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Urinary tract infection

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Urinary tract infection
Classification and external resources

Multiple white cells seen in the urine of a person with a urinary tract infection via microscopy
ICD-10 N39.0
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 part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection and when it affect the upper urinary tract it is known as pyelonephritis. Symptoms from a lower urinary tract include painful urination and either frequent urination or urge to urinate (or both), while those of pyelonephritis include fever and flank pain in addition to the symptoms of a lower UTI. In the elderly and the very young, symptoms may be vague. The main causal agent of both types is Escherichia coli, however other bacteria, viruses or fungus may rarely be the cause.

Urinary tract infections occur more commonly in women than men, with half of women having an infection at some point in their life. Recurrences are common. Risk factors include sexual intercourse as well as a family history. Pyelonephritis usually follows a bladder infection but may also occur from a blood borne infection. Diagnosis in young healthy women can be based on symptoms alone. In those with vague symptoms, diagnosis can be difficult because bacteria may be present without there being an infection. In complicated cases or if treatment has failed, a urine culture may be useful. In those with frequent infections, low dose antibiotics may be taken as a preventative measure.

In uncomplicated cases, urinary tract infections are easily treated with a short course of antibiotics, although resistance to many of the antibiotics used to treat this condition is increasing. In complicated cases, longer course or intravenous antibiotics may be needed, and if symptoms have not improved in two or three days, further diagnostic testing is needed. In women urinary tract infections are the most common form of bacterial infection with 10% getting urinary tract infections yearly.

Contents

[edit] Signs and symptoms

Urine may contain pus (a condition known as pyuria) as seen from a person with sepsis due to a urinary tract infection.

Lower urinary tract infection is also referred to as a bladder infection. The most common symptoms are burning with urination and having to urinate frequently (or an urge to urinate) in the absence of vaginal discharge and significant pain.[1] These symptoms may vary from mild to severe[2] and in healthy women last an average of six days.[3] 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.[2] Rarely the urine may appear bloody.[4]

[edit] In children

In young children, the only symptom of a urinary tract infection (UTI) may be a fever. Because of the lack of more obvious symptoms, when females under the age of two or uncircumcised males less than a year exhibit a fever, a culture of the urine is recommended. Infants may feed poorly, vomit, sleep more, or show signs of jaundice. In older children, new onset urinary incontinence (loss of bladder control) may occur.[5]

[edit] In the elderly

Urinary tract symptoms are frequently lacking in the elderly.[6] They may have vague presentations with incontinence, a change in mental status, or fatigue as the only symptoms.[2] Diagnosis can be complicated by the fact that many elderly people have preexisting incontinence.[6] Some elderly present to a health care provider with sepsis being the first symptoms.[4]

[edit] Cause

E. coli is the cause of 80–85% of urinary tract infections, with Staphylococcus saprophyticus being the cause in 5–10%.[1] Rarely they may be due to viral or fungal infections.[7] Other bacterial causes include: Klebsiella, Proteus, Pseudomonas, and Enterobacter. These are uncommon and typically related to abnormalities of the urinary system or urinary catheterization.[4] Urinary tract infections due to Staphylococcus aureus typically occurs secondary to blood born infections.[2]

[edit] Gender

In young sexually active women, sex is the cause of 75–90% of bladder infections, with the risk of infection related to the frequency of sex.[1] 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.[1]

Women are more prone to UTIs than men because, in females, the urethra is much shorter and closer to the anus.[8] As a women's estrogen levels decrease with menopause, her risk of urinary tract infections increase due to the loss of protective vaginal flora.[8]

[edit] Urinary catheters

Urinary catheterization increases the risk for urinary tract infections. The risk of bacteriuria (bacteria in the urine) is between three to six percent per day and prophylactic antibiotics are not effective in decreasing symptomatic infections.[8] 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.[9][10][11]

[edit] Others

A predisposition for bladder infections may run in families. Other risk factors include diabetes,[1] being uncircumcised, and having a large prostate.[2] Complicating factors are rather vague and include predisposing anatomic, functional, or metabolic abnormalities. A complicated UTI is more difficult to treat and usually requires more aggressive evaluation, treatment and follow-up.[12] In children UTIs are associated with vesicoureteral reflux (an abnormal movement of urine from the bladder into ureters or kidneys) and constipation.[5]

[edit] 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 usually come from the persons own bowels. After gaining entry to the bladder E. Coli attach to the bladder wall where they form a biofilm that resists the body's immune response.[4]

[edit] Prevention

A number of measures have not been confirmed to affect UTI frequency including: the use of birth control pills or condoms, urinating immediately after intercourse, the type of underwear used, personal hygiene methods used after urinating or defecating, or whether a person typically baths or showers.[1] There is similarly a lack of evidence surrounding the effect of holding one's urine,tampon use, and douching.[8]

In those with frequent urinary tract infections who use spermicide or a diaphragm as a method of contraception, they are advised to use alternative methods.[4] Cranberry (juice or capsules) may decrease the incidence in those with frequent infections, however, long term tolerance is an issue[13] with gastrointestinal upset occurring in more than 30%.[14] As of 2011, intravaginal probiotics require further study to determine if they are beneficial.[4]

[edit] Medications

For those with recurrent infections, a prolonged course of daily antibiotics is effective.[1] Medications frequently used include: nitrofurantoin or trimethoprim/sulfamethoxazole. In cases where infections are related to intercourse, taking antibiotics afterwards may be useful.[4] In post-menopausal women, topical vaginal estrogen has been found to reduce recurrence. As opposed to topical creams, the use of vaginal estrogen from pessaries has not been as useful as low dose antibiotics.[15] A number of vaccines are in development as of 2011.[4]

[edit] In children

The evidence that preventative antibiotics decrease urinary tract infections in children is poor.[16] However 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%) of chronic kidney disease in adults.[17]

[edit] Diagnosis

Multiple bacilli (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. In complicated or questionable cases, it may be useful to confirm the diagnosis via urinalysis, looking for the presence of urinary nitrites, white blood cells (leukocytes), 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. However, women with negative cultures may still improve with antibiotic treatment.[1] The diagnosis can be difficult in the elderly with no reliable test.[6]

[edit] Classification

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 as asymtomatic bacteriuria.[2] If a urinary tract infection involves the upper tract, the person has diabetes mellitus, is pregnant, is male, or immunocompromised it is considered complicated.[4][3] Otherwise if a women is a healthy and premenopausal it is considered uncomplicated.[3] In children when a urinary tract infection is associated with a fever, it is deemed to be a upper urinary tract infection.[5]

[edit] In children

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 105 CFU/mL is used for a "clean-catch" mid stream sample, 104 CFU/mL is used for catheter obtain specimens, and 102 CFU/mL is used for suprapubic aspirations (a sample drawn directly from the bladder with a needle). The use of "urine bags" to collect samples is discouraged by the World Health Organization due to the high rate of contamination when cultured, and catheterization is preferred in those not toilet trained. Some, such as the American Academy of Pediatrics recommends renal ultrasound and voiding cystourethrogram (watching a person's urethra and urinary bladder with real time x-rays while they urinate) in all children less than two year old who have had a urinary tract infection. However, because there is a lack of effective treatment if problems are found, others such as the National Institute for Clinical Excellence only recommends routine imaging in those less than six month old or who have unusual findings.[5]

[edit] Differential diagnosis

In women with cervicitis (inflammation of the cervix) or vaginitis (inflammation of the vagina) and in young men with UTI symptoms, a Chlamydia trachomatis or Neisseria gonorrheae infection may be the cause.[18][2] Vaginitis may also be due to a yeast infection.[19] 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.[20] Prostatitis (inflammation of the prostate) may also be considered in the differential diagnosis.[21]

[edit] Treatment

Phenazopyridine may be used in addition to antibiotics to help with the burning of a bladder infection.[22] However, it is no longer commonly recommended due to safety concerns with its use, specifically an elevated risk of methemoglobinemia (higher than normal level of methemoglobin in the blood).[23] Acetaminophen may be used for fevers.[24]

Women with recurrent simple UTIs may benefit from self-treatment upon occurrence of symptoms with medical follow-up only if the initial treatment fails. A prescription for antibiotics can be delivered to a pharmacist by phone.[1]

[edit] Uncomplicated

Uncomplicated infections can be diagnosed and treated based on symptoms alone.[1] Oral antibiotics such as trimethoprim/sulfamethoxazole (TMP/SMX), cephalosporins, nitrofurantoin, or a fluoroquinolone substantially shorten the time to recovery with all being equally effective.[25] A three-day treatment with trimethoprim, TMP/SMX, or a fluoroquinolone is usually sufficient, whereas nitrofurantoin requires 5-7 days.[1][26] With treatment, symptoms should improve within 36 hours.[3] About 50% of people will recover without treatment within a few days or weeks.[1] The Infectious Diseases Society of America does not recommend fluoroquinolones as first treatment due to the concern of generating resistance to this class of medication.[26] Despite this precaution, some resistance has developed in the community (ie. outside the health care environment) to all of these medications related to their widespread use.[1] Trimethoprim alone is deemed to be equivalent to TMP/SMX by some countries.[26] For simple UTIs, children often respond to a three-day course of antibiotics.[27]

[edit] Pyelonephritis

Pyelonephritis is treated more aggressively than a simple bladder infection using either a longer course of oral antibiotics or intravenous antibiotics.[28] Seven days of the oral fluoroquinolone ciprofloxacin is typically used in areas where the resistance rate is less than 10%. If the local resistance rates are greater than 10%, a dose of intravenous ceftriaxone often prescribed. In those who exhibit more severe symptoms, admission to a hospital for ongoing antibiotics may be needed.[28] Complications such as urinary obstruction from a kidney stone may be considered if symptoms do not improve following two or three days of treatment.[28][2]

[edit] Epidemiology

Urinary tract infections are the most frequent bacterial infection in women.[3] They occur most frequently between the ages of 16 and 35 years, with 10% of women getting an infection yearly and 60% having an infection at some point in their life.[1][4] Recurrences are common, with nearly half of people getting a second infection within a year. Urinary tract infections occur four times more frequently in females than males.[4] Pyelonephritis occurs between 20–30 times less frequently.[1] They are the most common cause of hospital acquired infections accounting for approximately 40%.[29] 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.[8] Rates of aysmtomatic bacteria in the urine among men over 75 are between 7-10%.[6]

Urinary tract infections may affect 10% of people during childhood.[4] Among children urinary tract infections are the most common in uncircumcised males less than three months of age, followed by females less than one year.[5] Estimates of frequency among children however vary widely. In a group of children with a fever, ranging in age between birth and two years, two to 20% where diagnosed with a UTI.[5]

[edit] Society and culture

In the United States, urinary tract infections account for nearly seven million office visits, a million emergency department visits, and one hundred thousand hospitalizations every year.[4] The cost of these infections is significant both in terms of lost time at work and costs of medical care. In the United States the direct cost of treatment is estimated at 1.6 billion USD yearly.[29]

[edit] History

Urinary tract infections have been described since ancient times with the first documented description in the Ebers Papyrus dated to circa 1550 BC.[30] It was described by the Egyptians as "sending forth heat from the bladder".[31] Effective treatment did not occur until the development and availability of antibiotics in the 1930s before which time herb, bloodletting and rest where recommended.[30]

[edit] In pregnancy

Urinary tract infections are more concerning in pregnancy due to the increased risk of kidney infections. During pregnancy, high progesterone 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. 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.[8] Thus if urine testing shows signs of an infection—even in the absence of symptoms—treatment is recommended. Cephalexin or nitrofurantoin are typically used because they are generally considered safe in pregnancy.[32] A kidney infection during pregnancy may result in premature birth or pre-eclampsia (a state of high blood pressure and kidney dysfunction during pregnancy that can lead to seizures).[8]

[edit] References

  1. ^ a b c d e f g h i j k l m n o Nicolle LE (2008). "Uncomplicated urinary tract infection in adults including uncomplicated pyelonephritis". Urol Clin North Am 35 (1): 1–12, v. doi:10.1016/j.ucl.2007.09.004. PMID 18061019. 
  2. ^ a b c d e f g h Lane, DR; Takhar, SS (2011 Aug). "Diagnosis and management of urinary tract infection and pyelonephritis.". Emergency medicine clinics of North America 29 (3): 539-52. PMID 21782073. 
  3. ^ a b c d e Colgan, R; Williams, M (2011 Oct 1). "Diagnosis and treatment of acute uncomplicated cystitis.". American family physician 84 (7): 771-6. PMID 22010614. 
  4. ^ a b c d e f g h i j k l m Salvatore, S; Salvatore, S, Cattoni, E, Siesto, G, Serati, M, Sorice, P, Torella, M (2011 Jun). "Urinary tract infections in women.". European journal of obstetrics, gynecology, and reproductive biology 156 (2): 131-6. PMID 21349630. 
  5. ^ a b c d e f Bhat, RG; Katy, TA, Place, FC (2011 Aug). "Pediatric urinary tract infections.". Emergency medicine clinics of North America 29 (3): 637-53. PMID 21782079. 
  6. ^ a b c d Woodford, HJ; George, J (2011 Feb). "Diagnosis and management of urinary infections in older people.". Clinical medicine (London, England) 11 (1): 80-3. PMID 21404794. 
  7. ^ Amdekar, S; Singh, V, Singh, DD (2011 Nov). "Probiotic therapy: immunomodulating approach toward urinary tract infection.". Current microbiology 63 (5): 484-90. PMID 21901556. 
  8. ^ a b c d e f g Dielubanza, EJ; Schaeffer, AJ (2011 Jan). "Urinary tract infections in women.". The Medical clinics of North America 95 (1): 27-41. PMID 21095409. 
  9. ^ Nicolle LE (2001). "The chronic indwelling catheter and urinary infection in long-term-care facility residents". Infect Control Hosp Epidemiol 22 (5): 316–21. doi:10.1086/501908. PMID 11428445. 
  10. ^ Phipps S, Lim YN, McClinton S, Barry C, Rane A, N'Dow J (2006). Short term urinary catheter policies following urogenital surgery in adults. In Phipps, Simon. "Cochrane Database of Systematic Reviews". Cochrane Database Syst Rev (2): CD004374. doi:10.1002/14651858.CD004374.pub2. PMID 16625600. 
  11. ^ Gould CV, Umscheid CA, Agarwal RK, Kuntz G, Pegues DA (2010). "Guideline for prevention of catheter-associated urinary tract infections 2009". Infect Control Hosp Epidemiol 31 (4): 319–26. doi:10.1086/651091. PMID 20156062. 
  12. ^ Infectious Disease, Chapter Seven, Urinary Tract Infections from Infectious Disease Section of Microbiology and Immunology On-line. By Charles Bryan MD. University of South Carolina. This page last changed on Wednesday, April 27, 2011
  13. ^ Jepson RG, Craig JC (2008). Cranberries for preventing urinary tract infections. In Jepson, Ruth G. "Cochrane Database of Systematic Reviews". Cochrane Database Syst Rev (1): CD001321. doi:10.1002/14651858.CD001321.pub4. PMID 18253990. 
  14. ^ Rossi, R; Porta, S, Canovi, B (2010 Sep). "Overview on cranberry and urinary tract infections in females.". Journal of clinical gastroenterology 44 Suppl 1: S61-2. PMID 20495471. 
  15. ^ Perrotta, C; Aznar, M, Mejia, R, Albert, X, Ng, CW (2008-04-16). "Oestrogens for preventing recurrent urinary tract infection in postmenopausal women.". Cochrane database of systematic reviews (Online) (2): CD005131. doi:10.1002/14651858.CD005131.pub2. PMID 18425910. 
  16. ^ Dai, B; Liu, Y; Jia, J; Mei, C (2010). "Long-term antibiotics for the prevention of recurrent urinary tract infection in children: a systematic review and meta-analysis". Archives of disease in childhood 95 (7): 499–508. doi:10.1136/adc.2009.173112. PMID 20457696. 
  17. ^ Salo, J; Ikäheimo, R, Tapiainen, T, Uhari, M (2011 Nov). "Childhood urinary tract infections as a cause of chronic kidney disease.". Pediatrics 128 (5): 840-7. PMID 21987701. 
  18. ^ Raynor, MC; Carson CC, 3rd (2011 Jan). "Urinary infections in men.". The Medical clinics of North America 95 (1): 43-54. PMID 21095410. 
  19. ^ Leung, David Hui ; edited by Alexander; Padwal, Raj. Approach to internal medicine : a resource book for clinical practice (3rd ed. ed.). New York: Springer. pp. 244. ISBN 9781441965042. http://books.google.ca/books?id=lnXNpj5ZzKMC&pg=PA244. 
  20. ^ Kursh, edited by Elroy D.; Ulchaker, James C. (2000). Office urology. Totowa, N.J.: Humana Press. pp. 131. ISBN 9780896037892. http://books.google.ca/books?id=AdYs-QwU8KQC&pg=PA131. 
  21. ^ Walls, authors, Nathan W. Mick, Jessica Radin Peters, Daniel Egan ; editor, Eric S. Nadel ; advisor, Ron (2006). Blueprints emergency medicine (2nd ed. ed.). Baltimore, Md.: Lippincott Williams & Wilkins. pp. 152. ISBN 9781405104616. http://books.google.ca/books?id=NvqaWHi1OTsC&pg=RA1-PA152. 
  22. ^ Gaines, KK (2004 Jun). "Phenazopyridine hydrochloride: the use and abuse of an old standby for UTI.". Urologic nursing 24 (3): 207-9. PMID 15311491. 
  23. ^ Aronson, edited by Jeffrey K. (2008). Meyler's side effects of analgesics and anti-inflammatory drugs. Amsterdam: Elsevier Science. pp. 219. ISBN 9780444532732. http://books.google.ca/books?id=2WxotnWiiWkC&pg=PA219. 
  24. ^ Glass, [edited by] Jill C. Cash, Cheryl A.. Family practice guidelines (2nd ed. ed.). New York: Springer. pp. 271. ISBN 9780826118127. http://books.google.ca/books?id=4uKsZZ4BoRUC&pg=PA271. 
  25. ^ Zalmanovici Trestioreanu A, Green H, Paul M, Yaphe J, Leibovici L (2010). Antimicrobial agents for treating uncomplicated urinary tract infection in women. In Zalmanovici Trestioreanu, Anca. "Cochrane Database of Systematic Reviews". Cochrane Database Syst Rev 10 (10): CD007182. doi:10.1002/14651858.CD007182.pub2. PMID 20927755. 
  26. ^ a b c Gupta, K; Hooton, TM, Naber, KG, Wullt, B, Colgan, R, Miller, LG, Moran, GJ, Nicolle, LE, Raz, R, Schaeffer, AJ, Soper, DE, Infectious Diseases Society of, America, European Society for Microbiology and Infectious, Diseases (2011 Mar 1). "International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: A 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases.". Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 52 (5): e103-20. PMID 21292654. 
  27. ^ "BestBets: Is a short course of antibiotics better than a long course in the treatment of UTI in children". http://www.bestbets.org/bets/bet.php?id=939. 
  28. ^ a b c Colgan, R; Williams, M, Johnson, JR (2011 Sep 1). "Diagnosis and treatment of acute pyelonephritis in women.". American family physician 84 (5): 519-26. PMID 21888302. 
  29. ^ a b Brunner & Suddarth's textbook of medical-surgical nursing. (12th ed. ed.). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. 2010. pp. 1359. ISBN 9780781785891. http://books.google.ca/books?id=SmtjSD1x688C&pg=PA1359. 
  30. ^ a b Al-Achi, Antoine (2008). An introduction to botanical medicines : history, science, uses, and dangers. Westport, Conn.: Praeger Publishers. pp. 126. ISBN 9780313350092. http://books.google.ca/books?id=HMzxKua4_rcC&pg=PA126. 
  31. ^ Wilson...], [general ed.: Graham (1990). Topley and Wilson's Principles of bacteriology, virology and immunity : in 4 volumes (8. ed. ed.). London: Arnold. pp. 198. ISBN 0713145919. 
  32. ^ Guinto VT, De Guia B, Festin MR, Dowswell T (2010). Different antibiotic regimens for treating asymptomatic bacteriuria in pregnancy. In Guinto, Valerie T. "Cochrane Database of Systematic Reviews". Cochrane Database Syst Rev (9): CD007855. doi:10.1002/14651858.CD007855.pub2. PMID 20824868. 

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