Intramural hematoma of the descending colon with intraperitoneal hemorrhage: a case report

　結腸壁内血腫は稀な疾患で，全消化管壁内血腫の4.4％とされている．消化管壁内血腫の原 因は外傷や抗血栓療法関連が多く，特発性は全体の1.1％とされている．医学中央雑誌では，結腸 壁内血腫の本邦報告例は29例で，そのうち腹腔内出血と関連した報告は３例のみである．誘因なく腹腔内出血を来した下行結腸壁内血腫の１例を報告する．症例は70歳台男性，X 月 X 日に明らかな誘因なく左側腹部痛を自覚した．様子をみたが改善なく翌日近医受診し，CT で下行結腸腫瘤 と腹水貯留を認め当院搬送された．当院の腹部超音波検査では，下行結腸内腔を圧排する粘膜下腫 瘍形態の境界明瞭な約70mm の腫瘤を認め，腸管壁と不可分であった．腫瘤内部は無エコー～高エコーが混在しており，color Doppler imaging で血流信号は認められず，腹腔内腫瘍の腸管浸潤を疑った．また，汎発性腹膜炎と腹腔内出血を認めた．造影 CT で，下行結腸腸管壁に連続した筋肉よりもわずかに低吸収の造影効果のない腫瘤と，腫瘤近傍に紡錘状の動脈瘤が認められた．腹腔内出血と結腸壁内血腫の疑いの診断で，同日緊急外科的治療が行われた．術中所見は，腹腔内に鮮紅色の血性腹水が貯留し，下行結腸の壁内血腫漿膜側が穿破し，同部から出血していた．手術標本では，血腫は粘膜下層から漿膜下層に認められ，主体は漿膜下層であった．明らかな動脈硬化性変化は認められなかった．結腸壁内血腫は粘膜下腫瘍形態を呈し，保存的加療が原則とされるが，腸閉塞，腹腔内出血，出血性ショックを伴うこともあり，その場合は外科的治療が選択される．診断は 造影 CT が有用である．腹部超音波所見では，粘膜下腫瘍形態で，腫瘤内に血流信号が認められないことが鑑別の一助となる可能性がある．本症例では，病歴や画像所見および組織学的所見から， 病態背景に分節性動脈中膜融解が存在していた可能性がある．　Intramural hematoma of the colon is a rare disease, accounting for 4.4% of all gastrointestinal intramural hematomas. The causes of these gastrointestinal intramural hematomas are mostly related to trauma and antithrombotic therapies and might be idiopathic in approximately 1.1% of the cases. A search of the Ichu-Shi Web (Japana Centra Revno Medicia, Japan Medical Abstract Society) database yielded 29 reported cases of intramural hematoma of the colon, of which only 3 cases were associated with intraperitoneal hemorrhage in Japan. Here we report a case of intramural hematoma of the descending colon that caused intraperitoneal hemorrhage without a history of trauma or antithrombotic therapy. The patient was a male in his 70s who presented to a local hospital complaining of left abdominal pain of sudden onset a day prior without any apparent trigger. Computed tomography (CT) revealed a mass in the descending colon and ascites, and he was referred to our hospital. In our hospital, abdominal ultrasonography (US) revealed a well-defined mass of approximately 70 mm, similar to the form of a submucosal tumor (SMT) that compressed the lumen of the descending colon and was inseparable from the intestinal wall. The mass was non-echoic and hyperechoic, and no blood flow signal was observed with color Doppler imaging. An intra-abdominal tumor infiltration into the colon wall was suspected. In addition, generalized peritonitis and intraperitoneal hemorrhage were observed. Contrast-enhanced CT (CE-CT) showed a mass with slightly lower density than that of the muscles, which continued with the intestinal wall of the descending colon and a spindle-shaped aneurysm in the vicinity of the mass. With a diagnosis of intramural hematoma of the descending colon complicated by peritoneal hemorrhage, an emergency surgical treatment was performed. Intraoperative findings showed that bloody red ascites had accumulated in the abdominal cavity, the serosa of the intramural hematoma of the descending colon was ruptured, and bleeding continued from the same site. Histology of the surgical specimen revealed that the hematoma was located from the submucosa to the subserosal layer, and the main component was located in the subserosal layer. There were no apparent arteriosclerotic changes in the surgical specimen. Intramural hematoma of the colon presents with SMT morphology and is generally treated conservatively. However, it may be accompanied by a gastrointestinal obstruction, intraperitoneal hemorrhage, and hemorrhagic shock, in which case surgical therapy is selected. CE-CT is useful for diagnosis. US shows an SMT morphology, and the absence of blood flow signals inside the mass may help in its differentiation. Based on the patient’s history, findings from imaging examinations, and histological findings, segmental arterial mediolysis might have been present in the pathological background of this patient