Colorectal Quiz: Episode 41 - Perineal Hypospadias

Prenatal hypospadias diagnosis has become part of routine prenatal care, whereas 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 perineal fistula, diverting colostomy is appropriate rather than primary repair.

Laparoscopic colostomy with three trocars allows precise selection of the sigmoid point, external meconium evacuation, and creation of separated 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 view allows confirmation of meconium removal and visualization of distal segment decompression.

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

A healthy, normally developed sacrum is not surprising given a low rectum with perineal fistula.

The key technical question in perineal fistula repair is how much anterior rectal wall needs to be mobilized.

A perineal fistula in most males 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 the anteriormost sphincter up to the base of the scrotum, center of scrotum, or even at the hypospadias exit.

In this case, the surgical approach is to leave the 3 cm long, 1 mm diameter fistula undissected and close to the urethra, working on the bulging rectal lumen without starting dissection from the perineal fistula, because there is essentially no wall between the urethra, spongiosum, and fistula.

The repair requires balancing adequate mobilization to avoid anastomotic tension while minimizing dissection, because less is more and significant damage can occur with anterior dissection.

This repair is essentially a glorified cutback with no need to dissect the anterior rectal wall; 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, being mucosally lined, could potentially be used by urology for hypospadias repair.

The pediatric surgeon managing the rectum does not need to chase the fistula, but the anterior rectal wall must be adequately dissected so it is completely separated with a healthy anterior edge of the anoplasty under no tension to prevent retraction.

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

This case will need a posterior sagittal incision, probably fairly close to the coccyx level, to achieve full rectal mobilization, but with the patient diverted the incision is less concerning.

The same approach of leaving a long fistula undissected applies to perineal fistulas without hypospadias when the meconium opening is at the base or middle of the scrotum; the long narrow fistula can be left alone and will disappear.

Pathologists will report no ganglia in transitional tissue from perineal fistulas, which can cause panic and lead to a confusing pathway ending in wrong decisions, especially in bulbar urethral fistulas where patients are likely constipated.

The plan is to have urology perform at least the first-step hypospadias repair with the colostomy still in place, at 6-9 months of age as a compromise between the urologist's preference for 1 year and the colorectal surgeon's preference for 6 months.

Colostomy closure would occur 6 months after urology completes the final hypospadias repair.