Intestinal Surgery in the Newborn—Atresias, Volvulus, and Everything Else

Pathophysiology

Intestinal atresia is the most common cause of obstruction in the neonate, affecting approximately 1.6 per 10,000 newborns, with duodenal atresia making up approximately 60%. Although all forms of intestinal atresia result from some anomaly in normal embryonic development, the clinical implications vary based on their anatomic locations.

Duodenal atresia occurs most commonly as an error in early embryonic development. In the past, it was thought that duodenal development required a series of complex proliferation followed by recanalization steps and that failure to recanalize in the proximal gut results in the obstruction or stenosis. However, there is little evidence to support this notion, and it is more likely that duodenal atresia reflects an error in the complex steps that underlie normal intestinal development. For reasons that are not well understood, there is a high association with cardiac and urogenital anomalies, VACTERL (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities), and other GI anomalies such as malrotation, annular pancreas, esophageal atresia, and imperforate anus. Approximately 30% of cases are associated with trisomy 21, and 3% to 8% of trisomy 21 patients are born with atresia. ^, Duodenal atresia is classified into three main categories, shown in Table 83.1 .

Jejunoileal atresia may occur anywhere in the remainder of the small bowel. In elegant experiments on dogs, vascular occlusion resulted in the development of intestinal changes that mimic atresia, although there is little evidence that ischemic insult acquired in utero during fetal development occurs in patients with atresia. Although some researchers have hypothesized that the affected bowel becomes necrotic and subsequently involutes and resorbs, leaving blind proximal and distal ends with a widely varied extent of involved or absent bowel, there is no evidence for necrosis or involution in patients with atresia. In-utero volvulus, internal hernia, and even in-utero intussusception may occur, leading to broad disruption of the gastrointestinal (GI) tract, but these are distinct entities from the commonly seen instances of intestinal atresia. In select cases, arterial vasoconstriction or thrombosis precipitated by maternal smoking, drug use, medications, or inherited thrombophilias have been thought to play a role, although the vast majority of cases of intestinal atresia lack any identifiable risk factor for thromboembolic disease. Similar to duodenal atresia, patterns of jejunoileal atresia have been classified into four main groups (see Table 83.1 ).

Colonic atresia is the least common location, and its etiology is unknown. It may be seen in conjunction with small-intestinal atresia and can be associated with Hirschsprung disease and gastroschisis.

Clinical Features

Prenatal diagnosis of intestinal atresia is increasingly common with improvements in sensitivity of ultrasound; however, fewer than half of patients are diagnosed before birth. Sonographic signs include polyhydramnios and dilatation of the proximal small bowel with distal decompression. Sensitivity increases with more proximal lesions, because the bowel becomes more distended with swallowed amniotic fluid that the short proximal segment is unable to fully absorb. Duodenal atresia classically exhibits a “double bubble” sign with distention of the stomach and first portion of the duodenum and is the most commonly discovered prenatally, whereas colonic atresia is infrequently prenatally diagnosed unless more proximal involvement is also present. ^,

Postnatally, infants will present with signs of intestinal obstruction including persistent or forceful emesis and abdominal distention; however, this varies by location and extent of involved bowel. Duodenal atresia will result in gastric distention and early emesis that may be bilious depending on the location of the atresia in relation to the ampulla of Vater. Passage of meconium is common in these infants. Neonates with jejunoileal atresia will typically have increased abdominal distention and bilious emesis within the first 2 days of life and usually will not pass meconium. Colonic atresia exhibits the most distended abdomen because the entire bowel may fill with air and enteric contents, and it tends to present the latest.

Evaluation

Prenatal suspicion (polyhydramnios, sonographic double bubble) or postnatal signs of obstruction (persistent emesis, abdominal distention) should trigger further evaluation for intestinal atresia including history, physical exam, and family history of associated congenital anomalies. The timing and onset of distention and emesis, presence or absence of bilious emesis, and passage of meconium should be noted and the abdomen assessed for tenderness and distention. Peritonitis may suggest the presence of intestinal perforation or compromised bowel. Inspection for associated congenital anomalies should be performed. Basic chemistry labs may reveal associated metabolic derangements secondary to persistent emesis.

Abdominal x-ray is generally the first imaging study to further assess the extent and pattern of intestinal dilatation and presence of free air or pneumatosis, which would prompt urgent operative exploration. The “double bubble” sign on plain film with gasless distal bowel is again seen in duodenal obstruction due to air-filled gastric and duodenal dilatation; however, this may not be seen in very proximal atresia. Findings of distal gas with a “double bubble” sign are more consistent with a partial duodenal obstruction or more rarely can be seen with anomalous bile duct anatomy. More distal obstruction will again exhibit a dilated proximal bowel with air fluid levels and decompressed gasless distal bowel. Colonic atresia will show dilated colonic loops, often with a ground-glass or soap-bubble appearance on plain radiograph. Preoperative screening echocardiography and head and abdominal ultrasound are performed to assess for associated anomalies that may affect timing of any planned intervention. Malrotation with or without midgut volvulus can mimic atresia, and an upper GI water-soluble contrast study should be performed emergently if the diagnosis is in doubt. This test may also demonstrate the location of atresia for preoperative planning. Contrast enema may also be performed to elucidate the extent and location of distal atresia and will often demonstrate a microcolon due to lack of use, as well as inability to advance contrast into the dilated proximal loops.

Management

Antenatal suspicion for intestinal atresia warrants transfer of care to a center with availability of pediatric surgical consultation. Initial postnatal management includes withholding of feeds and prompt placement of a decompressive nasogastric tube to prevent aspiration. Infants with significant emesis or enteric tube output are susceptible to dehydration and electrolyte abnormalities and should receive intravenous resuscitation and electrolyte replacement. Broad-spectrum intravenous antibiotics are started for sepsis prophylaxis against GI bacterial translocation and for perioperative prophylaxis.

Definitive management is surgical in all types of intestinal atresia, with the principles being relief of obstruction and restoration of continuity while preserving functional bowel and minimizing long-term complications. The operative approach differs by anatomic location and subtype, however. Multiple techniques have been described to repair duodenal atresia since its initial report by Ladd in 1931, including duodenojejunostomy, side-to-side duodenoduodenostomy, and partial web excision; however, the current standard described by Kimura is the diamond-shaped duodenoduodenostomy. The dilated duodenum is mobilized, and a handsewn anastomosis is performed between a transverse incision in the dilated proximal duodenum and a longitudinal incision in the distal duodenum. This technique was found to have earlier anastomotic function and lower long-term stricture rates. Certain cases of type 1 duodenal atresia may be amenable to simple excision of the duodenal web through an anterior duodenotomy; however, great care must be taken to identify and preserve the ampulla of Vater, as it is generally located at the same level as the web. Gentle compression of the gallbladder may aid in identification of the ampulla by visualization of bilious output in the duodenum. Some infants—typically those with extremely low birth weight—may benefit from a duodenojejunostomy due to its relative technical ease, and this is our strong preference. Laparoscopic repair of duodenal atresia is increasingly being used, and in experienced hands, long-term outcomes compared with open have been similar and with shorter hospital stays and time to advancement to full feeds.

Atresia of the jejunum is less amenable to laparoscopic repair due to obscuring distention of multiple loops of small bowel and is generally treated with an open approach. The atretic area or areas are identified and resected with primary end-to-end or end-to-side anastomosis. In very small or unstable infants with distal small bowel atresia, an end ileostomy or jejunostomy with mucous fistula may be performed with subsequent delayed bowel anastomosis at 2 to 4 months of age. Primary web excision through an enterotomy for type 1 lesions are seldom performed given the risk for recurrence and stricture.

Colonic atresia may develop into a closed loop obstruction if an intact ileocecal valve is present, and emergent surgical consultation is necessary. Colonic atresia is mostly treated with resection of atretic bowel and either primary anastomosis or staged anastomosis depending on the overall stability of the patient.

Due to the increased risk of multiple sites of atresia, saline or air should be injected intraoperatively into the distal bowel to detect additional sites of obstruction. Size mismatch of proximal and distal segments is an expected occurrence that may complicate primary anastomosis and lead to dysmotility. It is important to resect the proximal bowel for some distance to optimize motility and function. Tapering enteroplasty may be used in cases in which the intestine is very dilated, and it involves a longitudinal resection of the antimesenteric portion of the proximal dilated bowel to equilibrate the two sides of the anastomosis. We perform the tapering enteroplasty over a large red rubber catheter and use stapling devices to remove the antimesenteric dilated bowel. Concomitant anomalies requiring additional procedures at the time of the initial operation are also common. Those infants with intestinal malrotation should undergo a Ladd’s procedure with appendectomy at initial presentation, and those with imperforate anus should undergo initial temporary colostomy.

Long-Term Outcomes

Although postoperative complications are common after correction of intestinal atresia, overall long-term outcomes are quite good if treated promptly and appropriately. Postoperative adhesive bowel obstructions and anastomotic strictures can occur and may warrant reoperation. Other common perioperative complications include prolonged ileus, anastomotic leak, wound infection, late adhesive bowel obstruction, and colostomy prolapse and retraction. Duodenal atresia has 0% to 4% operative mortality and up to 10% overall mortality, mostly attributable to comorbid congenital anomalies including complex cardiac anomalies. ^, Jejunoileal atresia has a low association with complex cardiac malformations and therefore has low early mortality (<1%); however, it has greater overall major morbidity and mortality (16% overall in-hospital mortality) related to an increased extent of resection and complications of intestinal failure and sepsis. ^, Colonic atresia, if diagnosed early, has excellent prognosis with survival to discharge approaching 100% ; however, outcomes become significantly worse with delayed diagnosis and progression to gangrene and perforation. In long-term follow-up, patients with intestinal atresia grow up to have quality of life similar to that of healthy controls, with major differences attributed largely to associated conditions such as trisomy 21 and not to decreased GI quality of life.