Diagnostic Ultrasound - Abdomen and Pelvis

Portal Vein Gas
TERMINOLOGY
Abbreviations
• Portal vein (PV)
Definitions
• Gas within portal venous system
IMAGING
General Features
• Best diagnostic clue
○ Bright reflectors in portal veins on grayscale or color
Doppler
• Location
○ Portal venous system, hepatic parenchyma
Ultrasonographic Findings
• Grayscale ultrasound
○ Highly reflective foci in portal venous system
– Move with portal venous blood
– Few to numerous, related to amount of gas
○ Poorly defined, highly reflective parenchymal foci
– Scattered small patches to numerous or large areas
• Pulsed Doppler
○ High-intensity transient signals (HITS)
– Strong spikes superimposed on portal venous flow
pattern
– Pinging sound from audible Doppler output
– May be more sensitive than CT for detection of subtle
portal venous gas
• Color Doppler
○ Bright reflectors in portal venous system
○ May be multicolored (twinkling artifact)
Imaging Recommendations
• Best imaging tool
○ Grayscale or color Doppler for initial detection
○ NECT/CECT to determine source of gas
DIFFERENTIAL DIAGNOSIS
Biliary Tract Gas
• Bright reflections in biliary tree, adjacent to portal vein
branches
• Central concentration, near porta hepatis
• Stationary; move only with altered patient position
Biliary Calculi/Parenchymal Calcifications
• Not in portal venous system
• Sharply defined, immobile
• Strong posterior acoustic shadowing
Parenchymal Abscess
• May produce ill-defined echogenic patchy area in liver
• Localized, not multifocal
Echogenic Hepatic Metastases
• Well-defined margins
PATHOLOGY
General Features
• Etiology
○ 3 basic gas sources
– Gas under pressure
– Intravasation through injured mucosa
– Gas-forming organisms
○ Serious, life-threatening causes
– Necrotizing enterocolitis
– Bowel ischemia/infarction
– Peritoneal space abscess/infected gallbladder/liver
abscess
– Necrotizing pancreatitis
– Malignancies involving bowel
○ Benign causes
– Gastric or bowel distension, especially colon
– Inflammatory bowel disease
– Gastric ulcer
– Interventions: Endoscopic biopsy, liver mass ablation,
gastric tube, post surgery
– Benign pneumatosis intestinalis: e.g., emphysema
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Related to underlying disorder
Demographics
• Age: Newborns to adults
Natural History & Prognosis
• Usually sign of serious condition
• Sometimes inconsequential finding
Treatment
• Related to underlying disorder
DIAGNOSTIC CHECKLIST
Consider
• Rule out other conditions mimicking portal venous gas
○ Biliary tract gas, biliary calculi or hepatic calcification
• Rule out potential life-threatening causes of portal venous
gas such as necrotizing enterocolitis or bowel infarction
Image Interpretation Pearls
• Bright reflectors in portal veins on grayscale or color
Doppler
SELECTED REFERENCES
1. Sadatomo A et al: Hepatic portal venous gas after endoscopy in a patient
with anastomotic obstruction. World J Gastrointest Surg. 7(2):21-4, 2015
2. Bohnhorst B et al: Portal venous gas detected by ultrasound differentiates
surgical NEC from other acquired neonatal intestinal diseases. Eur J Pediatr
Surg. 21(1):12-7, 2011
3. Shah PA et al: Hepatic gas: widening spectrum of causes detected at CT and
US in the interventional era. Radiographics. 31(5):1403-13, 2011
4. Franken JM et al: Hepatic portal venous gas. J Gastrointestin Liver Dis.
19(4):360, 2010
5. Abboud B et al: Hepatic portal venous gas: physiopathology, etiology,
prognosis and treatment. World J Gastroenterol. 15(29):3585-90, 2009
Diagnoses: Liver
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