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 he 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.
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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.
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