Cat health glossary.
A plain-English UK reference of the feline urinary and kidney terms your vet uses — and what they actually mean for your cat.
- FLUTD (Feline Lower Urinary Tract Disease)
- Umbrella term for any disease of a cat's bladder or urethra.
- FLUTD covers UTIs, idiopathic cystitis (FIC), bladder stones and urethral obstruction. It is one of the most common reasons UK cats are seen by a vet, and the leading cause of urinary emergencies in male cats.
- UTI (Urinary Tract Infection)
- Bacterial infection of the bladder or urethra.
- Less common in cats than dogs, but more dangerous because cats hide symptoms. Untreated UTIs can progress to cystitis, blockage and kidney involvement. UK treatment cost: £40–£90 if caught early, £900–£2,500 if it leads to a blockage.
- Struvite crystals
- Magnesium-ammonium-phosphate crystals that form in alkaline urine.
- Struvites are the most common urinary crystal in UK cats. They precipitate when urine pH rises above ~6.8 and can plug the urethra in male cats. Diet correction (acidifying urinary diets) usually dissolves them.
- FIC (Feline Idiopathic Cystitis)
- Stress-driven bladder inflammation with no identifiable infection.
- FIC is the single most common UK feline urinary diagnosis and frequently mimics a UTI. Triggered by stress (new pets, moves, routine changes), it usually resolves in 5–10 days but recurs without environmental management.
- Urethral obstruction ("blocked cat")
- Life-threatening blockage of urine flow, almost always in male cats.
- Caused by crystals, mucus plugs or inflammation. Toxins back up into the bloodstream within hours. UK emergency cost: £1,200–£3,000+. Symptom: a cat straining repeatedly and producing little or no urine.
- CKD (Chronic Kidney Disease)
- Progressive loss of kidney function over months or years.
- Affects ~1 in 3 UK cats over age 10. Staged 1–4 by IRIS criteria. Stage 1 caught early is a manageable diet change; stage 4 caught late is end-of-life care. The earliest measurable signal is dilute urine and a drop in urine specific gravity.
- Specific gravity (USG)
- How concentrated a cat's urine is.
- Healthy cat USG sits above 1.035. As the kidneys lose concentrating ability, USG drops — often the first measurable change in CKD. Measured at a vet practice with a refractometer.
- Azotemia
- Elevated urea or creatinine in the bloodstream.
- Indicates the kidneys are no longer clearing waste effectively. Pre-renal azotemia is dehydration; renal azotemia is true CKD. Confirmed via blood panel (urea, creatinine, SDMA).
- SDMA
- A blood test marker that flags kidney decline earlier than creatinine.
- Symmetric Dimethylarginine. Rises when ~40% of kidney function is lost — versus creatinine, which only rises after ~70% loss. Now standard in UK senior cat panels.
- pH (urinary)
- How acidic or alkaline a cat's urine is.
- Healthy feline urine sits at pH 6.0–6.5. Alkaline shifts (>6.8) signal UTI or struvite risk. Acidic shifts can signal metabolic change or oxalate stone risk. Colour-changing litters such as Kittydoctor read pH directly in the tray.
- Polydipsia / Polyuria (PU/PD)
- Drinking and urinating more than usual.
- Often the very first sign of CKD, diabetes or hyperthyroidism. If your cat suddenly empties the water bowl daily or you're scooping noticeably more, ask your vet for a blood and urine panel.
- Hyperthyroidism
- Overactive thyroid, common in cats over 10.
- Causes weight loss despite a healthy or increased appetite, plus PU/PD and a faster heart rate. Easily diagnosed with a single blood test (T4) and very treatable with medication, prescription diet or radioactive iodine.
- Feline diabetes mellitus
- Insufficient insulin production or insulin resistance.
- Affects ~1 in 200 UK cats, more common in overweight middle-aged cats. Hallmark signs: increased thirst, urination, weight loss with good appetite, sweet-smelling urine. Catchable on a colour-changing litter via the glucose/ketone shift.
- Bilirubin
- A pigment indicating liver involvement when present in urine.
- Healthy cat urine should contain zero bilirubin. Even trace amounts indicate liver or red blood cell breakdown issues. A vet should investigate immediately.
- Haematuria
- Blood in the urine.
- Visible (gross) or microscopic. Causes: UTI, FIC, stones, trauma, tumours. Even microscopic traces show up red on a colour-changing litter that would be invisible in clay litter.
Reference is useful. Detection is what changes outcomes.
Shop Kittydoctor — £34.99 The terms above all describe conditions Kittydoctor flags first.
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