Urinary tract infection
A urinary tract infection is an infection that affects a part of the urinary tract, which includes the bladder, urethra and the kidney. Lower UTIs affect the bladder or urethra while upper UTIs affect the kidney. Symptoms from a lower UTI include burning or pain during urination, pain in the lower abdomen and the urge to urinate even when the bladder is empty. Symptoms of a kidney infection are more systemic and include fever or flank pain, usually in addition to the symptoms of a lower UTI. Rarely, the urine may appear bloody. Symptoms may be less clear in very young or old people.
The most common cause of infection is E. coli, though other bacteria or fungi may sometimes be the cause. Risk factors include being female, sexual intercourse, diabetes, using a catheter, and family history. Kidney infections usually occurs when a bladder infection spreads, but may also come from bacteria in the blood. Diagnosis in young healthy women can be based on symptoms alone. In those with vague symptoms, diagnosis can be harder because bacteria may be present even if there is no infection.
In uncomplicated cases, UTIs are usually treated with a short course of antibiotics. Resistance to many of the antibiotics used to treat this condition is increasing. In complicated cases, a longer course or intravenous antibiotics may be needed. If symptoms do not improve in two or three days, further diagnostic testing may be needed. People with bacteria or white blood cells in their urine but no symptoms usually do not need antibiotics. For people with recurrent infections, methenamine may be prescribed. Postmenopausal women may also be offered vaginal estrogen replacement. If these do not work, preventative antibiotics can be considered.
Approximately 400 million UTI cases occur each year. They are more common in women than men, and are the most common bacterial infection in women. 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. They occur most frequently between the ages of 16 and 35years. Recurrences are common. Urinary tract infections have been described since ancient times with the first documented description in the Ebers Papyrus dated to c. 1550 BC.
Signs and symptoms
The most common symptoms of a UTI are burning with urination and having to urinate frequently in the absence of vaginal discharge and significant pain. These symptoms may vary from mild to severe and in healthy women last an average of sixdays. Some pain above the pubic bone or in the lower back may be present. People experiencing an upper urinary tract infection, or pyelonephritis, may experience flank pain, fever, or nausea and vomiting in addition to the classic symptoms of a lower urinary tract infection. Rarely, there may be blood or visible pus in the urine.Children
In young children, the only symptom of a urinary tract infection may be a fever. 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. Infants may feed poorly, vomit, sleep more, or show signs of jaundice. In older children, new onset urinary incontinence may occur. About 1 in 400 infants of one to three months of age with a UTI also have bacterial meningitis.Elderly
Urinary tract symptoms are frequently lacking in the elderly. The presentations may be vague and include incontinence, a change in mental status, or fatigue as the only symptoms. Delirium can co-occur with UTIs in elderly people. Some present to a health care provider with sepsis, an infection of the blood, as the first symptoms. Diagnosis can be complicated by the fact that many elderly people have preexisting incontinence or dementia. Rarely, for UTIs associated with urinary catheders, the urine turns purple.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 advanced dementia is present. Systemic signs of infection include a fever or increase in temperature of more than from usual, chills, and an increased white blood cell count.
Cause
from the gut is the cause of 75% of uncomplicated UTIs, and 65% of complicated UTIs. Rarely they may be due to viral or fungal infections. Healthcare-associated urinary tract infections involve a much broader range of pathogens including: Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Enterococcus faecalis. These species can form biofilms and colonise catheders. In sub-Saharan Africa, Staphylococcus aureus, which typically occurs secondary to blood-borne infections is more common.Chlamydia trachomatis and Mycoplasma genitalium can infect the urethra but not the bladder. These infections are usually classified as a urethritis rather than urinary tract infection.
Intercourse
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. The term "honeymoon cystitis" has been applied to this phenomenon of frequent UTIs during early marriage. In post-menopausal women, sexual activity does not affect the risk of developing a UTI. Spermicide use, independent of sexual frequency, increases the risk of UTIs. Diaphragm use is also associated. Condom use without spermicide or use of birth control pills does not increase the risk of uncomplicated urinary tract infection.Anal intercourse may increase the risk of UTI in men and in women if followed by vaginal sex.
Although sex is a risk factor, UTIs are not classified as sexually transmitted infections.
Sex
Women are more prone to UTIs than men because, in females, the urethra is much shorter and closer to the anus. As a woman's estrogen levels decrease with menopause, her risk of urinary tract infections increases due to the loss of protective vaginal flora. Additionally, vaginal atrophy that can sometimes occur after menopause is associated with recurrent urinary tract infections.Chronic prostatitis in the forms of chronic prostatitis/chronic pelvic pain syndrome and chronic bacterial prostatitis may cause recurrent urinary tract infections in males. Risk of infections increases as males age. While bacteria is commonly present in the urine of older males this does not appear to affect the risk of urinary tract infections.
Urinary catheters
increases the risk for urinary tract infections. The risk of bacteriuria is between three and six percent per day and prophylactic antibiotics are not effective in decreasing symptomatic infections. The risk of an associated infection can be decreased by catheterizing only when necessary, using aseptic technique for insertion, and maintaining unobstructed closed drainage of the catheter.Male scuba divers using condom catheters and female divers using external catching devices for their dry suits are also susceptible to urinary tract infections.
Others
A predisposition for bladder infections may run in families. This is believed to be related to genetics. Other risk factors include diabetes, being uncircumcised, and having a large prostate. In children UTIs are associated with vesicoureteral reflux and constipation.Persons with spinal cord injury are at increased risk for urinary tract infection in part because of chronic use of catheter, and in part because of voiding dysfunction. It is the most common cause of infection in this population, as well as the most common cause of hospitalization.
Pathogenesis
The bacteria that cause urinary tract infections typically enter the bladder via the urethra. However, infection may also occur via the blood or lymph. It is believed that the bacteria are usually transmitted to the urethra from the bowel, with females at greater risk due to their anatomy. After gaining entry to the bladder, E. Coli are able to attach to the bladder wall and form a biofilm that resists the body's immune response.About half of the recurrent infection have the same strain as the first infection. This implies that there is a reservoir 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.
Diagnosis
In straightforward cases, a diagnosis may be made and treatment given based on symptoms alone without further laboratory confirmation.Urine analysis
In complicated or questionable cases, it may be useful to confirm the diagnosis via urinalysis. For instance, a nitrate 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. Other dipstick values useful for diagnosing UTIs are high pH, the presence of blood and or leukocyte esterase. Another test, urine microscopy, looks for the presence of red blood cells, white blood cells, or bacteria.Urine culture is deemed positive if it shows a bacterial colony count of greater than or equal to 103 colony-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.