図３〜図７の▲は壁が平滑な楕円形を示し胆嚢であるが，図６〜図１０の↑は辺縁が不整で胆嚢周囲膿瘍と読影すべきである．経皮的にドレナージし（図A）約20mlの黄白色膿が採取され，造影で胆嚢や周囲腸管との交通を確認できなかった．膿培養でcitrobacter freundiiが検出された．上下消化管内視鏡検査で異常を認めず胆嚢炎穿孔による周囲膿瘍の可能性が高い．

参考症例：40歳男性．1週間前から右上腹部痛と発熱がある．当日高熱を発し嘔吐したので来院．体温：37.9℃，右上腹部に圧痛がある．胆嚢が位置すべき部位に多胞性嚢胞性病変を認める（↑）が，胆嚢がどれか指摘できない．臨床的経過と所見も考慮し胆嚢周囲膿瘍と診断し，エコーガイド下に穿刺したら膿が採取され経皮的経肝的膿瘍ドレナージを施行し（図１０と図１１），後日萎縮した胆嚢を切除した．

文献考察：胆嚢穿孔
１）Ahrendt SA，Pitt HA．Biliary Tract．In：Sabiston's Textbook of Surgery，16th Ed．WB Saunders，Philadelphia．1597-1641．2004．

２）Radiographics. 2004 Jul-Aug;24(4):1117-35.
From the RSNA refresher courses: imaging evaluation for acute pain in the right upper quadrant.
Hanbidge AE, Buckler PM, O'Malley ME, Wilson SR.

Acute cholecystitis is the most common cause of acute pain in the right upper quadrant (RUQ), and urgent surgical removal of the gallbladder is the treatment of choice for uncomplicated disease. However, cross-sectional imaging is essential because more than one-third of patients with acute RUQ pain do not have acute cholecystitis. In addition, patients with complications of acute cholecystitis, such as perforation, are often best treated with supportive measures initially and elective cholecystectomy at a later date. Ultrasound (US) is the primary imaging modality for assessment of acute RUQ pain; US is both sensitive and specific in demonstrating gallstones, biliary dilatation, and features that suggest acute inflammatory disease. Occasionally, additional imaging modalities are indicated. Computed tomography is valuable, especially for confirming the extent and nature of the complications of acute cholecystitis. Magnetic resonance cholangiopancreatography is helpful in complicated ductal disease (eg, recurrent pyogenic cholangiohepatitis) when more detailed diagnostic information is required for treatment planning, whereas endoscopic retrograde cholangiopancreatography is used when biliary intervention is required (eg, treatment of choledocholithiasis). Successful imaging with all modalities requires familiarity with both the characteristic and the unusual features of a wide variety of pathologic conditions. In addition, potential pitfalls must be recognized and avoided（full text）.PMID: 15256633

上記2文献のまとめ：急性胆嚢炎の合併症として胆嚢穿孔は約10％に起こる．Niemeierの分類により，Type I：汎発性腹膜炎となるfree perforation（acute perforation：10〜30％），Type II：最も多い（50〜60%）穿孔の起こり方で，局所穿孔と胆嚢周囲膿瘍形成（pericholecystic abscess：subacute perforation），Type III：周囲管腔臓器（十二指腸が最も多い）への穿通および瘻孔形成（chronic perforation：20〜30％ ）に分類される．高齢者ではType Iが多いので注意を要する．死亡率は19〜24％．