Feline Medicine

Overview

Feline-specific clinical medicine addressing the unique metabolic vulnerabilities, stress physiology, and disease predispositions of domestic cats. Cats lack hepatic UDP-glucuronosyltransferase (UDP-GT) activity, making them sensitive to drugs metabolized by glucuronidation (acetaminophen, permethrin, NSAIDs). Stress-induced hyperglycemia is near-universal in veterinary settings and must be differentiated from diabetes mellitus. Common feline diseases include chronic kidney disease (IRIS staging), hyperthyroidism, FLUTD, diabetes (often reversible with dietary management), and viral infections (FIV, FeLV). Cats are obligate carnivores with minimal carbohydrate tolerance. Natural hiding behavior masks severe illness until late-stage presentation.

When to Use

• User presents a case or question involving feline medicine
• User asks about drug safety in cats (toxicology, metabolism)
• User discusses CKD staging, hyperthyroidism, or diabetes in cats
• User asks about FIV/FeLV status or FLUTD/lower urinary tract disease
• User questions stress hyperglycemia versus true diabetes
• Keywords: cat, feline, kitten, FeLV, FIV, CKD, hyperthyroid, FLUTD, diabetes, stress, glucuronidation, UDP-GT, hiding behavior, obligate carnivore

Clinical Reference Values (Adult)

Metabolic Vulnerabilities: Glucuronidation Deficiency

Cats are deficient in hepatic UDP-glucuronosyltransferase (UDP-GT) activity. This critical metabolic pathway detoxifies:

• Acetaminophen: Extremely toxic. Clinical signs (methemoglobinemia, facial/paw edema, cyanosis) reported at doses as low as 10 mg/kg. Hepatotoxicity and death at 50-100 mg/kg. There is no established safe dose. Do not use in cats under any circumstances.
• Permethrin: Neurotoxin in cats. Tremors, seizures, death at concentrations safe in dogs (topical flea treatments cause toxicity).
• Phenolic compounds: Disinfectants, essential oils (tea tree, citrus, eucalyptus, lavender), aspirin (minor).
• Certain NSAIDs: Ibuprofen metabolized by glucuronidation; use only feline-approved drugs (carprofen, meloxicam) at lowest effective doses.
• Lily toxins: True lilies (Lilium, Hemerocallis spp.) cause acute kidney injury; ingestion of even 1-2 petals or pollen can be fatal.

Stress Hyperglycemia vs. Diabetes Mellitus

Stress hyperglycemia is nearly universal in clinical cats. Blood glucose up to 300+ mg/dL is common from handling stress alone. Differentiate using fructosamine:

• Fructosamine > 400 μmol/L: Strongly suggests diabetes mellitus (reflects 2-3 week average).
• Fructosamine 340-400 μmol/L: Gray zone; requires clinical correlation and repeat testing.
• Fructosamine < 340 μmol/L: Consistent with stress hyperglycemia.
• Note: Diabetic remission is achievable in ~50% of cats on low-carbohydrate diets; insulin therapy should not preclude dietary trial.

Common Feline Diseases

Chronic Kidney Disease (CKD): Most common disease in geriatric cats (>50% of cats >15 years).

• IRIS staging: Requires creatinine + clinical signs. IRIS stages I-IV based on serum creatinine and proteinuria (UPC ratio). SDMA rises before creatinine.
• Clinical signs: Polyuria, polydipsia, weight loss, poor coat, anorexia. Cats hide illness; many owners report "no signs" until azotemia detected.
• Management: Therapeutic renal diet (restricted phosphate, moderate protein), ACE inhibitor if proteinuric, fluid therapy if dehydrated.

Hyperthyroidism: Often presents as weight loss + tachycardia + elevated T4.

• Diagnosis: Total T4 (beware euthyroid sick syndrome in concurrent disease; may require free T4 or suppression test).
• Treatment: Antithyroid drugs (propylthiouracil, methimazole), radioactive iodine (gold standard), dietary iodine restriction, or thyroidectomy.

Diabetes Mellitus: Often reversible with low-carbohydrate diet alone.

• Remission rates: >60% with low-carb diet initiation; 30% with insulin therapy alone.
• Complications: Diabetic ketoacidosis (DKA), peripheral neuropathy (resolves post-remission).

Feline Lower Urinary Tract Disease (FLUTD): Includes idiopathic cystitis, uroliths, strictures.

• IDIOPATHIC: Accounts for ~60% of cases. Stress-sensitive; environmental enrichment critical.
• Diagnosis: Urinalysis, imaging, cystoscopy as indicated.
• Management: Environmental enrichment, water intake, low-magnesium diets (if magnesium uroliths); antispasmodics or anxiolytics for idiopathic cases.

FIV/FeLV Status: Both retroviruses; FeLV more acute/severe; FIV more chronic/progressive.

• Testing: Combination antigen/antibody snap test (identifies FeLV antigen, FIV antibody). False positives occur; confirm with Western blot or IFA.
• Vaccine status: FeLV vaccine recommended for all kittens and outdoor cats. FIV vaccine less protective; post-vaccination serology indistinguishable from natural infection.

Feline Behavior and Illness Recognition

Cats are obligate introverts; illness is masked by hiding behavior.

• Red flags despite "no signs": Litter box changes (location, frequency, difficulty), reduced grooming, behavioral withdrawal, decrease in appetite (even subtle).
• Acute illness: Often presents as sudden collapse or severe crisis; subacute decline easily missed by owners.
• Handling stress: Cats are exquisitely stress-sensitive. Minimize restraint, use low-stress handling, and consider repeating bloodwork in calmer environment if results unexpected.

Limitations

• Glucuronidation deficiency information applies to domestic cats; wild felids have different metabolism profiles.
• Lab reference ranges vary by analyzer; always confirm with sending laboratory.
• Stress hyperglycemia classification (via fructosamine) requires serial testing; single values are limited.
• This skill provides clinical frameworks, not patient-specific treatment plans.
• Board-certified feline specialists should be consulted for complex cases (advanced CKD, DKA, difficult-to-manage FLUTD).