High SDMA with normal creatinine in cats: how to interpret it
15-year-old domestic shorthair cat with progressive weight loss, mild polyuria/polydipsia and marked muscle wasting (muscle condition score 1/3). Normal total T4 and blood pressure. Results confirmed on two samples 3 weeks apart:
| Parameter | Result | Reference |
|---|---|---|
| Creatinine | 1.5 mg/dL | 0.8–2.4 |
| SDMA | 22 µg/dL | 0–14 |
| Urine specific gravity | 1.019 | > 1.035 |
| UPC | 0.15 | < 0.2 |
How do you interpret these results?
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A. Normal renal function: creatinine is within range and SDMA is a false positive
Normal creatinine does not rule out CKD in an animal with little muscle mass. Moreover, the high SDMA is confirmed on two samples and urine specific gravity is inadequate in a cat with PU/PD.
B. Prerenal azotaemia due to dehydration
In prerenal azotaemia the kidney responds by concentrating urine (> 1.035 in cats). Here specific gravity is 1.019, indicating that the kidney is not concentrating.
C. Probable CKD: creatinine underestimates loss of function in a cat with little muscle; with persistent SDMA ≥ 18 µg/dL, IRIS suggests managing it as stage 2
Correct. Creatinine depends on muscle mass and may stay within range in sarcopenic cats despite reduced filtration; SDMA is barely affected by muscle. Together with poorly concentrated urine, this points to CKD. Creatinine alone gives stage 1, but a persistent SDMA ≥ 18 µg/dL justifies managing it as stage 2.
D. IRIS stage 1 with no further implications: SDMA is not used in staging
IRIS does incorporate SDMA: in stage 1 with persistent SDMA ≥ 18 µg/dL it recommends managing as stage 2, and in stage 2 with SDMA ≥ 25 as stage 3.
lightbulb Key takeaway
In cats and dogs with little muscle mass, a "normal" creatinine is misleading: interpret it together with SDMA and urine specific gravity. Stage only when the patient is stable and hydrated, and confirm a high SDMA on at least two samples.
References: IRIS Staging of CKD (modificado 2023)
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.