The urethral swab is a diagnostic test aimed at finding the microorganisms responsible for lower urinary tract infections. The test uses a simple and thin cotton swab, similar to a cotton bud, to be inserted through the urethral meatus (external orifice) for approximately 1 cm in women and 1-2 cm in men. The swab is then gently turned for a few seconds, in order to collect a certain quantity of cells and exudate.
The material remaining soaked in the urethral swab is subsequently analyzed in the laboratory, with the aim of identifying the etiological agent and testing its susceptibility to certain drugs. With the antibiogram, for example, the effect of various antibiotics on isolated bacterial species is evaluated. The choice of the most suitable antibiotic therefore allows the complete eradication of the microorganism, avoiding the appearance of dangerous resistance to antibiotics.
Let us briefly remember that the urethra is a small conduit that connects the urinary bladder to the outside, allowing the elimination of urine. Since in men this duct also carries sperm during ejaculation, the male urethral swab also represents a diagnostic tool for various sexually transmitted diseases, such as Chlamydia and Mycoplasma/ureaplasma. On the other hand, in women, given the anatomical proximity of the urethra and vagina, urinary infections are sometimes associated with vaginitis and cervicitis.
The most common etiological agent of lower urinary tract infections is bacteria Neisseria gonorrhoeae (in these cases we speak of gonococcal or gonorrheic urethritis). In women, due to the shorter anatomical length of the urethra, bladder infections (cystitis) are more frequent, while urethritis is more common in men.
In males, squeezing the penis improves the sensitivity of the test, as it favors the movement of any exudate along the urethra; sometimes rectal prostatic stimulation may also be necessary. In women the exam is generally painless, also due to the poor penetration of the swab, while in men it can cause a lot of discomfort.
In order to obtain a sufficiently large number of samples on which to search for potential pathogens, five or six urethral swabs are generally performed.
Preparation For Urethral Swab
To avoid affecting the outcome of the exam, it is best to:
abstain from sexual intercourse in the 24 hours preceding it;
suspend all antibiotic and antifungal therapy in the previous week;
avoid vaginal irrigations, local therapies in the vagina (ovules, candles, etc.) and tub baths in the 24 hours before the exam;
on the morning of the exam, take care of your external intimate hygiene with a little soap and water;
refrain from urinating in the previous three hours (the urethral swab is performed in the morning, before urination, in order to avoid the washing action of the urine on the walls of the urethra).
Failure to comply with these indications can produce false negatives, i.e. subjects who, according to the swab results, appear healthy when in reality they are ill.
When Is It Performed?
The urethral swab is performed in the presence of suspicions about the presence of a genitourinary infection and to evaluate the effectiveness of the therapy undertaken. Common symptoms of these conditions are frequent, painful and difficult urination (with a sense of incomplete emptying of the bladder), cloudy greenish-yellow urine, sometimes smelly with traces of blood or pus, discharge of secretions from the penis and vaginal discharge. If these symptoms appear, it is very important to promptly report them to the doctor, in order to eradicate the infection and prevent its often fearful complications (extension of the infectious process to adjacent structures leading to infertility).
The urethral swab, together with the vaginal/cervical one and sometimes the anal one, is also part of the prophylactic and control tests during pregnancy.