Description

·    The urine protein:creatinine (UPC) ratio is a simple and rapid test for the detection and quantification of proteinuria. Unlike other qualitative and semi-quantitative tests, the UPC ratio is not affected by urine concentration and volume. The urine protein:creatinine ratio offers the accuracy of 24-hour urine protein measurements without the need to perform the 24-hour urine collection.

·    The urine protein:creatinine ratio is obtained by dividing the protein concentration [UPRO] (mg/dL) by the creatinine concentration [UCRE] (mg/dL). The result is a unitless ratio.

·    Appropriate interpretation of urine protein:creatinine ratio results requires that you first localize the protein loss to the kidneys and then determine persistence.

Localization

Causes of proteinuria can be prerenal or postrenal. It is imperative that prerenal and postrenal causes of proteinuria are ruled out before assessing your UPC value. This can be done by examining the patient’s history and clinical signs, biochemical profile, CBC and complete urinalysis (including urine sediment examination and determination of urine specific gravity).

·    Prerenal: evaluate for Bence Jones proteinuria, myoglobinuria, hemoglobinuria

·    Postrenal: evaluate urine sediment for signs of hemorrhage, inflammation, infection and neoplasia

·    Renal: determine level of azotemia

Persistence

Determination of persistence of proteinuria is necessary to rule out transient elevations of urine protein. Determine persistence of proteinuria as needed given the level of azotemia and other clinical signs. In questionable cases, the 2004 ACVIM Forum Consensus Statement (Small Animal): Assessment and Management of Proteinuria in Dogs and Cats recommends repeating the UPC ratio on three or more occasions, at least two weeks apart.

Evaluation

Once you have addressed localization and determination of persistence, you should evaluate your urine protein:creatinine ratio results in light of the patient’s level of azotemia. The following ranges are in accordance with the recommendations from the 2004 ACVIM Forum Consensus Statement (Small Animal): Assessment and Management of Proteinuria in Dogs and Cats.

Nonazotemic and persistent proteinuria with inactive urine sediment (dogs and cats):

·    UPC <0.5 no significant proteinuria

·    UPC ≥0.5<1.0 requires further monitoring

·    UPC ≥1.0<2.0 proteinuria

·    UPC ≥2.0 significant proteinuria

Azotemic dogs and persistent proteinuria with inactive urine sediment (dogs):

·    UPC <0.5 no significant proteinuria

·    UPC ≥0.5 significant proteinuria

Azotemic cats and persistent proteinuria with inactive urine sediment (cats):

·    UPC <0.4 no significant proteinuria

·    UPC ≥0.4 significant proteinuria

Once renal disease is established, you should determine if any underlying cause is present and address that as needed. Potential beneficial ancillary tests include: radiology, ultrasonography, blood pressure evaluation, infectious disease testing, endocrine testing and autoimmune testing.

The urine protein:creatinine ratio can be used as a prognostic indicator, with higher ratios correlating to a worsening prognosis. However, it is worth noting that in severe cases of chronic renal disease, the urine P:C ratio may decrease. This is due to the fact that as plasma creatinine increases and the number of functioning nephrons decreases, the amount of urinary protein loss is reduced.

Diagnostic
Protocol