Specimen Collection for UTI Diagnosis

Last updated on June 11th, 2021

Urine sample should be collected and sent for culture only when there is strong evidence/suspicion of infections of the urinary tract to avoid detection of asymptomatic bacteriuria.

Common symptoms of UTI are:

Frequency of urination

Burning sensation during urination

Urgency

Dysuria (painful urination)

Pain above the pubic region

Cloudy, bloody or strong-smelling urine

Flank pain or pain above pubic area

Both noninvasive and invasive methods for collecting urine sample are available. Sample obtained from invasive methods are reliable as they are less likely to be contaminated and easy to interpret.

Urine collected by noninvasive methods passes through the contaminated milieu, so quantitative culture is used for the diagnosis of urinary tract infections (UTI) and to discriminate between contamination, colonization (asymptomatic bacteriuria), and infection.

Positive cultures could mean
Contamination
Colonization or
Infection

Commonly used methods for urine specimen collection

Suprapubic aspiration: Suprapubic aspiration is the best method to avoid contamination of specimens with bacteria in the distal urethra. Urine is withdrawn directly into a syringe through a percutaneously inserted needle.  This type of collection technique may be indicated in pediatric practice.

Straight catheter technique: Collection of urine by use of a single catheter (straight catheter technique) is the next-best technique for obtaining urine specimens with minimal contamination

Clean Catch Midstream Urine Collection: It is the least invasive technique and used widely. It has an obvious disadvantage compared to the techniques mentioned above. The chances of contamination from normal vaginal, perineal, and anterior urethral flora are high. Urine sample passes through the distal urethra and can become contaminated with commensal bacteria.

How to collect Midstream Specimen of Urine (MSU)?

Instructions for female patients

  1. Remove undergarments.
  2. Wash hands thoroughly with soap and water, rinse them, and dry them on a disposable paper towel or shake off excess water.
  3. Spread labia, with one hand, and keep them continuously apart.
  4. Open the WASH PACK and wash the urinary opening and the surrounding area. Discard the cloth in the wastebasket.
  5. Take the open sterile cup in the other hand without touching the rim or inner surface of the cup or lid.
  6. Void 20 to 25 ml into the toilet and catch a portion of the rest of the urine in the container without stopping the stream. Do not touch the legs, vulva, or clothing with the cup.
  7. Place the lid securely on the cup.
  8. Immediately transfer to the microbiology laboratory or follow the procedure as indicated by the Hospital personnel.

Instructions for male patients

  1. Remove undergarments.
  2. Wash hands.
  3. Retract the foreskin completely.
  4. Wipe the head of the penis in a single motion with the first towelette. Repeat with a second towelette. If not circumcised, hold foreskin back before cleansing.
  5. Void 20 to 25 ml into the toilet and catch a portion of the remaining urine in the cup without stopping the stream. Do not touch the cup with the penis.
  6. Place the lid on the cup securely
  7. Immediately transfer to the microbiology laboratory or follow the procedure as indicated by the Hospital personnel.

Indwelling Catheter: Specimen collection from patients with indwelling catheter requires scrupulous aseptic technique. The catheter tubing should be clamped off above the port to allow collection of freshly voided urine. The catheter port or wall of the tubing should then be cleaned vigorously with 70% ethanol, and urine aspirated via a needle or syringe; the integrity of the closed drainage system must be maintained to prevent the introduction of organisms in to the bladder.

Related Post: Microbial Etiology of Urinary Tract Infections (UTI)

Urine specimen collection techniques and frequency of their use: 

  1. Clean-catch midstream technique: Most urine specimens are obtained from adult patients via the clean-catch midstream technique
  2. Suprapubic aspiration: Used infrequently because it is not indicated clinically (except in rare circumstances), it is invasive and uncomfortable, and it requires too much time and too many resources to be practical.
  3. Straight catheter technique: It is not indicated clinically for most patients because it is too labor-intensive and costly for routine use. It is an invasive technique with added disadvantages because the process of inserting a catheter through the urethra can introduce bacteria into the bladder (and thereby cause UTI), and rare complications have been reported.
About Acharya Tankeshwar 473 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.

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