腹部単純写真図Aで腸管壊死を示唆する所見が3つある．遊離ガス（▲），肝内に樹枝状に広がる↑は胆管としてはやや細く，肝表面近くの末梢まで到達しているので門脈内ガス，△は壁内気腫である．CTでは図１と図２で遊離ガスがあり（G），↑は門脈内ガスである（下記文献参照）．図３でSMV（superior mesenteric vein：上腸間膜静脈）内にもガスを認め，図３〜図７の白矢印はその分枝内のガスである．肝臓は低濃度を示しアルコール性脂肪肝を意味する．図３〜図９の，ニボーを形成しない，腸管壁に沿った線状のガス像△はすべて小腸の壁内気腫であり，以上の所見から小腸の大量壊死と診断する．手術でTreitz靱帯から30cmの部位以下の全小腸が完全壊死に陥っていた．多臓器不全のため術後2日目に死亡した．下記参照症例で胆道内ガス（pneumobilia）を示す．

参考症例：49歳男性．上記症例同様アルコール依存症があり，1週間ほどほとんど食餌をとらず飲酒を続け，上腹部痛と嘔吐を訴え来院した．体温：37.5℃，腹部は腹膜刺激症状を認めた．肝内門脈内ガス（↑）と小腸壁内気腫（△）を認め，小腸壊死と思われる．IVCが極度に虚脱しており，小腸壊死の原因は強い脱水によるNOMI（non-occlusive mesenteric ischemia：非閉塞性腸間膜虚血）の可能性が高い．手術を拒否され翌日死亡した．

文献考察：門脈内ガス
１）Arch Surg. 2003 Dec;138(12):1367-70.
Hepatic portal gas in adults: review of the literature and presentation of a consecutive series of 11 cases.
Peloponissios N, Halkic N, Pugnale M, Jornod P, Nordback P, Meyer A, Gillet M.

BACKGROUND: Hepatic portal venous gas (HPVG) in adults is a rare entity. The underlying pathologic condition is usually an intestinal ischemia, but it has been reported in association with a variety of conditions. HYPOTHESIS: Miscomprehension of the underlying pathologic conditions has led to some confusion in the literature concerning its etiology, diagnostic methods, and clinical consequences. SETTING: Centre Hospitalier et Universitaire Vaudois, Lausanne, Switzerland, and District Hospital of Morges, Morges, Switzerland. METHOD: Between February 1, 1995, and May 30, 2000, eleven cases of HPVG were treated. These cases were retrospectively reviewed, together with a review of the literature to define the clinical significance of HPVG, the role of the computed tomographic scan, and the necessity of performing systematic emergency exploratory surgery. RESULTS: Two groups have to be distinguished-those who have HPVG with associated pneumatosis intestinalis and those who have HPVG without associated pneumatosis intestinalis. When associated with pneumatosis intestinalis, the cause is usually an intestinal ischemia and in a symptomatic patient it justifies systematic exploratory surgery. An abdominal computed tomographic scan including lung window settings to better identify air in the bowel wall will distinguish between these 2 groups. Pneumatosis intestinalis and HPVG due to bowel ischemia do not allow prediction of the severity of bowel wall damage. CONCLUSIONS: The cause of HPVG without pneumatosis intestinalis is variable. Good knowledge of the possible causes combined with the clinical picture and the abdominal computed tomographic scan is required to correctly identify the underlying cause of HPVG and to avoid unnecessary surgery.PMID: 14662541
追記：文献考察によると門脈内ガスの約75％は腸管壊死によるもの．腸管壁内ガスを伴う例は腸管壊死の可能性が極めて高く手術の適応である．腸管壊死以外の原因疾患は表１．胆管内ガスは胆汁の流れと逆方向へ上行してきたガスなので肝門部に限局し肝辺縁から２ｃｍ以内の末梢まで到達しない．他方門脈内ガスは門脈血の流れに沿って上行するので肝内の末梢まで広がり肝辺縁から２ｃｍ以内まで到達する．

２）Am J Emerg Med. 2004 May;22(3):214-8.
Hepatic portal venous gas: clinical significance of computed tomography findings.
Hou SK, Chern CH, How CK, Chen JD, Wang LM, Lee CH.

Hepatic portal venous gas (HPVG) is a rare radiographic finding of significance. Most cases with HPVG are related to mesenteric ischemia that have been associated with extended bowel necrosis and fatal outcome. With the help of computed tomography (CT) in early diagnosis of HPVG, the clinical outcome of patients with mesenteric ischemia has improved. There has been also an increasing rate of detection of HPVG with certain nonischemic conditions. In this report, we present two cases demonstrating HPVG unrelated to mesenteric ischemia. One patient with cholangitis presented abdominal pain with local peritonitis and survived after appropriate antibiotic treatment. Laparotomy was avoided as a result of lack of CT evidence of ischemic bowel disease besides the presence of HPVG. The other case had severe enteritis. Although his CT finding preluded ischemic bowel disease, conservative treatment was implemented because of the absence of peritoneal signs or clinical toxic symptoms. Therefore, whenever HPVG is detected on CT, urgent exploratory laparotomy is only mandatory in a patient with whom intestinal ischemia or infarction is suspected on the basis of radiologic and clinical findings. On the other hand, unnecessary exploratory laparotomy should be avoided in nonischemic conditions that are usually associated with a better clinical outcome if appropriate therapy is prompted for the underlying diseases. Patients with radiographic diagnosis of HPVG should receive a detailed history review and physical examination. The patient's underlying condition should be determined to provide a solid ground for exploratory laparotomy. A flow chart is presented for facilitating the management of patients with HPVG in the ED.PMID: 15138961
追記：腸管壁内ガスを伴う例は腸管壊死の可能性が極めて高く，手術の適応である．algorithm：表２．

３）門脈ガス血症を呈した後腹膜脂肪肉腫の1例(原著論文/症例報告)
　 Author：濱田賢司(松阪市民病院 外科), 高橋宏明, 岡村一則, 小坂篤, 勝田浩司
　 Source：日本臨床外科学会雑誌(1345-2843)64巻9号 Page2317-2321(2003.09)

要旨：門脈ガス血症本邦集計99例（表３）．腸管壊死によるものは59.6％，全体の死亡率は24.0％，腸管壊死や消化管穿孔例では35.4％．門脈内ガスの発生要因は，１．消化管粘膜の損傷（腸管梗塞，潰瘍など），２．消化管内圧上昇（消化管拡張），３．敗血症（血中におけるガス産生菌の存在，腸管壊死など）が重要視されている．本邦集計例で血液培養陽性例は11.1％で，菌の種類はE.coliとClostridiumが各4例と多く，次いでKlebsiella3例，Enterococcus1例であった．

４）急性虫垂炎穿孔と空腸壊死の合併により門脈ガス血症を認めた1例(原著論文/症例報告)
　 Author：花岡俊仁(住友別子病院), 鈴木栄治, 長井一信, 森秀暁, 藤井徹也, 川島邦裕, 石田数逸, 三原康生, 白川敦子
　 Source：外科(0016-593X)64巻2号 Page225-227(2002.02)

要旨：門脈ガス血症本邦集計79例．腸管壊死を伴うものは67％，腸管壊死を伴わない疾患は急性胃拡張，腹腔内膿瘍，急性虫垂炎穿孔，便秘による鼓腸，単純性イレウス，気腫性胆嚢炎，膵炎など．腸管壊死例の死亡率は40%であった．