STONE DISEASE

Diabetes Mellitus and Hypertension Associated With Shock Wave Lithotripsy of Renal and Proximal Ureteral Stones at 19 Years of Followup
Krambeck AE, Gettman MT, Rohlinger AL, Lohse CM, Patterson DE, Segura JW
Department of Urology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
J Urol. 2006; 175: 1742-7

• Purpose: SWL has revolutionized the management of nephrolithiasis and it is a preferred treatment for uncomplicated renal and proximal ureteral calculi. Since its introduction in 1982, conflicting reports of early adverse effects have been published. However, to our knowledge the long-term medical effects associated with SWL are unknown. We evaluated these adverse medical effects associated with SWL for renal and proximal ureteral stones.
• Materials and Methods: Chart review identified 630 patients treated with SWL at our institution in 1985. Questionnaires were sent to 578 patients who were alive in 2004. The response rate was 58.9%. Respondents were matched by age, sex and year of presentation to a cohort of patients with nephrolithiasis who were treated nonsurgically.
• Results: At 19 years of followup hypertension was more prevalent in the SWL group (OR 1.47, 95% CI 1.03, 2.10, p = 0.034). The development of hypertension was related to bilateral treatment (p = 0.033). In the SWL group diabetes mellitus developed in 16.8% of patients. Patients treated with SWL were more likely to have diabetes mellitus than controls (OR 3.23, 95% CI 1.73 to 6.02, p < 0.001). Multivariate analysis controlling for change in body mass index showed a persistent risk of diabetes mellitus in the SWL group (OR 3.75, 95% CI 1.56 to 9.02, p = 0.003). Diabetes mellitus was related to the number of administered shocks and treatment intensity (p = 0.005 and 0.007).
• Conclusions: At 19 years of followup SWL for renal and proximal ureteral stones was associated with the development of hypertension and diabetes mellitus. The incidence of these conditions was significantly higher than in a cohort of conservatively treated patients with nephrolithiasis.
  
  
• Editorial Comment
  This provocative study underscores the need for long-term studies of the impact of our interventions, be they medical or surgical. Specifically, it raises concerns of the development of hypertension and diabetes mellitus following shockwave lithotripsy. The data related to the development of diabetes is particularly compelling, with a high odds ratio (3.75) that persists despite controlling for body mass index, and demonstrates a dose-dependency (correlation with number and intensity of shocks) that supports the hypothesis that a true biological effect exists. Deterioration in pancreatic endocrine function has been reported in up to 30% of patients undergoing SWL for pancreatic stones, though whether this reflects underlying pancreatic disease or the effects of the SW has not been determined. It is also unclear whether the effects noted in this study are peculiar to the shock path and focal area of the Dornier HM-3, or if similar effects may be anticipated with current lithotripter designs.
  The data pertaining to hypertension is less compelling. Though more patients who underwent SWL developed hypertension, shockwave lithotripsy had no impact on the final prevalence of hypertension. In other words, the differences seen can be attributed to baseline differences in the rate of hypertension. It is plausible that other differences at baseline, in particular differences in stone size (those observed had smaller stones) reflect a bias that patients treated with SWL were further along in their disease process. Lastly, no dose-response correlation was noted with regards to number or intensity of shockwave and the development of hypertension, making it less likely that a true biological effect exists.
  It is important to also note a few weaknesses in study design. The method of follow-up was not consistent in the study – patients treated with SWL were followed by questionnaire while the control group was followed by chart review, though the authors acknowledge that less than 20% of their patients return to their institution for follow-up. No information was gathered regarding subsequent SWL or other therapies for stone disease in either group during the 13 year follow that may confound the analyses conducted.

Dr. Manoj Monga
Professor, Department of Urology
University of Minnesota
Edina, Minnesota, USA