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Kidney Week

Abstract: PO2537

Urine Supersaturation in Patients with Kidney Transplant Nephrolithiasis

Session Information

Category: Transplantation

  • 1902 Transplantation: Clinical

Authors

  • Bolen, Erin E., Mayo Clinic Arizona, Scottsdale, Arizona, United States
  • Humphreys, Mitchell, Mayo Clinic Arizona, Scottsdale, Arizona, United States
  • Stern, Karen L., Mayo Clinic Arizona, Scottsdale, Arizona, United States
  • Leavitt, Todd, Mayo Clinic Arizona, Scottsdale, Arizona, United States
  • Zhang, Nan, Mayo Clinic Arizona, Scottsdale, Arizona, United States
  • Keddis, Mira T., Mayo Clinic Arizona, Scottsdale, Arizona, United States
Background

Urine supersaturation (SS) has not been reported for kidney transplant (KTx) recipients with de novo transplant-derived nephrolithiasis. The objective of this study is to evaluate supersaturation studies, treatment, and stone and allograft outcomes in KTx recipients with allograft nephrolithiasis.

Methods

Retrospective review from 2009-2019 of KTx recipients with nephrolithiasis at Mayo Clinic was completed. Stone event was defined as radiologic evidence.

Results

Fifty six transplant nephrolithiasis cases were identified. Mean transplant age was 56.5 (±12.1) years, 32 (57.1%) were male, 46 (82.1%) receiving first KTx, 41 (75.9%) required dialysis, and 17 (30.9%) had stone event prior to KTx. Twenty one (37.5%) had at least 2 stones in the allograft, median stone size was 6 mm, and most common location was the lower pole (n=20 [41.7%]). Median time from KTx to stone event was 1 year. Thirty four (60.7%) had a 24-hour SS study at a median of 2 years after KTx. Select results are shown in Table 1. Of the 34, 14 (41.2%) had a stone event prior to KTx, and 6 (19.4%) had a donor-derived stone. Thirty one (91.2%) had increased SS of calcium oxalate, 17 (50%) calcium phosphate, and 9 (26.5%) uric acid. Thirty two (94.1%) had urine citrate <450mg/24hrs. Management of the initial 56 included potassium citrate in 13 (23.2%), calcium citrate in 10 (17.8%), and dietician referral in 18 (32.1%). Forty five (80.4%) were seen by urology, 28 (50%) needed surgical management, and 14 (27.5%) passed the stone. At median follow-up of 4 years after KTx, 37 (66.1%) had persistent stone disease in the allograft, 3 (5.4%) had graft failure, and 2 (3.6%) had died.

Conclusion

This is the first study of urine SS in patients with transplant-derived nephrolithiasis. Profound hypocitraturia was the most prevalent risk, and increased supersaturation for calcium oxalate crystals predominated. Allograft stone clearance was rare, and many required surgical intervention.

Table 1
Select 24-hr urine supersaturation parametersMedian (Range)
Volume (ml)2174.5 (745, 3960)
Sodium (mmol)125.5 (26.0, 400)
Calcium (mg)103.5 (26.0, 592)
Magnesium (mg)88.5 (22.0, 240)
Citrate (mg)124.5 (20.0, 763)
Oxalate (mg)34.35 (9.8, 136)
pH5.9 (5.1, 7.7)

Funding

  • Clinical Revenue Support