Interstitial emphysema associated with epidural anesthesia for extracorporeal shock-wave lithotripsy.

Interstitial emphysema was noted on abdominal radiographs in 38 (15%) of the first 150 patients treated by extracorporeal shock-wave lithotripsy at our hospital. All 38 patients had undergone successful or attempted epidural anesthesia for the lithotripsy. This finding was not seen in any patient who had not undergone epidural puncture. The emphysema is the result of the introduction of air into the paraspinal and back muscles or subcutaneous tissues during attempted or actual puncture of the epidural space. This air was apparent on abdominal radiographs taken after lumbar puncture in 38 (23%) of 167 patients who underwent attempted or actual puncture of the epidural space. The emphysema decreases over the ensuing days, is of no clinical significance, and bears no direct relationship to extracorporeal shock-wave lithotripsy. This finding should not be mistaken for emphysema caused by gas-producing or gas-containing retroperitoneal diseases.