STONE DISEASE

Impact of body mass index on cost and clinical outcomes after percutaneous nephrostolithotomy
Bagrodia A, Gupta A, Raman JD, Bensalah K, Pearle MS, Lotan Y
Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas
Urology. 2008; 72: 756-60

• Objectives: To evaluate the impact of body mass index (BMI) on clinical outcomes and costs associated with percutaneous nephrostolithotomy (PCNL).
• Methods: We reviewed charts of 200 consecutive patients who underwent PCNL between September 2005 and May 2007. We recorded patient and stone characteristics and perioperative outcomes. BMI was available for 150 patients (75%), who comprised our study group. We obtained direct and subcomponent costs (room and board, laboratory, pharmacy, radiology, operating room, surgical supplies, anesthesia, and recovery room). We divided patients into four BMI categories: normal weight (BMI < 25), overweight (25 </= BMI < 30), obese (30 </= BMI < 40), and morbidly obese (BMI >/= 40). We compared groups with regard to baseline characteristics, intraoperative parameters, stone-free and complication rates, and hospital length of stay.
• Results: Mean stone size and proportion of patients with staghorn, multiple, and bilateral calculi were similar among groups. The normal weight cohort had proportionately fewer recurrent stone formers and patients with a history of stone surgery, compared with the other groups (P = .005 and P = .03, respectively). We found no significant differences among groups with regard to stone-free and complication rates, operative time, length of stay, or need for multiple accesses. Median direct cost was marginally, but not significantly, higher in normal weight ($8124) compared with overweight ($6746), obese ($6740), and morbidly obese ($6719) patients (P = .75).
• Conclusions: Body mass index had no impact on efficacy or complication rates of PCNL. Despite greater perceived difficulty in performing these procedures in overweight and obese patients, it was not more costly.
  
  
• Editorial Comment
  The authors present a compelling argument that BMI should not impact the decision to consider percutaneous nephrolithotomy as safety, efficacy and cost are not affected. The authors note that these conclusions are based on the experience of a single expert-endourologist at a high-volume tertiary referral center.
  The authors noted a higher median length of stay (3 vs. 2 days) and higher cost for room and board for the normal weight patients. This could be a reflection of patient expectations. Patients who are experienced (ex. recurrent stone formers, history of stone disease) would have realistic expectations for post-operative recovery that might help drive them down a clinical treatment pathway to earlier discharge - the normal weight patients in this study were less experienced.
  Selection bias may impact the results of retrospective studies. There was a strong trend (p=0.06) to the morbidly obese patients being younger (45 years) than the rest of the study cohort (55 years). It is possibly that older morbidly obese patients are directed to ureteroscopy or other modalities. Similarly, the authors note that the ASA class severity was similar across BMI, suggesting that the normal weight patients may have had higher than expected comorbid conditions that may have lead to referral to their tertiary center. This would inflate the costs and length of stay in the otherwise “healthy control” weight category.
  One primary challenge in the morbidly obese is the initial percutaneous access.  It would be interesting to evaluate the fluoroscopy time, radiation dose, and time to access for this cohort.

Dr. Manoj Monga
Professor, Department of Urology
University of Minnesota
Edina, Minnesota, USA
E-mail: endourol@yahoo.com