宮坂 実木子

Mikiko MIYASAKA

国立成育医療研究センター放射線診療部

Department of Radiology, National Center for Child Health and Development

キーワード : children, ultrasound, normal variations, urinary tract infection, congenital urinary tract anomalies

超音波検査は，小児腎泌尿器疾患に対して第1選択となる画像診断検査である．検査目的は，尿路感染症，血尿，尿失禁，胎児水腎症，神経因性膀胱の精査など様々であり，腎尿路奇形のスクリーニングは大切である．尿路奇形は，超音波のみで診断可能なものが多い．主な尿路奇形は，尿路拡張する疾患であり，腎盂尿管移行部狭窄，膀胱尿管移行部狭窄，膀胱尿管逆流，重複腎盂尿管などである．また，超音波は，診断のみでなく経過観察としても用いられ，有用である．ただし，小児は，成長過程であるため，腎のサイズや実質輝度などが年齢に応じて変化する．また，いくつかの正常変異もあり，病変と間違わないように注意する必要がある．日常診療で遭遇する頻度の高い尿路感染症は，膀胱尿管逆流による上行感染によるところが多い．膀胱尿管逆流の診断は，透視下の排尿時膀胱尿道造影によるが，放射線被ばくも考慮され，その適応が見直されている．そのため，尿路感染症に対する超音波所見が次なる検査を決定する上で，重要な役割を担うようになっている．今回は，年齢に応じた正常変化および正常変異，日常診療で頻度の高い尿路感染症に対する超音波所見と関連する尿路奇形について解説する．

Ultrasound is a valuable tool for urinary tract diseases in pediatric patients. One of the most important features of ultrasound is its lack of ionizing radiation. Another advantage of ultrasound in the pediatric population is its excellent resolution, which is related to the size of the patients and the smaller amounts of body fat. Therefore, higher transmitted frequencies provide better image resolution. Recently, ultrasound has played an increasingly important role in urinary tract disease, particularly the evaluation of urinary tract infection. After revision of the guideline in 2011, the strategy of diagnostic imaging has changed. Use of voiding cystourethrography has decreased, and more emphasis is placed on ultrasonographic findings to determine the need for additional examinations. Normal neonate kidneys have unique features that differentiate them from the kidneys of older children and adults. For example, the echogenicity of the renal cortex is greater than or equal to that of the liver or spleen, whereas in older children and adults the cortex is hypoechoic relative to these structures. Moreover, there are some anatomic variations such as fetal lobulation or cortical fusion. It is important to understand these normal variations in diagnosis. The normal variations of kidneys and ultrasonographic findings of urinary tract infection including urinary tract anomalies are reviewed in this article.