Constipation in Imperforate Anus
Constipation is a problem in the great majority of patients who are born with an imperforate anus (a birth defect in which the anal canal fails to develop) and have an operation to repair the condition that includes the preservation of their original rectum.
This constipation seems to be the clinical manifestation of a hypomotility disorder (a slower than normal movement of food) through the rectosigmoid colon (the lower section of the colon that attaches to the rectum, where stool is usually stored until it is expelled from the body).
Further analysis of our cases shows that this problem of constipation is worse in lower defects. 1
We have found the reverse is also true: the higher the malformation, the more chances of suffering from fecal incontinence (the inability to control bowel movements voluntarily) and the less chance of having constipation.
"High" and "low" refer to the relationship of anorectal defects to the levator muscle complex, which elevates the organs and structures in the area. In "low" anorectal defects, the rectum descends through the levator muscle complex, while in high anorectal defects, the rectum fails to descend through the levator muscles.
Site of Colostomy Affects Severity of Constipation
The other primary factor affecting the degree of constipation appears to be the site of colostomy. A colostomy creates an artificial anus (stoma) to allow feces to pass out of the body and into a stoma bag. Patients who have had colostomies in the transverse section of the colon have a greater chance of having constipation than those who have had colostomies in the descending section of the colon.
In patients with transverse colostomies, distal colostograms, the most accurate diagnostic studies of the area, typically show severe dilatation of the rectosigmoid, especially if closure of the colostomy was delayed for a long period of time.
These patients suffer more severe constipation after repair of the anorectal malformation and closure of the colostomy. In fact, there is a direct relationship between the degree of rectosigmoid dilatation prior to colostomy closure and the degree of constipation the patient will suffer.
Loop Colostomies
Loop colostomies, particularly those that allow the passing of stool from proximal to distal stoma, will provoke the worse fecal impaction in the distal rectum, the worse megasigmoid syndrome (swelling in the sigmoid colon), and therefore, the worse constipation.
Tapering or not tapering the rectum in our series of cases, did not have any relationship with the degree of constipation that the patient suffers from.
Colostomy Closure
After colostomy closure, proper treatment of constipation is imperative. When constipation is not treated properly, the megasigmoid worsens.
More dilatation of the rectum leads to greater constipation and constipation becomes a self perpetuating and self aggravating condition. The lessons then seem to be very clear; we must try to keep the rectum as empty as possible to avoid rectosigmoid dilatation.
Constipation is a very serious problem because eventually it provokes fecal incontinence, even in patients who were born with a potential for bowel control. This is what we call over-flow pseudo-incontinence.
Treatment for Constipation
The treatment method for constipation depends on whether or not the patient has the potential for bowel control. We are very thorough about classifying patients according to their potential for bowel control and try to determine this from the very beginning of treatment.
A poorly formed sacrum (the lower part of the spine that forms part of the pelvis), a very high malformation (recto-bladderneck fistula or a long cloaca, the fusion of rectal, vaginal, and urinary channels into a single common channel), or the presence of a mass in front of the sacrum, usually means that the patient has no potential for bowel control.1
We define a poor sacrum as one with more than three vertebrae missing, or with a sacral ratio of less than 0.4. The sacral ratio is defined as the ratio of the distance from the bottom of the sacro-iliac joint to the tip of the sacrum divided by the distance from the top of the iliac bone to the bottom of the sacro-iliac joint.
Patients with Good Potential for Bowel Control
Conversely, patients with good potential for bowel control include those with a well formed sacrum, or a "benign" malformation, such as rectal atresia (lack of a normal opening in the rectum), perineal fistula (an abnormal anal opening), vestibular fistula, imperforate anus with no fistula, or rectourethal-bulbar fistula.1
Patients with Poor Potential for Bowel Control and Constipation
Patients with poor potential for bowel control and constipation should be treated with an enema every day. In these cases, hypomotility of the rectosigmoid represents an advantage because it makes the bowel management easier. Emphasis should be on cleaning the colon every day. This can be done with aggressive, large volume, salt water enemas. 2
The program should be implemented over a period of one week by trial and error. Daily abdominal X-rays allow reliable assessment of effectiveness of the enemas.
The volume and salt concentration of the enemas is increased until the patient's colon is effectively cleaned. This regimen is then continued on a daily basis, with the goal of keeping patients completely clean for 24 hours a day between enemas.
Patients with Good Potential for Bowel Control and Constipation
Patients with good potential for bowel control and constipation should be treated with laxatives. Trial and error determines the amount of laxatives that each patient needs. The amount of laxative that each patient needs is frequently very large.
The goal is to empty the rectum every day. Once bowel control has been achieved with laxatives, the patient is maintained on this regimen. If the amount required is enormous, a sigmoid resection may be offered, which will allow a reduction in the amount of laxative requirements.2, 3
Additional Conditions and Considerations
During surgery to treat imperforate anus, the rectosigmoid should never be surgically removed because this leads to fecal incontinence. This occurred in many patients treated in the past with a surgical procedure that is no longer used.
Tissue samples from the most distal part (the end) of the rectum and/or fistula (an abnormal passageway between two areas of the digestive tract) in patients with anorectal malformations may show evidence of nerve abnormalities, including neuronal intestinal dysplasia (NID) and/or aganglionosis, the absence of certain nerve cells known as ganglion cells. There is no way, however, to know the relevance of those findings. While it may be tempting to use these findings to try to explain the constipation, the cause of constipation in these patients is more likely to be related to a very distended rectosigmoid and therefore, impaired peristalsis, a wavelike movement of muscles that moves food and liquid through the gastrointestinal tract. Any hollow internal organ of the body that becomes overdistended for a long period of time loses its peristaltic ability.
Hirschsprung's Disease
We are very skeptical about the diagnosis of imperforate anus and Hirschpsrung's disease, a birth defect in which some nerve cells are lacking in the large intestine and the intestine cannot move stool through. As a result, the intestine gets blocked and the abdomen becomes swollen. The reason for this skepticism is that we have never seen a patient with imperforate anus develop enterocolitis, inflammation of both the large and small intestine. The correct diagnosis is necessary to implement proper treatment strategies and avoid surgery that could cure constipation but make the patient fecally incontinent.
Tethered Cord
Tethered cord, the abnormal attachment of the spinal cord to the bones of the spine, has occurred in 24% of patients in our study of anorectal malformations.4 The more complex and high the malformation, the higher the chances of tethered cord. Forty-three percent of our group of complex anorectal malformations have tethered cord, but it is present in only 11% of our patients with rectovestibular fistulas.
Tethered cord is clearly more common in patients with imperforate anus who suffer from fecal incontinence, but our study could not clarify whether or not the fecal incontinence was due to the presence of the tethered cord. This is because most of those patients had a very complex malformation, which alone could be responsible for the fecal incontinence. Eighteen of our patients underwent surgical untethering of the cord and none had any significant change in bowel or urinary function postoperatively. We could not find a single patient with tethered cord who experienced incontinence which could be attributed to the cord defect alone. Surgical untethering may be indicated for other reasons, but at the present time, there is no good evidence to demonstrate that surgical untethering improves the prognosis of these patients.
References:
- Peña A: Anorectal Malformations. Seminars in Pediatric Surgery 4(1):35-47, 1995.
- Peña A, Guardino K, Tovilla JM, Levitt MA, Rodriguez G, Torres, R: Bowel management for fecal incontinence in patients with anorectal malformations.
J Pediatr Surg 33(1):133-137, 1998. - Peña A, El-Behery M: Megasigmoid. A source of pseudo incontinence in children with repaired anorectal malformations. J Pediatr Surg 28(2):773-778, 1993.
- Levitt M, Patel M, Rodriguqez G, Gaylin D, Peña A: The tethered spinal cord in patients with anorectal malformations. J Pediatric Surg 32(3):462-468, 1997.
Contact the Colorectal Center
If you have any questions about the Colorectal Center at Cincinnati Children's Hospital Medical Center, please contact us.
