High Small Bowel Obstruction
High small bowel obstruction includes atresia or stenosis of the jejunum or proximal ileum. It is now generally accepted that intestinal atresia and ste a
Fig. 1.13a-c. "Whirpool" sign of midgut volvulus. A 12-day-old female with bilious vomiting. a Transverse B-mode sonography of the upper abdomen shows the twisting of bowel, mesentery, and superior mesenteric vein around the axis of the superior mesenteric artery. b Color Doppler image demonstrates a circle of vascularity that represents the superior mesenteric vein twisting around the superior mesenteric artery, producing the characteristic "Whirlpool sign". c Upper gastrointestinal series confirms midgut volvulus b a nosis below the duodenum are caused by an intraabdominal vascular accident during intrauterine life. The vascular accident may be primary or secondary to a mechanical obstruction, as in the case of in utero volvulus. This results not merely in a hindrance of growth, but also in an actual disappearance of the affected portion of the fetal bowel (Powell and Raffensperger 1982). Jejunoileal atresias are classified into four types based on their anatomic appearance (Touloukian 1993). Type I is a simple intraluminal diaphragm, and accounts for 32% of jejunal atresias. In type II, the proximal bowel terminates in a blind end and the distal bowel commences similarly, the two ends being joined by a fibrous band. In type III, the proximal and distal blind ends are completely separated with no connecting band. The adjoining mesentery always has a V-shaped defect corresponding to the missing segment. The familial form of multiple atresias is considered type IV. A rare form of inherited jejunal atresia is the "apple-peel mesentery", also called the "Christmas-tree mesentery." This abnormality is the result of a catastrophic in utero vascular accident, producing an interruption of the distal superior mesenteric artery that leads to atresia of a large segment of small bowel and mesentery. The proximal segment is dilated, whereas the collapsed distal segment is spiraled around its vascular supply and resembles an apple peel. The blood supply is retrograde through the anastomotic arcade of the inferior mesenteric artery (Leonidas et al. 1978; Manning et al. 1989). This defect has historically been associated with high mortality, although recent reports suggest an improved prognosis (Waldhausen and Sawin 1997).
Jejunal atresias comprise approximately 50% of small bowel atresias, and in 10% of the cases, there are multiple areas of atresia (De Lorimier et al. 1969). Jejunal atresia is clinically characterized by bilious vomiting, frequently delayed until after the first feeding, and abdominal distension. The lower the obstructive lesion in the small bowel, the more severe the abdominal distension, and the more difficult the accurate localization of the site of obstruction is (Godbole and Stringer 2002).
The diagnosis is usually apparent on the plain films. The abdominal radiograph shows a few dilated bowel loops (three or four air bubbles), more than in the case of duodenal atresia and fewer than in ileal atresia or in other causes of low bowel obstruction (Fig. 1.14). The loop just proximal to the site of the atresia is frequently disproportionately dilated with a bulbous end. There is no air in the lower portion of the abdomen; this is observed most clearly in the upright film (Rathaus and Grunebaum 1992) (Fig. 1.15). The colon cannot be identified and air
Fig. 1.14a,b. Jejunal atresia. a Supine radiograph shows a few dilated, air-filled intestinal loops, about four "bubbles", which indicates a high obstruction. b Surgical image demonstrates the location of the atresia (arrow), the dilated proximal jejunum, and the small caliber of the bowel distal to the atresia
Fig. 1.14a,b. Jejunal atresia. a Supine radiograph shows a few dilated, air-filled intestinal loops, about four "bubbles", which indicates a high obstruction. b Surgical image demonstrates the location of the atresia (arrow), the dilated proximal jejunum, and the small caliber of the bowel distal to the atresia is not found in the rectum. These signs indicate an obstructive lesion in the small intestine, and surgery is mandatory. Here, also when the obstruction can be definitely identified in the small intestine, there is no need to delay surgery to give contrast material orally. An upper gastrointestinal series is clearly not indicated. In fact, flocculation and dispersion of the contrast given orally may occur, due to the high mucus content of the distended segment, and little information is obtained. Occasionally, the dilated bowel loops may be fluid-filled giving an airless abdomen. In cases of doubt, aspiration and insufflation of air through a nasogastric tube should be carried out (Fig. 1.16).
Fig. 1.15a,b. Jejunal atresia. Anteroposterior (a) and lateral (b) upright radiographs show a few central air-fluid levels indicating high obstruction
Fig. 1.15a,b. Jejunal atresia. Anteroposterior (a) and lateral (b) upright radiographs show a few central air-fluid levels indicating high obstruction b a a
Fig. 1.16a,b. Jejunal atresia. a Supine radiograph shows an airless abdomen. b Aspiration and insufflation of air through a nasogastric tube was performed and adequately demonstrates the point of obstruction (arrow). Massively dilated loops of jejunum but only about three "bubbles" give indication of a high obstruction
Fig. 1.16a,b. Jejunal atresia. a Supine radiograph shows an airless abdomen. b Aspiration and insufflation of air through a nasogastric tube was performed and adequately demonstrates the point of obstruction (arrow). Massively dilated loops of jejunum but only about three "bubbles" give indication of a high obstruction b a
Although a patient with jejunal or proximal ileal atresia usually needs no further radiologic investigation, contrast material enema examinations are commonly performed to attempt to exclude second and third areas of atresia lower in the bowel. The colon in isolated jejunal and proximal ileal atresia, as in duodenal atresia, is normal or near normal in size. If a microcolon is encountered, additional distal atresia should be suspected (Hernanz-Schulman 1999). A contrast enema is especially indicated when the scout radiograph shows distension of the flanks and elevation of the diaphragms indicating the presence of multiple dilated loops of the bowel filled with fluid distal to the obstruction. If the ischemic event that produced the atresia caused a perforation, there may be evidence of meconium peritonitis with peritoneal calcification. The apple peel type of atresia does not have distinctive findings on plain film (Fig. 1.17).
Sonography has a role in high intestinal obstruction, especially in patients with lack of air in the gastrointestinal tract whenever marked distension of the flanks and elevation of the diaphragms is observed on the plain radiograph. In such cases, sonography is useful to differentiate the presence of multiple dilated loops filled with fluid from ascites (Fig. 1.18). It is also useful in demonstrating associ ated anomalies in the abdominal organs (HaYdeN 1991; Jouppila and Kirkinen 1984).
Severe congenital stenosis of the small bowel is usually accompanied by vomiting and abdominal distension, identical in severity to that seen in atresia. In less severe cases, these symptoms may be mild or even delayed for several days or weeks. Plain abdominal radiographs reveal dilatation of bowel loops proximal to the stenosis and normal or decreased quantity of air in the small bowel distal to the stenosis (McAlister et al. 1996).
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