Anorectal Anomalies

Definition

Definition of Anorectal Anomalies
Anorectal anomalies are medical problems affecting the structure of the anus and rectum. A person with an anorectal problem would have some sort of deformative feature of the anus or rectum, collectively known as an anorectal malformation.

Symptoms

Symptoms of Anorectal Anomalies
Symptoms vary according to the type of anorectal anomaly. They are classified into two types (high and low) depending on where the bowel ends.

1. If your child has a low anorectal anomaly, faeces cannot be removed from the body as usual, and so builds up in the bowel. Your child will not be able to pass meconium - the dark faeces passed in the first few days of life. The build up of faeces in the bowel can cause a swollen abdomen and vomiting.
2. If your child has a high anorectal anomaly without a fistula, he or she will not be able to pass meconium and will develop similar symptoms.
3. If your child has a high anorectal anomaly with a fistula, the faeces will be able to pass out of the body, usually through the vagina in girls or through the urethra in boys.

Causes

Causes of Anorectal Anomalies
Anorectal malformations (ARM) represent a spectrum of abnormalities ranging from mild anal anomalies to complex cloacal malformations. The etiology of such malformations remains unclear and is likely multifactorial. There are however reasons to believe there is a genetic componenet. As early as the 1950s, it was recognized that there was an increased risk for a sibling of a patient with ARM to be born with a malformation, as much as 1 in 100, compared with the incidence of about 1 in 5000 in the general population. Since that time there have been reports of families with 2 or more affected members and associations of ARMs with multisystem syndromes. In particular, mutations in specific genes encoding transcription factors have been described in patients having Townes-Broks syndrome, Currarino's syndrome, and Pallister-Hall syndrome, each of which have autosomal dominant modes of inheritance. In addition, it has been found that there is not only an increased incidence of ARM in patient with trisomy 21 (Down's syndrome), but that 95% of patients with trisomy 21 and ARM have imperforate anus without fistula, compared with only 5% of all patients with ARM. Based on this evidence, it is likely that the mutation of a variety of different genes can result in ARM, or that the etiology of ARM is multigenic.

Diagnosis

Diagnosis of Anorectal Anomalies
The radiologic evaluation of a newborn with imperforate anus includes an abdominal ultrasound to evaluate for urologic anomalies. In the case of persistent cloaca, a distended vagina (hydrocolpos) can be identified. Plain radiographs of the spine can show spinal anomalies such as spina bifida and spinal hemivertebrae. Plain radiographs of the sacrum in the anterior-posterior and lateral projections can demonstrate sacral anomalies such as a hemisacrum and sacral hemivertebrae. Also, the degree of sacral hypodevelopment can be assessed, and a sacral ratio can be calculated measuring the distances between key bony structures. A spinal ultrasound in the newborn period and up to age 3 months (at which time the sacrum becomes ossified) can look for evidence of a tethered spinal cord and other spinal anomalies. A crosstable lateral radiograph can help show the air column in the distal rectum in the small percentage of patients for whom clinical evidence does not delineate in 16–24 hours the likely anorectal anomaly.

Treatment

Treatment of Anorectal Anomalies
The early management of a newborn infant born with an anorectal anomaly is crucial and two important questions must be answered during the first 24 to 48 hours of life. First; are there associated anomalies that threaten the baby's life and should be dealt with right away? And second, should the infant undergo a primary procedure and no protective colostomy or a protective colostomy and a definitive repair at a later date? For babies born with persistent cloaca, the surgeon must also determine whether a dilated vagina is present and if it should be drained, as well as determining whether urinary diversion will be required. These maneuvers are intended to prevent sepsis or metabolic acidosis.

The decision to perform an anoplasty in the newborn period or to delay the repair and to perform a colostomy is based on the infant's physical examination, the appearance of the perineum, and any changes that occur over the first 24 hours of life.

Prognosis

Prognosis of Anorectal Anomalies
When evaluating the results of the treatment of anorectal defects, we feel that one cannot group patients according to the traditional nomenclature into "high," "intermediate," and "low" defects, as malformations classified in a same group can have different treatments and different prognoses. For instance, rectoprostatic fistula and bladderneck fistula, both considered as "high" defects are actually very different. We believe that an anatomic classification would have more clinical value. The functional results of the repair of anorectal anomalies seem to have significantly improved since the advent of the posterior sagittal approach. However, the results of this approach are difficult to compare with those of other methods because terminology and classification are not consistent.

Prevention

Prevention of Anorectal Anomalies
Consult with your doctor.