Urinary tract infection

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Urinary tract infection
Classification and external resources
Multiple white cells at urinary microscopy from a patient with urinary tract infection.
ICD-9	599.0
DiseasesDB	13657
MedlinePlus	000521
eMedicine	emerg/625 emerg/626
MeSH	D014552

A urinary tract infection (UTI) is a bacterial infection that affects any part of the urinary tract. The main causitive agent is:Escherichia coli. Although urine contains a variety of fluids, salts, and waste products, it usually does not have bacteria in it.^[1] When bacteria get into the bladder or kidney and multiply in the urine, they cause a UTI. The most common type of UTI is a bladder infection which is also often called cystitis. Another kind of UTI is a kidney infection, known as pyelonephritis, and is much more serious. Although they cause discomfort, urinary tract infections can usually be quickly and easily treated with a short course of antibiotics.^[2]

Symptoms

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For bladder infections

• Frequent urination along with the feeling of having to urinate even though there may be very little urine to pass.
• Nocturia: Need to urinate during the night.
• Urethritis: Discomfort, irritation or pain at the urethral meatus or a burning sensation throughout the urethra with urination (dysuria).
• Pain in the midline suprapubic region.
• Pyuria: Pus in the urine or discharge from the urethra.
• Hematuria: Blood in urine (not always seen to the naked eye, but often revealed during urine tests).
• 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 infection

• All of the above symptoms.
• Emesis: Vomiting is common.^[3]
• Back, side (flank) or groin pain.
• Abdominal pain or pressure.
• Shaking chills and high spiking fever.
• Night sweats.
• Extreme fatigue.
• Excessive thirst.

Epidemiology

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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.

Since bacteria can enter the urinary tract through the urethra (an ascending infection), poor toilet habits (such as wiping back to front for women) can predispose to infection, but other factors (pregnancy in women, prostate enlargement in men) are also important and in many cases the initiating event is unclear.

While ascending infections are generally the rule for lower urinary tract infections and cystitis, the same may not necessarily be true for upper urinary tract infections like pyelonephritis which may be hematogenous in origin.

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. Urinary tract infections after sexual intercourse can 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.

Staphylococcus epidermidis is commonest in patients using urinary catheters. Indwelling urinary catheters in women and men who are elderly, over placement of a temporary prostatic stent can be a major cause of UTIs. Also, people experiencing nervous system disorders, people who are convalescing or unconscious for long periods of time, will have an increased risk of urinary tract infection for a number of reasons. Scrupulous aseptic techniques may decrease these associated risks.

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.^{[clarification needed]} 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 men because in females, the urethra is much shorter and closer to the anus than in males,^[4] and they lack the bacteriostatic properties of prostatic secretions. Among the elderly, UTI frequency is in roughly equal proportions in women and men.

A common cause of UTI is an increase in sexual activity, such as vigorous sexual intercourse with a new partner, although the reason behind this is unclear. The term "honeymoon cystitis" has been applied to this phenomenon.

Multiple bacilli (rod-shaped bacteria, here shown as black and bean-shaped) shown between white cells at urinary microscopy. This is called bacteriuria and pyuria, respectively. These changes are indicative of a urinary tract infection.

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.

A negative urine test can also suggest the presence of unusual bacteria or viruses causing symptoms of UTI.

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

Most cases of lower urinary tract infections in females are benign and do not need exhaustive laboratory work-ups. However, UTI in young infants must receive some imaging study, typically a retrograde urethrogram, to ascertain the presence/absence of congenital urinary tract anomalies. Males too must be investigated further. Specific methods of investigation include x-ray, Nuclear Medicine, MRI and CAT scan technology.

Treatment

Uncomplicated UTIs

Most uncomplicated UTIs can be treated with oral antibiotics such as trimethoprim, cephalosporins, nitrofurantoin, or a fluoroquinolone (e.g., ciprofloxacin or levofloxacin). The Infectious Disease Society of America recommends SMX/TMP (trimethoprim and sulfamethoxazole) as a first line agent in uncomplicated UTIs rather than fluoroquinolones such as ciprofloxacin.^[5] Trimethoprim is one widely used antibiotic for UTIs and is usually taken for seven days. It is often recommended that trimethoprim be taken at night to ensure maximal urinary concentrations to increase its effectiveness.Trimethoprim/sulfamethoxazole was previously internationally used (and continues to be used in the U.S. and Canada); the addition of the sulfonamide gave little additional benefit compared to the trimethoprim component alone. However it is responsible for a high incidence of mild allergic reactions and rare but serious complications. A three-day treatment of trimethoprim/sulfamethoxazole or ciprofloxacin is usually all that is needed.

Clinical trials on humans have not shown that cranberry juice and supplements^[6] help with the treatment of UTIs, but they have been shown to help with the prevention of symptomatic UTIs due to the anti-adhesion activities of A Type Proanthocyanidin.^[7][8][9] See more notes on prevention below.

Pyelonephritis

If the patient has symptoms consistent with pyelonephritis, intravenous antibiotics may be indicated. Regimens vary, and include quinolones (e.g. levofloxacin). In the past, they have included aminoglycosides (such as gentamicin) 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. ^[10]

Children

For simple UTIs children often respond well to a three-day course of antibiotics.^[11]

Recurrent UTIs

See also Prevention (below)

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 treatment, 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).^[12] By working together, bacteria in biofilms build themselves into structures that are more firmly anchored in infected cells and are more resistant to immune system assaults and antibiotic treatments ^[13] This is often the cause of chronic Urinary Tract Infections.

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:

• Do not delay urination when it is necessary.^[14]
• 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.^[15]
• 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, called A Type Proanthocyanidin, found only in cranberries and blueberries prevents the adherence of certain pathogens (eg. E. coli) to the epithelium of the urinary bladder^[16]. 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".^[17] Over the counter products are in development that deliver a strong dose of A Type Proanthocyanidin. Even in the minimal prophylactic effects observed in females, the total cost of the cranberry tablets and juice exceeded $2000 per annum. It should be noted that there would be considerable difficulty in establishing compliance in a standard randomized double-blind study if the participants were required to bear this cost personally.^[6]

• However the tannins that are found in green tea drunk in a daily dose of around 600mls will provide an excellent and cost effective alternative to cranberry juice in the prevention and prevelance of chronic infection.^{[citation needed]}

• For post-menopausal women, a randomized controlled trial has shown that intravaginal application of topical estrogen cream can prevent recurrent cystitis.^[18]
• 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.^[19][20][21] One study showed that urinary tract infection occurrence was reduced by 50% for six months.^[22] However, this study has been criticized for several reasons.^[23] All of the studies are done by one research team without independent reproduction of results.
• Studies have shown that breastfeeding can reduce the risk of UTIs in infants.^[24]
• Keeping the Foley Catheter from clogging with biofilm will prevent stasis of urine in the bladder, which serves as a culture medium for bacterial growth.

See also

• Nosocomial infection
• Urethritis
• Vulvovaginal health

References

External links

• NIH articles on Urinary Tract Infections in Adults and in Children.
• MedlinePlus Overview urinarytractinfections
• Urinary tract infection at GPnotebook
• Urinary tract infection at the Open Directory Project
• Urinary Tract Infection Video
• Urethritis[1]