Impact of fasting on shockwave lithotripsy in renal stones: a randomized controlled trial

We evaluated the impact of fasting on the effectiveness of shockwave lithotripsy (SWL) in patients with renal calculi.

The study was a randomized controlled trial for patients with renal stones. Between May 2005 and November 2006, patients (n = 97) with a single radio-opaque renal stone (7-21 mm) who were candidates for SWL were enrolled. Patients were randomized to fasting (F, n = 49) and nonfasting (NF, n = 48) groups. F group patients were asked to fast for 12 hours before SWL. Urine specific gravity (SG) was measured after fasting. All patients were monitored every 2 weeks until complete stone clearance. Treatment effectiveness was defined as complete clearance up to 3 months.

There were 32 men in the F group and 28 men in the NF group. The mean age was 37.9 +/- 8.5 years in the F group and 39.1 +/- 7.7 years in the NF group. The mean body mass index was 22.8 +/- 2.5 and 23.1 +/- 2.6 in F and NF patients, respectively. The urine SG in the F group (1.036 +/- 0.004) was significantly higher than in the NF group (1.013 +/- 0.004; P < 0.001). At 3-month follow-up, the overall stone-free rate using SWL was 86.1% in the F group, which was higher than the rate of 72.9% in the NF group; however, the difference was not statistically significant (P = 0.16).

Fasting significantly changes the urine SG but does not have a significant impact on the effectiveness of SWL for isolated renal stones.