Contrast radiography and intestinal obstruction.

Radiologic techniques using contrast have emerged as a valuable addition in the management of patients with acute intestinal obstruction. Historically, the evaluation of such patients involved only conventional radiology, with upright and supine abdominal x-rays to confirm the diagnosis of obstruction and suggest the presence of ischemic changes. Gastrointestinal studies with barium and water-soluble oral contrast, computed tomography (CT) with oral contrast and, more recently, other techniques such as ultrasonography and magnetic resonance imaging have been employed in the management of these patients. Contrasted radiographic techniques may yield important information about several of the diagnostic issues that arise in the patient with suspected intestinal obstruction. One use is to clarify whether or not obstruction is present when the abdominal films and clinical evaluation are equivocal. Another is to clarify whether intestinal obstruction is partial or complete since this will have important implications in management. A third use is to identify the possible cause of obstruction. Finally, these techniques give additional information that may clarify whether or not ischemic changes are occurring. The role of contrast radiographic techniques in identifying obstruction in patients with an equivocal clinical presentation is well established. 1,2 Computed tomography with contrast and small bowel radiography with either barium or oral water soluble contrast can differentiate obstruction from ileus. Contrast radiography is also fairly accurate in determining partial versus complete intestinal obstruction. 1,2 Computed tomography with contrast will identify a transition point with decompressed distal bowel. Small bowel follow-through will likewise demonstrate a point of partial obstruction with movement of contrast beyond the point of narrowing if the obstruction is partial. Depending on the level of obstruction, contrast studies using barium may give more mucosal detail and more clearly delineate the anatomy. The relative importance of potential complications with these agents (e.g. aspiration of water-soluble contrast and barium peritonitis) is not clear. These techniques can also provide additional information about whether or not ischemic changes are developing in the bowel. Computed tomography is particularly valuable in this regard, as it may show earlier signs of ischemia than other contrast techniques or plain abdominal x-rays. The presence of pneumoperitoneum, bowel wall changes, mesenteric inflammation, and intraabdominal fluid collections can be ascertained. A final benefit of these techniques in diagnosis would be identifying a potential cause for the obstruction or ileus. Computed tomography may show other evidence of disease, such as in the adjacent mesentery, or other organs, such as the liver or pancreas. Furthermore, CT will give additional information about the colon, such as thickening suggestive of inflammatory bowel disease, even if contrast does not reach this level. In clinical studies, CT with contrast has proven the most versatile in assisting in these diagnostic aspects of intestinal obstruction. Peck et al. 2 studied 55 patients having both computed tomography and small bowel follow-through studies to evaluate possible small bowel obstruction. They found that CT was significantly more sensitive (90% versus 50%) and had similar specificity (57% versus 57%) compared with small bowel follow-through. Computed tomography was particularly accurate in identifying high-grade partial obstruction and complete bowel obstruction. When CT was inconclusive, the small bowel follow through clarified a low-grade partial obstruction in 6 additional patients, which improved the accuracy from 81% to 93%. Thus, CT is the initial procedure of choice and is superior for detecting the cause of obstruction and the presence of strangulation. Furthermore, it can be obtained fairly quickly and does not need the constant attention of a radiologist. A more controversial role for radiographic materials has been a therapeutic one. Does the use of these agents hasten the recovery of intestinal obstruction or increase the rate of nonoperative resolution? Furthermore, which of these different techniques is most valuable in the management of the patient with intestinal obstruction? Water-soluble hyperosmotic solutions tend to draw fluid into the lumen of the intestine and increase motility. They may also diminish bowel wall edema, all of which may promote earlier and more frequent resolution of bowel obstruction. Assalia et al. 3 studied 99 patients with a total of 107 episodes of adhesive small bowel obstruction. The patients were randomized and half received conventional resuscitation and nasogastric suction. The other half additionally received 100 mL of Gastrografin through the nasogastric tube. Patients underwent operation within 48 hours if there was failure of this management. They found that patients receiving Gastrografin had a much shorter time to their first bowel movement (6.2 hours versus 23.3 hours), a lower rate of operative treatment (10% versus 21%), and shorter mean hospital stay (2.2 days versus 4.4 days). They subsequently advocated the use of orally administrated Gastrografin to aid in the resolution of obstruction. In another study, Feigin et al. 4 performed a similar prospective randomized trial of 50 patients with postoperative small bowel obstruction, comparing nonoperative treatment with or without the addition of oral water-soluble contrast. They permitted 5 days of nonoperative treatment if there was no concern about strangulation or peritonitis. They found no significant difference in the need for surgery, the time for the resolution of symptoms nonoperatively, or the length of hospital stay. In both studies, there were no differences in complication rate or complications related to the contrast material. Thus, the therapeutic value of Gastrografin remains controversial. Choi et al., 5 in an article in this month’s Annals, report a prospective randomized study to, as they describe, assess the therapeutic value of Gastrografin in the management of adhesive small bowel obstruction following unsuccessful conservative treatment. However, their study really addresses its diagnostic value in predicting the need for surgery, rather than its therapeutic role. In their study, 101 patients treated nonoperatively resolved their symptoms or showed significant improvement within 48 hours and had conservative treatment continued. Thirty-five patients who showed no improvement within 48 hours were randomized to receive a Gastrografin radiologic study or to undergo prompt operation. Of the 19 patients undergoing the Gastrografin study, a partial obstruction was demonstrated in 14, and nonoperative treatment was continued. Five patients with complete obstruction went on to laparotomy. The authors found that Gastrografin study significantly reduced the need for surgery by 74%. The overall hospital stay, however, was similar in these two groups. Thus, they demonstrated that radiographic studies in patients who have not initially responded to nonoperative treatment may be useful in determining which ones have a partial obstruction and can be further treated nonoperatively. This has been well established previously in retrospective studies. 1,2 However, their study does not address the issue of whether or not the contrast agent is of therapeutic value itself. While this is an interesting study and does validate the role of contrast radiography in diagnosis, it has done little to resolve the controversy of whether or not oral contrast has additional therapeutic benefits. In my view, CT has proven to be much more valuable than other contrasted radiographic techniques in the management of patients with suspected intestinal obstruction. As delineated above, it has several advantages, including providing additional information about the cause of obstruction and other contributing factors. Furthermore, it would have many of the same benefits because of the use of water-soluble contrast agents as part of this modality. Conventional contrast small bowel radiography would appear to be most valuable in resolving the issue of low-grade partial obstruction when the CT scan is inconclusive. The use of routine administration of oral contrast material as a therapeutic maneuver, even without the intent to obtain radiographs, will need to be studied further before it should be a routine part in the management of these patients.