Urinary Tract Infection (UTI): Cystitis and Pyelonephritis

Urinary tract infections (UTIs) are among the most common bacterial infections, particularly in women. They range from simple bladder infection (cystitis) to kidney infection (pyelonephritis) and urosepsis. Good management depends on telling these apart and following local antibiotic guidance.

Types

• Lower UTI (cystitis): infection of the bladder.
• Upper UTI (acute pyelonephritis): infection of the kidney.
• Uncomplicated UTI: in non-pregnant women with a normal urinary tract.
• Complicated UTI: in men, pregnancy, abnormal urinary tract, catheters, stones, immunosuppression or kidney disease.
• Asymptomatic bacteriuria: bacteria in the urine without symptoms. It usually should not be treated, except in pregnancy and before some urological procedures.

Causes

• Escherichia coli — the most common cause.
• Klebsiella.
• Proteus — associated with stones.
• Enterococcus.
• Staphylococcus saprophyticus — in young women.
• Pseudomonas — mainly in hospital and with catheters.

Clinical features

• Cystitis:
  • pain or burning on passing urine (dysuria)
  • frequency and urgency
  • suprapubic pain
  • blood in the urine
  • cloudy or smelly urine
• Pyelonephritis:
  • fever and rigors
  • loin pain and renal angle tenderness
  • nausea and vomiting
  • often with cystitis symptoms
• Older people: may present only with confusion, falls or worsening incontinence. Do not diagnose UTI from urine dipstick alone in people over 65.

Investigations

• Urine dipstick: nitrites and leucocytes support infection in younger women with symptoms.
• Midstream urine culture for:
  • men
  • pregnancy
  • pyelonephritis
  • recurrent or complicated UTIs
  • treatment failure
• Blood tests and blood cultures if systemically unwell.
• Imaging (ultrasound or CT) for:
  • suspected obstruction or stones
  • recurrent UTI in men
  • pyelonephritis not responding to treatment

Treatment principles

Antibiotic choice must follow local guidelines and resistance patterns, and be adjusted once culture results are available.

• Uncomplicated cystitis in women: a short course of an agent such as nitrofurantoin or fosfomycin, depending on local guidance and kidney function.
• Men: usually a longer course. Consider prostatitis.
• Pregnancy: treat both symptomatic UTI and asymptomatic bacteriuria with pregnancy-safe antibiotics, and send a culture.
• Pyelonephritis: antibiotics with good kidney penetration (nitrofurantoin is not suitable). Admit if the patient is septic, vomiting, pregnant or not improving.
• Catheter-associated UTI: treat only if symptomatic, and change or remove the catheter.
• Obstructed, infected kidney: a urological emergency needing urgent drainage (nephrostomy or stent).

Prevention of recurrence

• Adequate fluid intake.
• Avoid holding urine for long periods.
• Treat constipation.
• Vaginal oestrogen in postmenopausal women.
• Prophylactic antibiotics in selected patients, after specialist review.

Exam pearls

• UTI in a man is always "complicated". Look for an underlying cause.
• Treat asymptomatic bacteriuria in pregnancy, because it increases the risk of pyelonephritis and preterm birth.
• Fever with loin pain and an obstructing stone means urgent decompression.

See also Kidney Stones, Sepsis and the urology section of our Surgery Companion.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. Most common cause of UTI:

   1. Pseudomonas
   2. Staphylococcus aureus
   3. Candida
   4. Proteus
   5. Escherichia coli
   Show answer

   Answer: E. Escherichia coli
   E. coli causes the majority of community UTIs.

2. Asymptomatic bacteriuria should be treated in:

   1. Nobody
   2. Catheterised patients
   3. Diabetics
   4. All elderly patients
   5. Pregnancy
   Show answer

   Answer: E. Pregnancy
   In pregnancy it increases the risk of pyelonephritis and preterm birth, so treat it.

3. Why is nitrofurantoin unsuitable for pyelonephritis?

   1. It is unsafe in women
   2. It does not reach adequate kidney tissue levels
   3. It only treats viruses
   4. It is too strong
   5. It causes kidney stones
   Show answer

   Answer: B. It does not reach adequate kidney tissue levels
   Nitrofurantoin concentrates in urine but not in renal tissue.

4. Fever, loin pain and an obstructing ureteric stone. Key management?

   1. Wait for stone to pass
   2. Urgent decompression (nephrostomy or stent) plus antibiotics
   3. Increase fluids only
   4. Painkillers only
   5. Oral antibiotics at home
   Show answer

   Answer: B. Urgent decompression (nephrostomy or stent) plus antibiotics
   An infected obstructed kidney is a urological emergency.

5. In people over 65, UTI diagnosis should NOT rely on:

   1. Urine culture
   2. Urine dipstick alone
   3. Clinical examination
   4. Symptoms
   5. Blood tests
   Show answer

   Answer: B. Urine dipstick alone
   Asymptomatic bacteriuria is common in older people, so dipsticks are misleading.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.