[Positive predictive value and negative predictive value of spiral CT in the diagnosis of closed loop obstruction complicated by intestinal ischemia].

PURPOSE: To assess the positive predictive value and the negative predictive value of spiral CT in the diagnosis of "closed-loop" obstruction complicated by intestinal ischaemia.

MATERIALS AND METHODS: Between January 1999 and January 2002, 120 patients with small intestine closed-loop obstruction who had undergone surgical laparotomy within 2-6 hours from abdominal and pelvic spiral CT were retrospectively reviewed. The CT scans were performed using 5-mm slice thickness, 1 s scan delay, 5 x 5-mm collimation and 1.5 pitch after administering i.v. iodinated contrast material (120 ml volume, 60 s scan delay, 2.5-3 ml/s rate) with an automatic injector. For the diagnosis of closed-loop obstruction the following CT findings were examined: identification of the transitional area, 'C', 'U' or 'beak' shape of the obstructed loops, radial distribution of the involved mesenteric vessels. For the diagnosis of loop ischaemia, the following findings were evaluated in addition to the CT signs described above: submucosal oedema, increased, reduced, or no enhancement of the loop walls, oedema of the mesenteric vessels, fluid within the loops or in the intraperitoneal spaces.

RESULTS: 'U', 'C', 'beak' loop configuration with poor or no contrast enhancement of the obstructed loop walls, ascites, rotation and engorgement of mesenteric vessels enabled the diagnosis of 26 cases of closed-loop obstruction complicated by ischaemia, infarction. U- or C-shaped loops with radial distribution and/or rotation of mesenteric vessels towards the obstruction site suggested the correct diagnosis in 94 cases, but did not allow identification of ischaemia in 25 cases. The positive predictive value of spiral CT related to ischaemic loop complications was 100%; the negative predictive value was 73%.

CONCLUSIONS: Spiral CT is a reliable imaging technique enabling the diagnosis of closed-loop obstruction with or without intestinal ischaemic complications. Any alterations detected in the trophic status of the loops or mesentery imply ischaemic complications requiring emergency surgery. On the contrary, if only CT signs of closed-loop obstruction are detected, the existence and/or development of ischaemia cannot be ruled out.