Urinary tract infection

Urinary tract infection
Bobjgalindo · CC BY-SA 4.0 · source
Name	Urinary tract infection
Symptoms	Dysuria, frequency, urgency, suprapubic pain
Complications	Pyelonephritis, sepsis, renal scarring
Medications	Antibiotics, analgesics
Specialty	Urology, Nephrology, Infectious disease

Urinary tract infection

Urinary tract infection (UTI) is an acute or chronic microbial infection of the urinary system manifesting with local and systemic features. It presents across age groups in outpatient and inpatient settings and intersects with surgical, nephrological, and obstetric care pathways.

Signs and symptoms

Typical presentations include dysuria, urinary frequency, urinary urgency, and suprapubic pain with or without hematuria; in older adults presentation may include altered mental status or functional decline. Patients may develop fever, flank pain, nausea, vomiting and costovertebral angle tenderness when infection ascends to involve kidneys; neonatal and pediatric cases can present with failure to thrive or jaundice. In pregnant patients, UTIs can be asymptomatic bacteriuria identified on screening; symptomatic lower urinary tract infection during pregnancy increases risk for pyelonephritis. Clinical assessment often requires correlation with laboratory and imaging studies in complicated presentations encountered in emergency departments, obstetric clinics, and long-term care facilities.

Causes and pathophysiology

Most infections are caused by uropathogenic bacteria that colonize periurethral and vaginal mucosa, ascend the urethra, and invade bladder urothelium; common pathogens include strains of Enterobacterales, notably Escherichia coli, and less commonly Klebsiella, Proteus, Enterococcus, and Staphylococcus saprophyticus. Pathogenesis involves bacterial adhesins binding to uroplakins and glycoproteins on urothelial cells, biofilm formation on indwelling devices, and evasion of host innate defenses such as Toll-like receptor signaling and antimicrobial peptides. Host factors that alter urinary tract defenses include vesicoureteral reflux, urinary obstruction from stones or prostatic hypertrophy, catheterization with device-associated biofilm communities, and immunosuppression from diabetes or corticosteroid therapy. In pregnancy, hormonal and mechanical changes in ureteral peristalsis and urinary stasis predispose to ascending infection; post-surgical and nosocomial settings facilitate colonization by multidrug-resistant organisms.

Diagnosis

Diagnosis integrates history, physical examination, urinalysis, urine culture, and imaging when indicated. Point-of-care dipstick testing assesses leukocyte esterase and nitrite but has limitations in sensitivity and specificity; microscopic urinalysis evaluates pyuria, bacteriuria, and hematuria. Definitive microbiological diagnosis relies on midstream clean-catch or catheter-obtained urine culture quantifying colony-forming units and identifying antimicrobial susceptibilities to guide targeted therapy. In complicated or recurrent cases, renal and bladder ultrasonography, voiding cystourethrography, computed tomography, or nuclear medicine studies delineate obstruction, calculi, abscess, or reflux. Invasive urological procedures may require preprocedural screening and culture-guided prophylaxis to reduce postoperative infectious complications.

Prevention

Preventive strategies include behavioral measures, device management, vaccination research, and antimicrobial stewardship. For community-acquired episodes, evidence-based counseling may address voiding habits and contraceptive choices; for catheter-associated infections, protocols emphasize aseptic insertion, timely removal, closed drainage systems, and catheter-material innovations. In recurrent cystitis, options include patient-initiated antibiotic therapy, postcoital prophylaxis, or continuous low-dose prophylaxis guided by risk-benefit analysis. Pregnant individuals undergo screening for asymptomatic bacteriuria with treatment to prevent pyelonephritis. Emerging preventive modalities under investigation include nonantibiotic prophylaxis, probiotic strains, bacterial lysate vaccines, and vaccines targeting adhesins or outer membrane proteins.

Treatment

Uncomplicated lower tract infections in nonpregnant adults are commonly treated with short-course oral antibiotics selected according to local resistance patterns and susceptibility results; agents include nitrofurantoin, fosfomycin, and trimethoprim-sulfamethoxazole where appropriate. Complicated infections, pyelonephritis, catheter-associated infections, and sepsis often require broader-spectrum intravenous antibiotics, source control, and urological intervention when obstruction or abscess is present. Analgesics, hydration, and symptomatic care complement antimicrobial therapy; renal dosing adjustments are necessary in impaired kidney function. Treatment in pregnancy favors beta-lactams and avoids teratogenic agents; severe infections may necessitate inpatient care and obstetric consultation. Stewardship principles emphasize narrow-spectrum therapy, shortest effective duration, and de-escalation based on culture data to limit antimicrobial resistance.

Epidemiology and risk factors

UTIs are among the most common bacterial infections worldwide, with substantial outpatient visits and antibiotic prescriptions annually across diverse healthcare systems; incidence is higher in females due to anatomical differences, with lifetime risk estimates varying by population. Other risk factors include sexual activity, postmenopausal estrogen deficiency, urinary tract abnormalities, diabetes mellitus, indwelling urinary catheters, recent instrumentation, pregnancy, and advanced age including residency in long-term care facilities. Geographic variation reflects differences in pathogen prevalence, antimicrobial resistance profiles, healthcare access, and public health interventions.

Complications and prognosis

When promptly recognized and treated, most uncomplicated infections resolve without sequelae; however, delayed or inadequate therapy can lead to ascending infection, acute pyelonephritis, renal cortical scarring, perinephric abscess, urosepsis, and mortality in severe cases. Recurrent infections may impair quality of life and increase healthcare utilization. Prognosis depends on host comorbidities, pathogen virulence, timeliness of appropriate antimicrobial therapy, and presence of obstructive uropathy requiring surgical correction. Vigilant follow-up and management of modifiable risk factors mitigate long-term renal and systemic complications.

Category:Infectious diseases