26th June 2023

Urinary Tract Infections

Presentation

A lower urinary tract infection (UTI) is an infection of the bladder typically caused by bacteria from the gastrointestinal tract.

Lower UTIs can present with increased urinary frequency, nocturia, urgency, dysuria, suprapubic pain, foul-smelling urine, or haematuria. In the elderly or those with cognitive impairment, UTIs may present with non-specific features such as delirium, anorexia, nausea, and vomiting.

A lower UTI can be complicated by persistent infection, treatment failure or recurrent infection. The risk factors for complications include structural or neurological abnormalities of the urinary tract, external sources of infection such as catheters and immunosuppressive comorbidities such as diabetes. A further complication is the spread of infection to the upper urinary tract giving rise to pyelonephritis. This presents with fever, rigors, and loin pain with renal angle tenderness on examination.

Investigation and treatment

In adults below the age of 65 with risk factors for complicated UTI, urine dipstick can be a basis to start treatment. A dipstick positive for nitrites or leucocytes and blood suggests a UTI. The sample should then be sent for microscopy and culture. Asymptomatic bacteriuria (the presence of bacteria in urine) should be treated in pregnancy as it increases the risk of preterm rupture of membranes. Note that the presence of bacteriuria is common in those over 65 and usually does not need to be treated unless symptomatic.

Antibiotic choice should be guided by sensitivities from culture, but the following are often used:

• Nitrofurantoin 100mg modified-release twice a day for three days
  • must be avoided if eGFR ≤45ml/minute
  • must be avoided in the last trimester of pregnancy due to the risk of haemolytic anaemia of the newborn
  • poor penetration of the kidney so not for complicated UTI
• Trimethoprim 200mg twice a day for three days (if low risk of resistance)

In pregnancy, cefalexin 500mg twice a day can also be considered. Men and pregnant women should be treated for seven rather than three days.