Best of AUA 2013: Stone Disease/Endourology

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Presented by Mantu Gupta, MD

Columbia University Medical Center, New York

• In 96 centers, successful stone-free percutaneous nephrolithotomy (PCNL) was predicted by many parameters, including stone volume. Researchers created a nephrolithometric nomogram with a predictive accuracy of 76%.

• With strict computed tomography imaging criteria for assessment of residual stone status, the S.T.O.N.E. (Surgical Classification System for Renal Stones) nephrolithometry scoring system is reproducible and predictive of treatment success. The system also showed good interobserver reliability.

• Nomograms can preoperatively predict which patients are likely to have residual fragments following PCNL. They can then be selected for earlier and stricter post-op imaging to identify residual fragments and undergo second-look procedures.

• Greater dietary intake of vegetables, fruits, and total dietary fiber were each associated with a reduced risk of stone disease in postmenopausal women. Only dietary fiber was an independent predictor. Greater vegetable intake was associated with a 12%-24% decreased risk of kidney stones, and greater fruit intake was associated with a 6%-21% decreased risk of stone formation in adjusted analyses.

• High caloric intake was indicative of future stone disease. But low calorie intake did not prevent kidney stone disease.

• Caloric intake and food products predicted whether stone disease would increase. In particular, total calories, fat grams, protein ounces, and fruits and vegetables correlated positively with an annual increase in stone disease, specifically dark green vegetables, flour, cereal products, corn products, and especially high-fructose corn syrup and other sugars.

• The incidence of nephrolithiasis is higher in geographic areas where the populations have low fruit and high sugar intake.

• The annual cost of urolithiasis related to obesity in the U.S. is expected to reach an additional $200 million per year by 2030 as obesity rates grow. Urologists may want to consider talking to patients in conjunction with nutritionists about heart-healthy diets.

• Aminobisphosphonates improve bone mineral density and slow lithogenic activity. Their administration in association with thiazides produces the same clinical effects and also reduces calciuria and improves bone mineral density.

• Stone analysis is recommended for each stone episode since composition may significantly change in subsequent stone analysis. Almost 30% of patients had a different stone composition on second analysis.

• In patients who form calcium phosphate stones, brushite stones were associated with higher urinary calcium excretion and higher urinary mean super saturation calcium phosphate when compared to hydroxyapatite stones. Aggressive measures to reduce urinary calcium may be helpful to prevent brushite stone formation.

• There is marked underutilization of 24-hour urine analysis in recurrent stone formers.

• Compared to extracorporeal shock wave lithotripsy, focused ultrasonic propulsion produced no detectable tissue injury to the renal parenchyma when using clinical treatment parameters. Efforts are under way for FDA approval of human feasibility studies of the ultrasonic propulsion technique.

• In ultrasound, a wide range of potentially therapeutic intensities have a low probability of causing injury.

• Pre-PCNL nephrostomy drainage with renal pelvic urine culture and culture-specific antibiotic treatment decreases sepsis rates in high-risk patient populations.

• Prophylactic antibiotics should be administered prior to ureteroscopic lithotripsy for stone disease, even with a negative urine culture.

• Mortality following PCNL is rare and is associated with low surgeon volume and high preoperative mortality risk.

• Routine post-op imaging is more expensive than selective imaging in patients with post-op pain, but prevention of renal loss and its attendant morbidity may justify the additional modest cost.

• Based on a porcine study, the best method of delivery of adjuvant therapy to the upper urinary tract for urothelial carcinoma may be an open-ended catheter.UT

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