Hepatic Gas: Widening Spectrum of Causes Detected at CT and US in the Interventional Era

Abstract

The spectrum of causes of hepatic gas detected at computed tomography (CT) and ultrasonography (US) is widening. There are many iatrogenic and noniatrogenic causes of hepatic parenchymal, biliary, hepatic venous, and portal venous gas. Hepatic gas may be an indicator of serious acute disease (infarct, infection, abscess, bowel inflammation, or trauma). In other clinical scenarios, it may be an expected finding related to therapeutic interventions (such as surgery; hepatic artery embolization for a tumor or for active bleeding in acute trauma cases; percutaneous tumor ablation performed with radiofrequency, cryotherapy, laser photocoagulation, or ethanol). In some cases, hepatic gas is an incidental finding of no clinical significance. Familiarity with the expanding list of newer intervention-related causes of hepatic gas detected at CT and US, knowledge of the patient's clinical history, and a careful search for associated clues on images are all factors that may allow the radiologist to better determine the clinical relevance of this finding.

Ultrasonographic differentiation between portal venous and parenchymal gas may be important for the prognosis of canine and feline hepatic emphysema: 37 cases

“…In human medicine, the detection of hepatic gas traditionally gives rise to concerns of serious disease with a high mortality rate, up to 75% . The gas is most often portal venous in location and it is considered a poor radiologic sign .…”

Hepatic Portal Venous Gas From Nonischemic Cause

“…Prognosis of the patient with this diagnostic sign is dependent on the insult that led to this finding. 3,8,9 In our patient, mesenteric ischemia seemed unlikely given his signs and symptoms, unremarkable lactate, and improving clinical status, while maintained on conservative treatments including fluids and antibiotics. Although liver abscess cannot be ruled out because of the limited noncontrast study, a more likely hypothesis is that a postoperative ileus caused increased intraluminal air to dissect into the surgically manipulated intestines, leading to these unusual radiological findings.…”

“…Iatrogenic causes have also been noted, which include surgical manipulation of gastrointestinal tract, endoscopic procedures, femoral central line placement, hepatic artery embolization, percutaneous tumor ablation, and most interestingly, cardiopulmonary resuscitation. 3,4 The nonischemic causes of HPGV carry a mortality rate of approximately 39%. 5 Although the exact mechanism of HPVG depends on the underlying initial insult, in most cases it is ischemic changes leading to intestinal mucosal damage and intestinal bacterial infection.…”

“…These luminal gases are primarily CO 2 and are easily reabsorbed in the portal system. 3,6 There are also case reports of patients with previous intestinal mucosal wall damaging conditions such as Crohn disease and was found to have developed HPGV after an episode of bowel obstruction. 7 Although the ischemic causes of HPGV warrant emergency surgery, the nonischemic HPGV cases have been noted to have good outcome when treated with conservative supportive treatment such as NGT gastric decompression and bowel rest.…”

Performance assessment of the Simplified Acute Physiology Score II, the Acute Physiology and Chronic Health Evaluation II score, and the Sequential Organ Failure Assessment score in predicting the outcomes of adult patients with hepatic portal venous gas in the ED

“…The SAPS II score is reported to provide an estimation of the risk of death without having to specify a primary diagnosis [13]. This is especially useful and practical for EPs in the prediction of the mortality rates of patients with HPVG in the ED because, in most situations, HPVG is revealed as a radiologic sign with no definite preliminary diagnosis [3,16,17]. Thus, the SAPS II score can be used in HPVG patients who are admitted to the ED even while their underlying etiology is not yet identified.…”