[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Asymptomatic bacteriuria [Conditions](https://durgical.com/en/conditions/) · [Nephrology and urology](https://durgical.com/en/conditions/) # Asymptomatic bacteriuria Bacteria in the urine without urinary symptoms. Screening and treatment help in pregnancy and before some urological procedures; usually it is left alone. Updated 2026-11-01 ## Structures involved Tap one to see what it is and open it in 3D. - [Urinary bladder](https://durgical.com/en/anatomy/urinary-bladder/) - [Kidneys](https://durgical.com/en/anatomy/kidney/) - [Ureters](https://durgical.com/en/anatomy/ureter/) - [Renal pelvis](https://durgical.com/en/anatomy/renal-pelvis/) - [Trigone of bladder](https://durgical.com/en/anatomy/trigone-of-bladder/) - [Urethra (female)](https://durgical.com/en/anatomy/female-urethra/) ## What it is The presence of a significant number of bacteria in a properly collected urine sample from a person with no symptoms or signs of urinary infection. It is colonisation, not infection, and in most groups it does not need antibiotics. ## Who gets it Common: it increases with age and is frequent in older women, nursing-home residents and people with long-term catheters, where it is almost universal. It occurs in roughly 2–10% of pregnant women. Colombian prenatal guidance includes urine culture screening early in pregnancy. ## Causes - Escherichia coli is the most common organism - Other gram-negative rods (Klebsiella, Proteus) and enterococci - Group B Streptococcus in pregnancy ## Risk factors - Female sex, sexual activity and older age - Pregnancy - Diabetes - Indwelling urinary catheter - Spinal cord injury or neurogenic bladder - Urinary obstruction, stones or [prostate](https://durgical.com/en/anatomy/prostate/) enlargement ## Pathophysiology Bacteria from the gut and perineum ascend the urethra and colonise the bladder, but the strains are often less virulent and the host does not mount a symptomatic inflammatory response. In pregnancy, progesterone relaxes smooth muscle and the enlarging uterus compresses the [ureters](https://durgical.com/en/anatomy/ureter/), causing physiological hydroureter and stasis, so bacteria ascend more easily to the [kidney](https://durgical.com/en/anatomy/kidney/). Untreated bacteriuria in pregnancy therefore carries a much higher risk of pyelonephritis, which is linked to preterm birth and low birth weight. ## Classification - Women: two consecutive clean-catch samples with the same organism at 10^5 CFU/mL or more - Men: a single clean-catch sample with 10^5 CFU/mL or more - Catheterised samples: 10^2 CFU/mL or more of one organism ## Symptoms and signs - By definition no dysuria, urgency, frequency, suprapubic pain, flank pain or fever - Cloudy or foul-smelling urine alone is not a symptom of infection and does not justify antibiotics ## Red flags - Fever, flank pain or chills in a pregnant woman (pyelonephritis) - Signs of sepsis in an older or catheterised patient - New urinary symptoms (it is then a urinary tract infection) ## Diagnosis **Clinical** Defined only by a positive urine culture in a person without urinary symptoms; pyuria alone does not mean infection. **Tests** Quantitative urine culture on a midstream clean-catch sample (or from a catheter). Screen only pregnant women, early in pregnancy, and patients before urological procedures that breach the mucosa. **Imaging** Not needed. Imaging is reserved for complicated infection or suspected obstruction. ## Differential diagnosis - Symptomatic urinary tract infection (cystitis) - Acute pyelonephritis - Contaminated sample (mixed organisms, poor collection) - Sterile pyuria (tuberculosis, stones, interstitial nephritis) ## Goal of treatment Treat only those who benefit (pregnant women and patients before mucosa-breaching urological procedures) and avoid unnecessary antibiotics in everyone else. ## Treatment **Conservative** No screening or treatment in non-pregnant women, older adults (including those with delirium or falls but no urinary or systemic signs), diabetes, [spinal cord](https://durgical.com/en/anatomy/spinal-cord/) injury, catheters or before non-urological surgery. **Medical** Pregnancy: a short course of a culture-guided antibiotic safe in pregnancy (for example beta-lactams, nitrofurantoin or fosfomycin, depending on trimester). **Follow-up** Pregnancy: repeat culture after treatment to confirm clearance and periodic cultures until delivery; watch for fever or flank pain. **Medical** Before endoscopic urological procedures with mucosal trauma: culture-guided antibiotics shortly before the procedure. ## Complications - Pyelonephritis in pregnancy - Preterm birth and low birth weight if untreated in pregnancy - Antibiotic resistance and Clostridioides difficile infection from unnecessary treatment ## Prognosis In non-pregnant adults it is benign and often clears or persists without harm. In pregnancy, treatment markedly reduces the risk of pyelonephritis. ## Prevention - Urine culture screening early in pregnancy as part of prenatal care - Removing urinary catheters as soon as they are not needed - Antibiotic stewardship: not ordering urine cultures in people without symptoms ## Test yourself Think of the answer, then tap the question to see it. ## In which two groups should asymptomatic bacteriuria be screened for and treated? Pregnant women and patients before urological procedures that breach the mucosa. ## Why is it treated in pregnancy? Hormonal and mechanical urinary stasis raise the risk of pyelonephritis, which is linked to preterm birth and low birth weight. ## An older nursing-home resident without urinary symptoms has a positive culture. What is the management? No antibiotics; asymptomatic bacteriuria should not be treated in this group. ## What culture count defines it in women? Two consecutive clean-catch samples with the same organism at 10^5 CFU/mL or more. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/asymptomatic-bacteriuria/) ## Related conditions - [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/) - [Acute pyelonephritis](https://durgical.com/en/conditions/acute-pyelonephritis/) - [Preterm labour and birth](https://durgical.com/en/conditions/preterm-labour-and-birth/) - [Type 2 diabetes mellitus](https://durgical.com/en/conditions/type-2-diabetes-mellitus/) - [Urinary incontinence in older adults (urge, overflow, functional)](https://durgical.com/en/conditions/urinary-incontinence-in-older-adults/) - [Benign prostatic hyperplasia](https://durgical.com/en/conditions/benign-prostatic-hyperplasia/) - [Spinal cord injury](https://durgical.com/en/conditions/spinal-cord-injury/) - [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/) - [Kidney stones (urolithiasis)](https://durgical.com/en/conditions/kidney-stones/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [Recommendation: Asymptomatic Bacteriuria in Adults: Screening | United States Preventive Services Taskforce](https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/asymptomatic-bacteriuria-in-adults-screening) (U.S. Preventive Services Task Force, 2019); [IDSA 2019 Clinical Practice Guideline Update for the Management of Asymptomatic Bacteriuria](https://www.idsociety.org/practice-guideline/asymptomatic-bacteriuria/) (Infectious Diseases Society of America, 2019). [← All conditions](https://durgical.com/en/conditions/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/conditions/asymptomatic-bacteriuria/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). 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