Alternate Names: Urine creatinine - spot collection

How Performed: Spot collection: obtain a sample of urine by urinating and saving part of the urine in a container

A 24-hour urine sample is needed.
The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.

• On day 1, urinate into the toilet upon arising in the morning.
• Collect all subsequent urine (in a special container) for the next 24-hours.
• On day 2, urinate into the container in the morning upon arising.
• Cap the container. Keep it in the refrigerator or a cool place during the collection period. Label the container with your name, the date, the time of completion, and return it as instructed.

How To Prepare: No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How It Feels: The test involves only normal urination, and there is no discomfort.

Risks: There are essentially no risks.

Why Performed: A measurement of the serum creatinine level is often used to evaluate kidney function. Urine creatinine levels can be used as a screening test to evaluate kidney function, or can be part of the creatinine clearance test.

Creatinine is a breakdown product of creatine, which is an important constituent of muscle. By far the most important source of energy inside cells are the high-energy phosphate bonds of the ATP molecule. When one of these bonds is broken, energy is released and ATP becomes ADP. Creatine phosphate represents a backup energy source for ATP, because it can quickly re-convert ADP back to ATP.

The creatine molecule gradually degrades to creatinine with time. Creatinine is a waste product, that is, it cannot be used by cells for any constructive purpose. The daily production of creatine and subsequently creatinine, depends on muscle mass, which fluctuates very little.

Creatinine is excreted from the body entirely by the kidneys. With normal kidney function, the serum (blood) creatinine level should remain constant and normal.

Normal Values: urine creatine (24-hour sample) 0.0 to .25 gm/24-hours
spot collection 25 to 400 mg/dl

Note: gm/24-hours = grams per 24-hours; mg/dl = milligrams per deciliter

Abnormal Results:

• acromegaly (rare)
• acute tubular necrosis (rare)
• dehydration
• diabetic nephropathy
• gigantism (rare)
• glomerulonephritis
• muscular dystrophy
• pyelonephritis
• reduced renal blood flow (e.g., shock, congestive heart failure)
• renal failure
• rhabdomyolysis
• urinary tract obstruction
• muscular dystrophy (late stage)
• myasthenia gravis
• high meat diet

• complicated UTI (pyelonephritis)
• Cushing’s syndrome caused by adrenal tumor
• pituitary Cushing’s (Cushing’s disease)
• prerenal azotemia

Cost:

Special Considerations: Drugs that can increase creatinine measurements include aminoglycosides (for example, gentamicin), cimetidine, heavy metal chemotherapeutic agents (for example, Cisplatin), and nephrotoxic drugs such as cephalosporins (for example, cefoxitin)