Anuria can occur when the kidneys stop producing urine or if there is a blockage in the outflow of urine from the kidneys. Acute kidney injury (AKI) is when a decrease in kidney function develops over a few days. End-stage kidney disease occurs when a gradual loss of kidney function reaches an advanced state and can ultimately cause anuria.
Causes of AKI can be broken into prerenal, intrarenal, and postrenal causes. Prerenal causes include anything that causes decreased blood flow into the kidneys, including hypovolemic states, such as a major hemorrhage; gastrointestinal losses, like with diarrhea or vomiting; renal losses, like with diuretics or osmotic diuresis in diabetic ketoacidosis; skin losses, like with severe burns; and sequestration of fluid, also known as third-spacing, which can occur in heart failure, liver disease, acute pancreatitis, or sepsis. Reduced blood flow to the kidneys can also result from renal artery stenosis when one or both renal arteries become narrowed.
Next, intrarenal AKI is caused by damage to the renal tubules, the glomerulus, or the kidney interstitium, which is the space between adjacent tubules. Ischemia, or loss of blood supply to the cells; nephrotoxins (e.g., aminoglycosides, heavy metals); or systemic disorders, such as certain infections or autoimmune conditions, like Sjogren syndrome, sarcoidosis, or systemic lupus erythematosus, can cause intrarenal AKI.
Finally, postrenal AKI can occur due to an outflow obstruction of urine from the kidneys. This most frequently occurs with benign prostatic hyperplasia or prostate cancer, both of which lead to compression of the urethra. Other causes include compression of the ureter by intra-abdominal tumors and kidney stones, which can become lodged in either the ureter or urethra. Typically, if one ureter is obstructed, but the other kidney works fine, renal function is preserved; however, if both ureters are obstructed, anuria is likely to occur.
