Home Topics Kidney FailureRenal Failure Diagnosis

Tools & Tests Used in Renal Failure Diagnosis

The first step in confirming a diagnosis of renal failure is establishing the underlying cause of the condition. In some cases, symptoms will point to acute kidney failure, which is often reversible. During the process of examining the patient's symptoms and test results, a physician can assess the extent of organ damage and take steps to prevent further damage if it is localized.

Azotemia, Hyponatremia, Creatinine Levels & Blood Tests

The results of blood tests provide information on kidney function. Blood tests often reveal high creatinine levels. Creatinine is an alkaline compound that is found in the blood, muscles, and urine. A high level of creatinine in the blood can be a sign of renal function problems.

In addition to high creatinine levels, blood tests can reveal a number of renal problems. Anemia and acidosis are often indications of renal failure. The list of indicators includes:

Acidosis: Acidosis indicates high levels of organic acids and phosphates, with a resultant drop in pH, in the bloodstream.
Anemia: Anemia is a condition in which tests show low levels of red blood cells and/or hemoglobin.
Azotemia: Azotemia is detected when blood tests show high levels of nitrogen.
Hyperkalemia: Hyperkalemia is the name of a condition in which high levels of potassium are found in the blood.
Hyponaturemia: Hyponaturemia indicates low levels of sodium in theblood.

Urinalysis & Proteinuria

A urinalysis is an important step in the kidney failure diagnosis. The urinarlysis measures sodium levels and examines urine sediment. High sodium levels indicate a renal problem. If the kidneys have been damaged, urinary sediment may contain tubular cells, the cells used to filter blood in the kidneys. A urinalysis may also detect high levels of urea, the main solid component of urine.

Proteinuria is a condition in which high levels of protein are present in the urine. Proteinuria occurs if protein that should remain in the body is filtered out through urine. The condition is one of the manifestations of nephrotic syndrome, a common symptom of renal failure.

X-Rays & Diagnostic Imaging

X-rays are used to detect the presence of kidney stones, and can provide information about the size of the kidneys. An x-ray has a ninety percent chance of detecting a stone, so the technique is favored over other diagnostic tools, including ultrasound, which has only an 80 to 85 percent chance of detecting stones.

A renal arteriography or venography may be used to locate blood flow obstructions. A dye is injected into the bloodstream, and then x-rays of the kidney are taken. The dye shows up on x-rays, revealing the blood vessels in and around the organ.

Ultrasounds and CT scans reveal the size of the affected organ. An ultrasound uses high frequency sound waves to generate a picture of the organ on a monitor, while a CT scan takes multiple x-rays and combines them into a computerized 3-dimensional picture. An enlarged kidney indicates an acute condition, which may be reversible. Alternatively, small kidneys with signs of scarring generally indicate a chronic condition with irreversible damage.

Biopsy Options

A biopsy provides a definitive diagnosis of renal failure. A long, thin needle is inserted into the organ, and a sample of tissue is removed. This sample is then examined for microscopic evidence of renal failure. Small, scarred kidneys are not usually good candidates for a biopsy.

Resources

Beers, M. H., & Berkow, R. (ed). Acute renal failure. The Merck Manual of Diagnosis and Therapy, 17th Edition. Merck Research Laboratories, NJ, 1999.

Beers, M. H., & Berkow, R. (ed). Chronic renal failure. The Merck Manual of Diagnosis and Therapy, 17th Edition. Merck Research Laboratories, NJ, 1999.

Mayo Foundation for Medical Education and Research. (2004). Kidney failure. MayoClinic.com.