Oliguria is defined as –
**Core Concept**
Oliguria is a clinical condition characterized by reduced urine output, which is a marker of renal dysfunction or failure. It is essential to distinguish between prerenal, intrinsic renal, and postrenal causes of oliguria to initiate appropriate management.
**Why the Correct Answer is Right**
Oliguria is typically defined as a urine output of less than 400 mL in 24 hours in adults. This decrease in urine output can result from reduced blood flow to the kidneys (prerenal causes), damage to the renal parenchyma (intrinsic renal causes), or obstruction of the urinary tract (postrenal causes). The exact mechanisms and pathophysiology vary depending on the underlying cause.
**Why Each Wrong Option is Incorrect**
**Option A:** Urine output of 500 mL in 24 hours is generally considered normal, so this option is incorrect because it does not meet the criteria for oliguria.
**Option B:** Oliguria is not defined by a specific duration of reduced urine output, making this option incorrect.
**Option C:** A urine output of less than 50 mL in 24 hours is typically considered anuria, not oliguria, making this option incorrect.
**Clinical Pearl / High-Yield Fact**
It is crucial to assess the patient's fluid status, blood pressure, and renal function tests to differentiate between prerenal, intrinsic renal, and postrenal causes of oliguria. A prompt diagnosis and management can prevent further renal damage and improve patient outcomes.
**Correct Answer: C. Less than 400 mL in 24 hours**