Blood in urine (dipstick) in cats and dogs

What it shows

The pad detects the peroxidase-like activity of heme, so it reacts to intact red blood cells, to free haemoglobin and to myoglobin from muscle (Merck, eClinPath). It is very sensitive: eClinPath notes that it can detect as few as 10 red cells per microlitre, and when the cells are intact the pad may look speckled. Merck advises confirming a positive pad by looking at the sediment under the microscope, where intact red cells can be counted. Merck also notes that fat droplets, common in the urine of dogs and cats, can be mistaken for red cells in the sediment.

Higher than reference — what it may be a sign of

• Red blood cells in urine (haematuria) — eClinPath calls it the most common cause of a positive pad. The bleeding can come from anywhere in the urinary tract: infection, stones, injury or tumours (VCA) — or from collecting the sample itself (see below).
• Free haemoglobin (haemoglobinuria) — from red cells breaking up inside blood vessels (intravascular haemolysis). The animal is anaemic, the plasma is pink to red, and the sediment has no red cells (eClinPath, Merck).
• Myoglobin (myoglobinuria) — from severe muscle injury; the plasma stays clear and CK in blood is very high (eClinPath, Merck).
• Red cells that broke up in the sample — in dilute urine (specific gravity below 1.010) or alkaline urine (pH 8 or higher) the pad can be positive with few or no intact cells visible; eClinPath still counts this as haematuria.
• False positives — bleach or other oxidising chemicals, and plant peroxidases from faecal contamination (eClinPath).

Lower than reference

Negative is the expected result. There is no meaningful “low” for this line. A small positive in a sample taken with a needle from the bladder is common and is not by itself a sign of disease (see “Reference range”).

Look at together with

• Urine sediment — intact red cells mean haematuria; none, with a positive pad, prompts a look at the blood.
• Hematocrit and RBC, plus plasma colour — anaemia with pink plasma points to haemolysis; clear plasma with no anaemia points to myoglobin (Merck).
• CK — a muscle enzyme, very high when myoglobin is the cause.
• Urine protein and UPC — blood in urine adds protein, so protein is read only after bleeding is excluded.
• Urine culture — if the sediment suggests infection.

Units and conversion

The dipstick result has no unit — it is a grade: negative, trace, then plus signs. How many plus signs the scale has depends on the strip; eClinPath’s analyser reports up to 5+. The grade is not a cell count; a strip is a guide, not an exact number, and no conversion applies. Red cells counted in the sediment are reported separately, per high-power field of the microscope.

Reference range

The reference range is on your lab’s form; for this line it is usually “negative”. How the urine was collected matters. Cystocentesis — taking urine with a needle straight from the bladder — and catheterisation can themselves cause a little bleeding (Merck). eClinPath notes that microscopic haematuria is common after cystocentesis, sometimes more than 100 red cells per high-power field, that it is hard to tell this from true bleeding, and that it is less likely in catheter or free-catch samples. That is why the vet reads the result together with the collection method.

Cats and dogs

Sources

1. eClinPath (Cornell University) — Urinalysis: chemical constituents
2. Whitbread TJ. Urinalysis. Merck Veterinary Manual
3. VCA Animal Hospitals — Urinalysis
4. Cornell Feline Health Center — Chronic Kidney Disease
5. IDEXX — Proteinuria: diagnostic update