ACVP Veterinary Pathology cheat sheet

Necrosis patterns: coagulative (ischemia, tissue architecture retained), caseous (tuberculosis, friable), liquefactive (brain, abscess), fat (pancreas), fibrinoid (vessel walls).

Cell injury sequence: reversible swelling and fatty change precede irreversible mitochondrial rupture, membrane loss, and nuclear changes (pyknosis, karyorrhexis, karyolysis).

Inflammation: neutrophils dominate acute/suppurative; macrophages and lymphocytes dominate chronic; eosinophils indicate parasites or hypersensitivity; granulomas have epithelioid macrophages plus giant cells.

Neoplasia criteria of malignancy: pleomorphism, high mitotic rate, anisokaryosis, invasion, metastasis; benign masses are encapsulated, well differentiated, and non-invasive.

Tumor nomenclature: benign = tissue + -oma; malignant mesenchymal = sarcoma; malignant epithelial = carcinoma; mixed mammary tumors contain both epithelial and myoepithelial elements.

Apoptosis versus necrosis: apoptosis is single-cell, energy-dependent, no inflammation; necrosis is grouped cells with membrane rupture and inflammatory response.

Special stains: Gram (bacteria), Ziehl-Neelsen (acid-fast), periodic acid-Schiff (fungi, glycogen), Masson trichrome (collagen), Prussian blue (iron), Congo red (amyloid).

Amyloid is eosinophilic, amorphous, extracellular material that shows apple-green birefringence under polarized light after Congo red staining.

Anemia classification by MCV: microcytic (iron deficiency, portosystemic shunt), normocytic (acute blood loss, chronic disease), macrocytic (regeneration, FeLV, B12/folate deficiency).

Reticulocyte response: absolute reticulocyte count and corrected reticulocyte percentage assess regeneration; a regenerative response peaks around 4-7 days after blood loss or hemolysis.

Hematocrit and total protein: both low suggests hemorrhage; low Hct with normal/high protein suggests hemolysis or dilution; high Hct with high protein suggests dehydration.

Leukogram interpretation: neutrophilia with left shift indicates inflammation/infection; stress leukogram = mature neutrophilia, lymphopenia, eosinopenia, monocytosis.

Platelet counts below roughly 50,000/uL carry bleeding risk; confirm thrombocytopenia by blood smear to exclude clumping artifacts.

Azotemia: prerenal (high BUN, concentrated urine, USG >1.030 in dogs), renal (isosthenuria, USG 1.008-1.012), postrenal (obstruction, elevated creatinine).

Liver enzymes: ALT and AST reflect hepatocellular injury; ALP and GGT reflect cholestasis or enzyme induction (steroids, phenobarbital).

Urinalysis: USG reflects concentrating ability; proteinuria confirmed by urine protein:creatinine ratio; casts indicate tubular origin; crystals suggest urolithiasis risk.

Coagulation: prolonged PT indicates extrinsic pathway (factor VII); prolonged aPTT indicates intrinsic pathway; both prolonged suggests common pathway or DIC.