SDMA: Scarlet Case Study

Background information

Name
Scarlet
Age
5 years
Breed
Golden retriever
Gender
Female

Presenting reason

Scarlet was brought in for her annual checkup and vaccines.

History

Scarlet’s owners shared that she had not been acting like herself the past few weeks. She had a couple of urinary tract infections in the past, though she had not recently been showing those types of signs. She had been less energetic, but appetite and drinking had seemed normal as far as they had been able to tell.

Physical examination

Scarlet was bright, alert, and responsive (BAR), appeared well-hydrated, and had good body condition with stable weight since last visit.

Diagnostic plan

Complete blood count (CBC); chemistry panel, including the IDEXX SDMA Test and electrolytes; complete urinalysis; and total T₄ were recommended.

Laboratory findings

Scarlet’s CBC was unremarkable, though her other blood and urine diagnostics identified some areas of concern.
She had an increased SDMA* of 17 μg/dL (0–14 μg/dL) and a low urine specific gravity of 1.026. Her creatinine was within the reference interval at 1.5 mg/dL.
Her total T₄ and free T₄ were both within reference intervals but were low normal.

Treatment plan and follow-up

Scarlet was started on L-thyroxine for treatment of presumptive hypothyroidism.
A recheck was scheduled in 2–3 weeks for follow-up CBC, chemistry, total T₄, and complete urinalysis.
Additional test considerations included diagnostic imaging of her kidneys and associated structures as well as evaluation of urine protein:creatinine (UPC) ratio and blood pressure.

2-week recheck: The pet owner reported that Scarlet seemed to be more active. Her total T₄ result was well within normal limits, her SDMA remained increased at 18 μg/dL, and her creatinine remained within the reference interval. Her urine specific gravity remained low at 1.027.

Action plan and results

Because of the persistent SDMA elevation, an ultrasound on Scarlet’s kidneys and associated structures was scheduled.
The ultrasound showed the left kidney was somewhat rounded and mildly irregular with some mild dilation of the renal pelvis with changes suspected to be the result of prior kidney infections.
A urine culture was negative; the UPC was 0.0 and her average systolic blood pressure was normal at 140 mm Hg.
Scarlet continued to show a persistence in SDMA elevation and abnormal kidney imaging. Following the International Renal Interest Society (IRIS) Chronic Kidney Disease (CKD) Staging Guidelines, these findings supported IRIS CKD Stage 2 disease, which was substaged as normotensive and nonproteinuric.
Scarlet’s treatment plan included initiating a kidney therapeutic diet and continuing with her L-thyroxine and access to fresh water sources at home, along with more regular appointments to monitor her kidney health. A 3-month recheck was scheduled to perform CBC, chemistry panel, total T₄, and complete urinalysis.

3-month recheck: Scarlet was reportedly doing well at home. Her total T₄ levels remained well within the reference interval, and CBC was unremarkable. Her SDMA was 15 μg/dL, and her creatinine remained within normal limits. Her urine specific gravity remained low at 1.027.

6-month recheck: Given Scarlet’s activity level, improving diagnostics, and reports from the pet owner, twice yearly checkups were recommended moving forward. At that time, Scarlet’s SDMA remained at 15 μg/dL, her creatinine was still within normal limits, and her urine specific gravity was at 1.026.

Discussion

SDMA is a more reliable biomarker for kidney disease than creatinine,^1–5 and it helped to define a thorough medical follow-up plan for Scarlet, even at early stages of kidney changes.

Early intervention and support of Scarlet’s kidney function with a kidney supportive diet helped lead to stabilized SDMA results in her follow-up rechecks. Evidence shows that SDMA can be relied upon for early detection of kidney disease and that dietary intervention prior to an elevation of creatinine can have health benefits for the kidneys.^1,2

Patient reports

Chemistry Reports (December 31)

Urinalysis Reports (December 31)

Total T₄ and Free T₄ (December 31)

Chemistry (January 18)

Total T₄ (January 18)

Chemistry (March 27)

*Symmetric dimethylarginine.

References

Hall JA, Yerramilli M, Obare E, Yerramilli M, Yu S, Jewell DE. Comparison of serum concentrations of symmetric dimethylarginine and creatinine as kidney function biomarkers in healthy geriatric cats fed reduced protein foods enriched with fish oil, L-carnitine, and medium-chain triglycerides. Vet J. 2014;202(3):588–596.
Hall JA, Yerramilli M, Obare E, Yerramilli M, Melendez LD, Jewell DE. Relationship between lean body mass and serum renal biomarkers in healthy dogs. J Vet Intern Med. 2015;29(3):808–814.
Nabity MB, Lees GE, Boggess M, et al. Symmetric dimethylarginine assay validation, stability, and evaluation as a marker for early detection of chronic kidney disease in dogs. J Vet Intern Med. 2015;29(4):1036–1044.
Hall JA, Yerramilli M, Obare E, Yerramilli M, Jewell DE. Comparison of serum concentrations of symmetric dimethylarginine and creatinine as kidney function biomarkers in cats with chronic kidney disease. J Vet Intern Med. 2014;28(6):1676–1683.
Hall JA, Yerramilli M, Obare E, Yerramilli M, Almes K, Jewell DE. Serum concentrations of symmetric dimethylarginine and creatinine in dogs with naturally occurring chronic kidney disease. J Vet Intern Med. 2016;30(3):794–802.

An SDMA case study: Scarlet