Hirschsprung disease (HD) is caused by congenital absence of ganglion cells in the distal rectum and extends for a variable distance proximally. It affects the rectum and part of the sigmoid colon in approximately 80 percent of patients, but it also can involve more proximal segments, the entire colon, or (in rare cases) most of the small bowel. There is an increased risk for HD among patients with trisomy 21 and several other genetic syndromes. Assessment by a clinical geneticist is valuable for all patients with syndromic features or anomalies, as well as for those with no apparent associated anomalies. 

●For all patients with HD, and particularly those with syndromic HD, genitourinary anomalies, hearing impairment, and visual impairment are common. Congenital heart disease is common among those with syndromic HD. The clinician should be alert for signs or symptoms of congenital anomalies in patients with suspected HD. Some authors have suggested routine screening for congenital anomalies of the kidney and urinary tract (CAKUT) and for hearing impairment.

●The majority of patients with HD are diagnosed in the neonatal period when they present with symptoms of distal intestinal obstruction, including bilious emesis, abdominal distension, and failure to pass stool. A high index of suspicion is appropriate for infants with a predisposing condition such as Down syndrome or for those with a family history of HD. Patients with less severe (short-segment or ultrashort-segment) HD may not be diagnosed until later in infancy or childhood. Such patients typically have a history of chronic constipation and failure to thrive. 

●An urgent full evaluation for HD is appropriate for newborns or young infants (<6 months old) with the following features:

•Symptoms of obstruction (bilious emesis, abdominal distension, and failure to pass stool)

•Failure to pass meconium within 48 hours of birth

•Constipation and trisomy 21 or other condition known to be associated with HD, or a family history of HD

•Constipation and physical examination suggestive of HD (tight anal sphincter; narrowed, empty rectum; or squirt sign on digital examination)

●Occasionally, affected infants may present with enterocolitis, a potentially life-threatening illness in which patients have a sepsis-like picture with fever, vomiting, diarrhea, and abdominal distension, which can progress to toxic megacolon. 

●Definitive diagnosis of HD is made by rectal biopsy, which may be supported by findings on abdominal radiographs, contrast enema, or anorectal manometry. The diagnostic steps depend on the level of suspicion for HD, whether there is concern about Hirschsprung-associated enterocolitis (HAEC; which requires emergency management), age of the child, and on the available resources and institutional/clinician preference. 

●The treatment for HD is surgical resection of the aganglionic segment of bowel. The normal ganglionic bowel is brought down and anastomosed just proximal to the anus, and injury to the anal sphincter is avoided. 

●Abnormalities of bowel function are common after definitive surgery for HD, although overall quality of life is generally good. The most common long-term complications are constipation and fecal incontinence. Postoperative enterocolitis may also occur and is a medical emergency. 

●The term "ultrashort-segment Hirschsprung disease" (USSHD) is sometimes used to describe a form of HD characterized by a very short-segment of aganglionosis extending 2 to 4 cm proximal to the internal anal sphincter. The clinical picture is similar to the classical short-segment HD (which involves most or all of the rectum and part of the sigmoid colon), except that the degree of constipation may be less severe. It is important to distinguish patients with USSHD from those with typical HD because they may not require a pull-through operation. 

From Up To Date: Congenital aganglionic megacolon (Hirschsprung disease)