Commonly Ordered Blood Tests

• Complete blood count
• Calcium, phosphorus, parathyroid hormone
• Potassium

Urine Protein Level

During the filtering process, the kidneys usually return protein to the circulation. With chronic kidney disease, the kidneys allow protein to leak into the urine. Different kinds of proteins can leak into the urine. Albumin is a protein that often appears in the urine of people who have chronic kidney disease caused by high blood pressure or diabetes.

Different tests can be used to check for protein in the urine.

• 24-hour urine protein—measures the amount of protein in urine produced over a 24-hour period
• Dipstick for urine protein—measures the amount of protein in a single urine sample taken first thing in the morning
• Microalbumin screening in type 1 and type 2 diabetic patients
• 24-hour urine albumin—measures the amount of albumin in a sample of all urine produced in 24 hours
• Dipstick for urine albumin—measures the amount of albumin in a single urine sample
• Protein-to-creatinine ratio—compares the amount of protein to the amount of creatinine in a urine sample
• Albumin-to-creatinine ratio—compares the amount of albumin to the amount of creatinine in a urine sample

Blood Urea Nitrogen (BUN) and Creatinine Levels

Creatinine and BUN are waste products that the kidneys usually remove from the blood. When the kidneys are damaged, the creatinine and BUN levels rise in the blood. A simple blood test can measure these levels.

Estimated Glomerular Filtration Rate

The glomerular filtration rate (GFR) is a measurement of how well the kidneys are processing wastes. Your doctor can calculate the GFR based on your:

• Gender
• Age
• Body size
• Blood creatinine level

The formula used in clinical practice is called the Cockcroft-Gault equation:

Creatinine clearance or GFR (mL per minute) = (140 – age) X body weight in kilogram ÷ 72 X serum creatinine. If calculating for a female, this product is multiplied by 0.85.

The GFR determines the stage of chronic renal disease.

Urinary Tract Ultrasound or CT Scan

Your doctor may order an ultrasound or a CT scan to evaluate your kidneys, ureters, and bladder. These tests can tell your doctor if you have a kidney stone, tumor, or other structural problem that may have caused the chronic kidney disease.

Kidney Biopsy

Your doctor may recommend a kidney biopsy, unless you have small kidneys or have end-stage renal disease. During a kidney biopsy, a small piece of kidney tissue is removed and examined under a microscope. The biopsy can tell how much kidney damage has already occurred. It also may determine the cause of your kidney disease.

Special Tests

Your doctor may order the following tests to determine the underlying disease causing your chronic kidney disease:

• Complements 3 and 4—collagen vascular disease, immune complex disease, or hepatitis C -related disease
• Antineutrophil cytoplasmic antibody assay—vasculitis
• Protein electophoresis—multiple myeloma