Colorectal Quiz: Episode 41 - Perineal Hypospadias

Hypospadias prenatal diagnosis has become part of routine prenatal care, whereas up to 5-7 years ago pediatric surgeons were never called for such counseling.

The combination of urologic defects (bladder atrophy, penoscrotal transposition, severe hypospadias) and anatomic changes in the pelvic region is commonly associated with perineal fistula.

In a newborn with severe hypospadias, penoscrotal transposition, and unclear connection between rectum and urinary tract, diverting colostomy is appropriate rather than primary repair.

Performing colostomy in the newborn period makes the subsequent rectal dissection easier.

Laparoscopic colostomy with three trocars allows precise selection of sigmoid location, external meconium evacuation, and creation of two separate stomas with no skin opening between them, which facilitates ostomy bag attachment.

Irrigating the distal colostomy segment by passing a large Foley catheter under laparoscopic visualization allows confirmation of meconium removal and distal segment decompression.

In this case, colostogram showed 2.5 cm distance from the perineal fistula to the bulging rectal lumen and urethral length of almost 3 cm.

A healthy, normally developed sacrum is not surprising in a patient with a perineal fistula, given that the rectum is so low.

For urologists, 5 months of age is quite early for hypospadias repair; they would ideally perform two-stage reconstruction closer to 1 year of age.

In most male perineal fistulas, the fistula is within the anteriormost portion of the sphincteric ellipse, allowing posterior rectal wall mobilization only with no anterior dissection and no possibility of urethral injury.

The perineal fistula opening can be located anywhere along the anterior midline raphe from within the sphincter ellipse all the way to the base of the scrotum, center of the scrotum, or even higher at the exit of the hypospadias.

In this case with a 3 cm long, 1 mm diameter fistula, the surgical approach is to leave the fistula undissected close to the urethra and work on the bulging rectal lumen without starting from the perineal fistula, because there is basically no wall between the urethra, the spongiosis, and the fistula.

The surgical goal is to achieve enough rectal mobilization that the anastomosis is not under tension, but less dissection is better because significant damage can occur with anterior dissection.

In perineal fistulas with long anterior tracts, the repair is essentially a glorified cutback with no need to dissect the anterior rectal wall at all; only posterior rectal wall mobilization is needed to fill the space.

The surgical approach is to mobilize the lip of anterior rectal wall and leave the fistula floating as it attaches adjacent to the urethra, to be addressed later by the urologist during urethral dissection.

The fistula tissue is mucosally lined and might potentially be used by urologists for hypospadias repair.

The anterior rectal wall must be adequately dissected so it is completely separated, creating a healthy anterior edge of the anoplasty with no tension so it does not pull back or retract.

In a typical newborn perineal fistula, if you can avoid a posterior sagittal incision, the rectum is usually right below the surface, and by the end of the case you can have no incision anterior or posterior to the anoplasty.

This case will need a posterior sagittal incision, probably fairly close to the level of the coccyx, to achieve full rectal mobilization.

The same approach of leaving a long narrow fistula undissected applies to perineal fistulas without hypospadias when the meconium opening is at the base or middle of the scrotum; there is no need to chase the fistula, it will disappear.

Pathologists will report 'no ganglia' on transitional tissue from perineal fistulas, which can cause panic and lead to a confusing diagnostic pathway ending in wrong decisions, especially in bulbar perineal fistula patients who are often constipated.

The planned timeline is to perform at least the first-stage hypospadias repair (the most complicated step) with the colostomy still in place between 6 to 9 months of age, then close the colostomy, with final urologic repair 6 months after colostomy closure.