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.