The use of surgical procedures to control morbid obesity, a condition that affects more than 5 million Americans , has been around for a long time. Currently, interest is focused on the stomach and various procedures to control its capacity and absorptive ability. Previously, a not uncommon procedure was jejunoileal bypass . This was introduced in 1963 but is no longer performed. However, it is possible that one will be called upon to examine the abdomen and GI tract of an individual who has undergone the procedure.
Jejunoileal bypass consists of bypassing most of the length of the small intestine, thereby limiting the amount of mucosa available for absorption. A variable amount of jejunum is anastomosed either to the distal or terminal ileum  or to the right colon . The bypassed portion of small bowel is then anastomosed either to the terminal ileum or to the colon [115,116]. Various complications may ensue, including inflammation of the bypassed segment [117,118], hyperoxaluria and renal lithiasis [119,120], and cholelithiasis .
Wade and his colleagues reported that during the first postoperative year both the length of the small bowel and its caliber will increase compared with baseline studies . This most likely represents an adaptive mechanism in response to the surgery. Because of the limited amount of mucosa available for water resorption, air-fluid levels are commonly seen postoperatively on horizontal beam radiographs . In addition most patients will show an increase in the thickness of the valvulae conniventes . In the distal ileum this may become so marked that the bowel resembles the more proximal jejunum, so-called jejunization of the ileum . The colon likewise dilates. Occasionally diffuse dilatation of the colon may be seen with the appearance of a so-called megacolon [115,122]. Another plain radiographic finding is that of pneumatosis intestinalis [118,123]. Besides being the location for bacterial overgrowth with resultant enteritis and malabsorption, the bypassed limb may be the site of jejunoileal intussusception [124-126]. Both CT and ultrasound scans have been reported to detect this complication. Routine contrast studies would not be expected to reflux into the bypassed loop to detect an intussusception. On ultrasound, an echogenic mass with a hyperechoic center and sonolucent rim may be seen . On CT images, the typical findings of an intussusception, with a target or doughnut configuration, have been described .
Contrast studies of the small bowel will demonstrate the increased diameter (Fig. 5.45) as well as the thickened valvulae conniventes (Fig. 5.46). More than 80% of patients will demonstrate reflux of the contrast medium into the bypassed segment of small bowel  (Fig. 5.46). The jejunoileal anastomosis is readily seen on contrast studies (Figs. 5.45 and 5.46). The distance refluxed into the bypassed limb is usually less than 30 cm and does not correlate with the amount of weight loss .
Figure 5.45. Jejunoileal bypass for obesity. Overhead film from a small-bowel series reveals a very short segment of opacified jejunum with considerable filling of the right colon with barium. Note the compensatory dilatation of the jejunum.
Figure 5.46. Jejunoileal bypass for obesity. Overhead film from a small-bowel series shows limited opacification of the jejunum secondary to a jejunoileal bypass. A small amount of contrast has refluxed into the bypassed segment of ileum in the right lower quadrant. Also evident is dilation and fold thickening with the jejunum, presumably an adaptive change following the bowel short-circuiting.
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