Radiology: Little evidence to support imaging use in IBS
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Although it is widely used and may be associated with up to $10 billion in related annual medical costs in the U.S., there is little evidence supporting radiologic imaging in the diagnosis of irritable bowel syndrome (IBS), according to a review of medical literature, the results of which were published online Dec. 9 in Radiology.

IBS lacks characteristic imaging features, according to study author Owen J. O’Connor, MD, of the department of radiology at Cork University Hospital in Cork, Ireland, and colleagues. Because of this, symptom-based criteria are recommended for diagnosis.

“In clinical practice, however, radiologic imaging is performed in many patients with IBS, particularly in those with so-called alarm symptoms (i.e., symptoms concerning for underlying structural disease, which might be misclassified as IBS),” wrote the authors. “There is a paucity of information regarding the appropriate use of abdominal imaging in patients with IBS, and few studies have investigated typical diagnostic yields in this setting.”

To determine just how much evidence existed to support the use of imaging in IBS, O’Connor and colleagues searched a variety of clinical databases for terms such as “irritable bowel syndrome” and “colonography,” targeting dates between January 1, 1985, and July 1, 2010.

The researchers were not able to find a systematic review that specifically examined radiologic imaging in IBS. However, five articles in secondary literature sources partially addressed the topic. A PubMed search of primary literature yielded 1,451 articles, but upon review of their abstracts, only 111 were potentially relevant in addressing radiologic imaging in IBS. Two systematic reviews and five primary research articles were identified in this group with the primary research examining colonic investigations (colonoscopy and barium enema exams), ultrasonography or both. The incidence of structural disease in patients with concerning symptoms was low.

Based on the limited evidence, the authors concluded patients who fulfill the symptom-based criteria for IBS but do not exhibit concerning symptoms or have a family history of colorectal cancer, inflammatory bowel disease or celiac sprue do not require radiologic imaging.

“Widespread imaging in patients with IBS-type symptoms possibly stems from a persisting perception that it constitutes a diagnosis of exclusion,” wrote the authors. “Symptoms can mimic other conditions, and physicians often fear missing structural disease. These concerns can precipitate over investigation, increased healthcare costs, exposure to ionizing radiation and adverse events.”

O’Connor et al presented bowel perforation as an example of a potential complication. The perforation rate for colonoscopy is 0.07 percent and for CT colonography is 0.02 percent. With regard to the resources used by imaging patients with IBS, the authors wrote that IBS accounts for $1.7 billion to $10 billion in direct medical costs in the U.S. despite the lack of supporting evidence.

“Radiologic imaging may not be required in patients with IBS without potentially concerning symptoms but should be considered where such symptoms exist, and choice of imaging study should be influenced by predominant symptoms,” concluded the authors, adding that more definitive recommendations must await further research.