Urinary excretion of iohexol after intestinal administration in rats with bowel ischaemia. The effects of mesenteric arterial and/or venous occlusion.

Serum and urinary levels of iohexol (Omnipaque) were evaluated in 28 rats after instillation of 1.5 ml of contrast medium directly into closed small bowel segments of equal length. Ten rats had a ligature applied to the anterior mesenteric artery and vein via laparotomy, 10 animals had a ligature of the vein only and 8 had no vascular occlusion (operated controls). In addition, 3 rats (non-operated controls, normals) were gavaged with a similar volume of the same contrast medium. Radiographs were obtained every hour. Biopsy samples and blood and urine tests were taken at the end of the 4-hour observation period. On radiographs, a marked increase of urinary bladder opacity was observed after 2 to 4 hours in the rats with both vessels tied. Correspondingly high iodine levels were measured in the urine and serum at 4 hours by x-ray fluorescence analysis. Urinary levels were 27 times and serum levels 8 times that of operated controls, respectively, and 81 and 25 times that of normals. Venous occlusion affected the bladder opacity to a lesser extent, giving urinary iodine levels 12 times and serum levels twice that of normal controls. Neither urinary nor serum iodine levels were significantly different from the operated controls. The operated controls had urinary concentrations of contrast medium 3 times that of the gavaged normal controls, but a barely visible urinary bladder on radiographs. Measuring iodine levels in serum or urine may be helpful in the evaluation of the degree of mucosal injury induced by intestinal ischaemia.