Urine culture

Urine sample — A “clean-catch” urine sample is performed by collecting the sample of urine in midstream. Men or boys should wipe clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well. A small amount of urine should initially fall into the toilet bowl before it is collected (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. The container is then given to the health care provider.

Also known as: Culture and sensitivity - urine

Definition

A urine culture is a lab test to check for bacteria or other germs in a urine sample.

How the test is performed

Most of the time, the sample will be collected as a clean catch urine sample in your doctor's office or home. You will use a special kit to collect the urine.

A urine sample is taken by inserting a thin rubber tube (catheter) through the urethra into the bladder. This is done by someone in your doctor's office or at the hospital. The urine drains into a sterile container, and the catheter is removed.

Rarely, the health care provider may choose to collect a urine sample by inserting a needle through the skin of the lower abdomen into the bladder.

The urine is taken to a lab to determine which, if any, bacteria or yeast are present in the urine. This takes 24 - 48 hours.

How to prepare for the test

If possible, collect the sample when urine has been in your bladder for 2 to 3 hours.

How the test will feel

When the catheter is inserted, you may feel pressure. A special gel is used to numb the urethra.

Why the test is performed

Your health care provider may order this test if you have symptoms of a urinary tract infection or bladder infection, such as pain or burning when urinating.

You may also have a urine culture after you have been treated for an infection, to make sure that all of the bacteria are gone.

Normal Values

"Normal growth" is a normal result. This means that there is no infection.

It takes 24 to 48 hours to get results.

What abnormal results mean

A "positive" or abnormal test is when bacteria or yeast are found in the culture. This likely means that you have a urinary tract infection or a bladder infection.

Other tests may help your health care provider know which bacteria or yeast are causing the infection, and which antibiotics will best treat it.

Sometimes more than one type of bacteria, or only a small amount may be found in the culture.

What the risks are

There is a very rare risk of a hole (perforation) in the urethra or bladder if your doctor or nurse uses a catheter.

Special considerations

You may have a false-negative urine culture if you've recently taken antibiotics.

References

Hooton TM, Bradley SF, Cardenas DD, et al. Diagnosis, prevention, and treatment of catheter-associated urinary tract infection in adults: 2009 International Clinical Practice Guidelines from the Infectious Diseases Society of America. Clin Infect Dis. 2010;50(5):625-663.

Ban KM, Easter JS. Selected urologic problems. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009: chap 97.

Dean AJ, Lee DC. Bedside laboratory and microbiologic procedures. In: Roberts JR, Hedges JR, eds. Clinical Procedures in Emergency Medicine. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2009:chap 68.

Review date:: May 6, 2011
Reviewed by:: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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