Urinary Tract Infection

Urinary Tract Infection (UTI) refers to the presence of pathogenic microorganisms in the urinary tract. Clinically, it is classified as 'uncomplicated' (healthy, non-pregnant women) or 'complicated' (males, pregnant women, catheterized patients, or those with structural/functional abnormalities). Cystitis is an infection of the bladder, presenting with frequency, urgency, and dysuria. Pyelonephritis is a more severe systemic infection involving the kidney parenchyma, characterized by loin pain, fever, and systemic upset. Escherichia coli is the causative organism in >70% of cases; others include Staphylococcus saprophyticus, Proteus mirabilis (associated with stones), and Klebsiella. Diagnosis in non-pregnant women under 65 can often be clinical if three or more symptoms are present. In other groups, dipstick testing or mid-stream urine (MSU) culture is mandatory. Management involves short courses of antibiotics for lower UTI and longer, potentially parenteral courses for pyelonephritis. Asymptomatic bacteriuria is only treated in pregnant patients due to the high risk of progression to pyelonephritis and preterm birth.

The urinary tract is normally sterile, maintained by the constant flushing of urine and antimicrobial properties of the bladder lining. UTIs typically occur when faecal flora ascend the urethra. Features promoting infection include short urethral length in females, urinary stasis (e.g., due to BPH or stones), and foreign bodies like catheters. Pathogenic E. coli possess virulence factors like P-pili, which allow them to adhere to the urothelium. If bacteria ascend to the renal pelvis, they trigger an inflammatory response in the parenchyma (pyelonephritis), leading to neutrophil infiltration and potential abscess formation or scarring. Structural abnormalities (vesicoureteric reflux) facilitate this ascent. In rare cases, UTIs result from haematogenous spread (e.g., S. aureus bacteraemia).

Cystitis presents with 'LUTS' (lower urinary tract symptoms): dysuria, frequency, urgency, suprapubic tenderness, and иногда haematuria. Pyelonephritis presents with systemic symptoms: high fever, rigors, nausea, vomiting, and flank/loin pain. In the elderly, UTIs can present atypically with confusion (delirium) or falls, even without classic urinary symptoms. Complications include urosepsis, perinephric abscess, and in chronically infected patients, staghorn calculi (associated with Proteus). Recurrent UTIs can indicate underlying pathology like bladder cancer or urolithiasis. In pregnancy, UTI is associated with pre-eclampsia and low birth weight. Red flags include visible haematuria (refer via 2-week wait if >45) and signs of sepsis.

Bedside: Urine dipstick (Nitrites are specific for Gram-negative bacteria; Leucocytes indicate inflammation). Note: Dipsticks are less reliable in age >65. Lab: Mid-stream urine (MSU) for microscopy, culture, and sensitivities (essential in pregnancy, males, children, and suspected pyelonephritis). Bloods: FBC, CRP, and U&Es in pyelonephritis/sepsis. Imaging: Ultrasound of the kidneys or CT KUB only if pyelonephritis is not responding to treatment or if structural abnormality is suspected (e.g., in a male with a first UTI).

Uncomplicated Cystitis (Women): Nitrofurantoin 100mg MR BD for 3 days (avoid if eGFR <45 mL/min — risk of inadequate urinary concentrations and peripheral neuropathy) or Trimethoprim 200mg BD for 3 days. Complicated/Male UTI: 7 days of antibiotics. Pregnancy: 7 days of treatment; avoid Trimethoprim in the 1st trimester (folate antagonist) and Nitrofurantoin at term (risk of neonatal haemolysis); also avoid Nitrofurantoin if eGFR <45 mL/min. Pyelonephritis: Ciprofloxacin 500mg BD for 7 days or Cefalexin for 7-14 days. If septic: IV Amoxicillin + Gentamicin or IV Ceftriaxone. Conservative: Increase fluid intake, wipe front-to-back, voiding after intercourse. Catheter-associated: Only treat if symptomatic; change the catheter if it has been in place for >7 days.