Types of intestinal atresia. From Sinha CK, et al. Intestinal Atresia. In: Handbook of Pediatric Surgery, Sinha CK, Davenport M, eds. Springer; 2010, pg. 97. Reprinted with permission.
Intestinal atresia is classified into four categories. Type I is the least common of the four, in which the serosa and muscularis layers of the intestine remain intact. In contrast to the other types of atresia, there is no discontinuity in the bowel and a slight decrease in diameter of the bowel distal to the atresia is the only abnormality visible external to the intestine. The obstruction in this type of atresia is due to a diaphragm of mucosa or submucosa, which occludes the lumen of the bowel. Intestinal stenosis, a condition in which the bowel lumen is merely narrowed and not completely obstructed, is associated with Type I deformities and managed similarly. In Type II intestinal atresia, no layers of the bowel wall are in continuity and a fibrous band connects the proximal and distal segments of intestine. The most common intestinal atresia is type III and it is divided into two subtypes. Type IIIA is similar to Type II; however, no fibrous band connects the segments of bowel in discontinuity. Type IIIB is also known as the apple peel or Christmas tree deformity. Both bowel and mesentery are in complete discontinuity allowing the distal bowel to corkscrew around its mesenteric arterial supply, giving it an apple peel appearance. Type IV atresia is a combination of multiple Type II and IIIA segments of atresia. Multiple areas of discontinuous bowel segments are involved, some of which are connected by fibrous bands (“chain of lake” appearance) . This atresia is likely a result of multiple insults to the small bowel vasculature, such as embolic debris .
Although typically diagnosed in the early postnatal stage, diagnosis of intestinal atresia with prenatal ultrasound is possible in about 30–40 % of cases. This allows planning for the delivery at an appropriate facility [4, 10]. Prenatal ultrasound can detect findings associated with intestinal atresia, such as dilated echogenic loops of bowel greater than 7 mm in internal diameter and ascites, during the late second trimester and onward [1, 4, 10–12] (Fig. 26.2). Polyhydramnios are present in about 15–20 % of cases . In general, proximal obstructions are more easily detected prenatally because bowel loops are more extensively dilated and polyhydramnios is more significant .
Dilated loops of bowel seen on prenatal ultrasound. From Couture A. Bowel Obstruction in Neonates and Children. In: Baud C, et al. Gastrointestinal Tract Sonography in Fetuses and Children: Springer; 2008, pp 131–251. Reprinted with permission.
Average gestational age at birth of infants with intestinal atresia is 36–37 weeks [4, 13]. The presentation varies according to the location of the obstruction. Patients with proximal obstructions most frequently present with bilious emesis in the first 24–48 h, while abdominal distension is the primary feature of distal lesions and vomiting is a late symptom . A focused physical exam can reveal findings suggestive of volume depletion, such as dry mucous membranes, sunken fontanelles, and decreased skin turgor. These infants are at high risk for aspiration and should be monitored closely for signs of respiratory compromise. After the initial exam, serial abdominal exams should be performed to assess progression of the obstruction and monitor for signs of perforation with peritonitis. Diagnosis of intestinal stenosis is more demanding. Patients will show more subtle symptoms associated with a partial obstruction and often present later with failure to thrive. No laboratory studies are indicative of intestinal atresia or stenosis; however, it is important to monitor and correct electrolyte and acid–base disturbances.
Once an intestinal obstruction is suspected, initial management consists of holding feeds, fluid resuscitation with electrolyte replacement, correction of acid–base disturbances, and gastric decompression with an orogastric or nasogastric tube to suction. Parenteral antibiotics are indicated if there is concern for sepsis. After these initial steps are taken, further workup including imaging studies can be carried out to determine the level and cause of obstruction. Supine and decubitus plain X-rays are the first imaging studies performed. Expected findings include dilated gas filled loops of small bowel and absence of distal air. Although non-specific, these radiographic findings frequently establish the diagnosis in combination with the clinical exam . If there is concern for volvulus, malrotation, or a partial obstruction, an upper GI study should be obtained. Water-soluble contrast enema can be indicated in selected cases prior to surgical repair to exclude concomitant colonic atresia. It is important to note that in the setting of pneumoperitoneum, shock, or peritonitis, these imaging studies should not delay surgical treatment (Fig. 26.3).
Abdominal X-ray at 24 h of life in infant with jejunal atresia. Proximal dilated loops of small bowel are seen with no gas in distal bowel. From Couture A. Bowel Obstruction in Neonates and Children. In: Baud C, et al. Gastrointestinal Tract Sonography in Fetuses and Children: Springer; 2008, pp 131–251. Reprinted with permission.
Early operative repair is preferred in order to decrease the risk of the perforation or necrosis of the bowel and aspiration pneumonia. There are several important considerations that should be made prior to surgery: Hirschsprung’s disease can mimic intestinal atresia and should be ruled out with rectal suction biopsies in suspected cases . Intestinal atresia can also occur alongside gastroschisis, which can significantly change the course of repair of the atresia. Surgical options include primary repair of the atresia during closure of the abdominal wall or a more conservative approach, involving abdominal wall closure with or without stoma and secondary repair.
Prior to surgery, all patients should be managed with gastric decompression via an orogastric or nasogastric tube and intravascular fluid resuscitation with correction of electrolyte and acid–base disturbances. Necessary laboratory studies include type and screen, complete blood count, basic metabolic panel, and coagulation profiles. Water-soluble contrast enema should be considered to confirm patency of the colon . Determining the appropriate timing of surgery requires balancing the advantages of optimization from a respiratory, cardiac, and metabolic perspective with the risks of delayed repair, such as vomiting, aspiration, sepsis, and parenteral nutrition .
In the operating room, basic laparoscopic instruments, a bowel stapler, suction, and a suction biopsy kit will be necessary.
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