Pathology and Pathophysiology
Core concepts
This domain links mechanism to manifestation. Understand cell injury and death (necrosis vs apoptosis), inflammation (acute vs chronic, granulomas), hemodynamic disorders (thrombosis, embolism, infarction, shock), neoplasia (benign vs malignant, grading vs staging, tumor markers), and the pathophysiology of major organ failure. Know the Virchow triad, the difference between transudate and exudate (protein and cells), and the mechanisms of edema, ascites, and jaundice. For neoplasia, distinguish dysplasia from carcinoma in situ and understand metastasis routes.
Common traps
Questions love distinguishing grading (differentiation) from staging (spread, prognosis). Transudate vs exudate is a classic trap: use Light's criteria for pleural fluid. Do not confuse apoptosis (energy-dependent, no inflammation) with necrosis (passive, inflammation). Shock types (hypovolemic, cardiogenic, distributive, obstructive) are often tested by hemodynamic profile - know that distributive shock has low systemic vascular resistance and warm skin early.
Worked example
A patient with cirrhosis develops ascites. Rule of thumb: ascites in cirrhosis is mainly transudative (low SAAG); a high SAAG suggests portal hypertension, while low SAAG suggests inflammation or malignancy - calculate serum-ascites albumin gradient to narrow the cause.
Rule of thumb
Ask "what is the mechanism?" for every finding; exam questions reward linking pathophysiology to clinical signs.