Acute Pyelonephritis and Urosepsis (UTI)

🦠 Acute Pyelonephritis is a bacterial infection of the renal parenchyma and collecting system that can lead to renal scarring if untreated. It represents the severe end of the UTI spectrum — from lower urinary tract infection to urosepsis. Prompt recognition and treatment are crucial to prevent complications.

🚀 Quick Guide (NICE-aligned)

• 👩 Simple UTI in women → 3 days of antibiotics.
• 👨 Men, pregnancy, or catheter → 7 days; if catheterized, replace catheter.
• 🚫 Do not treat asymptomatic bacteriuria in non-pregnant adults.
• 👵 Do not treat older adults (>65) based on dipstick alone — need symptoms.
• 🤰 In pregnancy, always send urine for culture and treat asymptomatic bacteriuria.

🧠 About

• ~1 in 3 women will experience a UTI in their lifetime; UTIs in men are uncommon and require investigation.
• Pyelonephritis = bacterial infection of the renal tissue → needs antibiotics that achieve renal concentrations.
• ♀️ Short female urethra → easier ascent of coliform bacteria such as E. coli.

📖 Key Definitions

• Bacteriuria = bacteria in urine. Pyuria = white cells (pus) in urine.
• Asymptomatic bacteriuria = bacteria >10⁵ CFU/mL but no symptoms or inflammatory response.
• UTI = bacteriuria + symptoms and/or inflammatory response.

💧 Urinalysis

• 🧫 Nitrites: suggest Gram-negative bacteria (more specific).
• 🧪 Leucocyte esterase: detects WBCs — sensitive but less specific.
• 📬 If both positive → send MSU for culture.
• ⚖️ Always correlate results with symptoms and clinical picture.

🦠 Aetiology

• Ascending infection from perineal flora (often post-intercourse or incomplete bladder emptying).
• Predisposing factors: stones, obstruction, vesicoureteric reflux, catheters, diabetes, pregnancy, immunosuppression.

🧫 Common Organisms

• Escherichia coli (60–80%)
• Proteus mirabilis (esp. with struvite stones)
• Klebsiella spp. (~20%)
• Enterococcus faecalis
• Staphylococcus saprophyticus — young sexually active women
• Staphylococcus aureus — may indicate haematogenous spread

🩺 Clinical Presentation

• 💧 Cystitis/Urethritis: Dysuria, frequency, malodorous urine, suprapubic tenderness, haematuria.
• 🔥 Pyelonephritis: Fever, rigors, flank pain, renal angle tenderness, nausea/vomiting.
• ⚡ Urosepsis: Hypotension, tachycardia, confusion/delirium, lactic acidosis.

⚠️ Complications: sepsis, perinephric abscess, renal papillary necrosis, renal failure, and preterm labour in pregnancy.

🔍 Investigations

• 🧪 Urinalysis: blood, leucocytes, nitrites.
• 💉 Urine culture: always send before antibiotics if possible.
• 🧬 FBC/CRP: raised WCC & CRP.
• 💧 U&E: assess renal function, check for AKI.
• 🩸 Blood cultures: if febrile or septic.
• 🩻 Renal ultrasound/CT: if not improving after 48 h → exclude stones, abscess, or obstruction.

💥 Complications

• 🧫 Bacteraemia / Sepsis
• 💣 Renal or perinephric abscess
• 🔥 Renal papillary necrosis
• 🪶 Chronic pyelonephritis → scarring → CKD

💎 Think stones if prior colicky flank pain, haematuria, or known urolithiasis. Obstruction + infection = emergency (risk of sepsis).

💊 Management of Pyelonephritis / Urosepsis

• 🏥 Admit if unwell, dehydrated, pregnant, unable to take PO meds, or any red flags for sepsis or obstruction.
• 🫀 ABC approach, IV fluids, IV antibiotics per sepsis pathway; monitor urine output.
• 💊 Analgesia: paracetamol ± ibuprofen if renal function normal.
• 💧 Encourage oral fluids once stable.

💉 Antibiotic Choices (Typical UK Practice — adjust to C&S)