Contrast Agents for Ileus and Obstruction

Following abdominal pelvic surgery, intestinal activity may be considerably decreased or even absent. This may be secondary to a postoperative ileus or an early small-bowel obstruction. Various studies have shown that postoperative electrical activity in the GI tract is recovered most rapidly in the small bowel, then the stomach, and finally in the colon [56-59]. This correlates well with multiple-contrast studies that showed the colon recovering last as well [60-64]. Therefore, there is good physiological basis for the postoperative appearance of an air-and fluid-distended small bowel with little or no colonic contents. The differentiation between ileus, incomplete and complete small-bowel obstruction is an important although difficult one. As many as 58% of patients with small-bowel obstruction in the early postoperative period require reoperation [65]. The administration of hyperosmolar water-soluble contrast medium has been proposed as a way of differentiating ileus from small-bowel obstruction [66-69] as well as a means of separating incomplete from complete small-bowel obstructions [70].

In addition, some authors have studied the possibility of a therapeutic effect of hyperosmolar water-soluble contrast medium in cases of small-bowel obstruction [70-72]. This hypothesis is based on the shift of fluid into the gut due to an osmotic gradient. The increased liquid content stimulates bowel motility, helping transport contents distally [73-75]. The results from this and other studies are disparate and contradictory. In addition, anecdotal reports of success and failure are almost as numerous as the number of surgeons and radiologists queried.

One large prospective but nonrandomized trial concluded that high osmolarity, water-soluble contrast medium did not aid in the resolution of ileus following gynecological surgery [69]. Another randomized trial revealed that high osmolarity, water-soluble contrast medium significantly shortened the hospital stays of patients with adhesive small-bowel obstruction [72]. Less surgical intervention was needed in patients receiving these contrast agents as well.

Another, albeit noncontrolled study showed that high osmolarity, water-soluble contrast media help differentiate incomplete from complete small-bowel obstructions [70]. The authors stated that contrast medium appearing in the colon in less than 8 hours from its administration had sensitivity of 90%, specificity of 100%, and accuracy of 93% in predicting nonsurgical outcome of these patients. However, contradicting these reports is another prospective, randomized trial that found no difference in length of stay, relief of symptoms, or rate of surgical intervention in patients given high osmolarity water-soluble contrast medium versus those treated conservatively [71].

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