NephrologyTier 1Disease (DEADMAN)

Urosepsis and pyelonephritis

Description

Pyelonephritis - upper UTI, renal parenchymal/collecting-system infection
Urosepsis - sepsis with a urinary source, usually complicated pyelonephritis or obstructed infected system
Obstruction + infection (infected obstructed system) is a urological emergency - antibiotics alone will not control sepsis until drained

Pyelonephritis F>M outside infancy/old age (shorter female urethra); M=F or M>F in the elderly (prostatic disease)
Urosepsis - one of the commonest identifiable sources of sepsis, especially in the elderly and catheterised

E. coli ~70-80% (uropathogenic strains with P-fimbriae for ascending infection); Klebsiella, Proteus, Enterococcus, Pseudomonas (esp. catheter-associated/nosocomial)
Ascending infection from bladder -> ureter -> kidney; occasionally haematogenous (S. aureus, especially with renal abscess)
Risk factors: obstruction (stone, stricture, BPH, tumour, pregnancy), vesicoureteric reflux, catheterisation, diabetes, immunosuppression, anatomical anomaly
Complicated pyelonephritis -> emphysematous pyelonephritis (gas-forming, esp. poorly controlled diabetes - necrotising, high mortality), renal/perinephric abscess

Clinical

Fever, rigors, loin pain/tenderness, nausea/vomiting +/- lower UTI symptoms
Sepsis features: tachycardia, hypotension, tachypnoea, altered mental state - calculate qSOFA/SOFA

Investigations

Urine MCS before antibiotics (do not delay antibiotics for results if septic)
Blood cultures if systemically unwell
FBE, UEC, CRP/lactate, VBG
Imaging (CT or ultrasound) if: failure to improve at 48-72h, recurrent pyelonephritis, suspected obstruction/stone, diabetes, immunosuppression, male, or severe sepsis at presentation
- Looks for obstruction, abscess, emphysematous change

Sepsis bundle first, regardless of source

Cultures, IV fluids, empirical IV antibiotics within 1h of recognised sepsis, lactate, source control

Empirical antibiotics - complicated UTI/pyelonephritis

IV gentamicin + amoxicillin, or IV ceftriaxone, per local guideline and resistance patterns; adjust once cultures return
Higher-dose beta-lactam regimens now recommended to ensure adequate tissue exposure against Enterobacterales
Step down to oral once afebrile and clinically improving (typically 48-72h)

Duration - shortened from historical teaching

5-7 days total if fluoroquinolone used, ~7 days for non-fluoroquinolone regimens once clinically responding - not the historical 10-14 days
Longer course (10-14 days) reserved for bacteraemia, abscess, or slow clinical response
Avoid fluoroquinolones if used in the preceding 12 months (resistance)

Source control - the step antibiotics cannot replace

Infected obstructed system -> urgent decompression - nephrostomy or ureteric stent, before/alongside antibiotics
Abscess >3-5 cm -> percutaneous drainage
Emphysematous pyelonephritis - aggressive resuscitation, urgent drainage +/- nephrectomy if extensive necrosis

Recurrent pyelonephritis -> renal scarring -> chronic kidney disease (esp. childhood VUR)
Renal/perinephric abscess, emphysematous pyelonephritis (diabetics)
Septic shock, AKI, DIC in severe urosepsis
Xanthogranulomatous pyelonephritis - chronic obstruction/infection, mimics renal malignancy

Uncomplicated pyelonephritis with prompt treatment - full recovery, no long-term renal impairment expected
Delayed/inadequate source control in an obstructed infected system - rapid progression to septic shock and death
Recurrent episodes warrant urological/renal tract assessment for an underlying structural cause

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