Aurinary tract infection (UTI) is aninfection that affects a part of theurinary tract, which includes thebladder,urethra and thekidney.[9] Lower UTIs affect the bladder (cystitis) or urethra while upper UTIs affect the kidney (pyelonephritis).[10] Symptoms from a lower UTI include burning orpain during urination, pain in the lower abdomen and the urge to urinate even when the bladder is empty.[9] Symptoms of a kidney infection are more systemic and includefever orflank pain, usually in addition to the symptoms of a lower UTI.[10] Rarely, the urine may appearbloody.[11] Symptoms may be less clear in very young or old people.[1][12]
The most common cause of infection isE. coli, though otherbacteria orfungi may sometimes be the cause.[2] Risk factors include being female,sexual intercourse,diabetes, using acatheter, and family history.[9][13][7] Kidney infections usually occurs when a bladder infection spreads, but may also come frombacteria in the blood.[14] Diagnosis in young healthy women can be based on symptoms alone.[4] In those with vague symptoms, diagnosis can be harder because bacteria may be present even if there is no infection.[15][3]
In uncomplicated cases, UTIs are usually treated with a short course ofantibiotics.[7]Resistance to many of the antibiotics used to treat this condition is increasing.[1] In complicated cases, a longer course orintravenous antibiotics may be needed.[11] If symptoms do not improve in two or three days, further diagnostic testing may be needed.[3] People with bacteria or white blood cells in their urine but no symptoms usually do not need antibiotics.[16] For people with recurrent infections,methenamine may be prescribed. Postmenopausal women may also be offeredvaginal estrogen replacement. If these do not work, preventative antibiotics can be considered.[7]
Approximately 400 million UTI cases occur each year.[8] They are more common in women than men,[11] and are the most common bacterial infection in women.[17] Up to 10% of women have a urinary tract infection in a given year, and half of women have at least one infection at some point in their lifetime.[4][11] They occur most frequently between the ages of 16 and 35years.[11] Recurrences are common.[11] Urinary tract infections have been described since ancient times with the first documented description in theEbers Papyrus dated to c. 1550 BC.[18]
Urine may contain pus (a condition known aspyuria) as seen from a person withsepsis due to a urinary tract infection.
The most common symptoms of a UTI areburning with urination and having to urinate frequently (or an urge to urinate) in the absence ofvaginal discharge and significant pain.[4] These symptoms may vary from mild to severe[10] and in healthy women last an average of sixdays.[17] Some pain above thepubic bone or in thelower back may be present. People experiencing an upper urinary tract infection, orpyelonephritis, may experienceflank pain,fever, or nausea andvomiting in addition to the classic symptoms of a lower urinary tract infection.[10] Rarely, there may beblood[11] or visiblepus in the urine.[19]
In young children, the only symptom of a urinary tract infection (UTI) may be a fever.[20] Because of the lack of more obvious symptoms, when girls under the age of two or uncircumcised boys less than a year exhibit a fever, a culture of the urine is recommended by many medical associations.[20] Infants may feed poorly, vomit, sleep more, or show signs ofjaundice.[20] In older children, new onseturinary incontinence (loss of bladder control) may occur.[20] About 1 in 400 infants of one to three months of age with a UTI also havebacterial meningitis.[21]
Urinary tract symptoms are frequently lacking in theelderly.[12] The presentations may be vague and include incontinence, achange in mental status, or fatigue as the only symptoms.[10]Delirium can co-occur with UTIs in elderly people.[22] Some present to a health care provider withsepsis, an infection of the blood, as the first symptoms.[11] Diagnosis can be complicated by the fact that many elderly people have preexisting incontinence ordementia.[12] Rarely, for UTIs associated with urinary catheders, the urine turns purple (purple urine bag syndrome).[23]
It is reasonable to obtain a urine culture in those with signs of systemic infection that may be unable to report urinary symptoms, such as when advanceddementia is present.[24] Systemic signs of infection include afever or increase in temperature of more than 1.1 °C (2.0 °F) from usual, chills, and anincreased white blood cell count.[24]
In young sexually active women, sexual activity is the cause of 75–90% of bladder infections, with the risk of infection related to the frequency of sex.[4] The term "honeymoon cystitis" has been applied to this phenomenon of frequent UTIs during early marriage. Inpost-menopausal women, sexual activity does not affect the risk of developing a UTI.[4]Spermicide use, independent of sexual frequency, increases the risk of UTIs.[4]Diaphragm use is also associated.[29] Condom use without spermicide or use ofbirth control pills does not increase the risk of uncomplicated urinary tract infection.[4][30]
Anal intercourse may increase the risk of UTI in men and in women if followed by vaginal sex.[31][32]
Women are more prone to UTIs than men because, in females, theurethra is much shorter and closer to theanus.[34] As a woman's estrogen levels decrease withmenopause, her risk of urinary tract infections increases due to the loss of protectivevaginal flora.[34] Additionally,vaginal atrophy that can sometimes occur after menopause is associated with recurrent urinary tract infections.[35]
Urinary catheterization increases the risk for urinary tract infections. The risk ofbacteriuria (bacteria in the urine) is between three and six percent per day and prophylactic antibiotics are not effective in decreasing symptomatic infections.[34] The risk of an associated infection can be decreased by catheterizing only when necessary, usingaseptic technique for insertion, and maintaining unobstructed closed drainage of the catheter.[37][38][39]
Persons withspinal cord injury are at increased risk for urinary tract infection in part because of chronic use of catheter, and in part because ofvoiding dysfunction.[44] It is the most common cause of infection in this population, as well as the most common cause of hospitalization.[44]
Thebacteria that cause urinary tract infections typically enter the bladder via the urethra. However, infection may also occur via the blood orlymph.[11] It is believed that the bacteria are usually transmitted to the urethra from the bowel, with females at greater risk due to their anatomy.[11] After gaining entry to the bladder,E. Coli are able to attach to the bladder wall and form abiofilm that resists the body's immune response.[11]
About half of the recurrent infection have the same strain as the first infection. This implies that there is areservoir of the pathogen somewhere in the body. Potential locations of these reservoirs are the gut or vaginal micriobiome, or even the bladder itself. Bacteria that cause UTIs have been found in all three locations.[25]
Multiplebacilli (rod-shaped bacteria, here shown as black and bean-shaped) shown between white blood cells in urinary microscopy. These changes are indicative of a urinary tract infection.
In straightforward cases, a diagnosis may be made and treatment given based on symptoms alone without further laboratory confirmation.[4]
In complicated or questionable cases, it may be useful to confirm the diagnosis viaurinalysis. For instance, anitrate test can diagnose some UTIs, as a subset of bacteria produce this. Not all bacteria do however, so a negative test does not exclude a UTI. Otherdipstick values useful for diagnosing UTIs are high pH (some bacteria spliturea), the presence of blood and orleukocyte esterase.[6] Another test,urine microscopy, looks for the presence ofred blood cells, white blood cells, or bacteria.[4]
Urineculture is deemed positive if it shows a bacterial colony count of greater than or equal to 103colony-forming units per mL of a typical urinary tract organism. Antibiotic sensitivity can also be tested with these cultures, making them useful in the selection of antibiotic treatment. As symptoms can be vague and without reliable tests for urinary tract infections, diagnosis can be difficult in the elderly.[12]
A urinary tract infection may involve only the lower urinary tract, in which case it is known as a bladder infection. Alternatively, it may involve the upper urinary tract, in which case it is known as pyelonephritis. If the urine contains significant bacteria but there are no symptoms, the condition is known asasymptomatic bacteriuria.[10] If a urinary tract infection involves the upper tract, and the person hasdiabetes mellitus, is pregnant, is male, orimmunocompromised, it is considered complicated.[11][17] Otherwise if a woman is healthy andpremenopausal it is considered uncomplicated.[17] In children when a urinary tract infection is associated with a fever, it is deemed to be an upper urinary tract infection.[20]
To make the diagnosis of a urinary tract infection in children, a positive urinary culture is required. Contamination poses a frequent challenge depending on the method of collection used, thus a cutoff of 105CFU/mL is used for a "clean-catch" mid stream sample, 104CFU/mL is used for catheter-obtained specimens, and 102CFU/mL is used forsuprapubic aspirations (a sample drawn directly from the bladder with a needle). The use of "urine bags" to collect samples is discouraged by theWorld Health Organization due to the high rate of contamination when cultured, and catheterization is preferred in those not toilet trained.[20]
Some, such as theAmerican Academy of Pediatrics recommendsrenal ultrasound andvoiding cystourethrogram (watching a person's urethra and urinary bladder with real time x-rays while they urinate) in all children less than two years old who have had a urinary tract infection. However, because there is a lack of effective treatment if problems are found, others such as theNational Institute for Health and Care Excellence only recommends routine imaging in those less than six months old or who have unusual findings.[20]
In women withcervicitis (inflammation of thecervix) orvaginitis (inflammation of thevagina) and in young men with UTI symptoms, aChlamydia trachomatis orNeisseria gonorrhoeae infection may be the cause.[10][45] These infections are typically classified as aurethritis rather than a urinary tract infection. Vaginitis may also be due to ayeast infection.[46]Interstitial cystitis (chronic pain in the bladder) may be considered for people who experience multiple episodes of UTI symptoms but urine cultures remain negative and not improved with antibiotics.[47]Prostatitis (inflammation of theprostate) may also be considered in the differential diagnosis.[48]
A number of behaviors are recommended to prevent UTIs from recurring. They include urinating after sex, avoidingdouching, wiping from front to back afterdefecation, and wearing breathable underwear. It is unclear how much these help; clinical guidelines typically regard the evidence as weak.[52] NICE also recommends not holding up urine frequently and drinking sufficiently.[53] There is lack of evidence surrounding the effect oftampon use.[34] In those with frequent urinary tract infections who usespermicide or adiaphragm as a method of contraception, they are advised to use alternative methods.[11]
Using urinary catheters as little and as short of time as possible and appropriate care of the catheter when used preventscatheter-associated urinary tract infections.[37] They should be inserted using sterile technique in hospital however non-sterile technique may be appropriate in those who self catheterize.[39] The urinary catheter set up should also be kept sealed.[39] Evidence does not support a significant decrease in risk when silver-alloy catheters are used.[54]
Forperi-menopausal or postmenopausal women with recurrent infections,topical vaginalestrogen has been found to reduce recurrence.[55][56] For other people, or if topical estrogen does not work sufficiently, a single dose of antibiotics after a triggering event (like intercourse) can be considered.[56]Methenamine is another medication used for prevention. As an anti-septic, antibiotic resistance does not develop against it.[7]
European guidelines, including the UK guidelines, recommend a prolonged course of daily antibiotics after other options are proven ineffective or inappropriate.[7][56] Where possible, the choice of antibiotic should be informed by a recent culture and the results of a susceptibility test.[7] TheAmerican Urological Association recommends continuous antibiotics as one of many first-line options for recurrent UTIs.[57]
Antibiotics following short term urinary catheterization decreases the subsequent risk of a bladder infection.[58] A number ofUTI vaccines are in development as of 2025.[25]
Low-dose antibiotics slightly reduces the risk of recurrent UTIs in children. However, the benefit is small, many children stop having repeat infections without antibiotics, and antibiotic use can increase the likelihood that future UTIs will be resistant to treatment.[59]Circumcision of boys has been observed to exhibit a strong protective effect against UTIs, with some research suggesting as much as a 90% reduction in symptomatic UTI incidence among male infants, if they are circumcised.[60][61] The protective effect is even stronger in boys born with urogenital abnormalities.[61]
Cranberry products can reduce the risk of UTIs in certain groups (women with reoccurring UTIs, children, and people having had clinical interventions), but not in pregnant women, the elderly or people withurination disorders.[62] They can also be used as anadjuvant to antibiotics and other standard treatments.[63] Some evidence suggests that cranberry juice is more effective at UTI control than dehydrated tablets or capsules.[63] Cranberry supplements are high in sugar content, which may worsen the risks associated with UTIs in patients withdiabetes mellitus.[64]
D-mannose is often marketed as adietary supplement that prevents UTIs; however, there is little evidence supporting its use. A randomised controlled trial compared daily d-mannose with a placebo (fructose) among women with recurrent urinary tract infections over 6 months. D-mannose offered no benefit over placebo in reducing UTIs.[65][66]
Certainprobiotics might help reduce UTI recurrence, but evidence is weaker than for cranberries.[67]
The mainstay of treatment isantibiotics.Fosfomycin can be used as an effective treatment for both UTIs and complicated UTIs including acute pyelonephritis.[68] The standard regimen for complicated UTIs is an oral 3 g dose administered once every 48 or 72 hours for a total of 3 doses or a 6 grams every 8 hours for 7 days to 14 days when fosfomycin is given in IV form.[68]Gepotidacin was approved for medical use in the United States in March 2025.[69] It is the first new antibiotic approved in the US for UTIs in nearly 30 years.[70][71]
Phenazopyridine is occasionally prescribed during the first few days in addition to antibiotics to help with the burning and urgency sometimes felt during a bladder infection.[72] However, it is not routinely recommended due to safety concerns with its use, specifically an elevated risk ofmethemoglobinemia (higher than normal level ofmethemoglobin in the blood).[73]Paracetamol may be used for fevers.[74] There is no good evidence for the use of cranberry products for treating current infections.[75][76]
Women with recurrent simple UTIs are over 90% accurate in identifying new infections.[4] They may benefit from self-treatment upon occurrence of symptoms with medical follow-up only if the initial treatment fails.[4]
For mild to moderate uncomplicated UTIs, antibiotics may be completely avoided initially, following discussion with the patient.[7] For instance,ibuprofen can be recommended while a culture is performed to confirm diagnosis and totest how susceptible the infection is to various antibiotics. Delaying or avoiding antibiotics leads to a longer recovery period, but many UTIs do resolve without antibiotics. The risk of progression to a kidney infection is higher than with antibiotic use, but remains low. A 'wait-and-see' antibiotic prescription can be provided. Overall, this strategy substantially reduces antibiotic use.[83]
Complicated UTIs are more difficult to treat and usually requires more aggressive evaluation, treatment, and follow-up.[84] It may require identifying and addressing the underlying complication.[85] Increasing antibiotic resistance is causing concern about the future of treating those with complicated and recurrent UTI.[86][87][88]
Those who have bacteria in the urine but no symptoms should not generally be treated with antibiotics.[89] This includes those who are old, those with spinal cord injuries, and those who have urinary catheters.[90][91] Pregnancy is an exception and it is recommended that women take sevendays of antibiotics.[92][93] If not treated it causes up to 30% of mothers to developpyelonephritis and increases risk oflow birth weight andpreterm birth.[94] Some also support treatment of those withdiabetes mellitus[95] and treatment before urinary tract procedures which will likely cause bleeding.[91]
Urinary tract infections, even asymptomatic presence of bacteria in the urine, are more concerning in pregnancy due to the increased risk of kidney infections.[34] During pregnancy, highprogesterone levels elevate the risk of decreased muscle tone of the ureters and bladder, which leads to a greater likelihood of reflux, where urine flows back up the ureters and towards the kidneys.[34] While pregnant women do not have an increased risk of asymptomatic bacteriuria, if bacteriuria is present they do have a 25–40% risk of a kidney infection.[34] Thus if urine testing shows signs of an infection—even in the absence of symptoms—treatment is recommended.[94][93]Cephalexin or nitrofurantoin are typically used because they are generally considered safe in pregnancy.[93] A kidney infection during pregnancy may result inpreterm birth orpre-eclampsia (a state ofhigh blood pressure and kidney dysfunction during pregnancy that can lead toseizures).[34] Some women have UTIs that keep coming back in pregnancy.[96] There is insufficient research on how to best treat these recurrent infections.[96]
Pyelonephritis is treated more aggressively than a simple bladder infection using either a longer course of oral antibiotics orintravenous antibiotics.[3] Seven days of the oral fluoroquinoloneciprofloxacin is typically used in areas where the resistance rate is less than 10%. If the local antibiotic resistance rates are greater than 10%, a dose of intravenousceftriaxone is often prescribed.[3] Trimethoprim/sulfamethoxazole or amoxicillin/clavulanate orally for 14 days is another reasonable option.[97] In those who exhibit more severe symptoms, admission to a hospital for ongoing antibiotics may be needed.[3] Complications such as ureteral obstruction from akidney stone may be considered if symptoms do not improve following two or three days of treatment.[10][3]
With treatment, symptoms generally improve within 36hours.[17] Up to 42% of uncomplicated infections may resolve on their own within a few days or weeks.[4][98]
15–25% of adults and children have chronic symptomatic UTIs including recurrent infections, persistent infections (infection with the same pathogen), a re-infection (new pathogen), or a relapsed infection (the same pathogen causes a new infection after it was completely gone).[99] Recurrent urinary tract infections are defined as at least two infections (episodes) in a six-month time period or three infections in twelve months, can occur in adults and in children.[99]
About 10–20% of children of upper urinary tract infection which involves the kidney (pyelonephritis) will go on and develop scarring of the affected kidney. Then, 10–20% of those develop scarring will have increased risk of hypertension in later life.[100] Recurrent UTIs are a rare cause of further kidney problems if there are no underlying abnormalities of the kidneys, resulting in less than a third of a percent (0.33%) ofchronic kidney disease in adults.[101]
Urinary tract infections occur almost four times more frequently in females than males.[25] Urinary tract infections are the most frequent bacterial infection in women.[17] They occur most frequently between the ages of 16 and 35years, with 10% of women getting an infection yearly and more than 40–60% having an infection at some point in their lives.[11][4] Recurrences are common, with nearly half of people getting a second infection within a year.
Pyelonephritis occurs between 20 and 30 times less frequently.[4] They are the most common cause ofhospital-acquired infections accounting for approximately 40%.[102] Rates of asymptomatic bacteria in the urine increase with age from two to seven percent in women of child-bearing age to as high as 50% in elderly women in care homes.[34] Rates of asymptomatic bacteria in the urine among men over 75 are between 7–10%.[12] 2–10% of pregnant women have asymptomatic bacteria in the urine and higher rates are reported in women who live in some underdeveloped countries.[94]
Urinary tract infections may affect 10% of people during childhood.[11] Among children, urinary tract infections are most common in uncircumcised males less than three months of age, followed by females less than one year.[20] Estimates of frequency among children, however, vary widely. In a group of children with a fever, ranging in age between birth and two years, 2–20% were diagnosed with a UTI.[20]
Urinary tract infections have been described since ancient times with the first documented description in theEbers Papyrus dated to c. 1550 BC.[18] It was described by the Egyptians as "sending forth heat from the bladder".[104] Effective treatment did not occur until the development and availability of antibiotics in the 1930s, before which time herbs,bloodletting and rest were recommended.[18]
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