This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood Vessels, Subject name: Pathology
Most common organ affected in polyarteritis nodosa? 
Select and explain. 
A. Lungs, B. Kidneys, C. Pancreas, D. Spleen
B: Kidneys
Answer: B: Kidneys 
Explanation: Ans. b (Kidneys). (Ref. Harrisons Medicine, 18th/ Chapter 326. The Vasculitis Syndromes)PAN is necrotising vasculitis of small and medium sized arteries.Descending order of frequency of involvement of organs in PAN is# Kidney# Heart# Liver# GIT# Muscle# Pancreas# Testis# CNS# Skin