New data may add to concerns over SWL, diabetes risk

Cleveland-A Mayo Clinic study published earlier this year raised more than a few eyebrows when its authors concluded that treatment of renal stones with shockwave lithotripsy appears to heighten the risk of diabetes mellitus and hypertension. More recently, researchers from Northwestern University reported a similar finding in patients with pancreatic stones-that SWL used in these patients may be associated with an increased risk of diabetes.

In their small, retrospective study, the Northwestern team evaluated the development of diabetes in patients who underwent SWL for pancreatic duct stones. Two new cases of diabetes developed at a follow-up of nearly 2 years, the researchers reported at the World Congress of Endourology here.

"Our thought was to do a study of shockwave lithotripsy to the pancreas, which is the organ that is immediately responsible for diabetes, and see if that had any effect on the development of diabetes afterwards," said Lee Zhao, MD, a urology resident at Northwestern's Feinberg School of Medicine, Chicago.

At a mean follow-up of 21 months, two additional patients (8%) developed diabetes.

Pancreatitis and diabetes risk

"Of course, our study is complicated by the fact that chronic pancreatitis, which all these patients have, predisposes the patients to diabetes anyway," Dr. Zhao pointed out. "In fact, there's an 80% cumulative risk of diabetes over 25 years with chronic pancreatitis.

"It is difficult to find out how much of the problem of diabetes after shockwave lithotripsy is due to biology of the disease versus what we did to them with the lithotripsy," he said, adding that his search of the literature was unable to uncover the 2-year risk of developing diabetes in patients with pancreatic stones.

While not conclusive, the findings of the Northwestern group are intriguing in light of a larger, longer-term study from the Mayo Clinic in Rochester, MN, which was led by the late Joseph Segura, MD (J Urol 2006; 175:1742-7). That study involved chart reviews of 630 patients treated in 1985 for renal and ureteral stones with SWL (HM-3 lithotripter, Dornier MedTech, Kennesaw, GA). Of 578 patients who were still alive in 2004, 59% responded to a questionnaire sent by the researchers.

Patients treated with lithotripsy were matched by age, gender, and initial time of presentation with a cohort of nephrolithiasis patients who received nonsurgical treatment. Results 19 years post-treatment showed that those treated with SWL had 3.75 times the risk of having diabetes as those receiving conservative treatment. Patients treated with lithotripsy also had 1.47 times the risk of having hypertension than those treated conservatively.

Both the Northwestern and Mayo Clinic papers suggest that further research, including studies of different lithotripter models, are needed to further explore the association between SWL and the development of diabetes.