Kidney transplant with Dr. Jonathan Merola

Hello everyone. Welcome back to another episode of the Stay Current podcast. I'm Cecilia Gigena, a research fellow at Cincinnati Children's Hospital. And along with Stay Current, we are sharing knowledge to improve child health around the globe. So today, we are talking about kidney transplants in pediatric patients. And for that, we have Dr. Jonathan Merola, a specialized transplant surgeon from Cincinnati Children's Hospital.

The most common diagnosis for kidney failure in children includes congenital anomalies

of the kidney and urinary tract. So this includes renal aplasia, hypoplasia, or dysplasia, as well as obstructive neuropathy from reflux and bladder obstruction. And together, they comprise 35 to 40% of pediatric patients undergoing kidney transplants. Other causes of kidney failure include focal segmental glomerular sclerosis, hereditary nephropathies, and chronic glomerulonephritis. In the US, approximately 800 kidney transplants are performed in children below 18 years old.

And as Dr. Merola said, the main causes are congenital abnormalities, glomerulonephritis like FSGS or focal segmental glomerular sclerosis, and hereditary nephropathy. Transplant for all of those three conditions is really curative. And so survival for a living in deceased donor kidney transplant in children often exceeds 30 years. And that is better than the weightless mortality, which is around 15 years.

One of the major challenges, however, is supporting children with renal failure to the point where they can successfully obtain an adult kidney transplant. Neonates can then be supported with specialized hemodialysis known as Carpe Diem or Cardio-Renal Pediatric Dialysis Emergency Machine, which basically serves as a CRRT for infants as small as two and a half kilos. So Carpe Diem is an innovative continuous renal replacement therapy or CRRT as Dr. Merola said.

This therapy is for small infants, specifically neonates where other CRRTs can't be used. After a short period on hemodialysis, we can then transition patients to perineal dialysis, which requires of at least a period of two to three weeks from the time of catheter insertion to when you can initiate it. That timeframe is really needed to mitigate the risk of perinitis. So for CRRT, we have hemodialysis and perineal dialysis.

To initiate perineal dialysis safety, we need a period from the catheter insertion to dialysis initiation of at least two to three weeks. And are there any other technical tips that help with catheter insertion? We found that if you do an omentectomy in these small babies, there's a much greater success of catheter insertion. Awesome. So when do we consider a kidney transplant? For all patients with stage four or five chronic kidney disease, we would recommend referral for kidney transplant.

So patients with kidney disease, stage four or five, should be referred for kidney transplant. And here Dr. Merola explains the considerations on size and age.

Unlike adults, however, size can limit successful transplant. And here at Cincinnati, we prefer children to be about 10 kilos or 80 centimeters in height to accommodate an adult kidney. And that's typically at two years of age. Okay. So to be able to be transplanted with an adult size kidney, they need to reach 10 kilograms or 80 centimeters of height. We have a close partnership with Urology, particularly for managing patients with posterior ureteral valves or a neurogenic bladder.

Partnering with Urology is key so that they can follow the patients assessing the need for complementary surgeries or treatment and bladder cycling. And so they work up these patients by performing voiding systo urethrograms and neurodynamics study and closely evaluate them prior to transplant and use the results of those studies to guide a bladder cycling and conditioning. Perfect.

So wait until they are at least eight to 10 kilos and follow them with Urology to check on the bladder size to see if they're need an augmentation or not. So what are the considerations we should have for these patients? Some of the unique considerations for pediatric population include size. So an adult size kidney should ideally be less than 10 or 12 centimeters to comfortably fit. Great. So the ideal size of a transplanted kidney should be less than 10 to 12 centimeters.

And what type of organs are considered for pediatric kidney transplant? Living in deceased donor kidney transplants can be considered for children. Living donor kidney transplants are the preferred grafts because they have a lower rejection risk and a longer overall survival. Living donors can be from a family member or a friend who comes forward and donates their kidney as an elective operation.

Advantages to this include that there's less delayed graft function, that there's more rapid organ access, particularly to patients who are not yet on dialysis. Great. So living donor recipients have better graft survival rates and less delayed graft function. Ten year graft survival is 75% for living donor kidneys and 65% in deceased donor kidney transplants in kids. So a very good outcomes overall. And we have to check if they have multiple vessels in the graft.

Additionally, kidneys with multiple vessels are more challenging to implant on the aorta and IVC and therefore those are considered higher risk grafts. Great. So again, check the donor's kidney size and vasculature.

And how is the surgery performed? So children typically receive kidney transplant through a retroperitoneal incision and the vascular andastomoses are performed to the common iliac vessels. And smaller patients, the aorta or IVC, inferior vena cava, allow for better vascular inflow and they both can be exposed using an intraperitoneal or extraperitoneal approach. Extraperitoneal is the preferred option at Cincinnati Children's. So let's hear the reason for that with Dr. Merola.

Here in Cincinnati, we prefer the extraperitoneal approach both to minimize the risk of bowel injury and allow for contained space in the setting of any required biopsy of the kidney allograft. Usually, an ipsilateral nephrectomy is performed to allow an adequate space for the graft. But also in the setting of polyuria or proteinuria or in the case of FSGS, where urine protein is an important marker for disease recurrence to be detected early.

So apart from graft space, prior diuresis and proteinuria has to be assessed in case patients need bilateral nephrectomies. In patients that require bilateral nephrectomy, like those with Wilms tumor or those who have FSGS where you really want to closely monitor proteinuria as a neural design, the disease recurrence, we usually take the contralateral kidney out in a separate setting from that transplant. Let's talk about complications after kidney transplant.

Surgical complications include vascular thrombosis and urine leak and those can occur in about 5% of patients. Rejection and infection are the two most significant non-surgical long-term complications in children following kidney transplant. So as in other transplants, these patients have to be immunosuppressed. But we have to carefully regulate it to avoid other complications that the immunosuppressors can cause, such as obesity for steroids or B-cell malignancies for T-cell suppressors.

Immunosuppression is required lifelong, but may predispose patients to viral infections, malignancies, and long-term can cause toxicity to the transplanted kidney. So kids have to be monitored very closely for all of these post-transplant. But how can we improve outcomes in our patients? For the past 5 decades, many of the advances in transplant have relied on better ways to treat and protect the host. But one of the areas I'm very interested in is actually in treating the graft.

Normothermic perfusion is a technique that circulates a warm perfusion solution through the renal vasculature, enabling the organ to recover from the ischemic injury. That also enables the opportunity to treat the organ. So taking care of the graft and not only the host seems to be the future in transplant.

Congenital kidney and urinary tract malformations are the top causes of pediatric kidney transplant. Teamwork is key with neonatologists, pediatric nephrologists, and pediatric urologists joining forces for success. Done right, a single donated kidney survival can exceed 25 to 30 years, especially if it is from a living donor.

Specific consideration in kids includes graft to child size, the need for a concurrent uni- or bilateral nephrectomy, and a careful regulation between immunosuppression and risk of infection or malignancy. Also, cutting-edge technologies like organ perfusion offers a promising way to treat organs outside the body to potentially extend their lifespan. And that was everything for today. Don't forget to subscribe to the Stay Current MD YouTube channel.

Follow our social media channels and download the Stay Current MD app for tons of content in pediatric surgery. Global Cast MD, along with Cincinnati Children's Hospital, sharing knowledge to improve child health around the globe.