本間 千夏, 西村 陽子, 古谷 菜摘, 近藤 春裕, 長谷川 潤一, 鈴木 直

Chika HOMMA, Yoko NISHIMURA, Natsumi FURUYA, Haruhiro KONDOU, Junichi HASEGAWA, Nao SUZUKI

聖マリアンナ医科大学・産婦人科学

Department of Obstetrics and Gynecology, St. Marianna University School of Medicine

キーワード : retained placenta, placenta accreta, ultrasonography, SMI

微細超音波ドプラ法SMI （Super-microvascular imaging, Canon medical systems）では，微細な末梢血管まで描出でき，胎盤の3次絨毛付近まで検出できる．そのため我々は，胎盤の病理像を超音波断層法で評価することを試みている．分娩後の胎盤娩出困難例に対して，本法で遺残している固着胎盤と癒着胎盤を区別できる可能性のある所見を認めたので報告する．1妊0産，前医で妊娠38週に陣痛発来の後，分娩に至った．胎盤が娩出されず用手剥離を行ったが不成功で，産褥3日目に麻酔下に胎盤を半分程度娩出し，産褥6日目に発熱を認めたため当院へ搬送となった．Bモードでは子宮筋層はすべてに部位で厚く子宮収縮した状態で，欠損，菲薄化はなかった．子宮内に4cm大の胎盤と考えられる，やや高エコーの腫瘤像が認められた．SMIで子宮筋層から絨毛間腔への血流はすべての胎盤付着面で観察でき，固着胎盤であると判断した．脊椎麻酔，超音波ガイド下に胎盤鉗子を用いて牽引すると胎盤をスムーズに娩出できた．実際癒着胎盤があれば，子宮筋層と絨毛が一塊となっているため，絨毛間腔の血流が減弱している可能性がある．その場合，SMIで絨毛間腔を流れる母体血流の散乱像を描出できず，無エコーになると考えられる．胎盤娩出困難例に対する治療戦略において，胎盤が遺残しているだけの固着胎盤と癒着胎盤を鑑別できることの臨床意義は大きい．その鑑別において，SMIを用いて子宮筋層から絨毛間腔へ流入する血流を評価することが一助になると考えられた．

Superb Microvascular Imaging (SMI; Canon Medical Systems) can be used to detect minute vessels, which allows us to demonstrate pathological findings of the placenta antenatally. We report a case in which the placenta was not completely expelled for 6 days after delivery, and which was diagnosed as simple retained placenta not on the placenta accreta spectrum using SMI. On gray-scale ultrasonography, the entire uterine myometrium was thick and contracted without defect or thinning. A slightly hyperechoic mass image (placenta 4 cm in size) was found in the uterus. Scatter image indicated the maternal blood flow in the intervillous space could be depicted on all the maternal placental surface without any defects. Ultrasound diagnosis of simple retained placenta not on the placenta accreta spectrum was made, and we attempted placental manual removal under spinal anesthesia. Using placental forceps, placental tissue was detached easily and was completely removed. In the case of placenta accreta spectrum, invasion of placental tissue into the uterine myometrium is so great that a narrow intervillous space and reduced blood flow in the intervillous space may be observed. During investigation with SMI at such sites, a blood flow defect from the uterine myometrium to the intervillous space would be observed. In this case, since such flows were preserved, we could make the diagnosis of retained placenta without placental invasion. When making the diagnosis and determining the treatment strategy in patients with retained placenta, it would be helpful to evaluate the blood flow from the uterine myometrium into the intervillous space using SMI.