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.

Urinary excretion of enteral iohexol in rats with intestinal ischaemia. The influence of size of ischaemic area and duration of exposure to contrast medium.

The urinary excretion of iohexol instilled via orogastric tube was evaluated in rats with ischaemic intestinal segments, simple bowel ligature, and normal bowel. The rats were observed for periods of 1, 2, 3, 4, 5, 6, and 8 h, respectively, after the instillation of 3 ml of contrast medium. Radiographs and blood and urine tests were taken at the end of each observation period. Distinct radiographic opacification of the urinary bladder of the rats with intestinal ischaemia was demonstrated already 2 h after the administration of contrast medium and onwards. Concurrently high iodine concentrations in the urine and serum were measured by an X-ray fluorescence technique. The bladder opacity and iodine levels in the urine varied in close proportion to the length of ischaemic bowel irrespective of the duration of enteric exposure to contrast medium. Overall mean urinary iodine levels were approximately 11 and 32 times that of normal controls in animals with ischaemic bowel segments of 15 and 45 cm, respectively. In comparison, the overall mean serum level in rats with 45-cm ischaemic segments was 16 times that of normals. The clinical implications are discussed.

Urinary excretion of iohexol administered enterally in rats with intestinal ischaemia. A transmural and transperitoneal route of transport.

Serum and urinary levels of iohexol (Omnipaque) were evaluated in 20 rats with 1.5 ml of contrast medium injected into closed segments of ischaemic small bowel. Ten rats had the small intestine situated inside, and 10 rats outside, the peritoneal cavity. Radiographs were taken every hour, and blood and urine were sampled for testing at the end of the 4-h observation period. A marked increase in opacity of the urinary bladder was seen on radiographs during the observation period in the rats with the bowel laid inside the peritoneal cavity. Correspondingly high concentrations of iodine in the urine and serum were measured by the X-ray fluorescence technique. In comparison, the animals with the bowel placed outside the peritoneal cavity had only traces of contrast medium in serum and urine. These differences between the two groups of rats were highly significant (p less than 0.001). The chief route of transport of contrast medium (greater than 90% of the total absorption) was transmurally and transperitoneally from the lumen of ischaemic bowel to blood before subsequent excretion via the kidneys.

Digital urography using stimulable phosphor. An experimental study in the rabbit.

In a urographic experimental study in six rabbits conventional film-screen images were compared with digitized images. Two digitized images were examined, one simulating the conventional film-screen combination, and one frequency modified. The nephrographic and excretory phases of four different doses of contrast medium (iohexol, 350 mg I/ml) were investigated in each rabbit (4, 2, 1, and 0.5 ml/kg body weight). No differences were found between the different doses of contrast medium for the two imaging systems. With digitized images the exposure (radiation dose) could be decreased to 12.5 per cent of the conventional film-screen combination without any loss of information.