Validation of a reference interval for symmetric dimethylarginine in healthy goats and its comparison to values in goats with obstructive urolithiasis

Abstract

Background: Symmetric dimethylarginine (SDMA), a sensitive biomarker for detecting renal injury, has not been characterized in goats. Obstructive urolithiasis (OU) is the most common urinary tract disease in male small ruminants.

Hypothesis/objective: Establish an SDMA reference interval (RI) in healthy adult goats and describe SDMA concentrations in goats with OU. We hypothesize that the SDMA RI in healthy adult goats will be similar to that of other adult veterinary species and that SDMA can be utilized to assess the renal function of goats experiencing OU.

Animals: Fifty-five healthy adult male and female goats from a university herd were enrolled for SDMA RI development. Twenty male and female goats from a university herd were enrolled for validation of the SDMA RI established. Thirteen male goats diagnosed with OU were enrolled.

Methods: Clinical trial. Serum samples for all animals enrolled were collected and analyzed for SDMA using an immunoassay (IDEXX Laboratories, Inc); goats with OU had additional blood work analyzed (PCV, total solids, and serum biochemistry). Symmetric dimethylarginine and other values in goats with OU were analyzed and compared at specific time points.

Results: The SDMA RI for healthy, adult goats is 8.03 μg/dL (90% CI 4.81-11.04) to 25.93 μg/dL (90% CI 22.88-28.97). There was no correlation identified between serum creatinine and SDMA in goats with OU.

Conclusions and clinical importance: The SDMA RI for adult goats is higher than in other adult large animal species. Use of SDMA in goats with OU is not useful in assessing their renal function.

Keywords: caprine; kidney; renal calculi; renal/urinary tract; small ruminant.

FIGURE 1

Histogram of (n = 59) symmetric dimethylarginine (SDMA) results (μg/dL) for control goats. Five intact males and 54 female goats were enrolled. Males were Boers (≥6 months old, approximately 1 year old); females were Boer crosses (n = 19, ≥6 months old; exact ages unknown) and lactating Alpine does (n = 35, 1st to 6th lactation). All animals were apparently healthy (health status determined by visual exam). The histogram depicts a nonnormally distributed study cohort and a right‐skewed distribution.

FIGURE 2

Box and whisker plot of symmetric dimethylarginine (SDMA) results (μg/dL) for goats diagnosed with clinical obstructive urolithiasis over sampling time points: 0‐, 24‐, 48‐, and 72‐hours after presentation. Thirteen male goats were enrolled (12 wethers and 1 buck). The breeds represented were: Mixed (n = 5), Pygmy (n = 3), Myotonic (n = 2), Nigerian Dwarf (n = 1), Nubian (n = 1), and French Alpine (n = 1). The age range was 9 months to 4 years old (median = 2 years). No statistical significance between time points was identified.