What are the diagnostic criteria for urosepsis according to the Sepsis‑3 definition and the older SIRS criteria?

Urosepsis Diagnostic Criteria

Urosepsis is diagnosed using the Sepsis-3 definition: life-threatening organ dysfunction (SOFA score increase ≥2 points) caused by a dysregulated host response to a urogenital tract infection. 1, 2

Sepsis-3 Criteria (Current Standard)

The modern diagnostic framework requires both components:

1. Documented or Suspected Urogenital Infection

• Positive urine culture or clinical evidence of urinary tract infection 1, 3
• Common sources include obstructive uropathy (ureterolithiasis most common), catheter-associated UTI, pyelonephritis, or post-operative urological infections 4, 5

2. Life-Threatening Organ Dysfunction

• SOFA score increase ≥2 points from baseline (associated with >10% in-hospital mortality) 1, 2
• The SOFA score assesses six organ systems with the following thresholds 2:
  • Respiratory: PaO₂/FiO₂ <300 or SpO₂ ≤90%
  • Cardiovascular: Hypotension (SBP <90 mmHg or MAP <70 mmHg) or vasopressor requirement
  • Renal: Creatinine >2.0 mg/dL or urine output <0.5 mL/kg/h for ≥2 hours
  • Hepatic: Bilirubin >2 mg/dL
  • Coagulation: Platelets <100,000/μL or INR >1.5
  • Neurological: Altered mental status or decreased Glasgow Coma Scale

Quick SOFA (qSOFA) for Rapid Bedside Screening

• Any 2 of 3 criteria suggest high risk and warrant full SOFA assessment 1, 2:
  • Respiratory rate ≥22 breaths/min
  • Altered mental status
  • Systolic blood pressure ≤100 mmHg

The qSOFA has excellent specificity (91.30%) and sensitivity (74.17%) for predicting mortality in urosepsis, with an AUC of 90.3% 6. However, qSOFA should not replace conventional triage protocols as it may miss early sepsis cases 6.

Septic Shock Criteria (Subset of Urosepsis)

Septic shock is diagnosed when urosepsis criteria are met plus either 2:

• Persistent hypotension requiring vasopressors to maintain MAP ≥65 mmHg after adequate fluid resuscitation, OR
• Serum lactate >4 mmol/L (or >2 mmol/L in some definitions)

Older SIRS Criteria (Discontinued for Sepsis Classification)

The Sepsis-3 guidelines explicitly discontinued SIRS criteria for classifying sepsis, though SIRS may still serve as an early screening tool 2. The historical SIRS criteria required ≥2 of the following 6:

• Temperature >38°C or <36°C
• Heart rate >90 bpm
• Respiratory rate >20 breaths/min or PaCO₂ <32 mmHg
• WBC >12,000/μL or <4,000/μL or >10% bands

Critical limitation: SIRS has poor specificity (24.1%) for urosepsis, as many catheterized ICU patients have positive urinalysis without true urosepsis 7.

Adjunctive Diagnostic Tools

Procalcitonin (PCT)

• PCT ≥1.5 ng/mL has 100% sensitivity and 72% specificity for sepsis 2
• PCT demonstrates excellent performance in urosepsis: 69.57% specificity and 77.33% sensitivity for predicting mortality 6
• PCT >2 SD above normal supports sepsis diagnosis when SOFA cannot be fully calculated 2

Imaging for Source Identification

• Ultrasound is the first-line imaging modality for suspected urosepsis due to portability and rapid acquisition 1, 3
• If ultrasound is negative or equivocal, proceed immediately to CT abdomen/pelvis with IV contrast (81.82% positive predictive value for identifying septic foci) 1, 2
• Major abnormalities (pyonephrosis, renal calculi) are found in 32% of imaged urosepsis patients, with 13% requiring urological intervention 1

Blood and Urine Cultures

• Obtain before initiating antibiotics 3
• Paired blood cultures from different sites plus urine culture with antimicrobial sensitivity testing 3
• Sensitivity: 100% of urosepsis patients have positive urinalysis and urine culture, but specificity is only 24.1% for urinalysis and 70.8% for urine culture 7

Common Pitfalls to Avoid

• Do not rely on SIRS criteria alone for sepsis diagnosis—they have been replaced by organ dysfunction-based criteria 2
• Do not delay imaging in suspected urosepsis; 9.5% of patients without initial imaging are readmitted within one year with recurrent urosepsis 1
• Do not use chest radiography alone for source identification—sensitivity is only 58% for pneumonia in septic patients 1, 2
• Do not wait for full SOFA calculation if qSOFA is positive—initiate empiric treatment immediately while completing assessment 1, 5
• Recognize age as a risk factor: urosepsis incidence increases significantly in patients >60 years, with average age of 69 years in septic shock and 71 years in deceased patients 6, 7