Urinary tract
Anatomy The urinary tract consists of the kidney, ureters, bladder, and urethra. Urinary tract infections can be either: upper or lower based primarily on the anatomic location of the infection.
Lower urinary tract encompasses bladder and urethra the upper urinary tract includes the ureters and kidneys.
Female is predisposed to the UTI infection Because of the shorter urethra, bacteria can reach the bladder more easily in the female host. Female urethra is short compared with male urethra and also is in close proximity to the warm, moist perirectal region, which has numerous enteric flora.
President microorganisms (normal flora) of the urinary tract. Some microflora normally colonizes urethral epithelium cells in the distal portion. Some potential pathogens, including: GNB (primarily E.coli) and occasionally yeasts are also present as transient colonizers.
All areas of the urinary tract above urethra are considered to be sterile. Also, urine in its nature is sterile. However, it gets contaminated with urethral flora. The most common urogenital flora are: Coagulase negative staphylococci (CNS) Viridans and non-hemolytic streptoccoci Lactobacilli spp Diphtheriods Nonpathogenic Neisseria spp Commensal Mycobacterium spp
Urinary tract infections Asymptomatic bacteriuria Acute cystitis Acute pyelonephritis Uncomplicated / complicated UTI
Epidemiology of UTI UTI is more common in females. (1-2% of young nonpregnant women) 40% of females will have a symptomatic UTI in their life time. In men: prevalence is 0.04%. Incidence of UTI increases in old age. (10% of men & 20% of women)
Risk factors for UTI in females: pregnancy, spermicidal contraceptives, diaphragm, estrogen deficiency, diabetes. In males: lack of circumcision, prostatic hypertrophy, use of condom catheter. in both : old age, obstruction, vesicoureteric reflux, instrumentation, neurogenic bladder, renal transplantation.
Infecting organisms E.coli Klebsiella Enterobacter Staphylococci Proteus Pseudomonas Enterococci Candida
Pathogenesis of UTI Host defences: Urinary bladder is usually resistant to bacterial colonisation. Bacteria accessing the bladder are eliminated by: - flushing mechanism - urine inhibitors (PH, osmolality, urea) - uroepithelial defences (cytokines,pmns) - Tamm- Horsfall protien (uromodulin)
Pathogenesis of UTI Organism features: Most E.coli causing UTI belong to O,K and H serotypes. Uropathogenic E.coli virulence factors: - Have fimbria (for adherence). - Secrete hemolysin & aerobactin. - Resist serum bacterical action. - Have higher K capsular antigen. Adherence is important in other bacteria.
Pathogenesis of UTI urethra are colonised by bacteria. Bacteria enter bladder in susceptable host. Adherence properties enable pathogens to colonise bladder. Pathogens attach to uroepithelial mucosa secretion of cytokines recruitment of PMNs inflammation. Pathogens may ascend through ureter to kidney pyelonephritis.
Clinical presentation of UTI Asymptomatic bacteriuria: Common in females & elderly. 25% develop symptomatic UTI. 25% clear spontaneously. Spontaneous cure & reinfection are common. Cystitis: Frequency, dysurea, urgency. discomfort +/- tenderness. Fever is often absent.
Clinical presentation of UTI Acute pyelonephritis: Fever, abdominal pain, vomiting. Dysuria,frequency, flank or loin pain. Flank or loin tenderness. In elderly: symptoms are often atypical. Bacteremia is common.
Special situations
Special situations UTI in pregnancy: Asymptomatic bacteriuria occurs in 4-8%. Of these: 25% develop acute pyelonephritis. Pyelonephritis in pregnancy predisposes to: - premature delivery. - low birth weight infant. - increased newborn mortality.
Special situations Catheter associated UTI : Bacteriuria occurs in 10-15% of cathed pts. All chronicly cathed pts. develop bacteriuria. Organisms: E.coli, Proteus, Klebsiella, Serratia Pseudomonas, Enterococci, Candida. Antibiotic resistance is common. Symptoms are often absent or minimal. Intermittent cathing reduces infections.
Diagnosis of UTI Urine dipstick: - leukocyte esterase - nitrite Urine microscopy: -WBCs, WBC casts, RBCs - Bacteria ( 1 bact/hpf = significant )
Diagnosis of UTI Urine culture: Significant bacteriuria= 100K cfu/ml symptoms: 1 +ve culture = infection Symptoms: 10K cfu/ml = propable infection Asymptomatic: 2 +ve cultures = infection False negative : antibiotics, antiseptics, urethral syndrome,tb kidney, diuresis.
Natural history of UTI Treatment of uncomplicated UTI leads to complete resolution and cure. Recurrences occur in some patients usually within 2-3 monthes of initial infection. Frequent recurrences usually occur in clusters followed by long remissions. Recurrent uncomplicated UTI does not lead to chronic renal impairment or failure. Recurrent complicated UTI may lead to renal failure. UTI may accelerate progression of underlying renal disease.
Treatment of UTI Acute pyelonephritis: Mild infections are treated orally. (fluoroquinolones,co-trimoxazole,cefuroxime) Moderate - severe infections parenteral trt. (aminoglycosides,ceftriaxone,aztreonam,tazocin) Therapy marked decline in bact.count after 48hrs. Persistant fever, +ve blood culture after 3 days of therapy..r/o obstruction, abscess. After defervescence..change to oral therapy to complete 2 weeks. In males look for a predisposing cause. FU urine cultures 2 weeks after end of therapy.
Treatment of UTI Cystitis: young females: 3 days of oral therapy (fluoroquinolone,cotrimoxazole,cefuroxime,augmentin) In females: symptoms x 7 days or history of previous infection 7 days therapy. In males : oral therapy for 7-10 days.
Treatment of UTI Asymptomatic bacteriuria No urgency to treat confirm by 2 cultures. Treatment is indicated in : - Pregnancy - Urinary obstruction Treatment is not indicated in : - Young nonpregnant women without structural abnormalities - Elderly patients
Structural abnormalities should be corrected
Treatment of UTI Relapse of infection: Relapse may be due to : - renal invovement - structural abnormalities - chronic bacterial prostatitis Relapses need to be treated for 2 weeks. Obstuction should be corrected. If uncorrectable obstruction: treatment is prolonged for 4-6 weeks or as required. The latter group needs FU by monthly cultures and annual assessment of kidneys. In males R/O chronic prostatitis.
Treatment of UTI Recurrent UTI: Infrequent symptomatic UTI : treat attacks. In females, reinfections may be related to sexual activity attacks may be reduced by: - avioding use of spermicidal contraceptives - voiding after intercourse - post coital single dose therapy If no precipitating factors long term prophylaxis. Long term prophylaxis is also indicated for frequent asymptomatic infection in: - Patients with obtructive uropathy
What is the prognosis?
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