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A man with abdominal pain

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Q1: What is the unusual feature on the plain abdominalx-ray?

The plain abdominal x-ray shows the presence of hepatic-portal venous gas (HPVG) (fig 2). The distribution of gas is towards the periphery of the liver, as opposed to gas in the biliary tree which is central in distribution. Distended loops of small bowel are also present.

Q2: What are the causes of this feature?

The conditions in which HPVG has been reported are listed in box 1.1 2

Q3: Is laparotomy indicated

The patient underwent laparotomy, which revealed ischaemic bowel in the distribution of the superior mesenteric artery. Attempts to revascularise the bowel failed and the patient died in the early postoperative period.

Box 1: Reported causes of HPVG

Non-iatrogenic
  • Necrotic bowel (72%)

  • Ulcerative colitis/Crohn's disease (8%)

  • Intra-abdominal abscess (6%)

  • Bowel obstruction (3%)

  • Peptic ulcer

  • Acute haemorrhagic pancreatitis

  • Diabetic ketoacidosis

  • Necrotising enterocolitis

  • Unknown

    Iatrogenic
  • Recent contrast enema

  • Endoscopy/ERCP

  • Recent liver transplantation

HPVG is not a specific disease entity and is merely another diagnostic clue in patients with acute abdominal pathology. HPVG is associated with various diverse conditions and its importance must be derived from the clinical context of the patient.

Treatment is therefore directed at the underlying cause. The majority of patients will have ischaemic bowel (72%) and will require exploratory laparotomy. However, patients with ulcerative colitis without other indication for laparotomy will not require exploration.3

Discussion

HPVG is an uncommon x-ray finding. It was first described in infants in 19551 and in adults in 1960.4 It appears as a branching radiolucency extending to within 2 cm of the liver capsule and x-rays are most revealing when taken in the left lateral decubitus position. The difference in distribution of gas in the biliary tree and portal venous gas is due to the fact that gas in the biliary tract is carried towards the porta hepatis by the centripetal flow of the bile and therefore appears central in the liver while the HPVG travels peripherally enhanced by the centrifugal flow of the blood.4

The factors that are thought to predispose to HPVG are5: mucosal damage, as seen in intestinal infarction, inflammatory bowel disease, and peptic ulcer disease; bowel distension as in small bowel obstruction; and sepsis due to bowel necrosis, spreading cellulitis or intra-abdominal abscess, although these factors are not identified in every patient.

With the increased use of computed tomography and ultrasound, HPVG has also been reported from iatrogenic causes, most of which will not require laparotomy,2 eg, recent contrast enema, endoscopy, ERCP, and post-liver transplantation.

Box 2: Learning points

  • HPVG on plain abdominalx-ray is uncommon.

  • The x-ray pattern of HPVG must be differentiated from that of biliary tract gas.

  • HPVG can be found in a variety of clinical settings.

  • The need for laparotomy is determined from the clinical context of the patient.

Final diagnosis

Hepatic-portal vein gas due to ischaemic bowel.

References

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