Urinary Tract Infection

Question 1

What is a UTI?

Answer 1

• Urinary tract infection (UTI) is the presence and multiplication of microorganisms in one or more structures of the urinary tract with organisms invading the surrounding tissue

Question 2

UTI includes a variety of clinical syndromes?

Answer 2

• acute and chronic pyelonephritis (kidney and renal pelvis)
• cystitis (bladder)
• urethritis (urethra)
• epididymitis (epididymis)
• prostitis (prostate)

Question 3

Pathophysiology?

Answer 3

Urinary tract infections that are caused by bacteria of faecal origin (the commonest cause) involve either the bladder, the upper urinary tract (ureter, pelvicalyceal system, kidney) or both.

Some facts about UTIs:

• the bladder is most commonly affected
• females are more commonly affected than men
• at least 50% of women suffer a UTI sometime in their life
• The pathogens may reach the urinary tract
• via haematogenous or lymphatic spread
• as an ascending infection from the urethra
• during bladder catheterization or instrumentation

Question 4

Clinical features of UTI?

Answer 4

UTIs can involve any part of the urinary tract. General features of a UTI include:

• dysuria, frequency, urgency and a sensation of incomplete bladder emptying - a very common presentation
• lower abdominal pain - often a presentation in children and young adults
• sudden development of incontinence - often a presentation in the elderly
• haematuria
• enuresis occurring in a previously ‘dry’ child
• non-specifically unwell if previously fit - presentation is seen in infants and elderly
• Symptoms and signs of lower UTI include:
• dysuria
• urgency
• frequency
• suprapubic tenderness
• strangury (a condition marked by slow, painful urination, caused by muscular spasms of the urethra and bladder)
• flank or back pain
• haematauria
• a change in the smell of urine (1,2)
• Three or more symptoms should be present to make a diagnosis of UTI (2). When both dysuria and frequency are present the probability of an UTI is >90% (3).

Symptoms of upper UTI include:

• loin pain
• flank tenderness
• fever
• rigors
• other manifestations of systemic inflammatory response (4)
• Upper UTI symptoms develops rapidly (1) and if accompanied by bacteraemia may be a life threatening condition (4)

Question 5

Investigations?

Answer 5

• The diagnosis is difficult in older patients since the likelihood of asymptomatic bacteria is higher as patients gets older
• in primary care - in a woman with uncomplicated cystitis urinary culture is not necessarily required, with nitrite and leucocyte tests being adequate
• urine microscopy, culture and sensitivity - this is required in patients with recurrent or complicated infections, during pregnancy, in suspected pyelonephritis, in men

Urine dipstick:

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

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
• 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

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

referral for assessment is not routinely indicatedhowever, referral for assessment should be considered for men who have:

symptoms of upper urinary tract infection (pyelonephritis)

• failure to respond to appropriate antibiotic therapy
• frequent episodes of urinary tract infection (UTI) - this is stated as two or more episodes in a 3-month period
• 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 cancerany 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