Urinary Tract Infections Flashcards
Define UTI.
Characterized by presence of >100,000 of colony-forming units per millilitre of urine.
Urinary tract infections (UTI) may affect bladder (cystitis), kidney (pyelonephritis) or prostate (prostatitis).
Describe the epidemiology of UTIs
Common in females:
30% of women experience UTI at some point in their lives.
UTI may be seen in 5% of pregnant women, 2% of young non-pregnant women, 20% of elderly living at home and 50% of institutionalized elderly.
UTI is rare in children and young men (if present, suspect an underlying cause).
Describe the pathogenesis of UTIs
Most UTIs result from organisms entering the urinary tract via the urethra and ascending to the bladder (➡️cystitis) or kidneys (➡️pyelonephritis).
Vasicoureteric reflux occurs in children and results from incompetence of the valve mechanism that prevents urine refluxing into the ureters during bladder contraction.
—Can lead to chronic pyelonephritis, renal scarring and eventual end-stage renal failure from reflux nephropathy.
What might a patient with a UTI describe in their history?
Cystitis
Pyelonephritis, acute
Prostatitis
May be clinically silent (asymptomatic bacteruria).
Cystitis: Frequency, urgency, dysuria (pain on micturition), haematuria, suprapubic pain, smelly urine.
Pyelonephritis (acute): Fever, malaise, rigors, loin/flank pain.
Prostatitis: Fever, low back/perineal pain, irritative and obstructive symptoms (e.g. hesitancy, urgency, intermittency, poor stream, dribbling).
Elderly: Malaise, nocturia, incontinence, confusion.
Up to 30% of women with UTI symptoms may not have bacteruria.
What would you find on examination of a patient with a UTI?
Cystitis
Pyelonephritis, acute
Prostatitis
May be asymptomatic.
Cystitis: Fever, abdominal/suprapubic/loin tenderness, bladder distension.
Pyelonephritis: Fever, loin/flank tenderness.
Prostatitis: Tender, swollen prostate.
What investigations would you request for a patient with a suspected UTI?
Mid-stream urine for:
Dipstick test: For blood, protein, leucocytes, nitrites (urinary bacteria reduce nitrates to nitrites).
Microscopy, culture and sensitivity:
•at least 100,000 colonies/mL indicates a significant bacteriuria,
•in the presence of UTI symptoms, the threshold is lower,
—in women (>100/mL)
—in men (>100,000/mL).
If there is sterile pyuria (pus cells with no organisms), consider if this may be:
•partially treated UTI,
•tuberculosis stones,
•tumour,
•interstitial nephritis
•renal papillary necrosis.
Imaging: Renal ultrasound or intravenous urogram may be considered in:
•women with frequent UTIs; and
•in children and men.
This is to exclude predisposing structural/functional abnormalities.
How would you treat a patient with a UTI?
Cystitis:
If symptomatic, consider local microbiological policies, commonly used agents are
—oral co-trimoxazole, trimethoprim, nitrofurantoin or amoxicillin (in females)
—ciprofloxacin (males).
Pyelonephritis:
IV gentamicin, cefuroxime or ciprofloxacin.
Catheterized patients:
•Obtain a culture and consider changing the catheter.
•Do not treat unless the patient is symptomatic as catheters invariably become colonized.
Prophylaxis:
•High fluid intake.
•Regular micturation to keep bladder empty.
•Cranberry- based products reduce the frequency of recurrence.
•In some cases, low-dose long-term (6–12 months) antibiotics for women with frequent UTIs.
Surgical:
•Rarely necessary.
•May be necessary for relief of any obstruction and removal of any renal calculi.
What complications might you expect in a patient with a UTI?
•Renal papillary necrosis (in those with underlying renal disease, e.g. diabetes mellitus or stones).
•Renal/perinephric abscess (seen on renal ultrasound).
•Pyonephrosis (pus in palvicalyceal system).
•Gram-negative septicaemia.
What prognosis would you expect for a patient with a UTI?
Mostly resolve with treatment.
Among pregnant women, 20% develop acute pyelonephritis if not treated;
there is a high relapse rate.
