Anal atresia is a malformation of the rectum with closure of the anal canal (anorectal malformation). The anal canal does not open into an anus, but ends blindly. Instead, there are often connections (fistulas) between the rectum and the urethra.
The causes of this malformation and how it can be treated are explained in the following text. You can also find selected anal atresia specialists and centers here.
Anal atresia is a congenital condition in which the anus (anus or anal canal) is closed from birth. Strictly speaking, the anus is already closed in the womb or is never properly formed, but symptoms only appear after birth.
Anal atresia therefore belongs to the broad spectrum of anorectal malformations, i.e. all hereditary diseases affecting the rectum. In addition to the anal canal, the urinary and reproductive tract(urogenital tract) can also be affected.
The frequency of the malformation varies greatly and is around one case per 2500 to 5000 births. With this frequency, anal atresia is a rare disease. In Germany, around 250 children per year are affected, boys slightly more frequently than girls.
However, a familial accumulation can be observed. If a child already has anal atresia, the risk of having another child with anal atresia is 1 to 2 percent. This is significantly higher than the risk in the normal population.
In the womb, the embryo's entire metabolism takes place via the placenta, so that anal atresia does not yet cause any symptoms. It is only after birth, when the first bowel movement (meconium, also known as puerperium) is passed, that the malformation becomes noticeable and causes problems. If the anal canal ends completely blind, i.e. has no connection to another hollow organ such as the bladder, urethra or vagina, it is a condition with an urgent indication for surgery.
In most cases, however, the blocked anal canal has a connecting passage (a so-called fistula) with the bladder, urethra or vagina.
or vagina. Depending on the course and opening of this connecting duct, a distinction is made between different forms:
Anal atresia in men: normal anatomy on the left, on the right with the anus moved into the urethra © rob3000 | AdobeStock
Anal atresia is due to a disorder during prenatal development (medically known as embryonic development). Between the fourth and twelfth week of pregnancy, different tissue structures and layers develop. These later develop into the urinary and intestinal tract. In the case of anal atresia, these structures are defective or inadequately formed. As a result, the urinary and intestinal tract do not develop normally.
The underlying causes of this developmental disorder are not yet fully understood. There are indications that it is an inherited disorder, although the exact genetic defect has not been clarified. An important indication of genetic causes of anorectal malformations is that they occur more frequently in connection with syndromic malformations, such as Down syndrome (trisomy 21).
However, there are also some indications of so-called teratogenic influencing factors. These are substances that can interfere with embryonic development. These include medications, in particular
However, chemical and physical causes, e.g. ionizing radiation, can also be the cause of anal atresia.
Anal atresia is one of the few congenital diseases for which there are no screening tests. The diagnosis is usually only made during the first physical examination immediately after birth. A prenatal indication of anal atresia can be, for example, a conspicuous umbilical cord, which consists of two (instead of three) umbilical cord vessels.
The affected children are conspicuous after birth due to the missing or unusually localized anal opening and possibly the presence of a fistula. In some cases, stool or even air is discharged via the vagina or urethra. A bloated abdomen is also common. Around half of affected children also show other malformations. These mostly affect the urinary tract, but anatomical anomalies of the heart or gastrointestinal tract also occur.
The most common malformations associated with anal atresia are described by the so-called VACTERL syndrome:
Overall, anorectal malformations show a very wide anatomical variance. Therefore, the treatment measures must be individually tailored to the affected children. The treatment measures depend crucially on whether a connecting duct is present and where it is located.
Depending on the findings, a decision is made as to whether an artificial anus is required in the colon area prior to corrective surgery. The severity and form of the malformation also determine the number of operations required (one to three or more procedures).
The first operation usually takes place a few days after birth. For newborns with a slight malformation, a superficial and nowadays largely standardized operation is performed. This involves moving the rectum into the correct position. If this works and heals without any problems, ideally no further operations are required afterwards.
Newborns with
require more extensive and complex treatment. In these children, an artificial anus is temporarily placed in the colon area on the first or second day of life. The technical terms for this are colostomy or anus praeter.
The small or large intestine is opened and one or both ends are sutured into the abdominal wall. One end is referred to as a "terminal colostomy", which is often the case when the rectum is sutured in. If the last section of the small intestine is fixed in the abdominal wall, a "double-barreled" colostomy is usually created. This means that both the feeding part of the severed intestine (coming from the stomach) and the draining part (leading towards the rectum) are sutured in. This prevents stool, fluid and bacteria from accumulating in the draining colon.
The artificial anus usually remains in place for one to six months to protect the subsequent corrective surgery.
The actual restoration of the anal opening is called pull-through surgery or PSARP (posterior sagittal anorectal plasty). It is usually performed during the first year of life.
The closed rectal stump is detached from the buttocks and any connecting ducts are closed. In the next step, the detached rectal stump is opened and an anus is modeled.
For some years now, keyhole surgery techniques have also been increasingly used for anal atresia. These minimally invasive methods only require very small incisions. They promise better results, especially for more complex malformations.
Following the operation, the anal opening is stretched with metal rods (so-called Hegar pins). This stretching process is also known as bougienage. The diameter of the rods used gradually increases until the average anus size of a child of the same age is achieved.
The surgical correction must now heal. Once an appropriate width of the anus has been achieved, stool continuity can be restored. The child can then defecate through the newly created anus.
For this purpose, the artificial anus is removed in a further procedure around one to three months after the corrective surgery. This involves detaching the ends of the bowel from the abdominal wall and stitching them together. The abdominal wound is closed and usually heals within a few weeks.
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