New method for the detection of intraperitoneal free air by sonography: Scissors maneuver

PURPOSE: This study was conducted to investigate the diagnostic value of a new sonographic technique for the detection of intraabdominal free air. METHODS: Seventy-two patients with a suspected gastrointestinal tract perforation were included in the study and prospectively evaluated by sonography and abdominal and chest radiography for the detection of intraperitoneal free air. A new sonographic technique (the scissors maneuver) was used to detect intraperitoneal free air superficial to the liver; the maneuver consists of applying and then releasing slight pressure onto the abdominal wall with the caudal part of a parasagittaly oriented linear-array probe. The results of the imaging studies were correlated with surgical findings when possible. RESULTS: Sixteen patients had a surgically proven gastrointestinal tract perforation causing pneumoperitoneum. Sonography and radiography each showed pneumoperitoneum in 15 patients, with 1 false-negative result for each modality. The sensitivity and specificity values of sonography and radiography were identical; sensitivity was 94% and specificity was 100% for both imaging modalities. The scissors maneuver was positive in all patients with sonographically detected pneumoperitoneum. CONCLUSIONS: Sonography is an effective tool in the diagnosis of pneumoperitoneum, with sensitivity and specificity equal to those of radiography. The scissors maneuver may be a useful adjunct for improving the diagnostic yield of sonography.