Constipated

Gastrointestinal System


Diagnosis and reasoning

This young man presented with a week-long history of progressive colicky abdominal pain and abdominal distension, in a background of chronic constipation. His initial examination additionally revealed mild generalized tenderness, hyperactive bowel sounds, and a high rectal fecal load.


The above constellation of findings was suggestive of a distal intestinal obstruction; a subsequent erect abdominal radiograph confirmed this, while also suggesting at fecal impaction. Therefore, he was kept nil-per-oral, an NG tube inserted, and the rectum evacuated manually.


With the acute presentation managed, it is now possible to further evaluate the underlying cause of the intestinal obstruction. Follow-up imaging with abdominal computed tomography (CT) rules out masses and pseudo-obstruction and confirms marked dilatation of the descending and sigmoid colon.


The question now is: what could be the cause of the dilatation? Functional constipation is unlikely, given the normal thyroid function test

s and serum electrolytes. Organic causes to consider include Hirschsprung disease, idiopathic megacolon, and colonic dysganglionosis.


Hirschsprung disease is far commoner than the other etiologies listed above; rectal suction biopsy is a fast and safe bedside screening procedure for this condition and a good next step. Here, this shows an absence of ganglion cells in all specimens, confirming the clinical suspicion.


While anorectal manometry has been historically used to diagnose Hirschsprung disease, this investigation has fallen out of favor in modern times due to high false-positive and false-negative rates. Colonoscopy is also best avoided, as it is both potentially harmful, and unlikely to provide any new information.


In adults with suspected Hirschsprung disease, the Duhamel-Martin procedure is the therapeutic procedure of choice. An intraoperative full-thickness frozen section biopsy of the distal colon is highly recommended to confirm aganglionosis of the affected segment.


A colostomy is a temporary measure and is not indicated if definitive surgery can be performed at the time of diagnosis. Neither is there any rationale for IV antibiotic therapy or the use of corticosteroids.

Discussion

Hirschsprung disease is a congenital malformation of the hindgut that causes varying degrees of aganglionosis of the colon. It is a key cause of chronic constipation in childhood, with an incidence of 1 in 5,000 to 1 in 10,000 births. Males are affected four times more often than females.


In affected persons, the neural crest cells that form the enteric nervous system of the hindgut fail to migrate to their final positions in the submucosal and myenteric plexuses. The subsequent lack of parasympathetic ganglions results in abnormal or absent relaxation of the involved colonic segments.

The extent of aganglionosis varies. In the majority of patients, this extends from the internal anal sphincter to the upper sigmoid colon; this is termed "short-segment" disease. In the remainder, the aganglionosis extends beyond this arbitrary point; this is termed 'long-segment' disease.

As might be apparent, the chronic contraction of the aganglionic segment results in functional obstruction of a varying degree; over time, this also results in dilatation of the healthy colon that is proximal to it.

Hirschsprung disease is genetically heterogeneous, with causative mutations being identified in 10 different genes. A familial nature is apparent, given its occurrence in 3-5% of male and 1% of female siblings of affected children. The condition is also associated with various congenital abnormalities particularly Down syndrome.

The length of the aganglionic segment plays a key role in determining the age and nature of the clinical presentation; as a rule of thumb, the longer the segment, the earlier the age of presentation and the more florid the symptoms.

Neonates may fail to pass meconium within the first 24 hours, or demonstrate obstipation and bilious vomiting. Infants may present with poor feeding, difficulty with bowel movements, and progressive abdominal distension within the first few months of life. In older children, the symptoms are more subtle, including malnutrition, failure to thrive, recurrent faecal impaction or progressive constipation.

During the physical examination, the key finding is a tight anal sphincter; there may be an explosive passage of stools and gas when digital rectal examination is performed.


Rectal suction biopsy (RSB) with staining for acetylcholine activity is the most accurate diagnostic test; anorectal manometry (ARM) is a slightly less sensitive option.

Plain abdominal radiographs are helpful to demonstrate dilated small bowel or colonic segments. Contrast computed tomography (CT) and contrast enemas are useful to estimate the extent of the disease.

These patients may be dehydrated and malnourished, while electrolyte disturbances may also be present. Their general condition should always be stabilized and optimized as a first priority.

Definitive management is via resection of the aganglionic bowel and anastomosis of the proximal segment to the anus (i.e. a pull-through) This may take the form of recto-colectomy with a colorectal anastomosis (i.e. the Rehbein procedure) or total colectomy with ileorectal anastomosis (i.e. modified Duhamel-Martin procedure). Both open and laparoscopic approaches may be attempted.


Patients with short-segment disease can undergo a primary pull-through; long-segment disease often requires staged surgeries. If the patient has comorbid enterocolitis, a colostomy can be performed as a temporary measure to allow the intestine to heal, following which definitive surgery can be attempted.

Take home messages

1. Between 2-15% of children with Down syndrome also have Hirschsprung disease.

2. Older children and adults with Hirschsprung disease may manifest only subtle symptoms, including malnutrition, failure to thrive, recurrent fecal impaction, and progressive constipation.

3. Rectal suction biopsy is the diagnostic technique of choice.

4. Surgical resection of the aganglionic segment followed by anastomosis of the remainder of the bowel to the anus is the gold-standard treatment.

References

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