竹沢 亜美¹, 近藤 敦², 細川 満由¹, 三谷 尚弘¹, 門岡 みずほ¹, 水谷 佳世², 古澤 嘉明¹, 佐藤 弘之², 末光 徳匡¹

Ami TAKESAWA¹, Atsushi KONDO², Mayu HOSOKAWA¹, Takahiro MITANI¹, Mizuho KADOOKA¹, Kayo MIZUTANI², Yoshiaki FURUSAWA¹, Hiroyuki SATO², Tokumasa SUEMITSU¹

¹医療法人鉄蕉会亀田総合病院産婦人科, ²医療法人鉄蕉会亀田総合病院新生児科

¹Department of Obstetrics and Gynecology, Kameda Medical Center, ²Department of Neonatology, Kameda Medical Center

キーワード : mediastinal cyst, pericardial cyst, isolated pericardial effusion, prenatal ultrasound

胎児超音波検査において心臓周囲に低エコー域を認めた場合，心囊液貯留や縦隔囊胞性病変などが鑑別疾患として挙げられる．いずれの疾患も病変が著明に増大すると，周囲臓器を圧排し呼吸循環障害をきたすことがある．しかし両疾患の出生時の対応は大きく異なるため，胎児期の正確な評価が重要となる．今回，胎児期に心囊液貯留として妊娠および分娩管理を行ったが，出生後に縦隔囊胞性病変と診断された症例を経験した．27歳の1経産婦に対して胎児スクリーニング超音波検査を施行し，妊娠30週で初めて左心室周囲に幅 2 mmの低エコー域を認めた．胎児精密超音波検査で心臓構築を含めた形態異常，胎児水腫および心不全を疑う所見を認めなかったため孤発性心囊液貯留であると判断した．低エコー域は経時的に拡大し妊娠36週に左心室と左肺を圧排する所見を認めたため，出生後に心囊穿刺を行う体制を整え，妊娠37週2日に選択的帝王切開術を施行した．新生児の呼吸循環動態は気管内挿管で安定し，超音波検査で囊胞性病変と判断したため心囊穿刺は行わなかった．日齢3に胸部 MRI検査を施行し縦隔囊胞性病変と診断した．生後10か月で囊胞の増大はなく，無症状で経過している．胎児の心臓周囲に低エコー域を認めた場合，心囊液貯留のみならず縦隔囊胞性病変を鑑別に挙げて慎重に診断すべきである．

A hypoechoic free space around the fetal heart can be differentiated with ultrasonography as pericardial effusion or a mediastinal cyst. Respiratory or circulatory failure may occur if the space becomes so enlarged as to put pressure on the heart and lungs. We report a case diagnosed with a neonatal mediastinal cyst after management as isolated pericardial effusion in pregnancy. The patient was 27 years old (para 1). A hypoechoic free space with a width of 2 mm around the left ventricle was detected on fetal ultrasonography at 30 weeks of gestation. The case was diagnosed as isolated pericardial effusion not complicated by fetal structural abnormalities or hydrops. Nevertheless, the hypoechoic area increased in size to 15 mm at 36 weeks of gestation, pressing on the left ventricle and the left lung; thus, a caesarean section was performed at 37 weeks and 2 days of gestation, while preparing for emergency pericardiocentesis. The neonate was stable with intubation, and a neonatal ultrasonographic examination showed the cystic lesion, which was recognized as fetal pericardial effusion; therefore, pericardiocentesis was not performed. A chest MRI diagnosed the mediastinal cyst 3 days after birth. The size of the cyst was unchanged, with no symptoms for 10 months. If a hypoechoic free space around the fetal heart is detected, we should carefully make the diagnosis, including mediastinal cyst in addition to pericardial effusion in the differential diagnosis.