Urinary tract infection in adults

Urinary tract infection (UTI) Childhood UTI: OHCS p174

Definitions

• Bacteriuria: Bacteria in the urine, may be asymptomatic or symptomatic.
• UTI: The presence of a pure growth of >105 organisms per mL of fresh MSU.
• UTI sites:
• urethra (urethritis),
• bladder (cystitis),
• prostate (prostatitis), or
• renal pelvis pyelonephritis).
• Up to ? of women with symptoms have bacteriuria; (=abacterial cystitis or the urethral syndrome).

Classification

• UTIs may be uncomplicated (normal renal tract and function) or complicated (abnormal renal/GU tract, ↓renal function, impaired host defences, or virulent organism eg Staph. aureus).
• Assume that UTI in men without risk factors (below) is complicated until proved otherwise.
• A recurrent UTI is a further infection with a new organism. A relapse is a further infection with the same organism. For urethritis, see p406.

Risk factors

• ♀, sexual intercourse, exposure to spermicide in ♀ (by diaphragm or condoms), pregnancy, menopause; 
• ↓host defence: immunosuppression, DM;
• urinary tract: obstruction (p286), stones, catheter, malformation.
• NB: in pregnancy, UTI is common and often asymptomatic, until serious pyelonephritis, premature delivery (± fetal death) supervenes, so do routine dipstix in pregnancy.
• Urine in catheterized bladders is almost always infected—it is pointless sending samples or treating unless the patient is ill.

Organisms

• E. coli is the main organism (>70% in the community but ¢41% in hospital).
• Staphylococcus saprophyticus
• Proteus mirabilis
• Rarer:
• Enterococcus faecalis,
• Klebsiella,
• Enterobacter and
• Acinetobacter species,
• Pseudomonas aeruginosa,
• Serratia marascens,
• Candida albicans, and
• Staph. aureus.

Symptoms

• Cystitis: Frequency, dysuria, urgency, strangury, haematuria, suprapubic pain. 
• Acute pyelonephritis: High fever, rigors, vomiting, loin pain and tenderness, oliguria (if acute renal failure). 
• Prostatitis: Flu-like symptoms, low backache, few urinary symptoms, swollen or tender prostate on PR.

Signs

• Fever, abdominal or loin tenderness, foul-smelling urine.
• Occasionally distended bladder, enlarged prostate.
• NB: see Vaginal discharge, p406.

Tests

• If symptoms are present, dipstick the urine and treat empirically if nitrites or leucocytes are positive.
• What is the predictive value of urinary symptoms and dipstick for diagnosing UTI? 
• This is a controversial area, with a meta-analysis on 70 studies concluding that in the general population, a combination of negative nitrite and leucocyte tests on dipstick was sufficient to rule out UTI. 
• However, a recent small prospective study (n=59) showed that although a negative dipstick test accurately predicted the absence of UTI according to urine culture, treating these patients with trimethoprim still reduced symptoms of dysuria, suggesting that the cause in these patients may be infection not detected by current urine dipstick or
  culture techniques.
• MSU for lab MC&S 
• To confirm UTI if dipstick negative
• Send a lab MSU anyway if male, a child (OHCS p174), pregnant, immunosuppressed or ill, or if symptoms don't resolve after one course of empirical treatment.
• A pure growth of >105 organisms per mL is diagnostic.
• If <105 organisms/mL and pyuria (eg >20 WBCS/mm3), the result may still be significant.
• Cultured organisms are tested for sensitivity to a range of antibiotics (p368).
• Blood tests:
• FBC, U&E, CRP, and blood cultures eg if systemically unwell.
• Ultrasound or IVU/cystoscopy: 
• Consider for
• UTI in children; men;
• if failure to respond to treatment;
• recurrent UTI (>2/year);
• pyelonephritis;
• unusual organism;
• persistent haematuria.
• In one study on men, ultrasound combined with plain XR of kidneys, ureters and bladder (KUB) was as effective as IVU in detecting urinary tract abnormalities, and avoided exposure to IV contrast.

Treatment

• Drink plenty of fluids; urinate often (don't ‘hold on’).
• In pregnancy, get expert help.
• Know your local pattern of resistance.
• Until the organism is known:
• Cystitis:
• Trimethoprim 200mg/12h PO (3d course in ♀, 7d in ♂).
• Alternative: cefalexin 1g/12h.
• 2nd line: ciprofloxacin or co-amoxiclav PO (7d course). 
• Acute pyelonephritis:
• Cefuroxime 1.5g/8h IV then oral × 7d course. 
• Prostatitis:
• Ciprofloxacin 500mg/12h PO for ~ 4wks.

Prevention

• Antibiotic prophylaxis, continuously or post-coital, ↓infection rates in women with recurrent UTIs.
• Self-treatment with a single antibiotic dose as symptoms start is an option.
• Drinking 200-750ml of cranberry or lingonberry juice a day, or taking cranberry concentrate tablets,
  reduces the risk of symptomatic recurrent infection in women by 10-20%, may be by inhibiting adherence of bacteria to bladder uroepithelial cells.
• There is no evidence that postcoital voiding or advice on wiping patterns in females is of benefit.