- Anorectal malformations comprise a wide spectrum of abnormalities
- Often associated with other anomalies
- Affects 1 in 5,000 live births
- Prognosis depends on
- The severity of the malformation
- The extent of other anomalies
- Early treatment of neonates with anorectal anomalies is important
- Important issues to consider are:
- Is there any other associated life threatening abnormality?
- Should the patient undergo primary repair with covering colostomy?
- Should the patient undergo defunctioning colostomy and later
definitive repair?
Clinical assessment
- Clinical inspection of the perineum is important
- In 80% patients, clinical examination and urinalysis allows decision
whether colostomy is required
- Flat perineum and absence of anal dimple suggest poor perineal
muscles
- These are associated with high malformation
- Meconium at the perineum, skin tag associated with anal dimple and
anal membrane
- These suggest a low malformation
- Even if perineal fistula is present meconium may not be passed for
24 hours
Picture provided by Luis Prera, Hospital General San
Juan de Dias, Guatemala City, Guatemala
- Approximately 50% of all patients with anorectal malformations have
an associated urogenital anomaly
- Renal abnormalities sometime present include:
- Renal agenesis
- Vesicoureteral reflux
- Neurogenic bladder
- Renal dysplasia
- Megaureter
- Hydronephrosis
- Ectopic ureter
- The percentages of patients with associated urogenital anomalies is
as follows:
- Rectovesical defect - 52%
- Recto-prostatic - 40%
- Rectovestibular - 9%
- Recto-bulbar - 4%
- Rectoperineal - Nil
Investigation
- If clinical signs are unclear than radiological investigations may
be useful
- Cross-table lateral x-ray with baby prone with a marker on the
perineum is useful initial study
- The presence of air in the distal rectum within 1 cm of the perineum
suggest primary repair may be possible
- Ultrasound may show feature of co-existent obstructive uropathy
- If a colostomy is fashioned, distal colography may demonstrate a
fistula to the urinary tract
- Plain x-ray of the spine and sacrum may show associated
abnormalities
Picture provided by Mohamed Abouhaba, Alexandria
University, Alexandria, Egypt
Management
- Intravenous fluids are required
- A nasogastric tube should be inserted
- Urinalysis may indicate the presence of a fistula to the urinary
tract
- Colostomy should be considered if there is:
- Recto-bulbar urethral fistula
- Recto-prostatic urethral fistula
- Rectovesical fistula
- Imperforate anus without fistula
- Rectal atresia
- Posterior sagittal anoplasty may be possible if there is low
abnormality with a rectoperineal fistula
- Avoids the need for colostomy
Surgery
- Repair of an anorectal malformation requires a meticulous and
delicate technique
- The posterior sagittal approach is an ideal method of defining and
repairing anorectal anomalies
- Patients are placed in the prone position with the pelvis elevated
- Anorectal abnormalities in 90% of male patients can be repaired with
a posterior sagittal approach alone
- Perineal fistulas are repaired with a minimal posterior sagittal
incision
- The external sphincter is mobilised to bring the anus back to the
center of the external sphincter
- This operation can be performed in the neonatal period without a
protective colostomy
- An electrical stimulator helps identify the location of the
sphincteric mechanism
- Postoperative anal dilatation is required
Outcome
- Postoperative constipation is common
- If unrecognised can result in megarectum
- 25% have patients have faecal incontinence
- Urinary incontinence may also occur
- Severe bowel disturbances and urinary incontinence are often
associated with sacral defects
Bibliography
Stites T, Lund D P. Common anorectal problems.
Semin Pediatr Surg 2007; 16: 71-78. |