Postrenal AKI is defined by which mechanism?

Postrenal AKI is defined by which mechanism?

• A. Obstruction to urine outflow
• B. Ischemia of renal tubules
• C. Inflammation of glomeruli
• D. Nephrotoxicity from toxins

Answer: (A)

Obstruction to urine outflow leads to postrenal AKI. When urine passage downstream of the kidneys is blocked, urine backs up and pressure rises in the renal pelvis and tubules. This back pressure decreases the glomerular filtration rate and, if the blockage involves both kidneys or a solitary functioning kidney, causes a rapid decline in kidney function. This mechanism is distinct from pre-renal AKI, which comes from reduced kidney perfusion, and from intrinsic renal causes like ischemic tubular injury, glomerular inflammation, or nephrotoxic damage. Common culprits include stones blocking the ureter, enlarged prostate, tumors, or ureteral strictures. Ultrasound may show hydronephrosis, supporting an obstructive cause.

Obstruction to urine outflow leads to postrenal AKI. When urine passage downstream of the kidneys is blocked, urine backs up and pressure rises in the renal pelvis and tubules. This back pressure decreases the glomerular filtration rate and, if the blockage involves both kidneys or a solitary functioning kidney, causes a rapid decline in kidney function. This mechanism is distinct from pre-renal AKI, which comes from reduced kidney perfusion, and from intrinsic renal causes like ischemic tubular injury, glomerular inflammation, or nephrotoxic damage. Common culprits include stones blocking the ureter, enlarged prostate, tumors, or ureteral strictures. Ultrasound may show hydronephrosis, supporting an obstructive cause.