This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Following circulatory shock, which of the following occurs: March 2009 
Select and explain. 
A. Acute tubular necrosis, B. Acute papillary necrosis, C. Both of the above, D. None of the above
A: Acute tubular necrosis
Answer: A: Acute tubular necrosis 
Explanation: Ans. A: Acute tubular necrosisAcute tubular necrosis (ATN) is caused by lack of oxygen to the kidney tissues (ischemia of the kidneys), or by exposure to materials that are poisonous to the kidney (nephrotoxic agents).The internal structures of the kidney, paicularly the tissues of the kidney tubule, become damaged or destroyed. ATN is one of the most common structural changes that can lead to acute renal failure.ATN is one of the most common causes of kidney failure in hospitalized patients.Renal papillary necrosis is a form of nephropathy involving the necrosis of the renal papilla, which is supplied by the vasa recta.Analgesic nephropathy is a cause of renal papillary necrosis. The damage is cumulative and most patients of renal papillary necrosis would have ingested at least 20kg of analgesics in the past. The risk is higher for phenacetin and acetaminophen compared to aspirin and other NSAIDs.