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Acute Renal Failure Differential Diagnosis

Water-soluble waste products and toxins are filtered out of the blood by the kidneys. These chemicals are then excreted in the urine. This makes the kidneys important in maintaining good health since a failure in their function leads to a buildup of dangerous chemicals in the blood. Short term, or acute, kidney failure can be due to several causes.

  1. The Kidneys

    • The normal human body has two kidneys. These are two bean-shaped organs located toward the rear of the abdominal cavity. Kidneys have thousands of small units called nephrons which do the work of filtering the water-soluble waste products and toxins out of the blood and out of the body in the urine. Nephrons have very small tubes and very small blood vessels, so damage to the nephrons is easy.

    Main Types of Causes

    • Because the kidneys receive so much blood, any condition that affects this blood flow damages the kidneys. Prerenal causes are those which prevent blood from properly flowing to the kidneys. Renal causes are are those that occur directly at the kidneys. Postrenal causes are those conditions which block the kidney's ability to excrete urine, thus backing up the urine into the kidneys.

    Prerenal Causes

    • Prerenal causes of acute kidney failure mostly involve conditions which slow or block the flow of blood to the kidneys. These conditions include poor cardiac output, where the heart is too weak to properly pump blood to the rest of the body. This causes lowered blood pressure. Certain drugs and loss of blood from trauma also cause decreased low blood pressure and damage to the kidneys. Restoring blood flow may prevent further damage but not necessarily undo it.

    Renal Causes

    • Damage to the nephrons can be caused by toxins and chemicals that are either created as byproducts in the body or ingested. For example, the cell membrane of destroyed red cells may plug the nephrons. This happens in certain bacterial infections or in reactions to some medications. Excessive levels of alcohol may also cause damage to the nephrons as do excessive levels of other chemicals. Conditions such as high blood sugar from diabetes also damage the small blood vessels in the nephrons.

    Postrenal Causes

    • Obstructions of the ureters, the tubes that deliver urine from the kidneys to the bladder, and obstruction of the urethra, the tube that delivers urine from the bladder out of the body, can also cause renal failure. Causes for these obstructions include kidney stones, inflammation from an infection, tumors or traumatic injuries. Urine backs up into the kidneys when this happens, and the toxins that were supposed to be excreted will then flood and damage the nephrons in the kidneys.

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