Noninvasive method for the detection of bowel ischemia: computed tomography detection of absorbed iodinated contrast material.

RATIONALE AND OBJECTIVES

Although systemic absorption of enterically administered iohexol and its excretion in urine has been previously documented in rats with ischemic bowel, a practical and sensitive method of detecting urinary iohexol has not been available. We proposed to detect the presence of iohexol in the urine of rats with normal and ischemic bowel by use of a computed tomography (CT) number increase in the bladder with the use of CT.

METHODS

Anesthetized rats (250 g) underwent either sham laparotomy (n = 6), ligation of two vascular arcades to the proximal jejunum (n = 5), ligation of six vascular arcades to the proximal jejunum (n = 6), or ligation of the superior mesenteric artery (n = 6). Rats were hydrated with saline (3.2 ml/hr intravenously). Each received a 3-ml enteric bolus of isotonic iohexol. Serial CT scans and plain film radiographs of the bladder were performed at 2, 4, and 6 hr to detect systemic absorption of contrast from the gut. Urine iohexol concentrations were measured by capillary electrophoresis. CT number and iohexol concentration were compared with evidence from plain film radiographs of bladder opacification. Intestinal ischemia was graded histologically.

RESULTS

Histologic evidence of ischemia was present in all six-arcade and five of six superior mesenteric artery (SMA)-ligated animals. No animals in the control or two-arcade group showed evidence of bowel ischemia. Statistically significant increases (P < 0.05) in bladder density were demonstrated in the six-arcade and SMA-ligated groups. No statistical difference was noted between the two-arcade ligation and control groups.

CONCLUSIONS

Experimental intestinal ischemia was reliably detected by bladder opacification after administration of enteric contrast. CT detection of systemic absorption of enteric iohexol was more sensitive than plain film radiographs and may be useful in the diagnosis of intestinal ischemia, although it may not be specific for ischemia.