Imaging recommendation · Abdomen · Pelvis

Sepsis without identified source — imaging workup

Q: What's the alternative imaging for sepsis without identified source — imaging workup when endocarditis on differential (persistent bacteremia, valve risk)?

TTE → TEE if TTE negative (see endocarditis) (no contrast).

Q: What's the alternative imaging for sepsis without identified source — imaging workup when suspected meningitis / encephalitis?

CT — CT head before LP if focal deficit / altered (see meningitis-suspected) (no contrast).

Q: What's the alternative imaging for sepsis without identified source — imaging workup when necrotizing soft-tissue infection suspected?

CT — CT of involved area — gas in soft tissues, fascial thickening (see soft-tissue-infection) (iv contrast).

Q: What's the alternative imaging for sepsis without identified source — imaging workup when spinal epidural abscess / discitis (back pain + bacteremia)?

MRI — MRI total spine with contrast (see spinal-epidural-abscess, osteomyelitis) (iv contrast).

Q: What's the alternative imaging for sepsis without identified source — imaging workup when hardware infection (joint prosthesis, vascular graft)?

NM — FDG-PET-CT or labeled WBC scan (see pji, aortic-graft-infection) (iv contrast).

Recommended: CT chest/abdomen/pelvis with IV contrast is the preferred imaging study for sepsis without identified source — imaging workup. When the source isn't clinically obvious despite blood cultures, urinalysis, and chest X-ray.

Recommended study

CT chest/abdomen/pelvis with IV contrast

CT IV contrast Preferred Abdomen · Pelvis EmergencyAcute inpatient Reviewed 2026-05

When the source isn't clinically obvious despite blood cultures, urinalysis, and chest X-ray. CT CAP captures most occult abdominal sources (abscess, perforation, cholangitis, urinary), thoracic sources (empyema, lung abscess, mediastinal), and pelvic (PID, TOA). Add echo (TTE → TEE) for endocarditis when bacteremia + risk factors. Suspected meningitis: emergent CT head → LP.

If the default doesn't apply

Endocarditis on differential (persistent bacteremia, valve risk)

TTE → TEE if TTE negative (see endocarditis) No contrast

Suspected meningitis / encephalitis

CT CT head before LP if focal deficit / altered (see meningitis-suspected) No contrast

Necrotizing soft-tissue infection suspected

CT CT of involved area — gas in soft tissues, fascial thickening (see soft-tissue-infection) IV contrast

Spinal epidural abscess / discitis (back pain + bacteremia)

MRI MRI total spine with contrast (see spinal-epidural-abscess, osteomyelitis) IV contrast

Hardware infection (joint prosthesis, vascular graft)

NM FDG-PET-CT or labeled WBC scan (see pji, aortic-graft-infection) IV contrast

Watch-outs

Don't delay source control for imaging

Hemodynamically unstable + obvious abdominal source on exam → straight to OR, not imaging. Stabilize → image when feasible.

Gallbladder source — acalculous cholecystitis in ICU

Hard to diagnose — wall thickening, pericholecystic fluid, sludge on US. CT often shows it when US is equivocal.

Back pain + bacteremia = spine MRI

Spinal epidural abscess / discitis is missed without targeted MRI — clinical exam is often initially soft.

Pearls

CT yield for occult source in sepsis: ~30–40% identifies a previously unrecognized source.
Don't forget the gallbladder — CT often shows what bedside US misses in critically ill ICU patients.
Tubo-ovarian abscess: pelvic exam + transvaginal US in females; CT pelvis if US non-diagnostic.
Bacteremia + back pain: MRI spine within 24 h, regardless of how soft the exam seems.