Urinary tract infection

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Template:DiseaseDisorder infobox Template:Search infobox Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: UTI

Overview

A urinary tract infection is a bacterial infection that affects any part of the urinary tract.

Pathophysiology

Although urine contains a variety of fluids, salts, and waste products, it usually does not have bacteria in it. When bacteria get into the bladder or kidney and multiply in the urine, they cause a UTI.

Cystitis

The most common type of UTI is a bladder infection which is also often called cystitis.

Pyelonephritis

Another kind of UTI is a kidney infection, known as pyelonephritis, and is much more serious.

Causes

Common organisms that cause UTIs include: Escherichia coli and Staphylococcus saprophyticus. Less common organisms include Proteus mirabilis, Klebsiella pneumoniae, Enterobacter spp., Pseudomonas and Enterococcus spp.

A mnemonic that can be used to remember the bacteria that cause UTIs is SEEK PP (Staph saprophyticus, E. coli, Enterococcus, Klebsiella, Proteus, Pseudomonas).

Natural History, Complications, Prognosis

Although they cause discomfort, urinary tract infections are usually quickly and easily treated by seeing a doctor promptly.

Diagnosis

Symptoms

For Bladder Infections

• Frequent urination along with the feeling of having to urinate even though little or no urine actually comes out.
• Nocturia: Need to urinate during the night.
• Urethritis: Discomfort or pain at the urethral meatus or a burning sensation throughout the urethra with urination (dysuria).
• Cystitis: Pain in the midline suprapubic region.
• Pyuria: Pus in the urine or discharge from the urethra.
• Hematuria: Blood in urine.
• Pyrexia: Mild fever
• Cloudy and foul-smelling urine
• Increased confusion and associated falls are common presentations to Emergency Departments for elderly patients with UTI.
• Some urinary tract infections are asymptomatic.

For Kidney Infections

• The above symptoms.
• Emesis: Vomiting is common.
• Back, side (flank) or groin pain.
• Abdominal pain or pressure.
• Shaking chills and high spiking fever.
• Night Sweats.
• Extreme Fatigue.

Diagnosis

A patient with dysuria (painful voiding) and urinary frequency generally has a spot mid-stream urine sample sent for urinalysis, specifically the presence of nitrites, leukocytes or leukocyte esterase. If there is a high bacterial load without the presence of leukocytes, it is most likely due to contamination. The diagnosis of UTI is confirmed by a urine culture.

If the urine culture is negative:

• symptoms of urethritis may point at Chlamydia trachomatis or Neisseria gonorrheae infection.
• symptoms of cystitis, may point at interstitial cystitis.
• in men, prostatitis may present with dysuria.

In severe infection, characterised by fever, rigors or flank pain, urea and creatinine measurements may be performed to assess whether renal function has been affected.

Prevention

The following are measures that studies suggest may reduce the incidence of urinary tract infections. These may be appropriate for people, especially women, with recurrent infections:

• Cleaning the urethral meatus (the opening of the urethra) after intercourse has been shown to be of some benefit; however, whether this is done with an antiseptic or a placebo ointment (an ointment containing no active ingredient) does not appear to matter.
• It has been advocated that cranberry juice can decrease the incidence of UTI (some of these opinions are referenced in External Links section). A specific type of tannin found only in cranberries and blueberries prevents the adherence of certain pathogens (eg. E. coli) to the epithelium of the urinary bladder. A review by the Cochrane Collaboration of randomized controlled trials states 'some evidence from trials to show cranberries (juice and capsules) can prevent recurrent infections in women. Many people in the trials stopped drinking the juice, suggesting it may not be a popular intervention'.
• For post-menopausal women, a randomized controlled trial has shown that intravaginal application of topical estrogen cream can prevent recurrent cystitis. In this study, patients in the experimental group applied 0.5 mg of estriol vaginal cream nightly for two weeks followed by twice-weekly applications for eight months.
• Often long courses of low dose antibiotics are taken at night to help prevent otherwise unexplained cases of recurring cystitis.
• Acupuncture has been shown to be effective in preventing new infections in recurrent cases. One study showed that urinary tract infection occurrence was reduced by 50% for 6 months. However, this study has been criticized for several reasons. Acupuncture appears to reduce the total amount of residual urine in the bladder. All of the studies are done by one research team without independent reproduction of results.

The following measures seem sensible, but have not been studied:

• Cleaning genital areas prior to and after sexual intercourse.
• For sexually active women, and to a lesser extent men, urinating within 15 minutes of sexual intercourse to allow the flow of urine to expel the bacteria before specialized extensions anchor the bacteria to the walls of the urethra.
• Having adequate fluid intake, especially water.
• Not resisting the urge to urinate.
• Taking showers, not baths, or urinating soon after taking a bath.
• Practicing good hygiene, including wiping from the front to the back to avoid contamination of the urinary tract by fecal pathogens.

Epidemiology

UTIs are most common in sexually active women, and increase in diabetics and people with sickle-cell disease or anatomical malformations of the urinary tract.

Allergies can be a hidden factor in urinary tract infections. For example, allergies to foods can irritate the bladder wall and increase susceptibility to urinary tract infections. Keep track of your diet and have allergy testing done to help eliminate foods that may be a problem. Urinary tract infections after sexual intercourse can be also be due to an allergy to latex condoms, spermicides, or oral contraceptives. In this case review alternative methods of birth control with your doctor.

The use of urinary catheters in both men and women who are elderly, people experiencing nervous system disorders and people who are convalescing or unconscious for long periods of time may result in an increased risk of urinary tract infection for a variety of reasons. Scrupulous aseptic technique may decrease this risk.

The bladder wall is coated with various mannosylated proteins, such as Tamm-Horsfall proteins (THP), which interfere with the binding of bacteria to the uroepithelium. As binding is an important factor in establishing pathogenicity for these organisms, its disruption results in reduced capacity for invasion of the tissues. Moreover, the unbound bacteria are more easily removed when voiding. The use of urinary catheters (or other physical trauma) may physically disturb this protective lining, thereby allowing bacteria to invade the exposed epithelium.

Elderly individuals, both men and women, are more likely to harbor bacteria in their genitourinary system at any time. These bacteria may be associated with symptoms and thus require treatment with an antibiotic. The presence of bacteria in the urinary tract of older adults, without symptoms or associated consequences, is also a well recognized phenomenon which may not require antibiotics. This is usually referred to as asymptomatic bacteriuria. The overuse of antibiotics in the context of bacteriuria among the elderly is a concerning and controversial issue.

Women are more prone to UTIs than males because in females, the urethra is much shorter and closer to the anus than in males, and they lack the bacteriostatic properties of prostatic secretions. The article on vulvovaginal health has some health tips for preventing UTIs.

A common cause of UTI is an increase in sexual activity, such as vigorous sexual intercourse with a new partner. The term "honeymoon cystitis", although somewhat demeaning, has been applied to this phenomenon[2].

Treatment

Most uncomplicated UTIs can be treated with oral antibiotics such as trimethoprim, cephalosporins, nitrofurantoin, or a fluoroquinolone (e.g. ciprofloxacin, levofloxacin). These are usually taken for 3 days in young adults, and 5 days in elderly. Whilst co-trimoxazole was previously internationally used (and continues to be used in the U.S.), the additional of the sulphonamide gave little additional benefit compared to the trimethoprim component alone, but was responsible for its both high incidence of mild allergic reactions and rare but serious complications.

If the patient has symptoms consistent with pyelonephritis, intravenous antibiotics may be indicated. Regimens vary, usually Aminoglycosides (such as Gentamicin) are used in combination with a beta-lactam, such as Ampicillin or Ceftriaxone. These are continued for 48 hours after fever subsides. The patient may then be discharged home on oral antibiotics for a further 5 days.

If the patient makes a poor response to IV antibiotics (marked by persistent fever, worsening renal function), then imaging is indicated to rule out formation of an abscess either within or around the kidney, or the presence of an obstructing lesion such as a stone or tumor. The gold-standard imaging modality is CT scan.

Recurrent UTIs

See also Prevention (above)

Patients with recurrent UTIs may need further investigation. This may include ultrasound scans of the kidneys and bladder or intravenous urography (X-rays of the urological system following intravenous injection of iodinated contrast material). If there is no response to treatments, interstitial cystitis may be a possibility.

During cystitis, uropathogenic Escherichia coli (UPEC) subvert innate defenses by invading superficial umbrella cells and rapidly increasing in numbers to form intracellular bacterial communities (IBCs).

Researchers at Center for Genomic Sciences, Allegheny Singer Research Institute, and the Department of Microbiology and Immunology, Drexel University College of Medicine have shown that biofilms are responsible for chronic infections and, from a clinical perspective, traditional antibiotic therapy will never be a successful treatment against biofilm bacteria.

See also

• Nosocomial infection

External links

• UTI Symptoms and Information
• NIH articles on Urinary Tract Infections in Adults and in Children.
• The IC Community (ICC)
• Interstitial Cystitis Advice (A Patient Based Community for People with IC)
• Drug Watch: Cranberry juice reduces bacteriuria and pyuria
• Template:MedlinePlusOverview
• Template:GPnotebook
• CNN article on kidney infections
• aboutinfections.com information on bladder infections
• Cranberry juice tannins can defeat E. coli bacteria Scientist Live
• Natural Remedies for Bladder Infections

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