Which option describes a post-renal cause of acute renal failure?

Which option describes a post-renal cause of acute renal failure?

• A. Fluid overload
• B. Urine outflow obstruction due to an enlarged prostate
• C. Reduced renal blood flow due to shock
• D. Nephron injury from trauma

Answer: (B)

Post-renal acute kidney injury happens when urine flow is obstructed somewhere after the kidneys, causing back pressure and reduced filtration. An enlarged prostate can block the bladder outlet, leading to urine retention and back-pressure on the ureters and kidneys. That blockage directly fits a post-renal mechanism. Fluid overload describes too much fluid in the body, which can accompany kidney issues but isn’t about an obstruction to urine flow. Reduced renal blood flow from shock is a pre-renal issue due to poor perfusion, not a blockage. Nephron injury from trauma is intrinsic kidney damage, not a blockage of urine outflow.

Post-renal acute kidney injury happens when urine flow is obstructed somewhere after the kidneys, causing back pressure and reduced filtration. An enlarged prostate can block the bladder outlet, leading to urine retention and back-pressure on the ureters and kidneys. That blockage directly fits a post-renal mechanism.

Fluid overload describes too much fluid in the body, which can accompany kidney issues but isn’t about an obstruction to urine flow. Reduced renal blood flow from shock is a pre-renal issue due to poor perfusion, not a blockage. Nephron injury from trauma is intrinsic kidney damage, not a blockage of urine outflow.