Caused by a congenital absence of innervation at the end of the bowel, Hirschsprung’s disease (HD) results in functional obstruction of the gut. The rectum and sigmoid colon are typically affected, but the entire large intestine and even part of the small intestine may be involved as well.
The etiology is believed to be due to the arrested migration of neuroblasts or, alternatively, the completed migration of these nerve cells that later undergo apoptosis (i.e. programmed cell death) or dysfunctional differentiation and/ or proliferation. Moreover, genes such as RET, ENDN3 and EDNRB have all been implicated in the pathogenesis of the disorder.
Failure of a newborn to pass stool within the first 24 – 48 hours of birth is suggestive of a potential HD diagnosis. Additional symptoms in infants include abdominal swelling, green or brown vomit and explosive stools after inserting a finger into the neonate’s rectum. In toddlers and older children, symptoms may differ slightly. There is slowed growth and constant difficulties going to the toilet.
In order to determine if a patient has HD, a physical exam, medical history, and diagnostic tests are conducted. Physical exams are conducted to review a child’s weight and height and for signs of poor nutrition. The abdomen is inspected for swelling and auscultated for bowel sounds. In the medical history, family history is acquired to help with a diagnosis of HD.
Rectal biopsies are the best tests to diagnose or rule out HD. In suction rectal biopsy, which is painless, a small piece of tissue is acquired from the lining of the rectum. In a full thickness rectal biopsy, more tissue is removed and this type of biopsy requires anesthesia as opposed to the suction biopsy. Tissue that is acquired is examined under a microscope.
X-rays are another set of tests that may be helpful in the diagnostic process. Abdominal x-rays can illustrate if there is intestinal obstruction present. Anorectal manometry may be done with the use of a small balloon that is inflated inside the rectum. HD is suspected if the muscles do not relax as they normally should. In addition to this test, a lower GI series x-ray exam can also be done, where contrast material is used to show if there are any changes or obstruction present in the bowel.
Managing HD depends on several factors including the extent of the intestines affected as well as the child’s age, medical history, and overall health. Furthermore, the child’s ability to handle drugs or surgical procedures is also taken into account with the expected outcomes. Treatment is primarily focused on how to remove or bypass the section of the intestine that does not have any innervation. Children that are candidates may receive a pull-through procedure that involves using an endoscope and other surgical tools to remove any blockage and aganglionic tissue. Subsequently, the healthy segments of the bowel are reconnected.
A colostomy can also be performed in other cases where the open end of the bowel is connected to the skin’s surface. This allows stool to exit the body through the hole that is created to the outside and confers protection to the area of bowel that was removed until it has properly healed. This may take up to 6 weeks after which the colostomy is closed off. Both the pull-through procedure and the colostomy are minimally invasive approaches and require only small incisions.
When it is impractical to immediately conduct the minimally invasive procedures, traditional or open approaches are done. These involve using large incisions to bring a part of the bowel to the skin’s surface in order to remove the blockage. Once the baby has recovered the parts of the bowel that lack nerve cells may then be removed using the minimally invasive procedures. The long-term outlook for surgically treated HD depends on how much intestine was removed. Removal of large sections of bowel can cause poor digestion and/or slow growth. However, most patients generally tend to recover after surgery without any significant problems.