Urology
Winter 2015

Johns Hopkins has been a world referral center for bladder exstrophy repair for nearly four decades, building on the pioneering work of pediatric urologists Robert Jeffs and John Gearhart. Now Heather Di Carlo is adding to that legacy with a new way to approach exstrophy closure: using MRI-guided navigation of the pelvic floor. 

Di Carlo and colleagues have received approval from the Food and Drug Administration and Johns Hopkins’ Internal Review Board to adapt a navigation system—one neurosurgeons and orthopaedists have been using for years—for urologic and reconstructive surgery.

Here’s how it works: The day before surgery, the patient gets an MRI. Di Carlo and pediatric radiologist Aylin Tekes identify important anatomic features like the anterior superior iliac spines and the pubic tubercles, the umbilicus, and anus. Just before surgery, Di Carlo secures a strap on the patient’s chest; the strap has three tiny microarrays that signal fixed spots. Then, using a registering pointer connected to the system, Di Carlo correlates the patient’s anatomy with the MRI. Next, pediatric orthopaedic surgeon Paul Sponseller corrects the pelvic bones and stabilizes them with an external fixator, “which changes the pelvic floor anatomy,” Di Carlo says, “but that doesn’t make any difference because we already registered the key landmarks.” A major reason why Johns Hopkins is a referral center, she notes, is that the dissection of the pelvic floor is so crucial to getting a secure closure to the bladder and pelvis. That is a crucial part of the operation. “When we’re operating,” she says, “we’re able to see those muscles, and we know  we’re getting those fibers completely dissected.”

The team has used the MRI-guided system on 10 patients, boys and girls, for primary closures and reclosures; all had osteotomies. “There have been no adverse events,” Di Carlo says.

Di Carlo hopes to expand the MRI-guided navigation to include other procedures such as cloacal exstrophy and epispadias repair.