creation date: 2024-12-29 14:08 tags: Pathologies
Uncomplicated Urinary Tract Infection
Background
Definitions
A simple or uncomplicated urinary tract infection (UTI) is an infection primarily affecting the lower urinary tract.
Unlike a complicated urinary tract infection, simple UTIs occur in otherwise healthy individuals without structural abnormalities or significant comorbidities.
UTIs in immunocompromised patients, males, pregnant patients, and those associated with fevers, stones, sepsis, obstruction, catheters, or upper urinary tract involvement are considered complicated.
Etiology
The most frequent microbial cause of simple UTIs is Escherichia coli, accounting for 75-95% of cases. Other occasional causes include klebseilla pneumoniae, proteus mirabilis, and staphylococcus saprophyticus.
In cases of patient with recent antimicrobial or health care exposures, causes may include other bacteria such as pseudomonas, enterococci, and staphylococci.
Pathogenesis
Introduction of pathogenic bacteria into the urethra is often due to ascension from the perineum and rectum to the periurethral area. These organisms continue to ascend the urethra and into the bladder where the mucosal wall is invaded and trigger an inflammatory reaction.
Bacterial growth is unfavourable when pH <5, high urea levels, hyperosmolality, presence of organic acids, proteins, and nitrites. Frequent urination and high urinary volume also decreases risk. Pathogenic bacteria may develop mechanisms to counteract these conditions such as breaking down urea into alkaline ammonia to increase pH.
Defects or injury to the bladder mucosal layers can result in increased risk of UTI and recurrence. Glycouria can also contribute to infection.
Clinical Presentation
Signs & Symptoms
Classically, simple UTIs presents with:
- Dysuria
- Urinary frequency
- Urinary urgency
- Suprapubic pain
- Hematuria
In older adults, symptoms may be more subtle and may present as:
- Chronic nocturia
- Incontinence
- General unwellness
- Falls
- Altered mental status
Systemic symptoms such as fever may warrant consideration of complicated urinary tract infection.
History & Physical Exam
History should involve detailed investigation of classic symptoms. Vaginal symptoms should be absent (eg. vaginal pruritus or discharge).
Examination should also include ruling out complicated UTI. This includes:
- Systemic symptoms such as fever, chills, malaise
- Flank pain
- Costovertebral angle tenderness
Risk factors
- Female sex (at least 4x more likely than male)
- Use of urinary catheter
- Kidney transplants
- Antibiotic use (contributing to bacterial resistance)
- Diabetes mellitus
- Abnormal urination or urinary tract anatomy
- Cystocele
- Dehydration
- Diarrhea / IBS
- History of UTI (especially before age 15)
- Immune system inadequacy
- Menopause
- Poor hygiene
- Sexual intercourse and/or new/multiple sexual partners
- Pregnancy
- Urinary tract calculi
Diagnosis
Criteria
Diagnosis is made clinically and can be confirmed with urinalysis.
Work-up
Urinalysis via microscopy or by dipstick (Sn 75%, Sp 82%) can be used for confirmation. This may be indicated if symptoms are atypical or if it is the first time the patient is experiencing an UTI.
A positive urine dipstick may show:
- High pH (8.5-9 compared to normal 4.5-8) - suggestive of urea-splitting bacteria such as proteus, klebsiella, or ureaplasma urealyticum.
- Nitrites - presence of gram-negative bacteria
- Leukocyte esterase - presence of WBCs in urine
- Hematuria - presence differentiates UTI from vaginitis/urethritis
Positive urinalysis via microscopy would also show:
- Bacteriuria
- High WBC count
Urine culture and susceptibility testing is typically not routine but can be performed based on individual risk factors. Diagnosis can be confirmed with a culture showing 1000 CFU/mL and symptomatically correlated.
Differential
A number of conditions may mimic the symptoms of a UTI.
Vaginitis - suspect with dysuria and vaginal discharge/odour with absence of urinary frequency and urgency.
Urethritis - suspect in sexually active females with dysuria without bacteriuria.
- STIs including chlamydia, gonorrhea, trichomoniasis
- Irritants such as contraceptive gel
Pelvic inflammatory disease - lower abdominal or pelvic pain with fever
Painful bladder syndrome - diagnosis of exclusion
Red Flags / Complications
- Progression of uncomplicated UTI to complicated UTI and/or pyelonephritis
- Chronic prostatitis
- Renal damage (failure or abscess)
Management
Lifestyle / Social
Patients at high risk of incidence and recurrence of UTI should be counselled on preventative practices:
- Urinating following sexual intercourse
- Wiping front to back
- Maintaining high-volume urine flow
- Opting for showers instead of baths
- Using liquid soap over bar soap
Pharmacological / Interventional
Choice of antibiotics is made based on the risk of infection with a multidrug-resistant (MDR) gram-negative organism.
MDR risk factors are if any of the following occurred in the prior 3 months:
- An MDR gram-negative urinary isolate (nonsusceptible to at least one agent in ≥3 antimicrobial classes)
- Inpatient stay in a facility
- Use of a fluoroquinolone, sulfamethoxazole-trimethoprim, or broad-spectrum beta-lactam
- Travel to parts of the world with high rates of MDR organisms (eg. Mexico, India, Spain)
For patients without MDR risk, treatment is typically chosen empirically. Common choices are:
- Nitrofurantoin 100mg PO BID for 5 days
- Sulfamethoxazole-trimethoprim 800/160mg PO BID for 3 days
- Fosfomycin 3g powder in water once
- Other beta-lactams
For patients with MDR risk, it is important to obtain urine culture and susceptibility testing. Empiric treatment can be started as above and adjusted once testing returns. Antibiotic choice does not need to be adjusted if symptoms are resolved. Delaying treatment for urine culture results may also be considered in cases complicated by resistance/intolerance.
It should be noted that bacteriuria without symptoms is considered asymptomatic bacteriuria and does not warrant treatment in most cases (exceptions incl. pregnancy or procedure).