Bowel
Obstruction
Introduction: This
term simply describes that the passage of food is obstructed in the bowel. This
can occur in the small bowel (most often), called small bowel obstruction, or
in the large bowel (not as common), called large bowel obstruction. It also can
be congenital in a newborn or acquired in an adult. There are a number of different
mechanisms that can cause bowel obstruction and I will describe these below.
Bowel
Obstruction In The Newborn Or Infant There are a
number of common conditions that I would like to mention here.
Hypertrophic
Pyloric Stenosis Here the baby usually feeds
well until the 4th to 6th week and then suddenly starts vomiting after every feeding.
Within a short period of time there is projectile vomiting where the milk is vomited
several feet out. This is due to a thickened (=hypertrophic) outlet from the stomach.
The baby has abdominal pain in the epigastric area and eventually no food will
pass leading to severe dehydration quickly. These infants need emergency attention
at the hospital with a referral to a pediatrician and pediatric surgeon. A relatively
small incision will be made and the hypertrophic muscle divided without entering
into the lumen of the pylorus. These infants do very well following this procedure
and thrive after that.
Meconium
Plug Syndrome Meconium is the name for the first
stool of a baby. It looks dark green, sometimes almost black and is of a tarry,
pasty consistence. In babies with cystic fibrosis the meconium that is formed
in the gut is more tenacious, stickier and can get stuck in the terminal ileum
before it would get into the colon. This meconium plug is the reason for a dangerous
syndrome where a bowel obstruction develops proximally to the meconium plug, but
the colon distally is empty and normal. The diapers do not show bowel movements,
but the small bowel shows dilated bowel loops, which very quickly leads to fluid
dysbalances in the blood stream. A pediatrician needs to stabilize the baby's
condition and diagnose the bowel obstruction due to the meconium plug syndrome.
Next a pediatric surgeon needs to get involved to see whether the plug will resolve
with diluted contrast medium enemas or whether it will need operative intervention.
Volvulus due to malrotation: this has been
dealt with under "volvulus" elsewhere.
Hirschsprung's
Disease (= Megacolon) In
this disease there is a segment of colon with a congenitally absent nerve plexus
(=aganglionic colon segment), which is usually located in the distal colon. It
may go unnoticed first, but as time progresses, the infant becomes more and more
constipated and at the same time there is bowel distension in the left lower and
mid abdomen as the stool is building up in front of the section that has no peristalsis.
Conceptually it is almost like a mini-ileus. The risk is that a megacolon develops,
which in time becomes filled with toxic substances and infection (="toxic
megacolon"). The infant or older child may fail to thrive, have no appetite,
have recurrent left abdominal pain and bowel distension with visible peristalsis
(= you can see a bowel loop move like a snake underneath the skin). This disease
needs urgent attention by a pediatric surgeon. The surgeon will either
do a one-stage or two-staged procedure. In the one-stage procedure (usually when
there is no toxic megacolon present) the surgeon removes the defective portion
of the colon and repairs the normal colon with an end-to-end anastomosis. With
a two-staged procedure the first stage is to do a colostomy(=create an opening
in the skin to which the proximal colon is connected). This reestablishes normal
emptying of the bowel contents from the healthy proximal colon. The colostomy
is covered with a bag that is changed regularly. At a future date when the megacolon
has settled down the resection of the defective part (with Hirschsprung's disease)
is removed and an end -to-end anastomosis is done. This way an high risk surgery
is broken down into two stages and the patient has a much better survival chance.
When all is done, the infant grows normally and has a normal life expectancy.
Anal
Atresia Occasionally a baby is born where the anal
opening is missing. This is called anal atresia. It is a developmental anomaly
where a membrane that was there in embryonic life has not disappeared. This is
an emergency and has to be taken care of right away. If it is missed on day 1,
it will develop into acute bowel obstruction with abdominal distension, pain and
vomiting on day 2. Usually the physician picks up the problem with the initial
examination of the newborn right after delivery and then arranges a referral to
a pediatric surgeon immediately. If it is a small problem, a minor surgery opens
the anal canal. However, often there are fistulas and other anomalies of the lower
urinary tract and of the vagina including pathological fistulas from these structures
to the rectum or the skin. Occasionally the surgeon will decide that a preliminary
colostomy is done to relieve the obstruction. At a future date when the child
has grown and the tissue structures are bigger, the definite corrective surgery
can be done with less fear of excessive scarring.
Bowel
Atresia Obstructive membranes can occur in
other parts of the gut, most commonly in the ileum(the last part of the small
bowel), followed by the duodenum, the jejunum(=upper part of small bowel) and
the colon. Symptoms are dictated by the location of the atresia. In other words
a high atresia(duodenum or jejunum) leads to regurgitation and vomiting much earlier
and might even be mistaken for a hypertrophic pyloric stenosis. With an atresia
of the ileum the symptoms are that of small bowel obstruction. Finally, with colonic
atresia the symptoms are those of large bowel obstruction with less violent symptoms,
less fluid problems and vomiting at a later time than with small bowel obstruction.
Bowel
Obstruction In The Adult In the adult the causes of bowel
obstruction are not usually congenital in nature, but are acquired. A common classification
is to distinguish between small and large bowel obstruction.
Small
Bowel Obstruction In The Adult As
indicated earlier, with small bowel obstruction is more acute in its presentation
as a lot of fluid can be lost into dilated small bowel loops. There might have
been a history of prior surgery and bands of scar formation(= adhesions) have
developed. These bands of scarring are made up of tough connective tissue and
attach to bowel loops from outside like suction devices that won't let go. As
the years go by the adhesion tissue loses water and retracts thus leading to kinking
of the attached bowel loops. This is when small bowel obstruction suddenly develops.
Symptoms: There might have been a few months or
even years where the patient felt discomfort after meals. But then it settled
again until that one day when it takes off. At that point there is acute abdominal
pain in the right and central abdomen, somewhat dictated where the obstruction
is. Also, if there is a volvulus present, where a bowel loop has turned around
itself and the circulation is cut off, the symptoms are more pronounced and there
is a higher priority for the physician to get in and rescue the bowel. There are
only up to 6 hours before the bowel becomes gangrenous and there is a danger of
perforation and peritonitis! Abdominal x-rays are quickly done, which often show
a ladder like formation of bowel loops with fluid levels in the standing views.
There is usually no cancer found in small bowel. Treatment:
It is important to get an assessment by a surgeon early on in these cases. A laparotomy
is arranged (=surgical opening of the abdominal cavity), which usually shows the
cause of the obstruction right away. About 25% to 30% of the small bowel obstructions
are strangulating (volvulus like). The surgical procedure depends on the findings
during the laparotomy and on the status of the patient at the time of surgery.
Often there might have to be a period of 2 to 3 hours prior to surgery where the
bowel is decompressed by placing a naso-intestinal drainage tube first , replacing
the fluid loss and balancing the electrolytes based on blood tests. When the patient
is stabilized in this manner, the surgical procedure is safer and the complication
rate is lower. Large
Bowel Obstruction In The Adult A bowel obstruction of the
large intestine (=colon), as mentioned above, is not as acute as that of the small
bowel. One of the common causes of colonic obstruction is diverticulitis with
a pericolic abscess formation, which can lead to obstruction. Another cause is
a circumferential cancerous growth inside the colon, which eloped detection until
it came to the point where obstruction occurred. Less common causes are colonic
Crohn's disease and volvulus of the cecum or of the sigmoid colon. Symptoms:
There is usually an increasing constipation problem, which is associated
more and more with abdominal distension and less frequent bowel movements. There
might be blood in the stool in the cases of a bleeding cancer, but this is a late
sign. A volvulus has a different , more acute presentation as the strangulation
leads to excruciating abdominal pain (see above under "volvulus"). Depending
on the underlying pathology as mentioned above, the symptoms are slightly modified.
For instance, with a volvulus in the cecum the pain is localized in the right
lower abdomen. However, with diverticulitis the abdominal pain is located either
in the mid abdomen (if the transverse colon has been affected) or in the left
mid or lower abdomen (with involvement of the descending or sigmoid colon). The
same is true for cancer of the colon, which mostly is located in the rectum, the
sigmoid colon or descending colon, all of which would give obstructive symptoms
with pain in the left mid and left lower abdomen and possibly with a rectal fullness
(in rectal cancer). Treatment: Treatment is similar
to small bowel obstruction in that the patient has to be stabilized first and
then a laparotomy is performed, which usually tells the surgeon exactly what is
going on and the appropriate procedure can be done to correct it. A cancer would
be removed in the healthy adjacent colon and the the two ends be reconnected.
Similiarly, with diverticulitis the affected colon segment has to be removed and
the healthy colon ends are then anastomosed as mentioned before. Often with diverticulitis
the tissue is very brittle or one of the diverticles has perforated and caused
a localized peritonitis, which was walled off by the fat apron (called "omentum").
In this case the surgeon may be forced to only do a colostomy (=opening from the
colon to the skin) and resection of the diseased bowel. The reconnection surgery
would have to wait 2 or 3 months until the infection has completely healed and
it is considered safe for the patient to undergo the surgery.
|
