Pediatric Nephrology and Urology

While the number of patients requiring kidney transplantation in the United States has grown steadily by 3,000 to 4,000 each year, the gap between allograft supply and demand has also continued to grow. With more than 100,000 individuals with end-stage kidney disease listed on the transplant waiting list at the United Network for Organ Sharing, an increase in the number of living donor allografts supply is needed to reduce this trend.

Recently, pediatric and adult nephrologists, a pediatric urologist, and transplant specialists at NewYork-Presbyterian Morgan Stanley Children’s Hospital and NewYork-Presbyterian/Columbia University Irving Medical Center, presented a rare case of a pediatric recipient of a living donor medullary sponge kidney transplant (MSK) and discuss the risks and benefits of accepting MSK allografts for this age group.

MSK disease predisposes patients to recurrent nephrolithiasis, a condition affecting one in every 5,000 people in the United States. Deciding whether to accept a living donor with MSK must be carefully considered due to the risk following transplant of urinary tract infection and recurrent nephrolithiasis that could lead to chronic kidney disease. The case study appeared in the June 2021 issue of Pediatric Transplantation.

Background

A 17-year-old boy presented with a history of orthotropic heart transplant in 2006 for dilated cardiomyopathy of unknown etiology, Epstein-Barr Virus viremia, and end-stage kidney disease secondary to calcineurin inhibitor toxicity. For living donation, the mother and two brothers (24 and 28 years old) were initially identified as potential donors. The mother, who requested to continue as the primary donor, was diagnosed with medullary sponge kidney as a child but had no recent kidney stones. The Columbia living donor team evaluated and found her to be a suitable live kidney donor.

Given the young age and history of previous heart transplant in the pediatric recipient, a living donor was preferred over a deceased donor due to overall better graft survival of the former. Although the mother had a distant history of nephrolithiasis with one stone 15 years prior to transplant, she had no stones at the time of evaluation for kidney donation. Ultimately, the mother was accepted as the donor with negative final CDC crossmatch and flow cytometry, as well as absence of donor-specific antibodies.

Transplant Procedure

Anastomosis time was 42 minutes. Postoperatively, the recipient did well with steady urine output and nadir serum creatinine at 1.3–1.4 mg/dl. A double J ureteral stent was placed at transplant with a plan for removal 4 weeks post-surgery. Post-transplant fluid intake goal was 2 to 3 liters. Given the known risk for nephrolithiasis in the donated medullary sponge kidney, a 24-hour urine stone profile was performed demonstrating the following risk factors for nephrolithiasis:

• Hypocitraturia <30 mg/day (goal range for male >450 mg/day, female >550 mg/day)
• Hyperuricosuria of 2.66 mg/day (0-1 mg/day)
• Urine pH of 5.18 (5.8-6.2)

Given these findings, he was started on potassium citrate and encouraged to increase fluid intake to 3 liters per day. He remained asymptomatic and did not have any hematuria, pain, fever, and stone passage noted in his urine.

Postoperative Follow-Up

One-month post-transplant, the patient was admitted with elevated serum creatinine on routine post-transplant laboratory assessment. He maintained adequate urine output but demonstrated worsening hydronephrosis on serial ultrasounds. CT scan showed a 4 mm non-obstructing stone, and a MAG 3 confirmed the absence of obstruction. Given these findings, the team proceeded to remove the ureteral stent. During cystoscopy, the stent was found to be completely encrusted but removed uneventfully. There was no individual stone noted during the cystoscopy procedure and the hydronephrosis resolved on follow-up imaging.

Fifteen months post-transplant, the patient underwent an ultrasound guided kidney transplant biopsy for acute elevations of serum creatinine to 1.6 mg/dl that demonstrated no evidence of T cell-mediated rejection nor antibody-mediated rejection, as well as absence of crystal deposits. His serum creatinine decreased to 1.4 mg/dl with continued hydration post the renal biopsy. He will continue to be evaluated with kidney transplant ultrasounds every 6 months to monitor for nephrolithiasis.

The Columbia team concluded that with increasing organ shortages, a variety of donors might need to be considered to expand the organ pool. Currently the patient’s mother is doing well without nephrolithiasis or urine infections post-donation. The authors noted, “In the absence of more studies showing long-term outcomes in donors and recipients with donor gifted nephrolithiasis, we should consider changes in determining donor eligibility with regards to transplant guidelines. In considering donors with MSK, these donors should be evaluated with stone risk profiles with correction and mitigation of high-risk factors prior to donation.”