MRIが診断に有用であった特発性縦隔血腫の1例

A Case of Spontaneous Mediastinal Hematoma Diagnosed by MR Imaging

　胸背部激痛を主訴に来院し，胸部CTにて後縦隔に腫瘤像を認め，経時的にMRIにて観察し血腫と診断した1例を経験した．症例は65歳，男性．高血圧，血液疾患などの既往はない．岸辺で投げ釣りをしていたところ，突然胸背部に激痛出現し救急搬入された．胸部X線写真では異常を認めなかったが，疼痛が3時間以上にわたり持続したため，胸部CTを施行したところ，気管分岐部以下のレベルで後縦隔に僅かに造影される腫瘤を認めた．経食道エコーでは左心房と下行大動脈間にlow echoic massを認めた．大動脈造影ではextravasationなどの所見なく，いずれの検査でも明らかな大動脈解離は認めなかった．後縦隔病変で確診所見が得られないため，経時的にMRIを施行し，T₁，T₂　imageの変化から血腫と診断した．特発性の縦隔血腫は非常に稀であり，また確定診断も困難なためMRIによる観察が極めて有用と考えられた．

A 65-year-old man was admitted to our hospital with acute onset of sharp tearing chest and back pain while he was fishing. Ile had no history of hypertension or hematological disorders. On examination, his blood pressure was 110/64mmHg and his heart rate was 117/ min with atrial fibrillation rhythm on electrocardio-gram. Chest X-ray films showed normal. Chest and back pain persisted over 3 hours and then computed tomography (CT) with intravenous contrast medium was carried out. It confirmed a slightly enhanced elliptic mass surrounding the esophagus and descending aorta at the posterior mediastinum. Transesophageal ultrasound examination showed a low echoic mass between the left atrium and the descending aorta. A digital subtraction aortogram performed 12 hours after onset showed no aortic abnormality. There was no evidence of intimal flap, false lumen or penetrating spot with these examinations.

We observed this lesion by magnetic resonance imag-ging (MRI) at both the acute and chronic phases. From changing patterns of spin echo images, this lesion wasdiagnosed as mediastinal hematoma. Spontaneous mediastinal hematoma is rarely encountered without any underlying disorders.

He was treated conservatively with no complication and remained well on follow-up 1 year later.

Thus MRI was an effective method for diagnosing this lesion.