Abstract: TH-PO1079
Urinary Cystine Excretion in an Adult Kidney Stone Cohort
Session Information
- Mineral Disease: Nephrolithiasis
November 02, 2017 | Location: Hall H, Morial Convention Center
Abstract Time: 10:00 AM - 10:00 AM
Category: Mineral Disease
- 1204 Mineral Disease: Nephrolithiasis
Authors
- Haley, William E., Mayo Clinic, Jacksonville, Florida, United States
- Enders, Felicity T., Mayo Clinic, Jacksonville, Florida, United States
- Mehta, Ramila A., Mayo Clinic, Rochester, MN, Rochester, Minnesota, United States
- Goldfarb, David S., New York Harbor VAMC, Hastings on Hudson, New York, United States
- Lieske, John C., Mayo Clinic, Jacksonville, Florida, United States
Background
Cystinuria is caused by mutations in the amino acid transporter coded by SLC3A1 and SLC7A9. Heterozygotes are not well defined or characterized. This study determined the distribution of urinary cystine (Ucys) in adult kidney stone formers and defined the prevalence of moderate to severe cystinuria.
Methods
Ucys, ornithine, lysine, and arginine (OLA) were analyzed by quantitative liquid chromatography – tandem mass spectrometry in all new adult patients in a tertiary stone clinic (2000 – 2014; N=1173; median follow up 1.4 yrs (IQR 2, 12)).
Results
Ucys excretion was abnormal in 15% (176/1173) of adult kidney stone formers. The majority were moderate, and 1% were severe (consistent with homozygous cystinuria). Patients with moderate Ucys differed from normal being more likely male with a greater percentage uric acid (UA) stones. Higher urinary levels of OAL were present with moderate and severe Ucys, suggesting the moderate group contains a subset of heterozygous cystinuria carriers. Non-cystine stones were present with moderate Ucys including a higher proportion UA stones compared to the normal Ucys group. Only a minority with severe Ucys excretion had a family history of cystinuria. In univariate models, predictors of moderate Ucys (>115 µmol/24h) and severe cystinuria (>1000 µmol/24h) were higher UNa, sulfate and OAL (P<0.001). In multivariate models, Usulfate, Ulysine, Uornithine remained significant.
Conclusion
A high index of suspicion and low threshold for screening are necessary since cystinuria requires specialized treatment for best outcomes. Moderate cystinuria may confer UA stone risk and requires further study.
Laboratory values and demographics (Median; Q1,Q3)
| Cystine group (µmol/24h) | < 115 | 115-1000 | > 1000 |
| N | 997 | 164 | 12 |
| Male % | 49 | 79 | 42 |
| FH Cystine stones (n (%)) | 0 | 0 | 3 (25) |
| FH any kidney stone (n (%)) | 277 (46) | 69 (44) | 6 (50) |
| U Cys (µmol/24h) | 51.0 (37, 71) | 151.0 (128, 192) | 2810 (2186, 3747) |
| U Ornithine (µmol/24h) | 13 (9, 18) | 32 (23, 44) | 2262 (1625, 3050) |
| U Lysine (µmol/24h) | 100 (57, 169) | 457 (302, 747) | 9955 (6595, 11551) |
| U Arginine (µmol/24h) | 24 (14, 49) | 42 (26, 88) | 4110 (2328, 4971) |
| U Ca (mg/24h) | 169 (108, 245) | 239 (165, 325) | 176 (145, 214) |
| Documented Cystine stone (n (%)) | 0 | 1 (0.01) | 9 (75) |
| Documented CaOx stone (n (%)) | 261 (72) | 50 (65) | 0 |
| Documented CaP stone (n (%)) | 67 (18) | 14 (18) | 0 |
| Documented uric acid stone (n (%)) | 29 (8) | 13 (17) | 0 |
Funding
- NIDDK Support