Red and white blood cells in urine sediment in cats and dogs

What it shows

Under the microscope white cells look round, colourless and slightly grainy, about one and a half to two times the size of a red cell; they are usually neutrophils. Red cells are smaller discs. Both are counted per high-power field, often as a range: none seen, under 5, 5–20, 20–100 or more than 100.

The form may also carry a dipstick line “Leukocytes”. That pad is considered inaccurate in dogs and cats, and Merck calls it not valid in animals. In cats it should not be used at all; in dogs it gives many false negatives, so it can miss white cells that the microscope sees. The microscope count is the result that counts.

Higher than reference — what it may be a sign of

• Red cells (haematuria) — bleeding anywhere in the urinary tract: stones, infection, clotting problems, injury or a tumour. The collection itself can cause bleeding: a needle sample from the bladder often contains red cells, sometimes more than 100 per field in urine that looks yellow. In a voided sample, red cells can come from the genital tract, for example in a dog in season.
• White cells (pyuria) — inflammation somewhere in the urinary or genital tract. A bacterial infection is a frequent cause, and bacteria may be visible; the vet may order a culture even when none are seen. Stones and tumours can also raise white cells without infection. In a clean needle sample even fewer than 5 per field may be abnormal.
• A positive leukocyte strip — not read on its own; only the microscope count is interpreted.

Lower than reference

None or a few cells is the expected result; there is no meaningful “low”. A low count is not always reassuring: in very dilute urine (specific gravity below 1.008) or strongly alkaline urine red cells break up and become faint “ghosts”, while the dipstick blood line can show 4+. Urine is best examined within 30 minutes of collection. A negative leukocyte strip in a dog does not exclude white cells.

Look at together with

• Blood in urine (dipstick) — a positive blood line with no red cells in the sediment points to broken-up cells, haemoglobin or myoglobin.
• Bacteria and urine culture — white cells plus bacteria support an infection.
• Specific gravity and pH — dilute or alkaline urine destroys cells and lowers counts.
• Urine protein — blood and inflammation add protein to urine.

Units and conversion

Sediment cells are reported per high-power field (/hpf; on Russian-language forms “в п/зр”) — the same unit, no conversion. Many labs write a range such as “5–20/hpf” rather than an exact number. The dipstick leukocyte line is a grade — negative, trace, 1+ to 3+ — not a count. If a form gives leukocytes “per field”, that is a microscope count, not the strip.

Reference range

The reference range is on your lab’s form. Commonly fewer than 5 red cells and fewer than 5 white cells per high-power field are accepted. For white cells one reference laboratory gives different limits depending on collection: 0–8 per field in a voided sample, 0–5 in a catheter sample and 0–3 in a needle sample from the bladder. A needle or catheter can add red cells, and either can bring in white cells from the urogenital tract, so the vet reads the count together with how the urine was taken.

Cats and dogs

Sources

1. eClinPath (Cornell University) — Urinalysis: cellular constituents
2. eClinPath (Cornell University) — Urinalysis: chemical constituents
3. Whitbread TJ. Urinalysis. Merck Veterinary Manual
4. IDEXX — Complete urinalysis panel: interpretation guide
5. IDEXX — Urinalysis and urine culture: diagnostic update
6. VCA Animal Hospitals — Urinalysis