A patient presented with pus in urine. Urine culture was done which was negative. After a sudden onset renal failure the patient died. On autopsy the following finding was seen in kidney. What is the most likely diagnosis?
**Core Concept**
The question tests the student's knowledge of the pathophysiology of renal tuberculosis (TB), a condition that can cause chronic kidney damage and eventual renal failure. Renal TB is a form of extrapulmonary tuberculosis that affects the kidneys, often resulting from the hematogenous spread of Mycobacterium tuberculosis from a primary focus elsewhere in the body.
**Why the Correct Answer is Right**
Renal TB typically presents with chronic kidney damage, including tubercles, caseation necrosis, and fibrosis. The tubercles are formed by the aggregation of immune cells, including macrophages and lymphocytes, in response to the presence of the tubercle bacillus. The caseation necrosis is a result of the infection causing damage to the renal parenchyma. The sudden onset of renal failure in this patient is likely due to the rupture of a tuberculous abscess or a tuberculous pyelonephritis, leading to a severe inflammatory response and subsequent renal failure. The negative urine culture result is not surprising, as Mycobacterium tuberculosis is a slow-growing organism that may not be detected in a routine urine culture.
**Why Each Wrong Option is Incorrect**
**Option A:** Infected renal cysts can cause a range of symptoms, including flank pain and hematuria, but they are not typically associated with a sudden onset of renal failure or a negative urine culture result.
**Option B:** Infected renal cysts are a possible cause of pyelonephritis, but they are not typically associated with the chronic kidney damage and renal failure seen in renal TB.
**Option C:** Renal cell carcinoma is a type of kidney cancer that can cause a range of symptoms, including hematuria and flank pain, but it is not typically associated with a sudden onset of renal failure or a negative urine culture result.
**Option D:** Renal stones can cause severe pain and obstructive uropathy, but they are not typically associated with a sudden onset of renal failure or a negative urine culture result.
**Clinical Pearl / High-Yield Fact**
Renal TB is a classic example of a condition that can cause chronic kidney damage and eventual renal failure, often presenting with a negative urine culture result due to the slow growth of Mycobacterium tuberculosis.
**✓ Correct Answer: A. TB kidney**