Renal Panel

A renal panel is a group of tests that may be performed together to evaluate kidney (renal) function. The tests measure the amounts of various substances, including several minerals, electrolytes, proteins, and glucose (sugar), in the blood to determine the current status of the kidneys.

The kidneys are a pair of bean-shaped organs that are located at the bottom of the ribcage in the right and left sides of the back. They normally filter about 170 litres of blood a day, removing waste products that form from the metabolism (breakdown) of food and from normal cell activity. The kidneys form urine to expel excess water from the body together with these waste products that are removed from the blood.

The kidneys help regulate pH and the amounts of necessary chemicals in the body including potassium, sodium, calcium, phosphorus, chloride, and bicarbonate (TCO2) by separating them out from the waste materials and releasing them back into the blood, getting rid of only as much or as little as needed to maintain normal blood concentrations.

If the kidneys are not functioning properly, waste products can accumulate in the blood and the amount of fluid can increase to dangerous levels, causing damage to the body or a potentially life-threatening situation. Numerous conditions and diseases can result in damage to the kidneys. The most common causes of and main risk factors for kidney disease are diabetes and hypertension. For more on the types and causes, see the article on Kidney Disease.

The individual tests included in a renal panel can vary by laboratory, but the tests typically performed include:

Blood Tests

Electrolytes – electrically charged chemicals that are vital to normal body processes, such as nerve and muscle function; among other things, they help regulate the amount of fluid in the body and maintain the acid-base balance. Electrolytes include:

• Sodium
• Potassium
• Chloride
• Bicarbonate (CO2)

Minerals

• Phosphorus – a mineral that is vital for energy production, muscle and nerve function, and bone growth; it also plays an important role as a buffer, helping to maintain the body's acid-base balance.
• Calcium – one of the most important minerals in the body; it essential for the proper functioning of muscles, nerves, and the heart and is required in blood clotting and in the formation of bones.

Protein

• Albumin – a protein that makes up about 60% of protein in the blood and has many roles such as keeping fluid from leaking out of blood vessels and transporting hormones, vitamins, drugs, and ions like calcium throughout the body.

Waste products

• Urea– urea is a nitrogen-containing waste product that forms from the metabolism of protein; it is released by the liver into the blood and is carried to the kidneys, where it is filtered out of the blood and eliminated in the urine.
• Creatinine – another waste product that is produced by the body's muscles; almost all creatinine is eliminated by the kidneys.

Sugar

• Glucose – energy source for the body; a steady supply must be available for use, and a relatively constant level of glucose must be maintained in the blood.
• HbA1c – is a longer term marker of sugar levels, particularly useful in establishing if diabetes mellitus is present and, if it is, how well it is controlled.

Two calculated values may also be reported with a renal panel:

• Estimated Glomerular Filtration Rate (eGFR) – a calculated estimate of the actual glomerular filtration rate (GFR, the amount of blood filtered by the glomeruli in the kidneys per minute) derived from creatinine concentrations in the blood; the formula takes into account the person's age, gender (sex), and sometimes height and weight.
• Anion gap – anion gap (AG or AGAP) is a value calculated using the results of an electrolyte panel. It evaluates the difference between measured and unmeasured electrical particles (ions or electrolytes) in the fluid portion of the blood.

Urine Tests

There are other laboratory tests that can be used to assess kidney function, including a urinalysis, urine protein or creatinine clearance. For those with diabetes or high blood pressure (hypertension), a urine albumin (microalbumin) test, which measures small amounts of albumin leakage from the blood into the urine, may also be used to detect early kidney damage. When both albumin and creatinine are measured in a random urine sample, an albumin/creatinine ratio (ACR) can be calculated. This may be done to more accurately determine how much albumin is escaping from the kidneys into the urine.