Kidney Stones in Women More Likely to Occur With Infection

Ricki Lewis, PhD

October 03, 2012

October 3, 2012 — Women are less likely than men to develop urinary tract obstructions, including kidney stones, but when they do, they're more than twice as likely to contract related infections, according to a study published online September 25 in the European Urology.

Increase in urolithiasis has been attributed to rising rates of obesity, metabolic syndrome, and diabetes, but the incidence is not known. Moreover, empirical evidence is lacking as to whether retrograde ureteral catheterization (RUC) or percutaneous nephrostomy (PCN), used to decompress the renal collecting system, is safer.

Jesse D. Sammon, DO, from the Vattikuti Urology Institute at Henry Ford Hospital in Detroit, Michigan, and colleagues analyzed data on 396,385 adults hospitalized with infected urolithiasis between 1999 and 2009 and included in the Nationwide Inpatient Sample. The researchers particularly noted whether each patient underwent RUC or PCN. Without such relief, infected and obstructive urolithiasis can significantly elevate risk for sepsis, destroy the renal parenchyma, and cause death.

During the decade-long study period, incidence of infected urolithiasis in women increased from 15.5 (95% confidence interval [CI], 15.3 - 15.6) to 27.6 (95% CI, 27.4 - 27.8) per 100,000, whereas in men it increased from 7.8 (95% CI, 7.7 - 7.9) to 12.1 (95% CI, 12.0 - 12.3) per 100,000.

Rates of associated sepsis in the study population as a whole increased during the study period from 6.9% to 8.5% (P = .013), and severe sepsis rose from 1.7% to 3.2%. However, the mortality rate remained steady at 0.25% in 1999 and 0.20% in 2009 (P = 0.15), indicating success in treating sepsis.

Among 113,459 (28.6%) of patients requiring immediate decompression, 99,492 (87.7%) had RUC. Those receiving PCN were more likely to be male, belong to an ethnic minority, and to have been treated at large, urban teaching centers. They were less likely to have private insurance.

Trend analysis on the use of PCN showed a decrease from 16.1% to 11.2% (P = .001), with an estimated annual percentage change of -2.8% (95% CI, -1.7% to -3.9%) over the decade. PCN was also associated with an elevated rate of sepsis (odds ratio [OR], 1.63; 95% CI, 1.52 - 1.74), severe sepsis (OR, 2.28; 95% CI, 2.06 - 2.52), prolonged length of hospital stay (OR, 3.18; 95% CI, 3.01 - 3.34), increased hospital expenses (OR, 2.71; 95% CI, 2.58 - 2.85), and mortality (OR, 3.14; 95% CI, 2.13 - 4.63).

The researchers consider their study to be hypothesis generating rather than conclusive because they did not quantify disease severity (such as white blood cell count). In addition, sicker patients may have been more likely to have undergone PCN because it does not require general anesthesia. However, the authors point out that reassessment of treatment choice is necessary because PCN is associated with complications of renal hemorrhage, chest injury, and bowel transgression.

Other limitations include lack of consideration of timing of the intervention; failure to note patients who had PCN after failed RUC; and no consideration of stone type, number, and size.

The authors have disclosed no relevant financial relationships.

Eur Urol. Published online September 25, 2012. Abstract