Our final assignment for Human Biology was to write a paper about a disease of the human body, specifically how it's diagnosed, treatment options and patient prognosis. Because Gabriel was diagnosed with it, I decided to write about Hirschsprung’s Disease. After spending weeks learning about the human body, I feel like I have a much better understanding of how and why things sometimes go wrong and after writing this paper I have an entirely new perspective on this disease. I understand now that we truly have no control over our genes and the chromosomes that randomly combine to form our children. As much as I wish Gabriel had been a healthy baby, I also realize that there is no other combination of genes that could have resulted in him. In other words, there is no version of Gabriel without Hirschsprung’s Disease. And for some reason, that makes me want learn more about Hirschsprung’s, to spread awareness of it, and to shed my feelings of anger and bitterness towards it.
(We were supposed to write our papers in "normal" non-medical language, but it was surprisingly difficult to do so after being immersed in anatomy for the past month. But hopefully this is a pretty comprehensible report even if you don't know anything about the digestive system.)
Hirschsprung’s Disease
Hirschsprung’s Disease is
a rare gastrointestinal disorder that affects the large intestine, most
commonly the upper rectum or both the rectum and the sigmoid colon. Undigested
food, water and other waste products are moved through the large intestine via
peristalsis, which is a wave-like motion that propels stool forward so that it
can be eliminated from the body. In order for the brain to coordinate
peristalsis in the gastrointestinal tract, it relies on special nerve cells
called ganglion nerves that line the walls of the entire gastrointestinal
tract. During early fetal development, these ganglion nerves are formed
throughout the entire GI tract, beginning with the mouth and ending with the
anus. In babies affected by Hirschsprung’s Disease, the ganglion nerves do not
finish forming during fetal development, resulting in an inability for the
brain to induce peristalsis in the lower part of the intestinal tract. Because
there is no other way for stool to pass through the large intestines,
oftentimes it will become obstructed in the area where ganglion nerves are
absent.
Because a person is born
with Hirschsprung’s Disease, doctors can usually diagnose a baby with this
condition shortly after birth. Newborns are often suspected of having
Hirschsprung’s Disease if they are unable to pass meconium (the substance that
is responsible for a newborn’s first bowel movement), within 24-48 hours
post-birth. Oftentimes this inability to pass meconium is accompanied by one or
more additional symptoms such as vomiting, abdominal distention, diarrhea, jaundice,
fever and lack of appetite. Nowadays, babies are not permitted to leave the
hospital if they are unable to pass meconium and it is routine to check for
disorders including Hirschsprung’s Disease if a newborn baby presents any of
these symptoms.
Doctors can run a few
basic tests to confirm the diagnosis of Hirschsprung’s Disease. Because
Hirschsprung’s Disease is characterized by the absence of ganglion nerve cells in the
large intestine, a biopsy of intestinal tissue is the best way to verify
suspicions. Doctors remove a small piece of the lining of the large
intestine and then use a microscope to check for the presence of ganglion nerve
cells. If ganglion nerves are seen, then Hirschsprung’s Disease can be ruled
out as an explanation for the blockage. Instead if ganglion nerves are missing,
the doctor can confirm that the child does indeed have Hirschsprung’s Disease.
There are a few other
tests that doctors can perform if they believe that a baby has this condition.
Abdominal x-rays are sometimes used to check for intestinal dilation which
signifies an intestinal blockage. Abnormal dilation of the colon is called
megacolon, the presence of which can be an indication of a serious GI disorder
such as Hirschsprung’s Disease. For some x-rays, doctors may administer a
barium enema beforehand, which involves injecting barium (a metallic liquid)
into the rectum and then using an x-ray to view the intestines. The barium
gives doctors a clearer image of the intestinal wall. Also, if Hirschsprung’s
Disease is suspected in an older child, a doctor may order an anorectal
manometry test. During this test, a small sensor is placed in the rectum and a
computer is used to measure the pressure and strength of the anal and rectal
muscles. Often, children with Hirschsprung’s Disease have a failure of the
relaxation reflex of the internal anal sphincter, a small muscle that relaxes
in order to initiate the elimination of stool from the body. In this case, a
rectal biopsy would be necessary to confirm the diagnosis of
Hirschsprung’s Disease.
If a baby is diagnosed
shortly after birth, there is a high chance that they will respond well to
treatment. Current treatment involves surgery in which surgeons remove the
segment of the colon and rectum that is missing ganglion nerve cells. They then
surgically attach the end of the remaining intestine to the anus. Depending on
how much of the intestinal tract is missing ganglion nerves, doctors may be
able to perform laparoscopic (minimally invasive) surgery or they may be able
to perform a transanal “pull-through” in which they operate on the intestines
through the anus. Other times, they may need to make an incision through the
abdomen in order to remove the necessary part of the intestines. In some cases,
a child may also require an operation called an ostomy if the doctors are
concerned about an infection in the intestines or if the intestines are
extremely dilated. An ostomy involves making a small opening in the belly,
called a stoma, and attaching the end of the intestines to this opening. This
allows stool to pass out of the body into an attached pouch, so that the
intestines can be washed out and have time to heal. It usually takes a few
months to a year for the intestines to fully heal and once they do, doctors can
then perform the necessary pull-through surgery. After surgery, children are
administered pain medication temporarily, but they do not require any lifelong
medication.
Fortunately, most patients
are able to fully recover from surgery and go on to have normal bowel habits.
In some cases, people may suffer from chronic constipation, diarrhea or enterocolitis,
which is an inflammation of the large intestines. Some children will die from
complications related to having Hirschsprung’s disease such as intestinal
failure, intestinal rupture and severe enterocolitis. The mortality rates
increase with the severity of the disease and among those children who have
other problems such as a congenital heart defect or Down syndrome. In mild
cases where only a small section of the colon is missing ganglion nerves and
surgery is able to be performed early on, children have an excellent rate of
survival and recovery and will ultimately grow up to have normal lives. In some
instances, children may be put on a special diet to reduce constipation or
other GI problems, but for the most part, they do not require any further
treatment.
Hirschsprung’s Disease is
an extremely rare congenital disorder that only occurs in 1 in every 5000-7000
live births. It affects males five times as often as females and children with
Down syndrome and other chromosomal anomalies are at higher risk of having it. The exact cause is unknown,
however the majority of scientists agree that it is a genetic disorder. There is a lot of
evidence to support the theory that Hirschsprung’s Disease has a hereditary
factor. For example, a couple who has a child with Hirschsprung’s Disease has on
average a 3%-25% chance of having another child who also has it. Also if one
parent has the disease, there is a greater probability that their children will
be affected. Newer research suggests the possibility that Hirschsprung’s
Disease may be autosomal dominant (resides on a non-sex chromosome and only
requires inheritance from one parent) in some families and may be caused by a
genetic mutation in other cases. Some scientists believe that Hirschsprung’s
Disease requires the mutation of at least two genes residing on two different
chromosomes. It is also possible that it is carried on the X chromosome since
it affects males at a significantly higher rate than females. Since boys only
have one X chromosome, they are more susceptible to X chromosome diseases than
girls who have two X chromosomes.
Rates of recurrence in a
family vary depending on the affected child’s gender and disease severity. A
couple is most likely to have another child with Hirschsprung’s Disease if they
already have a daughter with the most severe form of the disease, especially if
the next child is a boy. Instead if they have a son with the least severe form,
they may have as low as a 1% chance of having another child with Hirschsprung’s
Disease.
Despite growing research,
the exact cause is still unknown. So far, there are no known ways to prevent
the inheritance of Hirschsprung’s Disease and no external environmental factors
seem to be involved. There is also no cure, but genetic testing is available
for couples who want to know their risk of having a child with the disease.
