Your urinary tract is composed of two kidneys, two ureters, the bladder and the urethra that together collect, transport, store and expel urine1. Cells in the brain and the spinal cord coordinate the muscle movements required to perform these functions2.

Your kidneys participate in the elimination of waste products and toxins from the body, including urea, creatinine and uric acid3. They also make hormones such as erythropoietin to produce red blood cells and renin to control blood pressure3. The kidneys control the amount of water and electrolytes in the blood4. These electrolytes include sodium, phosphate, and potassium5. When the kidneys stop working properly, fluid starts building up, causing swelling and increased blood pressure5.

Biomarkers Include

BUN/Creatinine Ratio

Normal Range: 6:1-22:1

A BUN/Creatinine ratio is used to evaluate kidney disease. A low ratio might indicate insufficient protein intake, increased creatinine due to muscle breakdown (rhabdomyolysis) or reduced urea synthesis that might indicate advanced liver disease6. An increased ratio may indicate insufficient urea removal related to inadequate dialysis or decreased muscle mass (sarcopenia)7.

Calcuim

Normal Range: 8.6-10.3 mg/dL

You have more calcium in your body than any other mineral8. 99% of calcium is stored bones9, with the rest found in muscle, tissues and in the fluid between cells8. Your body needs calcium to maintain bone health and hormonal balance, help muscles and blood vessels contract and expand and help your nerve cells communicate with eachother9.

Creatinine

Normal Range: 0.60-1.35 mg/dL 

Creatine is a waste product of creatinine metabolism in muscle that is eliminated in urine6. The body produces creatinine at a constant rate, but the amount of creatinine produced depends on muscle bulk and diet3. Thus, ranges differ among men, women, and children. A creatinine test measures how well your kidneys are able to clear creatinine. If the capacity of the kidney to clear creatinine is diminished, creatinine levels increase in the blood3Increased values of serum creatine are indicative of renal impairment3. 

GFR

Normal Range: 120-125mL/min/1.73m2

The Glomerular filtration rate (GFR) is a test used to assess kidney function4. The GFR is the rate at which substances in plasma are filtered through the glomerulus, or the rate at which substances in plasma are cleared from the blood3. eGFR is estimated GFR; separate calculations are made for African-American and non-African-American estimates.

Urea Nitrogen (BUN)

Normal Range: 7-25 mg/dL

Urea is a waste product of protein metabolism in the liver6. During this process, blood urea nitrogen (BUN) is created and taken to the kidneys where urea is eliminated in the urine. Serum urea increases when renal clearance decreases and is thus a sign of acute or chronic renal failure3, and congestive heart failure10. A high protein diet might also increase urea in the blood. Low urea might indicate protein deficiency in the diet, starvation and severe liver disease3. Although serum creatinine is a more accurate reflection of renal function than urea; increased urea precedes abnormal creatinine levels in renal disorders3. BUN levels higher than 100 mg/dL indicate severe kidney damage10.