Outcomes of contemporary percutaneous nephrostolithotomy in morbidly obese patients

Purpose: The surgical management of renal and ureteral calculi presents unique challenges in the obese patient. We reviewed our recent experience with percutaneous nephrostolithotomy in patients with a body mass index greater than 30. Materials and Methods: We reviewed the records of 236 patients undergoing percutaneous nephrostolithotomy between August 1994 and March 1997 at 2 university and affiliated hospitals. Among this group 57 patients had a body mass index greater than 30 (mean plus or minus standard deviation 38.9 ± 7.4). Renal anomalies were present in 21% of patients and more than half(56%) had co-morbidities in addition to obesity. Staghorn calculi were present in 19 patients (31.7%). In the remaining patients the mean cumulative stone size for single or multiple stones was 14.5 ± 8.7 mm. Stone-free status after the procedure was determined by plain nephrotomograms or noncontrast computerized tomography. Results: A total of 96 procedures were performed on 60 renal units (1.6 procedures per renal unit). Average operative time for the initial procedure was 181.2 ± 91.4 minutes. Complications occurred in 8 patients (14%) and 5 (8.8%) received a blood transfusion. Average hospital stay was 4.9 ± 3.1 days. The overall stone- free rate was 88.3%, and stone-free rate for staghorn calculi was 84.2% compared with 90.2% for nonstaghorn calculi. Conclusions: Percutaneous nephrostolithotomy in obese patients yields a stone-free rate that is comparable to that achieved in an unselected patient population. The complication rate, transfusion rate and hospital stay are also similar. Modifications to standard technique and instrumentation are sometimes necessary to perform percutaneous nephrostolithotomy in this group of patients.