|
(See also Gastrointestinal Disorders in Neonates and Infants: Meconium Ileus; see Gastrointestinal Disorders in Neonates and Infants: Meconium Plug Syndrome.)
Obstruction of the jejunum and ileum can occur as the result of jejunoileal atresia, malrotation, intestinal duplication, or meconium ileus. Large-bowel obstruction is typically caused by Hirschsprung's disease, meconium plug syndrome, and colonic or anal atresia.
In 75% of cases, no history of maternal polyhydramnios exists because much of the swallowed amniotic fluid can be absorbed from the intestine proximal to the obstruction. These disorders, other than malrotation, intestinal duplication, and Hirschsprung's disease, typically manifest in the first few days of life with feeding problems, abdominal distention, and emesis that may be bilious or fecal. The neonate may pass a small amount of meconium initially but thereafter does not pass stools. Malrotation, intestinal duplication, and Hirschsprung's disease can manifest in the first several days of life or years later.
General diagnostic approach and preoperative management include giving nothing by mouth, placing an NGT to prevent further bowel distention or possible aspiration of vomitus, correcting fluid and electrolyte disturbances, taking a plain abdominal x-ray, and then doing a contrast enema to delineate the anatomy (the enema may also relieve obstruction in meconium plug syndrome or meconium ileus). For Hirschsprung's disease, a rectal biopsy is needed.
Jejunoileal Atresia
Jejunoileal atresia is incomplete formation of the jejunum, usually caused by an ischemic insult.
There are 5 major types of jejunoileal atresia:
Neonates with jejunoileal atresia usually present late during day 1 or on day 2 with increasing abdominal distention, failure to pass stools, and, finally, regurgitated feedings.
Plain abdominal x-rays are done; they may reveal dilated loops of small bowel with air-fluid levels and a paucity of air in the colon and rectum. Because about 10% of patients also have cystic fibrosis (nearly 100% if meconium ileus is also present), testing for that disease (see Cystic Fibrosis (CF): Diagnosis) should be done.
Treatment
Preoperative management consists of placing an NGT, giving nothing by mouth, and providing IV fluids. Surgical repair is the definitive therapy. During surgery, the entire intestine should be inspected for multiple areas of atresia. The atretic portion is resected, usually with a primary anastomosis. If the proximal portion of the ileum is extremely dilated and difficult to anastomose to the distal, unused part of the intestine, it is sometimes safer to do a double-barreled ileostomy and defer anastomosis until the caliber of the distended proximal intestine has diminished.
Prognosis is based on the length of remaining small bowel and the presence of the ileocecal valve. Infants who subsequently develop short bowel syndrome require TPN for extended periods. They should be provided continuous enteral feedings to promote gut adaptation, maximize absorption, and minimize the use of TPN. Infants should also be provided small amounts of nutrition by mouth to maintain sucking and swallowing.
Malrotation of the Bowel
Malrotation of the bowel is failure of the bowel to assume its normal place in the abdomen during intrauterine development.
During embryonic development, the primitive bowel protrudes from the abdominal cavity. As it returns to the abdomen, the large bowel normally rotates counterclockwise, with the cecum coming to rest in the right lower quadrant. Incomplete rotation, in which the cecum ends up elsewhere (usually in the right upper quadrant or midepigastrium), may cause bowel obstruction due to retroperitoneal bands (Ladd's bands) that stretch across the duodenum or due to a volvulus of the small bowel, which, lacking its normal peritoneal attachment, twists on its narrow, stalk-like mesentery. Other malformations occur in 30 to 60% of patients, most commonly other GI malformations (eg, gastroschisis, omphalocele, diaphragmatic hernia, intestinal atresia).
Patients with malrotation can present in infancy or in adulthood with acute abdominal pain and bilious emesis, with an acute volvulus, with typical reflux symptoms, or with chronic abdominal pain. Bilious emesis in an infant is an emergency and should be evaluated immediately to make sure the infant does not have malrotation and a midgut volvulus; untreated, the risk of bowel infarction and subsequent short bowel syndrome or death is high.
Plain films of the abdomen should be done immediately. If they show dilated small bowel, a paucity of bowel gas distal to the duodenum, or both (suggesting a midgut volvulus), further diagnosis and treatment must be done emergently. Barium enema typically identifies malrotation by showing the cecum outside the right lower quadrant. If the diagnosis remains uncertain, an upper GI series can be done cautiously.
The presence of malrotation and midgut volvulus is an emergency requiring immediate surgery, which consists of Ladd's procedure with lysis of the retroperitoneal bands and relief of the midgut volvulus.
Intestinal Duplication
Intestinal duplications are tubular structures attached to the intestines that share a common blood supply; their lining resembles that of the GI tract.
Intestinal duplications are uncommon. The most common site of duplication is the jejunum and ileum followed by the esophagus, stomach, colon, and duodenum. Colonic duplication is often associated with anomalies of the urogenital system. Intestinal duplications usually manifest in the 1st or 2nd yr of life. Duplications can be asymptomatic or cause obstructive symptoms, chronic pain, or abdominal mass. If they are detected, treatment is surgical with complete resection of the duplicated portion.
Hirschsprung's Disease
(Congenital Megacolon)
Hirschsprung's disease is a congenital anomaly of innervation of the lower intestine, usually limited to the colon, resulting in partial or total functional obstruction. Symptoms are obstipation and distention. Diagnosis is by barium enema and biopsy. Treatment is surgical.
Hirschsprung's disease is caused by congenital absence of Meissner's and Auerbach's autonomic plexus in the intestinal wall. The estimated incidence is 1 in 5000 live births. Disease is usually limited to the distal colon but can involve the entire colon or even the entire large and small bowel. Males are more commonly affected unless the entire colon is involved, in which case there is no gender difference. Peristalsis in the involved segment is absent or abnormal, resulting in continuous smooth muscle spasm and partial or complete obstruction with accumulation of intestinal contents and massive dilation of the more proximal, normally innervated intestine. Skip lesions almost never occur.
Symptoms and Signs
Patients most commonly present early in life; 15% in the first month, 60% by age 1 yr, and 85% by age 4 yr. Infants present with failure to pass meconium in the first 24 h of life, obstipation, abdominal distention, and, finally, vomiting as in other forms of distal bowel obstruction. Occasionally, infants with ultra-short segment aganglionosis have only mild or intermittent constipation, often with intervening bouts of mild diarrhea, resulting in delay in diagnosis. In older infants, symptoms and signs may include anorexia, lack of a physiologic urge to defecate, and, on digital rectal examination, an empty rectum with stool palpable higher up in the colon and an explosive passage of stool upon withdrawal of the examining finger (blast sign). The infant may also fail to thrive.
Diagnosis
Diagnosis should be made as soon as possible. The longer the disease goes untreated, the greater the chance of developing Hirschsprung's enterocolitis (toxic megacolon), which may be fulminant and fatal (see Congenital Gastrointestinal Anomalies: Hirschsprung's Enterocolitis). Most cases can be diagnosed in early infancy.
Initial approach is typically with barium enema or sometimes rectal suction biopsy. Barium enema may show a transition in diameter between the dilated, normally innervated colon proximal to the narrowed distal segment (which lacks normal innervation). Barium enema should be done without prior preparation, which can dilate the abnormal segment, rendering the test nondiagnostic. Because characteristic findings may not be present in the neonatal period, a 24-h postevacuation x-ray should be taken; if the colon is still filled with barium, Hirschsprung's disease is likely. A rectal suction biopsy can disclose the absence of ganglion cells. Acetylcholinesterase staining can be done to highlight the enlarged nerve trunks. Some centers also can do rectal manometrics, which can reveal the dysmotility characteristic of the abnormal innervation. Definitive diagnosis requires a full-thickness biopsy of the rectum.
Treatment
Treatment in the neonate typically involved a colostomy proximal to the aganglionic segment to decompress the colon and allow the neonate to grow before the 2nd stage of the procedure. Later resection of the entire aganglionic portion of the colon and a pull-through procedure was done. However, a number of centers now do a 1-stage procedure in the neonatal period. Results using laparoscopic technique are similar to those of the open method and are associated with shorter hospitalizations, earlier initiation of feeding, and less pain.
After definitive repair, the prognosis is good, although a number of infants have chronic dysmotility with constipation, obstructive problems, or both.
Hirschsprung's Enterocolitis
(Toxic Megacolon)
Hirschsprung's enterocolitis is a life-threatening complication of Hirschsprung's disease resulting in a grossly enlarged colon, often followed by sepsis and shock.
The etiology of Hirschsprung's enterocolitis seems to be marked proximal dilatation secondary to obstruction, with thinning of the colonic wall, bacterial overgrowth, and translocation of gut bacteria. Shock can develop, and death can follow rapidly; mortality rate is 10%. Close monitoring of infants with Hirschsprung's disease is therefore essential.
Hirschsprung's enterocolitis occurs most commonly in the first several months of life before surgical correction but can occur postoperatively, typically in the first year after surgery. Infants present with fever, abdominal distention, diarrhea (which may be bloody), and, subsequently, obstipation.
Initial treatment is supportive with fluid resuscitation, decompression with an NGT and rectal tube, and broad-spectrum antibiotics to include anaerobic coverage (eg, a combination of ampicillin, gentamicin, and clindamycin). Some experts advocate saline enemas to clean out the colon, but this must be done carefully so as not to increase colonic pressure and cause perforation. Surgery is the definitive treatment for infants who have not yet undergone surgical repair, as well as for infants with perforation or necrotic gut.
Anal Atresia
Anal atresia is an imperforate anus.
A fistula often extends from the anal pouch to the perineum or the urethra in males and to the vagina, the fourchette, or, rarely, the bladder in females. The blind anus and the skin of the perineum may be several centimeters apart or separated by just a thin membrane of skin covering the anal opening.
Anal atresia is obvious on routine physical examination of the neonate because the anus is not patent. If the diagnosis is missed and the neonate is fed, signs of distal bowel obstruction soon develop.
The urine should be filtered and examined for meconium, indicating the presence of a fistula to the urinary tract. Plain x-rays and fistulograms with the neonate in a lateral prone position can define the level of the lesion. A cutaneous fistula generally indicates low atresia. In such cases, definitive repair using a perineal approach is possible. If no perineal fistula exists, a high lesion is likely.
Definitive repair is usually deferred until the infant is older and the structures to be repaired are larger. Until then, a colostomy is done to relieve the obstruction.
Last full review/revision September 2009 by William J. Cochran, MD
Content last modified February 2012
| 
