Epithelial cells in urine sediment (squamous, transitional, renal) in cats and dogs

What it shows

Under the microscope the lab sees three kinds of lining cells. Squamous cells are large and flat; they come from the end of the urethra, the prepuce or the vagina, and keratinised ones from the skin or vulva. Transitional cells (urothelium) line the renal pelvis, ureters, bladder and the first part of the urethra. Renal tubular cells come from the kidney tubules and are rarely seen. Small transitional and renal cells are hard to tell from each other and from white cells in an unstained sample, so labs count any non-squamous cell as transitional unless shown otherwise, and stain the sediment for a closer look when unsure.

Higher than reference — what it may be a sign of

• Squamous cells — common contaminants of voided and catheter samples, picked up on the way out; a needle sample from the bladder should contain none. Large numbers in a male dog may point to a change in the prostate (squamous metaplasia) caused by excess oestrogen, usually from a testicular tumour.
• Transitional cells — none to a few are seen in healthy animals. A catheter can rub off many of them, even in sheets, and that alone is not a sign of disease. More cells can also accompany inflammation, stones, prostate problems in male dogs or a tumour.
• Abnormal-looking cells — tumours of the kidney, urinary or genital tract can shed cells into urine; transitional cell carcinoma is the urinary tumour that does this most often. Such cells are judged on a stained smear (cytology), not on a routine wet sample.
• Renal tubular cells — “moderate” or “many” support injury to the kidney tubules; they are read together with casts, which also form in the tubules.

Lower than reference

None or few is the expected result, and there is no meaningful “low”. Two things a clean sediment does not prove: the absence of tumour cells does not rule out a tumour, and the absence of renal cells does not rule out kidney disease.

Look at together with

• Casts — renal tubular cells plus cellular or granular casts point to tubular injury.
• Red and white cells in the sediment — bleeding and inflammation often accompany both excess transitional cells and urinary tumours.
• Creatinine and SDMA — show whether kidney function has changed when renal cells are reported.
• Collection method — the first thing to check before reading squamous and transitional cells.

Units and conversion

Epithelial cells are counted per microscope field or, more often, graded in words: “none”, “few”, “moderate”, “many”. Forms usually give a count per high-power field (/hpf, “в п/зр” on Russian-language forms); both mean the same and need no conversion. Some labs grade epithelial cells under low power instead, so a grade from one lab is best compared with the same lab’s next result.

Reference range

The reference range is on your lab’s form; it is usually “none to few” (one reference laboratory gives 0–few per high-power field). What counts as expected depends on how the urine was taken: squamous cells are normal in a voided sample and unexpected in a needle sample from the bladder, while a catheter sample may contain many transitional cells.

Cats and dogs

Sources

1. eClinPath (Cornell University) — Urinalysis: cellular constituents
2. Whitbread TJ. Urinalysis. Merck Veterinary Manual
3. IDEXX — Urine sediment guide
4. VCA Animal Hospitals — Urinalysis
5. eClinPath (Cornell University) — Urinalysis: casts