Postrenal acute renal failure (ARF) occurs when an obstruction in the urinary tract below the kidneys causes waste to build up in the kidneys. Postrenal acute renal failure accounts for about 5% of acute renal failure cases.¹

A blockage in the urinary tract may cause urine to build up in one or both kidneys. Over time, this fluid buildup can prevent the normal flow of urine out of the kidney. Conditions that may lead to postrenal acute renal failure include:

• Kidney stones. Kidney stones most often develop in the ureters. They may also develop in the urethra.
• An enlarged prostate (benign prostatic hyperplasia, or BPH). An enlarged prostate gland may put pressure on the urethra, causing urine to back up in the bladder.
• A bladder that doesn't empty properly. This may be caused by certain nervous system disorders, such as stroke, multiple sclerosis, spinal cord injury, or Parkinson's disease.
• Blood clots in the ureters or urethra.
• Cancer of the prostate, cervix, or colon.

Postrenal acute renal failure requires immediate treatment. When detected early, it usually can be reversed by removing or bypassing the obstruction in the urinary tract, before any permanent damage to the kidneys occurs. Most people regain normal kidney function if the condition is reversed promptly.

If the obstruction is not relieved, the waste buildup and pressure on the kidneys may damage kidney tissue. Acute renal failure is much more difficult to reverse after damage to the kidneys has occurred.