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Urinary Tract Infection

Title               

Ñ    Urinary Tract Infection

Definition

Ñ    Bacterial infection of the urinary tract

Aetiology

Organisms

Ñ    Escherichia coli

Ñ    Proteus mirabilis

Ñ    Klebsiella areogenes

Ñ    Enterococcus faecalis

Ñ    Staphylococcus

Pathogenesis

Routes of infection

Ñ    Ascending transurethral route

Ñ    Fistulae from neighbouring structures

Ñ    Haematogenous spread

Ñ    Lymphatic spread

Females

Ñ    Normal urinary tract may be infected

Males and children

Ñ    Urinary tract often abnormal

Ñ    Underlying systemic illness

Abnormal urinary tract

Ñ    Congenital abnormalities

Ñ    Obstruction to urinary flow

Ñ    Reflux uropathy

Obstruction to urinary flow

Could be due to:

Internal factors

Ñ    Stone

Ñ    Blood clot

Mural factors

Ñ    Stricture

Ñ    Posterior urethral valves

Ñ    Prostatic enlargement

Ñ    Pinhole urethral meatus

Ñ    Utero-vaginal prolapse

Systemic Factors

CNS

Ñ    Sacral plexus lesions

Ñ    Cauda equina lesions

Ñ    Spinal cord lesions

Reflux uropathy

Ñ    Bladder emptying associated with reflux of a jet of urine up the ureter due to incompetence of the valve mechanism at the junction of the ureter and bladder

Ñ    Urinary infections acquired in infancy and childhood

Ñ    Untreated leads to scarred kidneys

Underlying systemic illness

Ñ    Diabetes mellitus

Pathological Process

Acute Pyelonephritis

Ñ    Patchy suppurative inflammation

Ñ    Tubular necrosis

Ñ    Neutrophilic casts

Ñ    Abscesses

May progress to cause:

Ñ    Necrotising papillitis

Ñ    Pyonephrosis

Ñ    Perinephric abscess

Chronic Pyelonephritis

Ñ    Tubulointerstitial inflammation

Ñ    Discrete corticomedullary scars

These overlie:

Ñ    Dilated, blunted, deformed calyces

Clinical Features

Urinary tract infection may be:

Ñ    Single or isolated attack

Or

Ñ    Recurrent attacks

Which may be due to:

Ñ    Relapse

Ñ    Reinfection

Relapse

Ñ    Recurrence of bacteriuria within 7 days of treatment:

Same organism

Ñ    Failure to eradicate infection

Reinfection

Ñ    Absence of infection for 14 days

Ñ    Infection with different organism

Ñ    Reinvasion of susceptible urinary tract

E&M

Ñ    Fever:

Due to:

·          Pyelitis

·          Nephritis

·          Pyelonephritis

KUS

Cystitis

Ñ    Increased frequency of micturition

Ñ    Dysuria

Ñ    Haematuria

Ñ    Smelly urine

Ñ    Suprapubic pain

Pyelonephritis

Ñ    Loin pain and tenderness:

In addition to above

Investigations

Fluids

Blood

Haematology

Ñ    Neutrophilia:

Pyelonephritis

Urine

Haematology

Ñ    Dipstick detects esterases released from leucocytes:

Positive suggests pyuria

Biochemistry

Ñ    Bacteria reduce nitrates to nitrites:

Presence of nitrites suggests infection

Microbiology

Ñ    Culture specimen of clean midstream urine

Diagnostic Criteria

Symptomatic young females

Ñ    ³ 10²  organisms /mL with pyuria (> 10 WBC/mm³)

Or

Ñ    ³10⁵ organisms /mL

Or

Ñ    Any growth of pathogens from suprapubic specimen

Symptomatic men

Ñ    ³ 10³ pathogens /mL

Asymptomatic patients

Ñ    ³ 10⁵ pathogens /mL

Imaging

Ñ    Not for uncomplicated UTI

Indicated for:

Ñ    Recurrent UTI

Ñ    Severe symptoms

Ñ    Males

Ñ    Children

Plain X-ray

Ñ    KUB (kidneys, ureter, bladder):

Detects stones

Contrast Studies

IVU (intravenous urogram):

Ñ    Detect calculi

Ñ    Obstruction

Ñ    Incomplete emptying

Ultrasound

Ñ    Detect obstruction

Ñ    Allows early detection of pyonephrosis and drainage

CT Scan

Ñ    Study excretion

Ñ    Identify obstruction and complications

MRI

Ñ    For those with contrast allergies

Nuclear Medicine

Ñ    Assess renal function prior to surgery

Management

Cure

Drugs

Ñ    Amoxicillin

Ñ    Co-amoxiclav

Ñ    Trimethoprim

Ñ    Nitrofurantoin

Ñ    Oral cephalosporin

Pyelonephritis (severe)

Intravenous broad-spectrum antibiotics initially followed by oral therapy:

Ñ    Aztreonam

Ñ    Cephalosporin

Ñ    Ciprofloxacin

Ñ    Gentamicin

Surgery

Ñ    Drain pyonephrosis

Ñ    Stone removal

Control

Recurrent UTI

Drugs

Ñ    Low dose antibiotic prophylaxis:

Trimethoprim, cephalexin, nitrofurantoin, co-trimoxazole

Surgery

Ñ    Reimplantation of ureter:

To try and correct reflux uropathy

Ñ    Stone removal

Ñ    Correct abnormalities of urinary tract

Biological Agents

Ñ    Cranberry juice:

Contains proanthrocyanidins that prevent binding of E.coli to uroepithelium

Lifestyle Adjustments

Ñ    Increased fluid intake

Ñ    Frequent voiding

Ñ    Double micturition:

Vesico-ureteric reflux

Ñ    Micturition after sexual intercourse

Ñ    Avoid constipation

Ñ    Avoid spermicidal jellies

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