Urine specimens can easily become contaminated with periurethral, skin, perianal and vaginal flora. This contamination can be reduced to acceptable levels, if proper technique of urine collection is followed. The methods of collection differ according to the patient’s age, gender, clinical condition and history of catheterization. The common techniques of urine specimen collection are discussed below.
- Preferably, an early morning samples should be submitted for culture. Urine that has remained in the bladder for at least 4 hours has decreased chances of false negative results.
- Forcing fluids will dilute the bladder urine and decrease colony counts to below significant levels.
The sample should be processed within 2 hours after collection. If that is not possible then it should be refrigerated both during storage and transport, and processed within 24 hours. If refrigeration is not possible and delay is expected, at least 3 ml of sample should be collected in a container with preservatives (boric acid-glycerol or boric acid-Na formate).
- The submitted sample should be appropriately labeled with name, age, gender of the patient and mode and time of sample collection.
- Fungal cultures are included in the routine urine culture. For anaerobic culture, the sample should be a suprapubic aspirate submitted in a syringe.
- In infants, voided or bagged specimens should be discouraged.
Reject specimens from urinals or bedpans, bags of catheterized patients, leaky containers, unlabelled specimens, and unrefrigerated, unpreserved specimens over 2 hours old.
Midstream urine by clean catch method
This is the commonest technique used in adults and children (toilet trained). The patient should be conscious, able to pass urine, not catheterized and a female patient should not be menstruating.
Separate the labia and cleanse the urethral meatus twice with sterile sponges soaked in plain soap and water from front to back and then rinse with sterile water or saline sponges twice. The same should be done for uncircumcised males after retracting the foreskin. No preparation is necessary for circumcised males.
After discarding the first 10 ml, collect at least 5-10 ml of voided urine in a sterile leak-proof container by moving into the stream of urine without halting or restarting the stream. Screw on the top of the container after making sure that there is no leakage.
Clamp the catheter till the patient senses the urge to urinate or the bladder becomes palpable. Clean the catheter port with 70% alcohol and collect 10 ml urine using a needle and syringe. Remove the clamp.
Straight catheter (in and out):
This technique is used by physician or trained health professional to collect the specimen from infants, or patients with neurogenic bladders. Urine is obtained directly from the bladder after cleansing the meatus with plain soap and water (as previously mentioned). Discard the first 15-30 ml and submit the next flow for culture.
Remove external device, cleanse the stoma with 70% alcohol, then iodine and then remove iodine with alcohol. Insert catheter tip into cleansed stoma to a depth beyond the fascial level and collect urine.
This is the preferred method of urine collection from infants and where interpretation of voided urine culture is difficult or anaerobic bacteria are suspected as cause of UTI. However this technique should be performed by physician or trained health professionals.
- Bladder should be full and palpable. Shave and disinfect the skin over the bladder.
Make a small wound through the epidermis above the symphysis pubis and aspirate using a needle and syringe. Submit specimen in syringe or carefully sealed sterile container.
1– Henry D Isenberg. Clinical Microbiology Procedure Handbook, 2nd ed. Vol. 1 ASM press.