Shock wave lithotripsy is not predictive of hypertension among community stone formers at long-term followup

Abstract

Purpose: Concern exists over the subsequent development of hypertension after shock wave lithotripsy for the treatment of symptomatic urolithiasis. Referral bias and lack of long-term followup have been limitations of prior studies.

Materials and methods: We identified all Olmsted County, Minnesota residents with a diagnosis of urolithiasis from 1985 to 2008. The charts were electronically queried for hypertension and obesity by diagnostic codes, and use of shock wave lithotripsy by surgical codes. All patients first diagnosed with hypertension before or up to 90 days after the first documented kidney stone were considered to have prevalent hypertension and were excluded from analysis. Cox proportional hazards models were used to assess the association of shock wave lithotripsy with a subsequent diagnosis of hypertension.

Results: We identified 6,077 patients with incident urolithiasis with more than 90 days of followup. We excluded 1,295 (21.3%) members of the population for prevalent hypertension leaving 4,782 patients with incident urolithiasis for analysis. During an average followup of 8.7 years new onset hypertension was diagnosed in 983 (20.6%) members of the cohort at a mean of 6.0 years from the index stone date. Only 400 (8.4%) patients in the cohort were treated with shock wave lithotripsy. There was no significant association between shock wave lithotripsy and the development of hypertension in univariate (p = 0.33) and multivariate modeling controlling for age, gender and obesity (HR 1.03; 95% CI 0.84, 1.27; p = 0.77).

Conclusions: In a large population based cohort of kidney stone formers we failed to identify an association between shock wave lithotripsy and the subsequent long-term risk of hypertension.

Figure 1. Diagram of stone former selection based on diagnoses codes

Only those patients without prior stone episodes and greater than 90 days follow-up were analyzed. All patients with history of hypertension (HTN) were excluded. Of the patients without hypertension, 264 were treated with shock wave lithotripsy (SWL), and 126 went on to develop hypertension.

Figure 2. Time from index stone to Shock wave lithotripsy (SWL)

Of the 400 patients treated with SWL, 72% had SWL performed within 2 years of the index stone diagnosis.

Figure 3. Risk of subsequent hypertension events among patients treated with and without SWL

A) Compares risk of hypertension over 15 years among patients treated with and without SWL starting at time of incident stone. B) Compares the same risk starting at 2 years post incident stone, stratified on SWL in first 2 years among those still at risk (landmark method).

Figure 3. Risk of subsequent hypertension events among patients treated with and without SWL

A) Compares risk of hypertension over 15 years among patients treated with and without SWL starting at time of incident stone. B) Compares the same risk starting at 2 years post incident stone, stratified on SWL in first 2 years among those still at risk (landmark method).