Endourology/Stones: Care utilization for stones growing rapidly in older adults

The safety and viability of outpatient percutaneous nephrolithotomy and predictors of success after shock wave lithotripsy were among the research highlights in endourology/stones at the AUA annual meeting. The take-home messages in endourology/stones were presented by Alana Christina Desai, MD, of Washington University, St. Louis.

Health care utilization for urinary stone disease is growing rapidly among older adults and faster than in younger age groups.

In stone formers, both body mass index and hemoglobin A1c were positively correlated with urinary oxalate, suggesting an explanation for the relationship of nephrolithiasis with both obesity and diabetes.

The number of metabolic syndrome traits in calcium oxalate stone formers is associated with disease severity and increased odds of hypercalciuria, suggesting that calcium oxalate stone disease should be regarded as a systemic disorder linked to metabolic syndrome.

Diabetes and hypertension were more closely linked to calcium oxalate monohydrate stones than to calcium oxalate dihydrate stones, suggesting the two stone types may be clinically and metabolically different and thus may have different etiology.

Obese and diabetic mice on ultra-low oxalate diets had increased urinary oxalate and glycolate excretion compared with controls, suggesting that obesity may increase endogenous oxalate synthesis via pathways linked to glycolate production.

Continue to the next page for more take-home messages.

• Good glycemic control in stone formers with diabetes reduced risk factors for uric acid calculi.

• Differences in the upper urinary tract microbiome in urinary stone patients were strongly associated with patient age and stone type.

• Limitations of sequencing platforms should be considered in microbiome studies of urologic diseases because different sequencing platforms can underestimate microbiome diversity and exhibit significant compositional differences.

• Antibiotic treatment in rats affected the gut microbiome and was associated with increased urinary calcium excretion.

• In another animal model, oxalate exposure exhibited broad stimulatory and inhibitory effects on the metagenome of the gut microbiome beyond just that of oxalate-degrading bacteria.

• Prior antibiotic exposure was strongly associated with increased odds of incident kidney stones, and the greatest risk occurred with more recent and early life exposure.

• Results of two randomized controlled trials showed no benefit for prolonged antibiotic use in patients at low risk for infection-related complications undergoing percutaneous nephrolithotomy (PCNL).

• PCNL is a feasible alternative to nephrectomy to preserve ipsilateral renal function in select patients with xanthogranulomatous pyelonephritis, but postoperative infectious complications are common.

• Outpatient PCNL is safe and feasible.

• Physicians practicing at academic institutions or who are fellowship trained in North America or Europe are most likely to perform PCNL in patients on aspirin.

Next: Continuing aspirin in patients undergoing PCNL

• Continuing aspirin does not increase blood loss, the need for blood transfusion, or the occurrence of high-grade complications in patients undergoing PCNL.

• PCNL is a safe option in elderly patients and associated with stone-free rates similar to those in younger patients.

• Active stone removal was associated with a decrease in stone-related deaths and possibly prolonged survival in patients with poor performance status, but the investigators noted further study is warranted.

• Bilateral ureteroscopic stone extraction is safe and effective.

• When defined by strict computed tomography criteria, stone-free rates of flexible ureteroscopy for renal calculi are “dismal,” but the majority of residual fragments are 2 mm to 4 mm and can be observed as a more cost-effective strategy.

• Investigators from the University of Washington, Seattle are continuing to improve their novel technique of ultrasonic propulsion of kidney stones.

• The YouCare Tech fiberoptic ureteroscope had resolution comparable to another fiberoptic ureteroscope (Cobra), but it did not match visualization provided by the LithoVue digital ureteroscope.

• The LithoVue ureteroscope was safe, had a low failure rate, and may be cost saving with regard to OR time and repair costs, but was found in one study to have limitations with visualization beyond the stricture and with the use of electric cautery.

• The Pusen single-use ureteroscope was comparable to a reusable ureteroscope and suggested to be a valid method that may decrease maintenance costs.

• Results of studies investigating causes of unplanned care after ureteroscopy suggest that the development of a clinical care pathway that includes patients on self-pulled stents and pain management may minimize these encounters and improve treatment quality and cost.

• Mean stone length, mean stone density, stone heterogeneity index, mean stone density-stone heterogeneity index, and variation coefficient of stone density were all identified as predictors of success after shock wave lithotripsy (SWL).

• An analytic model incorporating nine parameters accurately predicted treatment success and complications after SWL.

• Performing air removal and appropriate case selection are key to achieving higher success rates in SWL.