Small Animal Internal Medicine
Core concepts
SAIM integrates problem-based reasoning across endocrine, gastrointestinal, hepatic, renal, and hematologic systems. Master the approach to polyuria/polydipsia (diabetes mellitus, hyperadrenocorticism, hypercalcemia, renal disease, pyometra), vomiting/diarrhea (differentiate small vs. large bowel by frequency, volume, weight loss, and melena), and jaundice (prehepatic, hepatic, posthepatic). Know endocrine testing: low-dose dexamethasone suppression and ACTH stimulation for Cushing's; fructosamine and glucose curves for diabetes. Understand CKD staging (IRIS) and proteinuria (UPC). Recognize immune-mediated hemolytic anemia (spherocytes, Coombs) and immune-mediated thrombocytopenia. For vomiting, distinguish pancreatitis (cPLI) from dietary indiscretion and obstruction.
Common traps
- Treating PU/PD without confirming the diagnosis-glucose and urine specific gravity first.
- Misinterpreting a single cortisol value without context.
- Forgetting that cats with hyperthyroidism can mask renal disease.
- Assuming all diarrhea is dietary-consider parasitism, IBD, and neoplasia.
- Overlooking that IMHA can be triggered by drugs or infection.
Worked rule of thumb
A middle-aged dog with PU/PD, polyphagia, and weight loss: check glucose and urine ketones-if hyperglycemic with ketonuria, treat as diabetic ketoacidosis with fluids, insulin, and electrolyte monitoring. A cat with weight loss and a palpable thyroid: measure T4 before assuming CKD.