Sonographic features of intra-abdominal abscess caused by spilled stones during laparoscopic cholecystectomy

Spillage of stones into the abdominal cavity resulting from perforation of the gallbladder is one of the common complications of laparoscopic cholecystectomy. Although many surgeons know that stones left in the abdominal cavity can cause late visceral abscess requiring surgical treatment, the sonographic features of such abscesses have not yet to be thoroughly investigated. We investigated the sonographic features of intra-abdominal abscesses caused by spilled stones after laparoscopic cholecystectomy using Hitachi Model EUB-525 (3.5 MHz) and Aloka Model SSD-5500 (3.75 MHz) ultrasound systems. Two thousand thirty-six laparoscopic cholecystectomy procedures were carried out at this institution from 1990 through 2001. During this period, we encountered seven cases of intra-abdominal abscess. Three of these cases were symptomatic, but abscess, granulation, or both, were found incidentally by ultrasonography in the other four patients during routine annual health examinations. Laparotomy and open drainage of pus and gallstones from the intra-abdominal abscess were necessary in five cases. Ultrasonography revealed a mass in six of the seven patients. The abscesses were located in either the right subphrenic or subhepatic space on the surface of the liver and were sometimes difficult to distinguish from liver tumors. Ultrasound showed the abscesses as oval, low-echoic, solid masses with posterior enhancement. They ranged from 20 to 58 mm in diameter, had clear margins and highly echoic peripheral rims, and showed lateral shadowing. The lesions also contained several highly echoic spots with acoustic shadows that were thought to be the spilled stones. We conclude that visceral abscess should be considered after laparoscopic cholecystectomy, and that careful observation using ultrasonography is required, especially when the gallbladder is perforated and bile and stones have spilled out.