Urinary Tract Infection & Pyelonephritis Flashcards
What is a urinary tract infection (UTI)?
Infection of the urinary tract most commonly caused by bacteria from patient’s own bowel flora that usually ascends the urethra.
UTI can be divided into lower and upper UTI.
i. Lower UTI = cystitis ; prostatitis
ii. Upper UTI = pyelonephritis (infection of kidney and renal pelvis)
Bacteriuria confirms UTI
Rarely, UTI from bloodstream or lymphatics infection
What are the common organisms to cause UTI?
Usually anaerobes and gram -ve bacteria from bowel and vagina flora
E. Coli
Staphylococcus epidermidis / Staphylococcus saprophytic (skin commensal)
Psuedomonas
Klebsiella
How well an organism adheres to the urothelium determines its virulence
What makes E.coli an ideal pathogen in UTI?
E. coli :
=> flagella for motility
=> haemolysis to form pores
=> fimbriae (adhesions that attach organisms to the perineum and urothelium)
=> aerobactin (to acquire iron)
What are the innate host defence mechanism?
- Neutrophil : activation of neutrophil essential for bacterial killing
- Urine osmolality and pH : very low or high pH reduce bacterial survival
- Complement : mucosal IgA production by uroepithelium important defence against UTI
- Commensal organisms : eradication of commensal organisms by spermicidal jelly or antibiotics = overgrowth of E.coli
- Urine flow : good urine flow and micturition wash out bacteria
=> urine stasis promotes UTI - Uroepithelium : cranberry and blueberry juice contain large molecular weight factor => prevents binding of E. coli to the uroepithelium
Who does it commonly affect?
Women because shorter urethra => 10-20% / year
Rarely men or children
> 65yrs men (10%) and women (20%) have asymptomatic bacteriuria
What are the risk factors for UTI?
Increased bacterial inoculation: => sexual activity => urinary incontinence => faecal incontinence => constipation
Increased binding of uropathogenic bacteria:
=> spermicide use
=> low oestrogen
=> menopause
Reduced urine flow:
=> dehydration
=> urinary tract obstruction
=> urinary stasis
Increased bacterial growth: => diabetes => immunosuppression => obstruction => stones => catheter => renal tract malformation => pregnancy
How is UTI classified?
UTI is classified into:
Uncomplicated: normal renal tract structure and function
Complicated: structural/functional abnormality of genitourinary e.g. obstruction, catheter, stones, neurogenic bladder, renal transplant
What are the symptoms of UTI (cystitis)?
Asymptomatic or:
Frequency day and night
Dysuria (painful voiding)
Urgency
Suprapubic pain & tenderness
Polyuria
Haematuria
Smelly urine
New confusion (can be the only symptom in elderly)
What are the symptoms of acute pyelonephritis?
Fever
Loin pain/tenderness
Rigor / Chills
Night sweats
Vomiting
Costo-vertebral pain
Associated cystitis symptoms
Septic shock
=> significant bacteriuria implying kidney infection
What are the symptoms of prostatitis?
Pain in perineum, rectum, scrotum, penis, bladder, lower back
Fever
Malaise
Nausea
Urinary symptoms
Swollen, tender prostate on digital rectal exam
What are the signs of UTI?
Fever
Abdominal or loin tenderness
Distended bladder
Enlarged prostate
How do you diagnose an uncomplicated UTI (cystitis) in a young non-pregnant women <65yrs?
Non-pregnant women:
=> If 3 or more symptoms or 1 severe symptom of cystitis present
=> No vaginal discharge
=> Then treat empirically without any further test
=> If fail to respond to treatment, do mid-stream urine culture
If less than 3 symptoms => do a dipstick
=> negative dipstick reduces likelihood of UTI
How do you diagnose an uncomplicated UTI (cystitis) in a pregnant women, men and children?
Mid stream urine culture
How do you diagnose a UTI in a systemically unwell patient?
Blood test: FBC, U&E, CRP and blood culture (+ve in 10-25% of pyelonephritis)
Imaging: ultrasound and referral to urology for cystoscopy, urodynamics and CT in :
=> men with upper UTI
=> failure to respond to treatment
=> recurrent UTI >2/year
=> pyelonephritis
=> unusual organism
=> persistent haematuria
What is the difference between relapsing UTI and re-infection with UTI?
Relapse: recurrence of bacteria with the same organism within 7 days of completion of antibacterial treatment.
=> treatment failure due to stones, scarred kidneys, polycystic disease or bacterial prostatitis
Re-infection: bacteriuria is absent after treatment for at least 14 days, followed by recurrence of infection with the same or different organism
=> this is not due to failure of treatment but re-infection
=> 80% of recurrent infection due to re-infection
What is a possible diagnosis for when urine culture is negative but symptoms persist?
Abacteriuric frequency or dysuria (urethral syndrome)
Due to:
=> bladder trauma after intercourse
=> vaginitis
=> atrophic TB in symptomatic young women with sterile pyuria
What are the histological features of acute pyelonephritis?
Focal infiltration of polymorphonuclear leucocytes
Polymorphs in tubular lumina
Small renal cortical abscesses
Streaks of pus in renal medulla
What characteristics of acute pyelonephritis can be seen on CT?
Wedge shaped areas of inflammation => renal function impaired
Reflux nephropathy is also known as chronic pyelonephritis or atrophic pyelonephritis.
Which two factors can lead to reflux nephropathy?
- Vesicoureteric reflux
2. Infection acquired in infancy or early childhood
What is the underlying pathology behind reflux nephropathy?
- Vesicoureteric junction is a one way valve, closed during bladder contraction => prevents urine reflux
- Valve malfunction => reflux up the ureter
- Consequence of this = incomplete bladder emptying because reflux urine returns to bladder after voiding
- Stasis of urine in bladder => risk of infection => reflux of infected urine = infected kidney + damage
What changes are seen in reflux nephropathy on CT?
Clubbed calyces
Reduction in renal size
Cortical scarring
Papillary damage
Tubulointerstitial nephritis
Ultrasound is used in complicated UTI i.e. if infection is recurrent or UTI in men or children or in severe symptoms.
What kind of pathology does ultrasound detect?
Calculi
Obstruction
Abnormal urinary anatomy
Incomplete bladder emptying (post micturition scan)
=> useful in suspected pyelonephritis or obstructed, infected kidney
How do you treat lower UTI in non-pregnant women?
If 3 or more symptoms or one severe symptom of cystitis and no vaginal discharge then:
=> treat empirically with 3 day course of trimethoprim or nitrofurantoin (if eGFR >30)
If first line treatment fails, culture urine & treat according to antibiotic sensitivity
How do you treat upper UTI in non-pregnant women?
Urine culture and treat initially with broad-spectrum antibiotic using local guideline/sensitivity e.g. co-amoxiclav
Hospitalisation should be considered due to antibiotic resistance
How do you treat UTI in pregnant women?
UTI in pregnancy assoc. with acute pyelonephritis, preterm labour and intrauterine growth restriction
Asymptomatic bacteriuria should be confirmed on 2nd sample
Treat with antibiotic (guideline or sensitivity)
AVOID ciprofloxacin, trimethoprim in 1st trimester and nitrofurantoin in 3rd trimester
Get EXPERT HELP
DO NOT treat with antibiotics in asymptomatic bacteriuria in:
=> non-pregnant women
=> men
=> adults with catheters
INFO CARD
How do you treat UTI in men?
Treat lower UTI with 7 day course of trimethoprim or nitrofurantoin (if GFR>30)
If upper UTI => refer to urology
If prostatitis symptoms i.e. pain in pelvis, genitals (recurrent epididymis-orchitis), lower back, buttocks, treat with
=> 4 week course of fluoroquinolone (ciprofloxacin) due to ability to penetrate prostate fluid
How do you treat UTI in catheterised patients?
All catheterised patients are bacteriuric.
Send mid stream urine only if symptomatic
Symptoms may be atypical i.e. fever, flank/suprapubic pain, change in voiding pattern, vomiting, confusion or sepsis.
=> change catheter before starting antibiotic (narrow spectrum according to sensitivity, if poss)
Re-infection of UTI implies patient has a predisposition of peri-urethral colonisation or poor bladder defence mechanisms.
How do you treat UTI re-infection?
I) Daily 2L fluid intake
II) Voiding 2/3 hour interval
III) Voiding before bedtime and after sex
IV) Avoid spermicidal jellies, bubble bath, other chemicals in
V) Avoid constipation as this may impair bladder emptying
Xathogranulomatous pyelonephritis is an uncommon chronic interstitial infection of the kidney.
What is the clinical presentation?
How do you treat it?
- Fever
- Weight loss
- Loin pain
- Palpable enlarged kidney
=> Unilateral assoc. with stag horn calculi & UTI
Treatment with nephrectomy
Antibacterial doesn’t eradicate the treatment
