Dr. Greene's Answer
The gastrointestinal system is a long convoluted tube extending from the mouth, through the body, down to the anus. During development a portion of the tube may not form. This is called atresia (for example, in esophageal atresia, a section of the esophagus is missing). More commonly, a portion of the tube is too narrow. This is called stenosis. In pyloric stenosis for example, the pylorus (the valve at the outlet of the stomach) is too tight to permit stomach contents to pass through easily. Anorectal anomalies occur in about 1 of every 4,000 live births and include a wide spectrum of defects — some are minor and easily treated, some are complex and very difficult to manage.
Very early in development, the urinary tract and the embryonic rectum and anus are all part of the same structure. They separate by the seventh week of gestation. At the time of separation, the urinary tract already has an opening on the skin, but the anus is covered by a thin membrane. By eight weeks of gestation, the anal opening typically appears.
What is Anal Stenosis?
Anal stenosis refers to a narrowing of the anal opening, which makes it difficult for stool contents to pass through easily. Symptomatic children tend to be particularly colicky babies, because of the discomfort associated with the stool backing up. The stool may exit under pressure and look almost like a squirt gun. Treatment of this disorder usually involves gentle dilation of the anal opening. This is typically done twice a day. Every week a slightly larger lubricated dilator is passed to stretch the anus until it reaches normal size. In very mild cases, softening the stool may be sufficient until the anus grows sufficiently. Suppositories can make the child comfortable in the short run, but do run the risk of dependence. At around 4 months, apple or even prune juice may help the child to pass stool. Rarely, surgery is needed to insure an opening of adequate caliber. If this is an isolated anomaly, the prognosis is excellent.
Some children are born with no anal opening at all. This is called an imperforate anus. The rectum ends in a blind pouch, about 2 cm inside the perianal skin. Usually the sphincters are well developed. For these children, a colostomy is indicated during the newborn period, but once the final surgery corrects the defect, the prognosis is likewise excellent.
Who Gets Anal Stenosis?
The most frequent anorectal defect seen in boys is the recto-urethral fistula, or a communication between the rectum and the lower part of the urethra. These children also require a colostomy before the definitive repair period. The long term prognosis for normal urethral and rectal function is good.
The rectovesical fistula is a communication between the rectum and the bladder. These children usually also have poorly developed sacral bones and sphincters. The prognosis for normal bowel function is poor.
For all anorectal malformations, there is a very good correlation between the degree of development of the sacral bone with the final bowel and bladder functioning after correction. Children with an absent sacrum will almost certainly have permanent incontinence. Those with a well-developed sacrum will generally have an excellent outcome.
Based on the treatment your doctor has prescribed, I can only assume your daughter has a very mild case of anal stenosis. Although her condition is concerning to you now, in a few months you will probably be privileged to change many dirty diapers each week.