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SDMA case study: Reese

SDMA helps lead to the diagnosis and treatment of suspect pyelonephritis and improvement in kidney function

Background information

Name: Reese
Age: 16 years
Breed: Domestic shorthair
Gender: Spayed female

Presenting reason and history
Reese presented for her annual wellness examination. The owners felt that Reese was doing well for a senior cat. Her appetite was good, and they had not noticed any weight loss, coughing, sneezing, vomiting, diarrhea, or change in thirst or urination.

Physical examination
Reese was bright, alert, responsive, and hydrated. She was a little overweight with a body condition score (BCS) of 6 on a 9-point scale. Her temperature, pulse, and respiration were within normal limits. Thoracic auscultation and abdominal palpation were normal, and the remainder of the physical examination was unremarkable.

Diagnostic plan

Complete blood count (CBC); chemistry panel, including the IDEXX SDMA Test and electrolytes; complete urinalysis; and total T4 were recommended for a senior wellness minimum database. Reese’s CBC results were within normal limits. Other findings are shown here.

Diagnostic review

Reese’s diagnostic results showed an increased SDMA* along with a normal creatinine and increased BUN. She also had inappropriate urine concentrating ability with a urine specific gravity of 1.018. In addition, Reese had an active urine sediment with >100 WBC/hpf and marked bacteriuria. Based on these findings, a urine culture and susceptibility were performed and >100,000 organisms/mL of Escherichia coli were grown that were susceptible to most antibiotics, including amoxicillin and amoxicillin/clavulanic acid.

Assessment

Based on Reese’s increased SDMA with an inappropriately low urine specific gravity, it was clear that she had decreased kidney function in addition to having a urinary tract infection.

Differentials at this time included:

  • Active or acute kidney injury (AKI) secondary to pyelonephritis.
  • Chronic kidney disease (CKD) with a concurrent lower urinary tract infection (UTI).
  • AKI from pyelonephritis superimposed on CKD, causing a worsening of existing kidney disease.
     

Plan

Investigate
Additional diagnostics that should have been considered to investigate further but were not performed:

  • Abdominal ultrasound to look for evidence of pyelonephritis and rule out urolithiasis
  • Blood pressure, since hypertension is a common confounding factor with kidney disease, and measurement of a urine protein:creatinine ratio or UPC
     

Manage
Treatment initiated: 

  • Amoxicillin/clavulanic acid 62.5 mg by mouth twice daily for 1 month for possible pyelonephritis
  • Fresh, clean water sources available at all times
  • Diet changed to kidney-therapeutic diet
     

Monitor 
Recheck visit: 

  • Ideally, recheck is scheduled in 2 weeks to determine response to treatment.
  • However, recheck was done in 1 month to see if infection cleared and if kidney function improved.
  • Follow-up diagnostics revealed that the SDMA concentration had decreased from 19 μg/dL to 15 μg/dL, there were no white blood cells or bacteria on the urine sediment, and the culture was negative.
     

Diagnosis and long-term management

Diagnosis

  • Suspect pyelonephritis based on improvement in kidney function after treatment of UTI.
  • Acute kidney injury (AKI) from pyelonephritis superimposed on CKD.
     

Long-term management

Patient reports

INITIAL RESULTS

Chemistry

IDEXX SDMA additional testing report screenshot for Reese case study

Total T4

Screenshot of Total T4 results for Reese Case Study

Urinalysis

Urinalysis reports screenshot for Reese case study

Urine culture and MIC susceptibility

Urine culture report screenshot for Reese case study

 

RECHECK RESULTS

Chemistry

Screenshot of Urine Chemistry recheck for Reese Case Study

Urinalysis

Urinalysis follow up reports screenshot for Reese case study

Urine culture

Urine culture follow up report screenshot for Reese case study

 

Discussion

  • SDMA is a more sensitive indicator of kidney function than creatinine in AKI as well as CKD and increases earlier.2–4
  • In pets like Reese, an increased SDMA in the face of a urinary tract infection should lead to additional investigation and a consideration for more aggressive treatment for pyelonephritis.
  • Long-term management and monitoring of these pets can help detect future infections promptly for early treatment and slow progression of CKD.

*Symmetric dimethylarginine.

References

  1. International Renal Interest Society. IRIS Guidelines. www.iris-kidney.com/guidelines. Accessed January 22, 2019.
  2. 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.
  3. 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.
  4. 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.