Diagnostic Ultrasound - Abdomen and Pelvis

Portal Vein Gas
Diagnoses: Liver
TERMINOLOGY
• Gas within portal venous system
IMAGING
• Grayscale ultrasound
○ Highly reflective foci in portal venous system
– Move along with blood
○ Poorly defined, highly reflective parenchymal foci
– Scattered small patches to numerous or large areas
• Pulsed Doppler ultrasound
○ High-intensity transient signals (HITS)
– Strong transient spikes superimposed on portal
venous flow pattern
• Color Doppler ultrasound
○ Bright reflectors in portal venous system
TOP DIFFERENTIAL DIAGNOSES
• Biliary tract gas
• Parenchymal abscess
KEY FACTS
• Biliary calculi/parenchymal calcifications
• Echogenic hepatic metastases
PATHOLOGY
• Serious conditions
○ Necrotizing enterocolitis, bowel ischemia/infarction
• Benign conditions
○ Bowel distension, intervention-related, benign
pneumatosis intestinalis
CLINICAL ISSUES
• Often sign of serious condition; sometimes inconsequential
finding
DIAGNOSTIC CHECKLIST
• Rule out other conditions mimicking portal venous gas
○ Biliary tract gas, biliary calculi, or hepatic calcification
• Best imaging clue:Bright reflectors in portal veins on
grayscale or color Doppler
(Left) Oblique ultrasound of
the liver shows several
echogenic foci in the portal
vein ſt representing gas
bubbles. Brightly echogenic
patches st in the liver more
peripherally represent
parenchymal gas. (Right)
Oblique pulsed Doppler
ultrasound in the same patient
with portal venous gas shows
strong, high-intensity transient
signals (HITS) ſt that appear
as vertical spikes within the
main portal vein interrogation.
Spikes are in the same
direction as the flow direction
of the portal vein.
(Left) Oblique abdominal
pulsed Doppler ultrasound in a
patient with portal venous gas
secondary to small bowel
ischemia and pneumatosis
shows strong, high-intensity
transient signals (HITS) ſt
superimposed upon the main
portal vein waveform. (Right)
Axial NECT shows extensive
portal venous gas ſt
branching peripherally in the
portal veins of the liver.
Peripheral predominance of
portal venous gas helps
distinguish it from biliary gas,
which tends to be more
centrally located.
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