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Urinary Tract Infection

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Last Update: June 23, 2021.

Continuing Education Activity

Forty percent of women in the United States will develop a urinary tract infection (UTI) at some point in her lifetime, making this one of the most common infections in women. Uncomplicated urinary tract infections, also known as cystitis or lower urinary tract infections, are bacterial infections of the bladder and associated structures. Uncomplicated urinary tract infections occur in female patients with no structural abnormality or comorbidities such as diabetes, old age, pregnancy, or immunocompromised status. Complicated urinary tract infections occur in patients with structural abnormalities or comorbidities such as diabetes, old age, pregnancy, or immunocompromised status. This activity reviews the evaluation and management of urinary tract infections and highlights the role of interprofessional team members in collaborating to provide well-coordinated care and enhance outcomes for affected patients.

Objectives:

  • Identify the pathophysiology of UTI.
  • Outline the presentation of a patient with UTI.
  • Summarize the treatment and management options available for UTI.
  • Review interprofessional team strategies for improving care and outcomes in patients with UTI.
Access free multiple choice questions on this topic.

Introduction

An uncomplicated urinary tract infection (UTI) is a bacterial infection of the bladder and associated structures. These are patients with no structural abnormality and no comorbidities, such as diabetes, immunocompromised state, or pregnancy. Uncomplicated UTI is also known as cystitis or lower UTI. Bacteriuria alone does not constitute a UTI without symptoms. Typical symptoms include urinary frequency, urgency, suprapubic discomfort and dysuria. Forty percent of women in the United States will develop a UTI during their lifetime, making it one of the most common infections in women. UTIs are uncommon in circumcised males, and by definition, any male UTI is usually considered complicated.

Many cases of uncomplicated UTIs will resolve spontaneously, without treatment, but many patients seek therapy for symptom relief. Treatment is aimed at preventing spread to the kidneys or developing into upper tract disease/pyelonephritis, which can cause the destruction of the delicate structures in the nephrons and eventually lead to hypertension.[1][2][3]

E.coli causes the vast majority of UTIs but other organisms of importance include proteus, klebsiella, and enterococcus. The diagnosis of UTI is made from the clinical history (symptoms) and urinalysis with confirmation by a urine culture, but the proper collection of the urine sample is important.

Etiology

Pathogenic bacteria ascend from the perineum, causing the UTI. Women have shorter urethras than men and therefore are far more susceptible to UTI. Very few uncomplicated UTIs are caused by blood-borne bacteria. Escherichia coli is the most common organism in uncomplicated UTI by a large margin.[4]

A major risk factor for UTI is the use of a catheter. Manipulation of the urethra is also a risk factor. Sexual intercourse and the use of spermicides and diaphragms are also risk factors for UTI. Frequent pelvic exams and the presence of anatomical abnormalities of the urinary tract can also predispose one to a UTI.

UTIs are very common after a kidney transplant. The two triggers include the use of immunosuppressive drugs and vesicoureteral reflux. Other risk factors include the use of antibiotics and diabetes mellitus.

Epidemiology

Urinary tract infections are very frequent bacterial infections in women. They usually occur between the ages of 16 and 35 years, with 10% of women getting an infection yearly and more than 40% to 60% having an infection at least once in their lives. Recurrences are common, with nearly half getting a second infection within a year. Urinary tract infections occur at least four times more frequently in females than males.[5][6]

Pathophysiology

An uncomplicated UTI usually only involves the bladder. When bacteria invade the bladder mucosal wall, an inflammatory reaction called cystitis is produced. The majority of organisms causing a UTI are enteric coliforms that typically inhabit the periurethral vaginal introitus. These organisms ascend the urethra into the bladder and cause the UTI. Sexual intercourse is a common cause of a UTI as it promotes the migration of bacteria into the bladder. People who frequently void and empty the bladder tend to have a lower risk of a UTI.[7]

Urine is an ideal medium for bacterial growth. Factors that make it less favorable for bacterial growth include: a pH less than 5, the presence of organic acids and high levels of urea. Frequent urination and high urinary volumes are also known to decrease the risk of UTI.

Bacteria that cause UTIs tend to have adhesins on their surface which allow the organism to attach to the urothelial mucosal surface. In addition, a short urethra also makes it easier for the uropathogen to invade the urinary tract. Premenopausal women have large concentrations of lactobacilli in the vagina and an acidic pH which prevents colonization with uropathogens. However, the use of antibiotics can erase this protective effect.

History and Physical

Symptoms of uncomplicated UTIs are pain on urination (dysuria), frequent urination (frequency), inability to start the urine stream (hesitancy), sudden onset of the need to urinate (urgency), and blood in the urine (hematuria). Usually, patients with uncomplicated UTI do not have fever, chills, nausea, vomiting, or back pain, which are signs of kidney involvement or upper tract disease/pyelonephritis. Clinical symptoms can overlap, and in some cases, it can be hard to distinguish an uncomplicated UTI from a kidney or ore serious infection. When in doubt, treat aggressively for possible upper urinary tract disease.

Diagnosis of a urinary tract infection is a combination of signs, symptoms, and urinalysis results confirmed with urine cultures. Be careful of literature that is based on the results of the urinalysis of asymptomatic patients.

Patients with spinal cord injury or those who are paralyzed may present with:

  • Autonomic instability (autonomic dysreflexia)
  • Fatigue
  • Fever
  • Cloudly, foul-smelling urine
  • Chills

Patients with permanent indwelling Foley catheters or suprapubic tubes will sometimes tend to have vague symptoms that may include an elevated WBC count and fever. Most patients withi catheters will have pyuria and elevated bacterial colony counts in the urine. This is not a true urinary tract infection (and should not be treated) unless there are also symptoms of pain, hematuria or other abnormal bladder activity.

Evaluation

A good, clean, urinalysis (UA) specimen is vital to the workup. A clean catch specimen in non-obese women is preferred. Most obese women cannot give a clean specimen, and epithelial cells in the UA means the urine sample was exposed to the genital surface and did not come directly out of the urethra. Get a clean sample, with very few epithelial cells. This might require a quick catheterization. In-and-out catheterization of the bladder will cause UTI in uninfected women about 1% of the time. Men should start the urine stream to clean the urethra and then obtain a midstream sample. Urine should be sent to the lab immediately or refrigerated because bacteria grow rapidly when the sample is left at room temperature, causing an overestimate of the infection's severity.[8][9]

Do not base the diagnosis of a UTI upon visual inspection of the urine. Cloudy urine can be aseptic; the cloudiness can come from protein or calcium phosphate debris in the sample, not necessarily from an infection. Crystal clear urine can be grossly infected. All urines undergo dipstick testing, which can be done at the bedside. Helpful values are pH, nitrites, leukocyte esterase, and blood. Remember that in patients with symptoms of a UTI, a negative dipstick does not rule out the UTI, but positive findings can suggest and help make the diagnosis. Look for the presence of bacteria and/or white blood cells (WBC) in the urine on microscopic urinalysis.  

Normal urine pH is slightly acidic, with usual values of 6.0 to 7.5, but the normal range is 4.5 to 8.0. A urine pH of 8.5 or 9.0 is often indicative of a urea-splitting organism, such as Proteus, Klebsiella, or Ureaplasma urealyticum.  An alkaline urine pH can signify struvite kidney stones, which are also known as “infection stones".

The most accurate dipstick test is the nitrite test because bacteria must be present in the urine to convert nitrates to nitrites. This takes 6 hours and is why urologists often request the first-morning urine for testing, particularly in males. The specificity of this test is greater than 90%. This is direct confirmation of bacteria in the urine, which is a UTI by definition in patients with symptoms. Several bacteria do not convert the nitrates to nitrites, but those are usually involved in complicated UTIs, such as those involving Enterococcus, Pseudomonas, and Acinetobacter.

Leukocyte esterase (LE) identifies the presence of WBCs in the urine. The WBCs release the LE, presumably in response to bacteria in the urine. This is why the dipstick LE is a secondary test with a specificity of only 55% for UTI. LE is good at detecting WBCs in the urine, but WBCs can be in the bladder for other reasons, like inflammatory disorders.

Hematuria can be helpful because bacterial infections of the transitional cell lining of the bladder can cause bleeding. This helps distinguish UTI from vaginitis and urethritis which do not cause blood in the urine.

In many labs, the presence of nitrites or leukocyte esterase will automatically trigger a microscopic evaluation of the urine for bacteria, WBCs, and RBCs. On microscopy, there should be no bacteria in uninfected urine, so any bacteria on Gram-stained urine under high field microscopy is highly correlated to UTIs. A good urine sample with greater than 5 to 10 WBC/HPF is abnormal and highly suggestive of a UTI in symptomatic patients.

Urine cultures are not usually needed in uncomplicated UTI but are recommended due to increasing antibiotic resistance and to help differentiate recurrent from relapsing infections. Urine should be cultured in all men and all patients with diabetes mellitus, who are immunosuppressed, and women who are pregnant. Classic teaching on urine culture sets the gold standard for infected urine at greater than 10 colony forming units (CFU). Recent literature states that a patient who presents with symptoms and greater than 10 CFU is diagnostic of infection. Urine cultures rarely help in the emergency department, except with recurrent UTI, but can make subsequent treatment easier if patients do not respond to the initial antibiotic used. 

Collecting urine is key. Midstream voided specimens are very accurate as long as the correct technique is followed. The presence of lactobacilli and squamous cells indicates contamination and a catheterized specimen may be necessary. In young children and those with spinal cord injuries, suprapubic aspiration may need to be done to collect a urine specimen.

Treatment / Management

The treatment has varied historically from 3 days to 6 weeks. There are excellent cure rates with “mini-dose therapy” which involves three days of treatment. E. coli resistance to common antimicrobials varies in different areas of the country, and if the resistance rate is greater than 50% choose another drug.

Trimethoprim/Sulfamethoxazole for 3 days is good mini-dose therapy, but resistance rates are high in many areas. It should not be used if local resistance is >20%. First-generation cephalosporins are good choices for mini-dose therapy. Nitrofurantoin is a good choice for uncomplicated UTI, but it is bacteriostatic, not bacteriocidal, and must be used for 5 to 7 days. Fluoroquinolones have high resistance but are a favorite of urologists because of high tissue penetration levels, especially in the prostate. For this reason, fluoroquinolones are not preferred except for complicated infections and those involving the prostate. Recent precautions from the FDA about fluoroquinolone side effects should be heeded.[10][11][12]

Recently, the FDA approved fosfomycin as a single-dose therapy for uncomplicated UTIs caused by E coli. Adjunctive therapy with phenazopyridine for several days may help provide additional symptom relief.

Even without treatment, most UTIs will spontaneously resolve in about 20% of women; especially if increased hydration is used. The likelihood that a healthy female will develop acute pyelonephritis is very small.

Asymptomatic bacteriuria is quite common and requires no treatment, except in pregnant women, those who are immunosuppressed, have had a transplant or recently underwent a urological, surgical procedure.

Treatment of "Recurrent Urinary Tract Infections" and "Complicated Urinary Tract Infections" are covered elsewhere.

Differential Diagnosis

  • Pyelonephritis
  • Renal stone
  • Vaginitis
  • PID
  • Herpes simplex

Prognosis

Even withproper  antibiotic treatment, most UTI symptoms can last several days. In women with recurrent UTIs, the quality of life is poor. About 25% of women experience such recurrences. Factors that indicate a poor outlook include:

  • Poor overall health
  • Advanced age
  • Presence of renal calculi
  • Diabetes (especially if poorly controlled)
  • Sickle cell anemia
  • Presence of malignancy
  • Catheterization
  • Ongoing chemotherapy
  • Incontinence
  • Chronic diarrhea

While mortality rates are low, the morbidity of UTI is enormous. Besides the annoying symptoms, the cost of management is prohibitive. Missing work and school are common reasons and sometimes, hospital admission is required because of the severe symptoms.

Pearls and Other Issues

Although there is no proof of prevention, women should urinate after sexual intercourse because bacteria in the bladder can increase by ten-fold after intercourse. After urination, women should wipe from front to back, not from the anal area forward, which seems to drag pathogenic organisms nearer to the urethra. Vigorous urine flow is helpful to prevention. Baths should be avoided in favor of showers. A gentle, liquid soap should be used in bathing (such as Ivory or Dial) or a liquid baby soap such as Johnson's baby shampoo which is very acceptable for the vagina.  The soap should be applied using a clean, soft cotton or microfiber washcloth and the vaginal area should be cleaned first to avoid unnecessary contamination of the area with germs. 

Enhancing Healthcare Team Outcomes

UTI is best managed in an interprofessional fashion, and besides physicians, most nurses will encounter a patient with a UTI. The key to preventing recurrences is the education of the patient. Once a UTI has been diagnosed the patient should be encouraged to drink more fluids. Sexually active women should try to void right after sexual intercourse as this can help flush the bacteria out of the bladder. Some women with recurrent UTIs may benefit from prophylactic use of antibiotics. Several other non-medical remedies may help some women with UTI. Anecdotal reports indicate that the use of cranberry juice and probiotics may help reduce the severity and frequency of UTI in some women. Primary clinicians should refer patients with recurrent UTI to the urologist to rule out reflux and anatomical defects. Clinicians should work closely with a pharmacist to ensure the best antibiotic choices for treatment, with the pharmacist verifying appropriate coverage, dosing, and duration. Patient and community safety are affected by ensuring the prescribing of the best antibiotic and medication compliance. Nursing can chart progress and counsel the patient on compliance, as well as answering any patient questions, and reporting concerns or results to the clinical team. The earlier UTI is managed, the better the outcomes, and interprofessional team involvement is a significant enhancement to outcomes. [Level 5] [13][14] (Level V)

Outcomes

The majority of women with a UTI have an excellent outcome. Following treatment with an antibiotic, the duration of symptoms is 2 to 4 days. Unfortunately, nearly 30% of women will have a recurrence of the infection. Morbidity is usually seen in older debilitated patients, those with renal calculi and in patients. Other factors linked to recurrence include the presence of diabetes, underlying malignancy, chemotherapy and chronic catheterization of the bladder. The mortality after a UTI is close to zero. [15][16](Level 5)

Review Questions

References

1.
Five-day nitrofurantoin is better than single-dose fosfomycin at resolving UTI symptoms. Drug Ther Bull. 2018 Nov;56(11):131. [PubMed: 30297448]
2.
Long B, Koyfman A. The Emergency Department Diagnosis and Management of Urinary Tract Infection. Emerg Med Clin North Am. 2018 Nov;36(4):685-710. [PubMed: 30296999]
3.
Tang M, Quanstrom K, Jin C, Suskind AM. Recurrent Urinary Tract Infections are Associated With Frailty in Older Adults. Urology. 2019 Jan;123:24-27. [PMC free article: PMC8528015] [PubMed: 30296501]
4.
Yamaji R, Friedman CR, Rubin J, Suh J, Thys E, McDermott P, Hung-Fan M, Riley LW. A Population-Based Surveillance Study of Shared Genotypes of Escherichia coli Isolates from Retail Meat and Suspected Cases of Urinary Tract Infections. mSphere. 2018 Aug 15;3(4) [PMC free article: PMC6094058] [PubMed: 30111626]
5.
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6.
Alperin M, Burnett L, Lukacz E, Brubaker L. The mysteries of menopause and urogynecologic health: clinical and scientific gaps. Menopause. 2019 Jan;26(1):103-111. [PMC free article: PMC6376984] [PubMed: 30300297]
7.
Maharjan G, Khadka P, Siddhi Shilpakar G, Chapagain G, Dhungana GR. Catheter-Associated Urinary Tract Infection and Obstinate Biofilm Producers. Can J Infect Dis Med Microbiol. 2018;2018:7624857. [PMC free article: PMC6129315] [PubMed: 30224941]
8.
Richards KA, Cesario S, Best SL, Deeren SM, Bushman W, Safdar N. Reflex urine culture testing in an ambulatory urology clinic: Implications for antibiotic stewardship in urology. Int J Urol. 2019 Jan;26(1):69-74. [PubMed: 30221416]
9.
Araujo da Silva AR, Marques AF, Biscaia di Biase C, Zingg W, Dramowski A, Sharland M. Interventions to prevent urinary catheter-associated infections in children and neonates: a systematic review. J Pediatr Urol. 2018 Dec;14(6):556.e1-556.e9. [PubMed: 30126746]
10.
O'Grady MC, Barry L, Corcoran GD, Hooton C, Sleator RD, Lucey B. Empirical treatment of urinary tract infections: how rational are our guidelines? J Antimicrob Chemother. 2019 Jan 01;74(1):214-217. [PubMed: 30295780]
11.
Ditkoff EL, Theofanides M, Aisen CM, Kowalik CG, Cohn JA, Sui W, Rutman M, Adam RA, Dmochowski RR, Cooper KL. Assessment of practices in screening and treating women with bacteriuria. Can J Urol. 2018 Oct;25(5):9486-9496. [PubMed: 30281006]
12.
Ganzeboom KMJ, Uijen AA, Teunissen DTAM, Assendelft WJJ, Peters HJG, Hautvast JLA, Van Jaarsveld CHM. Urine cultures and antibiotics for urinary tract infections in Dutch general practice. Prim Health Care Res Dev. 2018 Aug 31;:1-8. [PMC free article: PMC6536752] [PubMed: 30168406]
13.
Li F, Song M, Xu L, Deng B, Zhu S, Li X. Risk factors for catheter-associated urinary tract infection among hospitalized patients: A systematic review and meta-analysis of observational studies. J Adv Nurs. 2019 Mar;75(3):517-527. [PubMed: 30259542]
14.
Lengetti E, Kronk R, Ulmer KW, Wilf K, Murphy D, Rosanelli M, Taylor A. An innovative approach to educating nurses to clinical competence: A randomized controlled trial. Nurse Educ Pract. 2018 Nov;33:159-163. [PubMed: 30253916]
15.
Hooton TM, Vecchio M, Iroz A, Tack I, Dornic Q, Seksek I, Lotan Y. Effect of Increased Daily Water Intake in Premenopausal Women With Recurrent Urinary Tract Infections: A Randomized Clinical Trial. JAMA Intern Med. 2018 Nov 01;178(11):1509-1515. [PMC free article: PMC6584323] [PubMed: 30285042]
16.
Liu Y, Xiao D, Shi XH. Urinary tract infection control in intensive care patients. Medicine (Baltimore). 2018 Sep;97(38):e12195. [PMC free article: PMC6160021] [PubMed: 30235665]
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