Sonographic demonstration of free air in perforated peptic ulcers: comparison of sonography with radiography.

Abdominal sonography was performed in 283 patients with acute abdominal pain. Of these patients, 10 were diagnosed as having an acute perforated peptic ulcer (PPU) and 2 were diagnosed as having a sealed-off PPU. Sonographic findings of acute PPU are summarized. The presence of an interference echo with the shifting phenomenon is a very strong indication of the presence of free air in the abdominal cavity. Using these sonographic criteria, intraperitoneal free air was diagnosed as 9/10 patients with PPU in comparison to 8/10 by abdominal and chest radiographs. Two patients with sonographic evidence of free air, but negative X-ray studies, were later found to have free air in the subsequent radiographic studies. These findings suggest that sonography is highly sensitive in the small number of patients in whom air is found. Sonographic studies also have the advantage of detecting other changes associated with PPU, such as fluid accumulation, inflammatory mass, and thickening of the gallbladder.