Practical urinalysis in the cat: 1: Urine macroscopic examination 'tips and traps'

Abstract

Series outline: This is the first article in a two-part series on urinalysis in the cat. The focus of Part 1 is urine macroscopic examination. Part 2, to appear in the May 2016 issue, discusses urine microscopic examination.

Practical relevance: Urinalysis is an essential procedure in feline medicine but often little attention is paid to optimising the data yielded or minimising factors that can affect the results.

Clinical challenges: For the best results, appropriately collected urine should be prepared promptly by specialist laboratory personnel for the relevant tests and assessed by a clinical pathologist. This is invariably impractical in clinical settings but careful attention can minimise artefacts and allow maximum useful information to be obtained from this seemingly simple process.

Audience: Clinical pathologists would be familiar with the information provided in this article, but it is rarely available to general or specialist practitioners, and both can potentially benefit.

Equipment: Most of the required equipment is routinely available to veterinarians. However, instructions have been provided to give practical alternatives for specialist procedures in some instances.

Evidence base: Evidence for much of the data on urinalysis in cats is lacking. Validation of the human equipment used routinely, such as dipsticks, is also lacking. As such, the evidence base for feline urinalysis is quite poor and information has largely been extrapolated from the human literature. Information from feline studies has been included where available. In addition, practical clinicopathological and clinical observations are provided.

Figure 1

An appropriate collection container for cat urine

Figure 2

Examples of an appropriate tube for aliquoting cat urine for centrifugation

Figure 3

Cat urine samples displaying a range of colours and turbidity, with obvious discoloration noted in the two samples on the far left. Increased turbidity, evident because background print is obscured, is present in the three samples on the left

Figure 4

(a) A temperature-compensated optical veterinary refractometer and (b) the reticle viewed through the eye-piece when the refractometer is held up to the light

Figure 5

Photograph of the reticle in the optical veterinary refractometer shown in Figure 4 measuring the USG of a cat urine sample. The line representing the junction between the dark and light areas on the reticle in the viewing field indicates that the cat’s USG is approximately 1.023–1.024. In this case the poor demarcation of the line was due to a slightly cloudy urine sample. Ideally the USG should have been measured on a postcentrifugation supernatant sample from the urine

Figure 6

(a,b) Examples of commercially available urine dipsticks that may be used to perform urinalysis in cats. Note that of the multiple test pads available on these dipsticks, only six (protein, pH, blood, ketones, bilirubin and glucose) provide meaningful and reliable information in cats. The other test pads (urobilinogen, leukocytes, nitrite and USG) are either unnecessary or provide unreliable results in cats. It should always be ensured that dipsticks have not reached their expiry date and are stored and read according to the manufacturer’s instructions

Figure 7

Keto-Diastix urinalysis strips may be used at home by cat owners (in collaboration with their veterinarian) to monitor diabetic cats for any evidence of ketonaemia – which would prompt immediate medical intervention. Simultaneously, the strips can be used to identify consistent negative glucosuria, consistent with hypoglycaemia due to insulin overdose or remission