Abstract: TH-PO1079

Urinary Cystine Excretion in an Adult Kidney Stone Cohort

Session Information

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)< 115115-1000> 1000
N99716412
Male %497942
FH Cystine stones (n (%))003 (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 (%))01 (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