Water-Soluble Contrast Agents in Small Bowel Obstruction: A Useful Discriminator

Abstract

AJR 2012; 199:W783 0361–803X/12/1996–W783 © American Roentgen Ray Society Water-Soluble Contrast Agents in Small Bowel Obstruction: A Useful Discriminator We read with great interest the review article, “Small Bowel Obstruction,” by Mullan et al. [1] in the February 2012 issue of the AJR. The article provides a practical overview of a frequently occurring situation in abdominal diagnostic radiology. However, we disagree with the authors on a significant topic: namely, the usefulness of abdominal radiography after ingestion of a water-soluble contrast agent. We would like to suggest the use of water-soluble contrast agents not only for diagnostic but also for therapeutic purposes. This practice may eliminate the need for surgery and decrease the length of hospital stays. Over the past decade, the use of watersoluble contrast agents in small bowel obstruction caused by adhesions has been the subject of several randomized controlled trials published in surgical journals. Its use has therefore been incorporated in the diagnostic workup of patients who present with small bowel obstruction suspected to be due to adhesions. Consequently, we receive an increasing number of requests for a conventional abdominal radiography in patients who have ingested a water-soluble contrast agent. The appearance of contrast medium in the colon within 24 hours after ingestion of a water-soluble contrast agent predicts resolution of the obstruction without the need for surgery with high sensitivity (0.97), specificity (0.96), and receiver operating characteristic value (0.98) [2]. The administration of watersoluble contrast agents significantly reduced the length of hospital stay. A reduction in the need for surgery is claimed by some authors [3, 4] but denied by others [2]. Figure 1 shows that contrast medium has progressed to the jejunum at 8 hours after administration and the ascending colon at 24 hours. The proposed therapeutic mechanism of water-soluble contrast agents is related to their hyperosmolarity (approximately six times that of extracellular fluid). This promotes shifting of fluid into the bowel lumen, which decreases the pressure gradient over the obstruction, which distends collapsed bowel segments, dilutes the contents, and facilitates passage of water that is attracted to the hyperosmolar contrast medium [3]. Water-soluble contrast agents are relatively safe to use, even if a perforation occurs. Barium contrast material does not appear to be a useful alternative. The use of barium holds risks because it may lead to complete obstruction by decreasing the viscosity of bowel contents. Moreover, in case of perforation, leakage of barium to the abdominal cavity is potentially lethal [3]. In conclusion, the use of water-soluble contrast agents can be of diagnostic and therapeutic effect in cases of adhesive small bowel obstruction. Hein P. Stallmann Jaap Borstlap Thomas L. Bollen St. Antonius Hospital, Nieuwegein, The Netherlands