藤井 喜充, 神田 枝理子, 金子 一成

Yoshimitsu FUJII, Eriko KANDA, Kazunari KANEKO

関西医科大学小児科学講座

Department of Pediatrics, Kansai Medical University

キーワード : ultrasonography, hypertrophic pyloric stenosis, intestinal malrotation, intestinal atresia, necrotizing enterocolitis

新生児期に嘔吐と腹部膨満をきたす代表的な疾患の超音波像を解説する．1）肥厚性幽門狭窄症は，筋層部の厚さが4 mm以上で長さが15 mm以上の幽門輪が描出され，かつ胃内容物の通過を認めない場合に診断が確定する．胃拡張とともに幽門輪が右後方に移動するので，探触子の位置も移動が必要である．2）腸回転異常は中腸軸捻転をおこしていれば，whirlpool signがみられるので診断は容易である．Whirlpool signが陰性の場合は十二指腸水平脚の有無で診断するが，内容物の通過方向に矛盾のないことを確認する必要がある．3）十二指腸閉鎖では拡張した十二指腸下行脚を，胆嚢の左側で確認する．小腸閉鎖は閉鎖部位より口側の腸管が嚢胞状に拡張している像と，肛門側の虚脱した腸管が隣接している像がみられる．4）壊死性腸炎は腸管壁の浮腫状肥厚の中に，腸管壁内ガスの点状から顆粒状の高エコー像が確認される．求肝性の門脈内ガスの気泡はBモードで直接確認が可能で，腹側の肝実質に高エコー域としてトラップ像が出現する．これらの壁内点状高エコーと門脈内ガスは，Ｘ線では捉えられない疑診段階から，超音波検査であれば確認できる．

The abdominal ultrasonographic findings of neonates with vomiting and abdominal distension are presented. (1) Hypertrophic pyloric stenosis can be diagnosed if the muscular layer thickness is more than 4 mm with a length exceeding 15 mm at the pyloric ring and the passage of the gastric contents is disturbed. Because gastric dilatation causes the pyloric ring to move to the right posterior portion, the position of the probe must be adjusted accordingly. (2) Intestinal malrotation with midgut volvulus is easily diagnosed based on a positive “whirlpool sign.” In the absence of this sign, passage of the contents of the third portion of the duodenum in the normal direction rules out intestinal malrotation without midgut volvulus. (3) Duodenal atresia involving the second portion of the duodenum will causes enlargement of the left side of the gallbladder. In small intestinal atresia, the enlarged small intestine above the atresial site will have a common boundary with the collapsed gastrointestinal tract below this site. (4) Necrotizing enterocolits presents as multiple hyperechoic dots in the edematously thickened wall of the gastrointestinal tract. The dots represent foci of intestinal pneumatosis. Gas in the portal vein adjacent to the liver will also present as hyperechoic dots on B-mode, whereas gas trapped in the liver are visible as a ventral hyperechoic area of the liver parenchyma. Hyperechoic dots and portal vein gas are characteristic of the early stage of necrotizing enterocolitis. These findings can be detected by ultrasonographic examination while it is impossible to do so by X-ray.