Anorectal Malformation

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

Etiology/Pathophysiology:
Due to defective development of the hindgut and cloaca, and includes a wide spectrum ranging from minor anal anomalies to complex malformations of the terminal bowel and genitourinary tract. Fistulas commonly extend from the rectal sac to the perineum or genital tract in a female, or to the urinary tract in a male. Classification is based on the relationship of the terminal colon to the levator sling muscles of the pelvic flood. High lesions terminate above the sling and low lesions terminate below the sling a short distance from the perineum. Determining if the lesion is high or low is key because high lesions require colonic diversion and delayed repair while low lesions can be repaired primarily. High lesions have no perineal opening. Low lesions are often associated with fistulas to the perineum or posterior vaginal fourchette.

Pathology:
Not applicable

Imaging Findings:
An inverted lateral view is obtained with the infant held in an inverted position for at least five minutes to allow air to enter the terminal bowel. The level of the anomaly is determined by the relationship of the terminal bowel to the levator sling, with the levator sling level being determined by the M point which lies at the level of the junction of the middle and distal third of the ischium.

Any perineal opening should be injected with contrast to demonstrate the level of the lesion.

Forty percent of high lesions and 25% of low lesions have urinary tract defects. Plain films of the spine as well as renal ultrasound and voiding cystourethrography studies must be ordered in each patient.

DDX:

• Not applicable

References:

• Correlapedia
• Correlapedia

Section Top | Title Page

URL: http://www.virtualpediatrichospital.org/