PNEUMOBILIA VS PORTAL VEIN GAS

NORMAL ANATOMY

BILIARY SYSTEM

PORTAL SYSTEM

PNEUMOBILIA Pneumobilia, also known as aerobilia, is

accumulation of air in the biliary tree.

CAUSES

Recent biliary instrumentation

ERCP

Percutaneous or intraoperative cholangiography

Incompetent sphincter of Oddi

Sphincterotomy (~ 50% have pneumobilia at 1 year)

Following passage of a gallstone

Scarring e.g. chronic pancreatitis

Drugs e.g. Atropine

Congenital(small amount of air only)

Biliary-enteric surgical anastomosis

Cholecystoenterostomy

Choledochoduodenostomy (with or without bile sump syndrome)

Whipple procedure

Spontaneous biliary-enteric fistula (cholecystoduodenal accounts for ~70% )

Gallstone ileus/ Bouveret's Syndrome

Peptic ulcer disease

Traumatic procedure

Neoplasm, eg. cholangiocarcinoma, ampullary cancer

Infection (rare)

Cholangitis

Emphysematous cholecystitis (usually gallbladder gas only, ~20% will have air in biliary tree also)

Liver abscess (if contains gas and communicates with biliary tree)

Bronchopleuralbiliary fistula (rare)

EMPHYSEMATOUS GB

CAUSES

All the causes of pneumobilia

Emphysematous cholecystitis >Gas forming organisms >Diabetes in 20% cases

_ Pneumobilia present in 20% cases only_ Erect Xray Abdomen may show air-bile

interface.

RIGLER’S TRIAD

A triad of these findings in gall stone ileus:

Pneumobilia Small bowel obstruction Gall stone in right iliac fossa

RADIOGRAPHIC FEATURES

Linear branching air within the liver most prominent in central large caliber ducts

PLAIN FILM

Saber sign > Supine radiographs __ sword-shaped

lucency in the right paraspinal region representing gas from the common bile duct and the left hepatic duct.

>Present in ~ 50% of patients with pneumobilia.

ULTRASOUND

Very sensitive in detecting gas within the liver

Regions of high echogenicity with prominent shadowing or reverberation.

Gas moves with change in patient’s position

Liver has a 'striped appearance'.

Multiple “comet tail” artifacts

Pseudopneumobilia Produced by periductal fat that normally

surrounds & parallels major biliary channels.

Continuous with extraperitoneal fat surrounding liver

Wider than non-obstructed biliary channels Less radiolucent than gas in biliary ducts Doesn’t involve intrahepatic portion of biliary

tree

CT Branching air-density regions within the liver.

Gas within the biliary tree tends to be more central.

Biliary gas is ante-dependent.

Typically fills the left lobe of the liver.

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DIFFERENTIAL DIAGNOSIS

Portal venous gas Patients usually very ill (e.g. ischemic bowel) Gas more peripheral in liver Doppler imaging may help

Hepatic artery calcification (on ultrasound)

Often seen in those with chronic renal failure Mimic pneumobilia on ultrasound

PORTAL VENOUS GAS The accumulation of gas in the portal vein

and its branches.

Gas shadows extend to within 2 cm of liver capsule. Might be present in portal and mesenteric veins and bowel wall.

PATHOPHYSIOLOGY

Some combination of Bowel distension Damage to mucosa Intra-abdominal sepsis

Mesenteric artery Mechanical

Occlusion obstruction.

Bowel wall necrosis

penetration of gas into

vessel wall

intrahepatic portal

venous gas

Infection of bowel wall

Bowel wall necrosis

penetration of gas into

vessel wall

portal venous gas

CAUSES

Child Umbilical vein catheterisation Necrotising enterocolitis (NEC) Neonatal gastroenteritis Erythroblastosis fetalis Postoperative finding in corrective bowel

surgery

AdultAlterations of bowel wall Ischaemic bowel (usually mural gas as well

as mesenteric gas : mortality of 75 - 90% : but gas is not an independent predictor)

Necrotic / ulcerated colorectal carcinoma (CRC)

Inflammatory bowel disease (IBD)

Perforated peptic ulcer

Bowel luminal distention Iatrogenic gastric and bowel dilatation (e.g

upper and lower endoscopic procedures, enemas)

Paralytic ileus / mechanical obstruction

Acute gastric dilatation (in bed ridden young people. Recovery

following decompression with NG tube)

Barotrauma

Intra-abdominal sepsis

Diverticulitis Pelvic abscess Cholecystitis and cholangitis Appendicitis Pancreatitis

Unknown mechanism

Pneumatosis intestinalis (primary) Chronic obstructive pulmonary disease

(COPD) Corticosteroid usage Pneumonia

CLINICAL FINDINGS

Will depend on the cause!

IMAGING FINDINGS

Can be diagnosed on conventional radiography, CT or ultrasound

Branching, air-containing structures near or at the periphery of the liver _from centrifugal flow of blood in portal vein

More air accumulates in left portal vein as it is more anterior, but air is seen more easily on plain films in right lobe of liver

Thinner lucencies than air in branches of biliary tree (pneumobilia)

PLAIN X-RAY ABDOMEN

ULTRASOUND

Ultrasound shows bright, echogenic foci in the periphery of the liver with centrifugal flow.

CT

Branching pattern of gas, distributed periphraly, reaching upto 2 cm of liver capsule

DIFFERENTIAL DIAGNOSIS

Pneumobilia

TREATMENT

Surgery __for ischemic bowel disease, especially for those with signs of perforation, sepsis or peritonitis.

PROGNOSIS

With bowel necrosis, mortality remains high (45-65%)

Without bowel necrosis, may spontaneously and quickly resolve without significant mortality.

PNEUMOBILIA VS PORTAL VENOUS GAS

A SIMPLE MNEMONIC

Portal venous gas = Peripheral Common bile duct gas = Central

FEW CASES