Urinalysis: when it is needed and what it reveals

A urine test is not reserved for sick animals. It belongs to the baseline checks alongside blood work, especially as the animal ages, because many kidney diseases stay silent until they are advanced and the urine is often the first thing to change. In the adult and senior cat in particular, the ability to concentrate urine tends to decline before other parameters move, which makes it a valuable early signal.

Alongside scheduled checks there are situations where the test becomes a direct request from the clinic, because a symptom points towards the urinary tract or the metabolism. In these cases it also helps to collect the sample before starting any treatment, when possible, so the picture is not already altered.

• The animal drinks and urinates far more than usual, or on the contrary produces very little urine.
• It struggles to urinate, cries out, keeps going to the litter tray or leaves drops of blood.
• It has lost weight, appetite or energy with no obvious cause.
• It is over seven or eight years old and is having a periodic health check.
• It has an already known disease, such as kidney disease or diabetes, that needs following over time.
• It faces an anaesthetic or a treatment that passes through the kidneys, and a starting picture is needed.
• The cat is using the litter tray differently than usual, with frequent visits or vocalising.

A sample collected at home from free voiding is convenient, low stress and suitable for many analyses, provided you follow a few rules. The aim is a clean container, a fresh sample and quick transport. For the dog collection is usually simple during a walk, while for the cat it takes a little preparation of the litter tray.

1. 1

   Prepare a clean container

   A sterile urine pot from the pharmacy or a clean dry container with no detergent residue will do. Ask the clinic in advance whether it prefers a specific container or a particular preservative.

2. 2

   For the dog, catch mid stream

   Let the first flow start, then catch it with a long handled container or a clean tray. The middle stream is less contaminated by cells and bacteria from the end of the urethra.

3. 3

   For the cat, use a non absorbent litter

   Empty and wash the tray, then add purpose made non absorbent granules or leave the tray empty and clean. After voiding, collect the liquid with a needleless syringe or by pouring it into the container.

4. 4

   Note the date and time of collection

   The time elapsed since voiding changes several results, so the clinic needs to know when the sample was produced. Write it down straight away, together with the method used.

5. 5

   Prefer the first sample of the morning

   Overnight urine is more concentrated and makes both specific gravity and sediment easier to read. If possible, collect that one and bring it in early.

6. 6

   Refrigerate and transport quickly

   If you cannot deliver it within about an hour, keep the sample in the fridge and bring it as soon as possible, returning it to room temperature before analysis. Do not leave it long in heat or light.

Specific gravity measures how concentrated the urine is, that is how much dissolved matter the kidney has held back or removed relative to water. It is one of the most useful pieces of the whole test because it tells you whether the kidneys are doing their concentrating job and whether the animal is well hydrated. On its own it does not make a diagnosis, but it steers many decisions.

Reading it correctly depends on context. Very concentrated urine in a dehydrated animal shows the kidneys are responding well, while dilute urine in an animal that drinks a great deal takes on quite a different meaning. This is precisely why the vet cross references specific gravity with the blood kidney values, the hydration status and the amount of urine produced. Reagent strips are not reliable for this measure: a refractometer is used, one more reason to rely on the laboratory.

The chemical analysis uses a reagent strip that changes colour according to various substances, while the sediment is what is left at the bottom after spinning and is examined under the microscope. The two parts must be read together, because one line alone almost never explains a picture. The table summarises what each line may suggest, without replacing the vet's judgement, who weighs the results in the light of the exam and the other tests.

A detail that surprises many owners is that crystals can form in the container after collection, especially if the sample sits for a long time or in the fridge, without anything being wrong with the animal. It is another reason why the time between voiding and analysis matters, and why a single isolated finding should not be turned into a diagnosis on your own.

Not all samples are equal, and the method by which the urine is collected changes which questions it can answer. There are three main ways, each with a different trade off between convenience and reliability. The choice belongs to the vet according to what needs to be known.

Cystocentesis often worries the owner because it involves a needle, but in the clinic's hands it is quick and well tolerated, and it has the advantage of avoiding contamination from the genitals and the lower tract. So when the question is whether an infection truly exists, the free voided sample collected at home helps to point the way while the confirmation comes from a sample taken in a controlled manner.

A good sample loses value if it waits too long. As the hours pass at room temperature several parameters change: some elements of the sediment break down, others form, and the reading drifts away from the animal's reality. A few precautions keep the sample reliable until analysis.

1. Deliver the sample within an hour of collection when you can, because that is the window in which results are most faithful.
2. If that is not possible, keep it in the fridge and bring it back to room temperature before analysis, avoiding heat and direct light.
3. Never freeze the sample, because it ruins the sediment and makes many lines unreadable.
4. Carry the sample in the closed container the clinic asked for, without needless transfers that add contamination.
5. Remind the vet of the date and time of collection and the method used, because they change the interpretation.

As for when to repeat, there is no single rule for everyone, because it depends on the reason for the first test and on the results. In a healthy animal the test falls within periodic checks, at a frequency that grows with age. In an animal with a known disease, such as kidney disease or diabetes, repetition is part of monitoring and helps show whether the treatment is working or whether something is changing. When a result is doubtful, it is often a repeat some time later, perhaps with a different sampling method, that clarifies whether the finding was real or tied to the sample.