Feline Medicine

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).