The Colorectal Quiz Episode 1: ARM - Low Bulbar Fistula

Anorectal malformation patients require screening for VACTERL association: vertebral abnormalities (plain X-ray), cardiac defects (exam and echo), esophageal atresia (NG tube pass), renal abnormalities (kidney ultrasound), and limb abnormalities (physical exam).

Sacral ratio measurement should wait until the child is 3 months of age for true measurements, though early imaging gives a feel for pelvic development.

Spinal ultrasound in anorectal malformation patients should include evaluation of the presacral space to screen for presacral masses.

Presacral masses are rare in typical imperforate anus but occur in almost half of anal stenosis or rectal atresia cases, which require MRI evaluation.

Cross-table lateral X-ray should be obtained at approximately 24 hours of life to assess the air column position relative to the perineal skin, with the baby positioned prone to allow air to rise to the buttocks.

The cross-table lateral film should include a marker at the expected anal location to allow measurement of the distance between the air column and the perineal skin.

A sacral ratio greater than 0.7 connotes very good prognosis for bowel control and provides peace of mind for families regarding potty training and school readiness at 4 years of age.

Well-formed buttocks, visible sphincter mechanism location, and well-developed sacrum together predict good prognosis for continence.

The key to deciding whether to perform primary posterior sagittal anorectoplasty is knowing where the rectum is located; the danger is finding midline white structures like urethra, bladder neck, or bladder instead of rectum.

Colostomies and distal colostograms are performed to know exactly where the rectum is and whether to approach it perineally or laparoscopically.

The surgeon should never attempt posterior sagittal approach blind; imaging must confirm that the first structure encountered will be the air pocket of the distal rectum.

Colostomy is the safe choice for anorectal malformation repair, though it carries risks of complications from both the colostomy creation and the subsequent closure.

Surgeons have performed primary anorectoplasty on low anorectal malformations without knowing about a fistula, resulting in children later urinating out of the anus.

During primary posterior sagittal anorectoplasty, the surgeon should open the posterior wall of the rectum and inspect the anterior wall to rule out a fistula.

A bulbar fistula is located at the elbow of the urethra, using anatomic nomenclature based on the urethral location.

95% of Down syndrome patients with imperforate anus have no fistula, but 5% do have a fistula, so distal colostogram is still indicated.