Investigation in an adult

The diagnosis is difficult in older patients since the likelihood of asymptomatic bacteria is higher as patients gets older (1).

• The Scottish Intercollegiate Guidelines Network guideline on management of suspected bacterial lower urinary tract infection in adult women advises that a dipstick test should be performed in women under 65 who have 2 or more of the following urinary symptoms: (2)
• dysuria
• frequency
• urgency
• visible haematuria
• nocturia

Urine microscopy, culture and sensitivity is required in patients with recurrent or complicated infections, during pregnancy, in suspected pyelonephritis, and in men

Urine dipstick:

• used in women with minimal signs and symptoms (two symptoms or less)
• a negative test does not rule out bacteriuria (1) Laboratory investigations of UTI usually include microscopy and quantitative culture (3)

Urine microscopy, culture and sensitivity is required in patients -

• with recurrent or complicated infections
• during pregnancy
• in suspected pyelonephritis (temp >=39.4; rigors; nausea; vomiting; diarrhoea; loin pain or tenderness)
• in men
• suspected UTI in children, any sick child and every young child with unexplained fever
• catheterised patients: Send sample only if features of systemic infection, as bacteriuria is usual
• abnormalities of genitourinary tract
• failed antibiotic treatment or persistent symptoms
• in elderly patients presence of two signs of infection (especially dysuria, fever >38 or new incontinence) is needed before taking a sample (1)
• a bacterial count of >=10^5 is generally regarded as significant bacteriuria (3) but in men with signs and symptoms of UTI, a count of >=10^3 (with 80% of the growth is of one organism) is sufficient for the diagnosis (1). The health protection agency has issued the following colony counts as diagnostic values:
  • culture of single organisms >=10^4 colony forming units (CFUs)/mL + urinary symptom
  • >=10^3 CFU/mL of Escherichia coli or Staphylococcus saprophyticus (1)

Further investigations may be indicated if there are recurrent UTIs in a woman e.g. ultrasound, IVU. A child with a single episode of urinary tract infection previously required referral for specialist investigation but now the criteria for referral for investigation depends on other factors (see linked item).

With respect to UTIs in a man then further investigation/referral depends on various factors (4)

• referral for assessment is not routinely indicated
  • however, referral for assessment should be considered for men who have:
    • symptoms of upper urinary tract infection (pyelonephritis) (1)
    • failure to respond to appropriate antibiotic therapy (1)
    • frequent episodes of urinary tract infection (UTI) - this is stated as two or more episodes in a 3-month period (1)
    • features of urinary obstruction (e.g. in older men, enlarged prostate)
    • history of pyelonephritis, calculi, or previous genitourinary tract surgery
  • urgent referral is indicated for men with suspected cancer
    • any age with painless macroscopic haematuria:
      • if haematuria is associated with symptoms of UTI
        • culture the urine before referring
        • if UTI is not confirmed by urine culture, or if haematuria does not resolve with treatment of the UTI
          • refer urgently
    • recurrent or persistent UTI associated with haematuria, in a male aged 40 years or older
    • unexplained microscopic haematuria, in a male aged 50 years or older
    • with an abdominal mass identified clinically or on imaging that is thought to arise from the urinary tract

Imaging of the kidneys, ureters, and bladder by computed tomography (CT), ultrasound, or intravenous urogram in men should be reserved for those who have voiding dysfunction without a clearly identifiable cause such as BPH, cases of treatment failure, those with persistent haematuria and those with signs of upper tract infection. (5) Ultrasound is not as effective as an IVU at detecting renal tract stones but the addition of a plain X-ray solves this problem. (6)

Reference:

• 1. SIGN (2006) Management of suspected bacterial urinary tract infection in adults: a national clinical guideline. Scottish Intercollegiate Guidelines Network.
• 2. Scottish Intercollegiate Guidelines Network. Management of suspected bacterial lower urinary tract infection in adult women. Sep 2020
• 3. Lee HS, Le J. Urinary tract infections. In: PSAP 2018 book 1: Infectious diseases. Lenexa, KS: ACCP; 2018:7-28.
• 4. Lipsky BA, Schaberg DR. Managing urinary tract infections in men. Hosp Prac. 2000 Jan 15;35(1):53-9.
• 5. Ulleryd P, Zackrisson B, Aus G, et al. Selective urological evaluation in men with febrile urinary tract infection. BJU Int. 2001 Jul;88(1):15-20.
• 6. Andresws ST et al (2002). Ultrasonography and abdominal radiography versus intravenous urography in investigation of urinary tract infection in men: prospective incident cohort study. BMJ;324:454-6.