Background: Rhabdomyolysis is a well-known cause of renal failure and is most commonly caused by ischemia/reperfusion or crush injury. We describe a new cause of this syndrome in a series of 6 patients who underwent necrosis of the gluteal muscles after bariatric surgery, 3 of whom eventually died of renal failure. Methods: Potential etiologic factors were studied by comparing these patients with a consecutive series of 100 patients undergoing primary uncomplicated bariatric surgery during a 1-year period. Demographics, preoperative BMI, co-morbidities, duration, of operation, and postoperative creatinine phosphokinase (CPK) levels. Results: All patients presented with an area of buttock skin breakdown initially diagnosed as a simple decubitus ulcer. All had extensive myonecrosis of the medial gluteal muscles requiring extensive debridement: 5 of the 6 patients were male, with median BMI 67 compared with a median BMI 55 in the control group (P=0.0022). The patients were on the operating-room table for a median of 5.7 hours compared with 4.0 in the control group (P=0.01). 3 of the 6 developed renal failure requiring dialysis, which was fatal in all. One other patient developed a transient elevation of BUN and creatinine which did not require dialysis. Since recognition of this pattern, we now routinely perform serial CPK measurements. Median CPK rise in uncomplicated patients was to 1,200 mg/dl (SD 450-9,000), while CPK in affected patients ranged from 26,000 to 29,000 IU/l. We now routinely add addtional buttock padding in very obese patients and institute aggressive hydration and mannitol diuresis if CPK rises above 5,000. No cases have occurred in the past 18 months in 220 patients. Conclusions: This is an important and potentially fatal complication of bariatric surgery. Very obese male patients with prolonged surgery are at risk of gluteal muscle necrosis with consequent renal failure, which we hypothesize is due to pressure by the operating-table leading to rhabdomyolysis and the creation of a compartment syndrome. Prevention may be aided by attention to intraoperative padding and positioning, and by limiting the duration of the operation.
