BIOMED - Pathophysiology

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©️ Cincinnati Children's

Imperforate Anus

This congenital birth defect falls under an umbrella term of anomalies labelled anorectal malformations (ARMS). In the case of an imperforate anus, the fetus' rectum and anus are not properly developed, causing constipation, fecal and/or urinary in intense, infections, and others. Prognosis can be very positive long-term, however complex malformations can affect multiple areas of life including sexual function and urinary/bowel control.

Incidence
Anorectal malformations occur in around 1 in 5'000 births, and are slightly more common in males. The cause is unknown, and does not appear to be passed through family history, however it is thought to be associated with a genetic cause.

As per the Cincinnati Children's website, here are the most common types of ARMs:

Associated Conditions with ARMS
About 50% of babies born with an ARM also have another defect present, which can be referred to as a VACTERL association, or VACTERL/VATER syndrome.

This stands for the following defects:

Usually, children diagnosed with having a VACTERL association usually have three or more of these anomalies, and thus, it is important children receive specialist care to treat these in a coordinated way.

Diagnosis
ARMS are commonly diagnosed on first exam post birth, where it will be noted the anus may be not present or situated in the wrong place. Sometimes, this may be picked up on pre-natal ultrasound, where the families are referred to maternal-fetal medicine (MFM).

Once diagnosis is made, tests are performed to understand the type and anatomy of the defect, to determine the care necessary.

Abdominal X-ray shows anomaly location and look for associated VACTERL associations of the spine and sacrum.

Renal Ultrasound for assessment of kidney, bladder, and urinary tract.

Pelvic Ultrasound to evaluate how the ARM affects reproductive organs in girls.

Spinal ultrasound to assess spinal integrity, including spinal cord that can cause neurological issues, urinary and fecal incontinence and leg weakness with growth of the child.

Magnetic resonance imaging (MRI) to make a definitive diagnosis of tethered spinal cord or other spinal cord abnormalities, as well as viewing the pelvic muscles and reproductive organs.

Echocardiogram to detect cardiac defects.

Treatment
Treatment depend on the type of ARM present, and associated defects. Posterior Sagittarius Anorectoplasty (PSARP) is a surgery to correct the effect, and involves moving the anus to the location within the anal sphincter, and may occur soon after birth.

Temporary colostomy (stoma) formation may be done before a PSARP surgery to facilitate waste removal until the PSARP can take place. This will be closed a few months after the PSARP and bowel function will be monitored to ensure surgery has been successful.

Follow-Up & Management
Monitoring for signs of infection post-operatively is important, as well as bowel movements. There may be need to be a high-fibre diet implemented depending on whether the baby has constipation, and follow up in the clinic post discharge is required to check progress and address concerns.

Children who have been born with an ARM are slower to toilet train than other children, and may not have good bowel control, however toilet training should still start at the usual age of 3-4 years old. However long term, these children are usually able to gain good control.

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