SBFT is performed by having the patient ingest multiple cups of thin liquid barium and fluoroscopically evaluating the contrast column from the duodenal bulb to the terminal ileum. Frequent palpation under fluoroscopy should be performed to efface the small bowel loops to visualize aphthous ulcers and other radiographic features, in addition to assessing peristalsis and fixation of small bowel loops. Occasional overhead images provide a global view of diseased loops and their location. While large volumes of barium are generally used to speed the examination and unmask strictures and obstructing lesions, smaller volumes can also be used in patients unwilling to ingest the large volumes necessary for CT and MR enterography.

Several studies of patients with known or suspected Crohn’s disease who underwent cross-sectional enterography and SBFT by experienced fluoroscopists have been performed. They demonstrate slight but significantly decreased sensitivity and unchanged specificity for SBFT compared to CT enterography for detecting active mural inflammation [14–17]. When intubation of the terminal ileum can be successfully accomplished at colonoscopy, there is little improvement in cost effectiveness when performing additional SBFT; however, incremental effectiveness is substantial when terminal ileal intubation cannot be performed [18].

SBFT has several relative strengths compared to CT and MR enterography, which should be exploited in the appropriate clinical contexts. Real-time examination permits the best and easiest distinction between spasm, collapse and stricture. During CT enterography, usually only one acquisition of the bowel is performed to minimize radiation dose. Observation over time is permitted at fluoroscopy. Additionally, inexperienced radiologists not infrequently overlook jejunal inflammation at CT enterography (manifested by asymmetric wall thickening and hyperenhancement) or confuse it with the normal feathery appearance of the valvulae conniventes or jejunal collapse, which is observed in approximately one-third of routine CT enterography cases. Advanced jejunal inflammation can be entirely occult at routine abdominopelvic CT, when bowel loops are not distended. At fluoroscopy, advanced inflammatory changes cannot be confused with the jejunal fold pattern of the valvulae conniventes, as the bowel loops are markedly distorted by cobblestoning, linear ulcers with sacculation, and stricture formation (Fig. 3.5). While fluoroscopy can take longer when smaller volumes of barium are ingested, fluoroscopists can examine the patient over multiple time-points (sometimes several hours), so patients that are unwilling to consume large volumes of enteric contrast can be imaged. As such, fluoroscopy provides the best overview for complex postoperative anatomy, stricture mapping, as well as providing the easiest method for estimating small bowel length [19] (Fig. 3.6). As such, side-to-side anastomoses are sometimes mistaken at cross-sectional enterography for dilated segments proximal to a stricture, and such postoperative changes are easily determined at fluoroscopy.

Peroral pneumocolon is performed after a SBFT by insufflating air into the colon (Fig. 3.2). Air refluxes into the terminal or neo-terminal ileum to provide exquisite double contrast images of the ileal mucosa (Fig. 3.7). This double contrast technique is extremely useful as the distention allows excellent evaluation of anastomotic and ileal strictures (Fig. 3.8).

There are no prospective studies that we are aware of comparing cross-sectional imaging techniques to the SBFT with peroral pneumocolon for the detection of active inflammation. The strengths of this exam are that by achieving maximum distension spasm can be differentiated from strictures, and that double contrast visualization of the terminal ileal mucosa is achieved. Apthous ulcers can be detected. These findings can be particularly useful after ileocolic anastomosis, where there is generally some nonspecific inflammation at endoscopy and hyperenhancement at cross-sectional enterography (Fig. 3.9). Peroral pneumocolon is probably the best method to assess for mucosal inflammation at fluoroscopy in the presence of an ileocolic anastomosis, as air is easily refluxed into the distal small bowel.

There are several weaknesses of the SBFT, which should be considered. As mentioned, there is a sensitivity penalty in not performing cross-sectional enterography [14, 16], but in the presence of low probability of disease, the SBFT can add substantial confidence to ileocolonoscopy in making the correct diagnosis [18]. Mild jejunal disease can still be challenging, but moderate and advanced inflammation can be reliably detected. Unlike cross-sectional enterography, the mesentery, colon, anus, and appendix are not imaged, so the SBFT alone cannot reliably stage the full extent of Crohn’s involvement along the GI tract. Additionally, to detect penetrating disease by SBFT, barium must fill sinus tracts or fistulae. In contradistinction, fistulae and sinus tracts at cross-sectional enterography often do not contain enteric contrast but are easily recognized as enhancing, extraenteric tracts that stand out from the surrounding mesenteric fat and which cause tethering of involved small bowel loops [15, 17, 20]. The SBFT can be performed in patients with a small bowel obstruction but is rarely needed and is often unfruitful owing to the time required for examination.