What are anorectal malformations?

Anorectal malformations (ARMs) are a group of congenital defects that affect the structure and function of the anus and rectum. These malformations occur when the anus and rectum don’t develop properly during foetal growth. The severity and specific nature of anorectal malformations can vary widely, most often requiring surgical intervention.

What are the various types of anorectal malformations?

The main types of anorectal malformations include:

• Imperforate anus: The absence of an anal opening. Imperforate anus is classified into low-type imperforate anus and high-type imperforate anus.
• Rectal atresia: The rectum is present but there is a discontinuity, meaning it doesn’t form a continuous passage to the anus.
• Fistulas: Abnormal connections between the rectum and other structures. Fistulas can be classified based on their location: rectourethral fistula, rectovesical fistula, rectovaginal fistula, and rectoperineal fistula.
• Cloaca: A complex type of malformation where the rectum, vagina, and urethra converge into a single common channel.
• Anal stenosis: The anus is narrower than usual, leading to difficulty in passing stool.

What are the signs of anorectal malformations?

The signs that may indicate the presence of an anorectal malformation can vary widely depending on the specific type and severity of the defect.

Signs in newborns may include:

• the anal opening is missing or located in an abnormal position
• failure to pass meconium (their first stool) within the first 24-48 hours after birth
• the abdomen is swollen or distended
• stool passes through an abnormal opening
• there is a visible fistula near the genitals or perineum
• persistent vomiting

Signs in infants may include:

• excessive straining
• discomfort or pain when trying to pass stool
• a narrow anal opening
• recurrent urinary tract infections (UTIs)
• the anus is located in an unusual position
• poor weight gain and growth

What are the causes of anorectal malformations?

The exact cause of anorectal malformations is still unclear, but it is believed to result from disruptions in embryonic development of the lower digestive tract due to a combination of genetic and environmental factors:

• Genetic factors: Specific genetic mutations may play a role in the development of anorectal malformations. Certain chromosomal abnormalities, such as trisomy 21 (Down’s syndrome), trisomy 18, and trisomy 13, are also associated with a higher risk of anorectal malformations.
• Environmental factors: Poor maternal nutrition, particularly deficiencies in folic acid, and maternal illnesses during pregnancy may increase the risk of anorectal malformations. Exposure to certain medications, drugs, or environmental toxins during pregnancy can also interfere with foetal development and increase the risk of congenital anomalies, including anorectal malformations.

How are anorectal malformations diagnosed?

Anorectal malformations are usually diagnosed shortly after birth through a combination of physical examination and various imaging studies. Imaging studies may include abdominal X-rays to assess the position of the rectum, ultrasounds to visualise internal organs and identify any associated anomalies, and MRI scans to identify the precise anatomy of the malformation and any associated fistulas.

What treatments are available for anorectal malformations?

Treatment for anorectal malformations involves surgical intervention to correct the defect and create a functional anus and rectum. The specific treatment plan depends on the type and severity of the malformation. The main surgical procedures available are:

• Colostomy: The surgeon creates an opening (stoma) in the abdominal wall and connects the colon to it, allowing stool to exit into a colostomy bag. This helps to avoid infection and allows time for the baby to grow before definitive surgery. After the definitive repair, if a colostomy was performed, a second surgery is carried out to close the stoma and reconnect the bowel internally.
• Posterior sagittal anorectoplasty (PSARP): The surgeon makes an incision in the perineum and carefully dissects and positions the rectum within the muscle complex to create a new anus. Regular dilations may then be needed to prevent the newly created anus from narrowing (stenosis).
• Anoplasty: The surgeon creates or enlarges the anal opening to ensure proper stool passage.
• Pull-through procedures: The surgeon pulls the rectum down to the perineum and connects it to a newly created anal opening.
• Reconstructive surgery for fistulas: The specific approach depends on the location and type of fistula. It may involve separating the rectum from the urinary or genital tract and closing the abnormal connection.

How soon should my child undergo surgery for their anorectal malformation?

The timing of surgery for anorectal malformations is individualised and based on a variety of factors. Surgery is typically performed within the first few months of life, typically between 1 and 6 months of age, but the exact timing depends on the specific circumstances of each case.

Early surgical intervention is important for several reasons:

• It allows for the correction of anatomical defects early in life, promoting healthy bowel function and minimising the risk of complications.
• It helps prevent long-term issues such as chronic constipation, faecal incontinence, and social or psychological challenges associated with living with an anorectal malformation.

With timely and appropriate surgical intervention, many children with anorectal malformations can achieve good outcomes, including the ability to pass stool and achieve continence. Long-term follow-up and ongoing medical care are essential for monitoring bowel and bladder function, ensuring growth and development, and preventing potential complications.