Parasite eggs in urine sediment (Capillaria / Pearsonema, kidney worm) in cats and dogs

Parasite eggs are rarely seen in urine. When they are, they usually belong to the bladder worms Pearsonema (formerly Capillaria) or, more rarely, to the giant kidney worm Dioctophyme renale. Just as important is telling them apart from eggs of intestinal worms that got into a voided sample from faeces.

SectionUrinalysis

SampleUrine (sediment under the microscope); a sample taken by needle from the bladder (cystocentesis) excludes contamination with faeces

Unitsкачественно

On forms—

What it shows

The lab looks for eggs at low magnification while examining the sediment. The eggs that come from the urinary tract itself are:

Pearsonema plica (= Capillaria plica) — a thread-like worm of the bladder in dogs and cats, less often of the ureters and kidney pelvis; and Pearsonema feliscati (= Capillaria feliscati), a rarer related species of cats. Their eggs are colourless and oval, with flattened plugs at both ends and a slightly pitted shell, about 63–68 × 24–27 µm.
Dioctophyme renale, the giant kidney worm — lives mainly in a kidney, most often the right one. Its eggs are barrel-shaped, yellow-brown, with a thick pitted shell, about 71–84 × 45–52 µm.

Heartworm microfilariae (Dirofilaria immitis larvae) may occasionally be seen in urine too.

Higher than reference — what it may be a sign of

Pearsonema eggs — the animal carries bladder worms. Dogs and cats become infected by eating earthworms carrying larvae. Most infections cause no signs; heavy infections can cause bladder inflammation (cystitis). Eggs appear in urine about 2 months after infection.
Dioctophyme renale eggs — the giant kidney worm. Animals are infected by eating raw fish or frogs, or the aquatic worms that carry larvae. Because usually only one kidney is affected and the other compensates, signs may be absent; blood in urine and back or belly pain can occur. In dogs the worm often does not reach the kidney and lives free in the abdomen.
Eggs from faeces — in a voided sample, eggs of intestinal parasites can contaminate urine. Whipworm (Trichuris) eggs are smooth and yellowish, with plugs that look like the screw of a light bulb; Pearsonema eggs are rougher and often have one straighter side.
Look-alikes — pollen is the thing most often mistaken for parasite eggs; plant and paper fibres can resemble larvae.

Lower than reference

“Not found” is the usual result. It does not exclude infection: Pearsonema eggs appear only about 2 months after infection, and kidney worm eggs reach urine only if worms of both sexes are in the kidney and the ureter is open. The kidney worm may first be suspected from an enlarged right kidney on X-ray or ultrasound.

Look at together with

Red and white cells in the sediment and blood in urine — the kidney worm can cause blood and white cells in urine; heavy bladder worm infection, cystitis.
Protein in urine — protein loss can accompany kidney worm infection, and bladder worm infection may be associated with kidney amyloidosis.
Faecal flotation — helps when eggs in a voided sample may have come from faeces.
Heartworm tests — if microfilariae are seen in urine.

Units and conversion

This line has no unit and nothing to convert. The result is written as “not found” or “found”, usually with the type of egg named (for example “Capillaria ova”).

Reference range

The reference range is on your lab’s form; the expected result is “not found”. The collection method decides how a finding is read: if eggs are seen in a well-handled sample taken by needle from the bladder, faecal contamination is ruled out, while eggs in a voided sample may have come from faeces. A positive line is worth discussing with the vet even if the form shows no flag.

Cats and dogs

Cats

Cats can carry Pearsonema plica and the cat-specific P. feliscati; the sources list the giant kidney worm for dogs rather than cats. Most feline bladder worm infections cause no signs. In a cat’s voided urine, tapeworm (Dipylidium caninum) eggs from faeces have been seen as a contaminant.

Dogs

Dogs can carry Pearsonema plica and Dioctophyme renale; in dogs the kidney worm may take 4–5 months before eggs appear, and the right kidney is most often affected. Bladder worms have no known public health risk; kidney worm infection has been reported in people who eat raw or undercooked fish or frogs.

In the app

Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.

Open the app

Sources

This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.