Predictors of Cost and Clinical Outcomes of Percutaneous Nephrostolithotomy

Purpose: There is a paucity of information on the association of preoperative parameters with surgical outcomes and cost. We identified preoperative predictors of direct cost and examined the association of these factors with the perioperative outcomes of percutaneous nephrostolithotomy. Materials and Methods: We reviewed the records of 200 consecutive patients who underwent percutaneous nephrostolithotomy at our hospital from September 2005 to May 2007. Complete cost and clinical information were available on 179 patients (89.5%). Patient and stone characteristics, and perioperative outcomes were recorded. Direct and component costs, including room and board, laboratory, pharmacy, radiology, operating room, surgical supplies, anesthesia and recovery room, were obtained from our hospital billing department. Univariate and multivariate linear regression analyses were performed to identify preoperative predictors of cost. We evaluated the association of independent predictors of cost with perioperative outcomes. Results: On univariate analysis stone size category, preoperative urinary tract infection and allopurinol were associated with direct cost. On multivariate analysis only stone burden was an independent predictor of nephrostolithotomy cost. Large stone burden was associated with an increased need for multiple access (p = 0.0003), longer operative time (p<0.0001), longer hospitalization duration (p<0.0001), a lower stone-free rate (p = 0.038) and the need for second look flexible nephroscopy (p = 0.0005). Large stone burden was not associated with a greater transfusion requirement (p = 0.25) or an increased complication rate (p = 0.46). Conclusions: A large stone burden independently predicts higher costs in patients who undergo percutaneous nephrostolithotomy despite no associated increase in the complication or transfusion rate. Other patient characteristics, including age, body mass index and comorbidity status, do not increase cost.