Mucus, sperm and fat droplets in urine sediment of cats and dogs
A urine sediment report sometimes lists mucus, spermatozoa or fat droplets. All three are usually of little clinical importance on their own: sperm mostly tells the lab that the animal is an intact male, fat droplets are common in both species, and mucus is uncommon in cats and dogs. Their main practical role is not to be mistaken for something more important.
What it shows
This article covers three lines of the form. The main one is mucus.
- Mucus threads — irregular strands with ragged borders and tapered ends. They are a real component of urine, not an outside contaminant, but are far less frequent in cats and dogs than in horses.
- Spermatozoa — sperm cells, easy to recognise by their heads and tails.
- Fat (lipid) droplets — round droplets of different sizes. They float up under the coverslip, so they sit in a different focal plane from the cells.
Higher than reference — what it may be a sign of
- Mucus. Small amounts are often found in free-catch samples. Mucus can make urine cloudy. Its main importance is that strands can mimic hyaline casts, especially in ordinary light microscopy; mucus is more irregular, with tapered ends.
- Spermatozoa. Sperm in urine is generally significant only as evidence that the animal is an intact male. It can be seen in urine from males whether it was collected by voiding, catheter or needle from the bladder, and it is normal in intact male dogs. It is rarely seen in voided urine of a recently bred female.
- Fat droplets. Droplets of free fat are fairly commonly seen in urine of both dogs and cats. They come mainly from degenerating cells lining the urinary tract. On its own the finding is often not clinically significant and is not considered a disease sign; there is no clear link with high blood fats. Fat inside casts (fatty casts) is a different finding; it may occur with disorders of fat metabolism such as diabetes mellitus.
Lower than reference
“Not found” is the usual result for all three lines, and there is no meaningful “lower”. The absence of sperm or fat tells the vet nothing about health.
Look at together with
- Casts — mucus strands can be mistaken for hyaline casts; fatty casts are read separately from free fat droplets.
- Red and white cells in the sediment — fat droplets can be mistaken for red cells.
- Epithelium in the sediment — fat comes mainly from degenerating lining cells, and in cats the kidney tubule cells carry fat.
- Colour and clarity — mucus, fat and semen are among the causes of cloudy urine.
- Yeast — another line of the same sediment report.
Units and conversion
These lines have no unit and nothing to convert. They are written in words — “not found”, “few”, “present”, “many” — and fat droplets are sometimes counted per microscope field at high magnification. Some forms simply mark sperm as “present” or “absent”.
Reference range
The reference range is on your lab’s form; for these lines it is usually “not found” or “few”, and a finding is rarely flagged. Context matters more than the number: the sex and neuter status of the animal, recent mating and how the urine was collected. Contamination mostly reflects how the sample was collected and handled, and refrigeration is the best general way to preserve a sample until it is examined.
Cats and dogs
In cats, the cells of the proximal kidney tubules contain numerous fat droplets, and free fat droplets are fairly common in a cat’s urine sediment. Sperm in a cat’s urine points to an intact tom. As in dogs, mucus is uncommon.
Sperm is a normal finding in urine of intact male dogs, whatever the collection method. In a recently bred bitch it is rarely seen in voided urine. Fat droplets are also fairly common in dogs, and small amounts of mucus are often found in free-catch samples.
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.
Sources
- eClinPath (Cornell University) — Urinalysis: other constituents
- eClinPath (Cornell University) — Urinalysis: cellular constituents
- eClinPath (Cornell University) — Fat droplets from a renal tubular epithelial cell in a cat (image)
- Whitbread TJ. Urinalysis. Merck Veterinary Manual
- VCA Animal Hospitals — Urinalysis
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.