Hirschsprung's disease (HD) also called Congenital megacolon is a disorder of the abdomen that occurs when part or all of the large intestine or antecedent parts of the gastrointestinal tract have no nerves and therefore cannot function. During normal fetal development, cells from the neural crest migrate into the large intestine (colon) to form a network of nerves called Auerbach's plexus. In Hirschprung's disease, the migration is not complete and part of the colon lacks these nerve bodies that regulate the activity of the colon. The affected segment of the colon cannot contract and therefore pass stool through the colon, creating an obstruction.[1] In most affected people, the disorder affects the part of the colon that is nearest the anus. In rare cases, the lack of nerve bodies involves more of the colon. In five percent of cases, the entire colon is affected. Stomach and esophagus may be affected too. Hirschsprung's disease is also sometimes called congenital aganglionic megacolon.
TESTS AND EXAMS
Milder cases may not be diagnosed until a later age.During a physical examination, the doctor may be able to feel loops of bowel in the swollen belly. A rectal examination may reveal a loss of muscle tone in the rectal muscles.
Tests used to help diagnose Hirschsprung's disease may include:
Abdominal x-ray
Anal manometry (a balloon is inflated in the rectum to measure pressure in the area)
Barium enema
Rectal biopsy
PATHOPHYSIOLOGY
The most accepted theory of the cause of Hirschsprung is that there is a defect in the craniocaudal migration of neuroblasts originating from the neural crest that occurs during the first 12 weeks of gestation. Defects in the differentiation of neuroblasts into ganglion cells and accelerated ganglion cell destruction within the intestine may also contribute to the disorder. This lack of ganglion cells in the myenteric and submucosal plexus is well-documented in Hirschsprung's disease.With Hirschsprung's disease, the segment lacking neurons (aganglionic) becomes constricted, causing the normal, proximal section of bowel to become distended with feces. This narrowing of the distal colon and the failure of relaxation in the aganglionic segment are thought to be caused by the lack of neurons containing nitric oxide synthase
CAUSES
It's not clear what causes Hirschsprung's disease. It sometimes occurs in families and may in some cases be associated with a genetic mutation.Hirschsprung's disease occurs when nerve cells in the colon don't form completely. Nerve cells are critical to the functioning of the colon. They control the regular muscle contractions that keep food moving through the bowels.As a baby develops before birth, bundles of nerve cells (ganglia) normally begin to form between the muscle layers along the length of the colon. This process begins at the top of the colon and ends at the bottom (rectum). In children who have Hirschsprung's disease, the nerve-growing process fails to finish. Most commonly, ganglia fail to form (aganglia) in the last segment of the colon — the rectum and the sigmoid colon. Sometimes aganglia affects the entire colon and even part of the small intestine.
CLINICAL MANIFESTATION
Typically, Hirschsprung's disease is diagnosed shortly after birth, although it may develop well into adulthood, because of the presence of megacolon, or because the baby fails to pass the first stool (meconium) within 48 hours of delivery. Normally, 90% of babies pass their first meconium within 24 hours, and 99% within 48 hours. Other symptoms include: green or brown vomit, explosive stools after a doctor inserts a finger into the rectum, swelling of the abdomen, lots of gas and bloody diarrhea.
Some cases are diagnosed later, into childhood, but usually before age 10.The child may experience fecal retention, constipation, or abdominal distention. With an incidence of one in 5,000 births, the most cited feature is absence of ganglion cells: notably in males, 75 percent have none in the end of the colon (recto-sigmoid) and eight percent lack ganglion cells in the entire colon. The enlarged section of the bowel is found proximally, while the narrowed, aganglionic section is found distally, closer to the end of the bowel. The absence of ganglion cells results in a persistent over-stimulation of nerves in the affected region, resulting in contraction.
Some, extremely rare cases, the absence of ganglion cells continues to spread after the corrective surgery, resulting in multiple surgeries. Usually, the over-stimulated colon will actually absorb little, or no nutrition to benefit the patient. Those patients that also have thyroid cancer, may be able to digest food properly, but may not be able to use the nutrients properly. The equivalent disease in horses is Lethal white syndrome.
TREATMENT
Treatment of Hirschsprung's disease consists of surgical removal (resection) of the abnormal section of the colon, followed by reanastomosis.
Colostomy
The first stage of treatment used to be a reversible colotomy. In this approach, the healthy end of the large intestine is cut and attached to an opening created on the front of the abdomen. The contents of the bowel are discharged through the hole in the abdomen and into a bag. Later, when the child’s weight, age, and condition is right, the "new" functional end of the bowel is connected with the anus. The first surgical treatment involving surgical resection followed by reanastomosis without a colostomy occurred as early as 1933 by Doctor Baird in Birmingham on a one year old boy.
Swenson, Soave, Duhamel, and Boley procedures
Orvar Swenson, who discovered the cause of Hirschsprung’s, first performed its surgical treatment, the pull-through surgery in 1948. The pull-through procedure repairs the colon by connecting the functioning portion of the bowel to the anus. The pull-through procedure is the typical method for treating Hirschsprung’s in younger patients. Swenson devised the original procedure, and the pull-through surgery has been modified many times.Currently, there are several different surgical approaches, which include: the Swenson, Soave, Duhamel, and Boley procedures. The Swenson procedure leaves a small portion of the diseased bowel. The Soave procedure leaves the outer wall of the colon unaltered. The Boley procedure is a small modification of the Soave procedure, so the term "Soave-Boley" procedure is sometimes used. The Duhamel procedure uses a surgical stapler to connect the good and bad bowel.For the 15 percent of children who do not obtain full bowel control, other treatments are available. Constipation may be remedied by laxatives or a high fiber diet. In thoese patients, serious dehydration can play a major factor in their lifestyle. A lack of bowel control may be addressed by a stoma, similar to a colostomy. The Malone antegrade colonic enema (ACE) is also an option. In a Malone ACE, a tube goes through the abdominal wall to the appendix or, if available, to the colon. The bowel is then flushed daily. Children as young as 6 years of age may administer this daily flush on their own.If the affected portion of the lower intestine is restricted to the lower portion of the rectum, other surgical procedures may be performed, such as a posterior rectal myectomy.The prognosis is good in 17 percent of cases. Chronic post-operative constipation is present in 7 to 8 percent of the operated cases. Post-operative is a severe manifestation that is present in the 10%–20% of operated patients.
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