Intestinal and Peritoneal Absorption of Radioiodinated Cholografin and Renografin as an Experimental Test of Gastrointestinal Perforation

Abstract

During radiographic gastrointestinal examinations with water-soluble diatrizoate compounds (1–5), several investigators (1–3) have observed radiopaque substances in the urinary tract when gastrointestinal perforation was demonstrated. Since it is known that the water-soluble compounds are rapidly eliminated from the blood stream by renal excretion (6), these observations were interpreted as indicating that in the presence of intestinal perforation, significant absorption into the blood stream via the peritoneum occurs. The normal adult intestinal tract rarely absorbs significant amounts of diatrizoates (2, 7). From the previous studies, it seemed that a clinical test for intestinal perforation could be devised from these findings. The authors therefore performed a series of experiments to test the validity of the clinical evaluations and, further, to determine the absorption and distribution of radioisotope-tagged diatrizoate methyl glucarnine (Renografin I125) and iodipamide sodium (Cholografin I131) from the gastrointestinal tract and pertioneal cavity in dogs. In addition, the absorption of Renografin I125 from the gastrointestinal tract in normal man was determined. The use of the radioisotope-labeled compounds suggested an additional means of diagnosis of intestinal perforation which could be rapidly and simply performed at the bedside. Method A. Laboratory Animals: Nine experiments were performed in 7 adult mongrel dogs, 6 female and 1 male, weighing between 11 and 17 kg. Pentobarbital sodium (30 mg/kg, intravenous) was used for anesthesia. The different experiments performed are listed in Table I. Unilateral femoral artery polyethylene cannulas were employed to monitor the blood pressure and to obtain arterial blood samples. In 2 animals hypotension was induced by hemorrhage. Mean aortic blood pressure in these dogs was maintained in the range of 45 to 75 mm mercury. The hypotensive animals were intubated and respirations sustained with a Harvard respirator; in all other dogs only indwelling tracheal intubation was performed. Jugular vein catheters were introduced in 2 dogs and advanced to the level of the right atrium. Urine samples were obtained from the females by in-dwelling soft rubber urethral catheters. In the male, bilateral polyethylene ureteral catheters were inserted through a lateral abdominal extraperitoneal exposure. The test agents were introduced orally by means of rubber gastric tubes. Intra peritoneal injection was accomplished by direct needle puncture of the abdominal wall with a 21 gauge needle. A 1 to 2 ml volume of the test agent was introduced with a 2 cc tuberculin syringe. In dogs receiving the agents orally, an additional 5 ml of isotonic saline was used to express residual test material from the gastric tube into the stomach. The position of the tip of gastric tubes in the stomach was confirmed by auscultation and a test injection of air.