications, either from anesthesia or the surgical procedure, were observed in the patients. Two of the patients had to stay for 24 hours to screen for pulmonary and cardiac signs in the intensive care unit after PCNL.

CONCLUSIONS

Larger stones or shock wave lithotripsy-refractory stones can be managed safely and effectively with PCNL in patients with scoliosis when they have been appropriately assessed before PCNL.

Urologists versus radiologists made PCNL tracts: the U.K. experience

We aim to explore the practice of who makes the PCNL tract in the U.K. and Northern Ireland as well as presenting our data for two different approaches to PCNL tracts in Northern Ireland. A national questionnaire survey was carried out across the National Health Services hospitals in U.K. In addition, a retrospective analysis of 134 PCNL cases was carried out. Group I included 103 (77%) cases with urologist-made tracts, while group II included 31 (23%) cases with radiologists-made tracts. The survey suggested that 45% (42) of the hospitals adopted a radiologist-made tract, 44% (41) use urologist-made tract, while the remaining 11% (11) use both. Most of the radiologists' performed tracts in our series were for complex cases. Failed access occurred in 6 (5.8%) in group I and none in Group II. The overall stone-free rate was 92 and 50% for group I and II, respectively. There is a better stone clearance rate in Group I (p = 0.0016). This however is likely to be attributed to the complexity of the cases in group II. However, urologist made percutaneous tract is safe and efficacious but a team approach with radiology is needed for more complex cases.

Chapitre A-3 - Lithiase du haut appareil et vessie neurologique: spécificités thérapeutiques

Upper tract stones are a frequent complication in neurourology and require specific treatment according to modalities adapted to the clinical setting. All modern treatment modalities for stones can be proposed: extracorporeal lithotripsy (ESWL), percutaneous nephrolithotomy and open surgery depending on the local conditions. The treatment objectives in the neurologically disabled population must be to combine a maximum of fragmentation and elimination in the same treatment session. ESWL therefore has a more limited place in this population. On the other hand, a renal stone measuring 1.5 cm must be treated by percutaneous surgery. Finally, management of upper tract stones depends on evaluation and stabilization of the lower tract (pressures, urinary tract infection, residual urine) to decrease the risk of recurrent stones.

Challenge of percutaneous nephrolithotomy in patients with spinal neuropathy

OBJECTIVE

To assess the technical difficulties, associated complications and stone clearance rates in patients with spinal neuropathy undergoing percutaneous nephrolithotomy.

METHODS

Twenty-nine patients with spinal neuropathy underwent percutaneous nephrolithotomy in the two centers studied between October 1995 and January 2002. They were nine patients with traumatic spinal cord injury, 10 patients with spina bifida and 10 with other heterogeneous causes for their spinal neuropathy. The group included 12 men and 17 women, with an average age of 44 years (14-80). Patients' medical records were reviewed retrospectively for data relating to their renal lithiasis.

RESULTS

A total of 39 percutaneous nephrolithotomy procedures were undertaken on 32 kidneys. Thirteen procedures were for staghorn calculi. Preoperatively, eight kidneys required nephrostomy and 5 J stent decompression. The average American Society of Anesthesiologists (ASA) score was 3, and one patient had percutaneous nephrolithotomy performed under local anaesthetic as the risk of general anaesthetic was felt to be too high. The associated morbidity and mortality in this group is significant. There were two postoperative deaths. Major complications were associated with three procedures, and consisted of seizures, aspiration pneumonia and pressure necrosis. Nine patients experienced minor complications including fever, hypotension and nephrostomy site leakage. Nine patients required intensive therapy unit care postoperatively and the average hospital stay for the group was 13.32 days. Only 18 (62%) patients were rendered stone-free from their initial percutaneous nephrolithotomy. Seven patients required a further procedure for stone clearance: four underwent extracorporeal shock-wave lithotripsy, two ureteroscopy and one nephrectomy.

CONCLUSIONS

Patients with spinal neuropathy and renal lithiasis pose a significant operative challenge. Technical difficulties and potential complications should be considered carefully before undertaking percutaneous nephrolithotomy in these patients.

Urolithiasis in patients with spinal cord injuries: risk factors, management, and outcomes

PURPOSE OF REVIEW

Despite major advances in the urological care of spinal cord injury patients, the incidence of urolithiasis has not changed. Although the incidence of kidneys lost to staghorn calculus disease has decreased considerably, stone disease is still a significant cause of morbidity and concern. The purpose of this review is to summarize the risk factors for the development of stone diseases in the spinal cord injury patient population and present the outcomes of current endourologic treatment modalities.

RECENT FINDINGS

Recurrent urinary tract infections, indwelling catheters, vesicoureteral reflux, and immobilization hypercalcuria are a few of the major risk factors for the development of urolithiasis among spinal cord injury patients. Retrograde endourologic techniques are often not possible to address stone disease due to lower extremity contractures, spinal curvature, and pelvic tilt. Extracorporeal shockwave lithotripsy success rates vary from 50 to 90%, but clearance rates are often delayed. Success rates for percutaneous nephrolithotomy match those quoted in the general population ( > 90%), but at the expense of a higher rate of complications (6-20%). Meticulous planning with regard to appropriate prophylactic antibiotics and body position will maximize efficacious outcomes.

SUMMARY

Early identification and treatment of urolithiasis in spinal cord injury patients will aid in preserving renal function and minimizing associated complications. Despite variation in common urological practices between spinal cord injury units and the lack of clear cut guidelines for follow-up, the increased incidence of risks associated with urolithiasis lends support for routine genitourinary imaging in order to identify and treat those individuals at highest risk.

Outcome from percutaneous nephrolithotomy in patients with spinal cord injury, using a single-stage dilator for access

OBJECTIVE

To present our experience of percutaneous nephrolithotomy (PCNL) for treating urolithiasis in patients with spinal cord injury (SCI) using a single-stage dilator for percutaneous access.

PATIENTS AND METHODS

A prospective database of patients with SCI having PCNL using the single-stage dilator was assessed, analysing patient data, stone-free rates, morbidity and the follow-up outcome.

RESULTS

In all, 26 patients had 54 PCNLs on 32 kidneys; 20 had unilateral and six bilateral stone disease; there were many staghorn calculi (24/54). Major complications occurred in three of 54 PCNLs (6%). The complete stone-clearance rate was 87% for PCNL alone, rising to 29 of 32 kidneys (91%) or 24 of 26 patients (92%) with adjuvant procedures. A further three kidneys required no further treatment and were monitored, having residual fragments of < or = 2 mm.

CONCLUSIONS

PCNL has a high success rate and acceptable complication rate compared to extracorporeal shock-wave lithotripsy, and remains a valid first-line treatment option for kidney stones in patients with SCI.

Safety and efficacy of percutaneous nephrolithotomy in patients with neurogenic bladder dysfunction

OBJECTIVES

To review our experience performing percutaneous nephrolithotomy (PNL) on patients with neurogenic bladder dysfunction with special attention paid to the risks of surgical complications and stone recurrence. Patients with neurogenic bladder dysfunction with or without urinary diversion are at increased risk of urolithiasis, surgical complications, and recurrent stone disease.

METHODS

We retrospectively reviewed the 23 patients with neurogenic bladder dysfunction who underwent PNL at our institution. Neurologic lesions included spina bifida, traumatic spinal cord injury, exstrophy/epispadias, neonatal meningitis, stroke, and spine chondrosarcoma. Bladder management included ileal conduit (n = 8), intermittent catheterization (n = 7), indwelling catheter (n = 7), and ureterosigmoidostomy (n = 1).

RESULTS

We performed 100 procedures on 47 renal units (17 bilateral, 7 with recurrent stones). Urinary tract infection/colonization was seen in 21 of 23 patients, most of whom had more than one organism. The stone-free rate was 96%. Six patients required three or more procedures, each had a complete staghorn calculus. In an average of 36 months of follow-up, 10 patients (46%) had recurrent stone disease requiring intervention, and 5 patients (23%) underwent repeat PNL. The stone composition analysis revealed mainly infection-related stones.

CONCLUSIONS

PNL in patients with neurogenic voiding dysfunction is safe and effective, with outcomes comparable to that of patients without such lesions. The complication rate is small but statistically significant. It is important to obtain adequate urine cultures, because renal pelvis and bladder culture data may differ and affect the outcome. Risk factors for recurrent stone disease include a high spinal cord lesion, indwelling urinary catheter, and ureterosigmoidostomy.

Atrophy of kidney following extra corporeal shock wave lithotripsy of renal calculus in a paraplegic patient with marked spinal curvature

OBJECTIVES

To discuss a rare complication of extra corporeal shock wave lithotripsy (ESWL) of renal calculus in a paraplegic patient, who had marked curvature of thoracic and lumbar spine.

DESIGN

A case report of a paraplegic patient, who developed renal atrophy and hypertension after undergoing ESWL of staghorn calculus.

SETTING

Regional Spinal Injuries Centre, Southport and Mersey Regional Lithotripsy Unit, Royal Liverpool University Hospital, Liverpool, UK.

PARTICIPANT

A 28-year-old male with spina bifida, paraplegia at L-1 level and considerable curvature of spine and tilting of pelvis.

METHOD

ESWL was carried out in three sessions by delivering 1934, 1876, and 2025 shock waves respectively. Localisation of the staghorn calculus was difficult because of spinal curvature and pelvic tilt.

RESULTS

A follow-up IVU, performed 3 months after last ESWL treatment, revealed no residual stone in the left kidney, apart from a little low-density calcification in the renal parenchyma adjacent to the lower pole calyx. There were no calculi in the left ureter. The left kidney had become small, though still functioning. MAG-3 isotope renogram showed the left kidney to be markedly atrophic. Relative renal function: right kidney, 94%; and left kidney, 6%. He developed hypertension and a laparoscopic left nephrectomy was performed at another hospital.

CONCLUSION

Difficulty in localisation of renal calculi for ESWL must be anticipated in spinal bifida and spinal cord injury patients, who have significant spinal curvature. Because of problems in the positioning of a patient with marked curvature of spine and pelvic tilt, and consequent difficulties in accurate localisation of renal calculi for lithotripsy, these patients may be at increased risk of developing renal parenchymal and vascular damage following ESWL.

Gastric patch pyeloplasty: development of an animal model to produce upper tract urinary acidification for treating struvite urinary calculi

PURPOSE

Struvite calculi form in an alkaline environment created by urease producing uropathogens. We developed a viable upper tract urinary acidification model by performing gastric patch pyeloplasty in the rabbit. This model produces urinary acidification sufficient for the treatment and prevention of struvite renal calculi. We evaluated the physiological, metabolic and surgical outcomes.

MATERIALS AND METHODS

gastric segment was harvested based on branches of the left gastro-epiploic artery. The flap was folded along the transverse axis and the adjacent edges were closed. The mouth of this reconfigured pouch provided optimal dimensions for anastomosis with the diminutive renal pelvis. Half of the rabbits were treated with internal stenting and H-2 blockade. Urinary pH was assessed by weekly cage collection and direct collection from the cannulated ureters. Urine culture was done, and serum gastrin and electrolytes were assessed at regular intervals. The rabbits were sacrificed at 3 to 26 weeks. Histological examination was routinely performed.

RESULTS

A total of 15 rabbits were available for complete assessment. Sustained urinary acidification was produced in 7 animals (47%) with a mean pH decrease of 2.27. In another 2 rabbits (13%) the urine was initially acidic but subsequently became alkaline due to ureteral obstruction. Electrolytes and gastrin were unchanged in these rabbits and urine culture was positive in 2. Histological testing revealed nonspecific inflammatory changes of the renal pelvis. Anastomotic complications were the most common surgical complication and the most common cause of failed acidification. The cohort treated without stents and H-2 blockade was at significantly greater risk for anastomotic leakage.

CONCLUSIONS

Gastric patch pyeloplasty may significantly increase urinary acidity in the rabbit model without altering the serum electrolyte balance or gastrin level. The procedure utilizes common techniques of reconstructive urology and may be possible with laparoscopy. Further study is required to assess the in vivo effect of this procedure for treating and preventing upper tract struvite calculi.

Infection stones

The pathogenesis and epidemiology of infection stones are well understood. While percutaneous lithotripsy and extracorporeal shock wave lithotripsy have emerged as the mainstay of extirpative therapy, surgical lithotomy is the standard to which other therapies must be compared. Adjunctive therapy with pharmacological agents that inhibit urease with few side effects and effective urinary acidifiers favor chemolysis. Diet and chemotherapy offer the hope of slowing stone growth and/or recurrence in patients with chronic urease-producing bacteriuria.