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 : cystic renal disease of children, ultrasound, MCDK, ARPKD, ADPKD

腎嚢胞性疾患の診断のきっかけは，胎児超音波検査によるスクリーニング，奇形症候群や家族歴のある患児の腹部精査，尿路感染症，血尿，腹部腫瘤など様々である．腎嚢胞性疾患は，非遺伝性と遺伝性疾患の2つに大別される．非遺伝性の嚢胞性疾患として最も頻度が高いのは，多嚢胞性異形成腎（multicystic dysplastic kidney: MCDK）である．代表的な遺伝性嚢胞性疾患は，常染色体劣性多発性嚢胞腎（autosomal-recessive polycystic kidney disease: ARPKD）と常染色体優性多発性嚢胞腎（autosomal-dominant polycystic kidney disease: ADPKD）である．遺伝性嚢胞性疾患は，繊毛病のひとつと考えられている．画像診断検査は，超音波検査が第1選択であり，初期発見および診断，フォローアップに用いられる．特徴的な超音波所見がそれぞれの診断の中核となり，臨床症状，家族歴などを考慮して総合的に診断される．MCDKは，ぶどう房状の嚢胞の集簇であり，正常な腎実質は認めない．ARPKDとADPKDでは，腎のサイズや実質輝度，嚢胞の大きさや部位などのほか，さらに肝や膵臓などの腹部実質臓器の異常所見についても検索することが大切である．本稿では，代表的な腎嚢胞性疾患の超音波所見を中心に解説する．

Cystic renal disease is divided into two categories: non-hereditary and hereditary disease. The most common type of nonhereditary cystic renal disease is multicystic dysplastic kidney (MCDK). MCDK is a subtype of dysplastic kidney. Typical types of hereditary disease include autosomal recessive polycystic kidney disease (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD). Defects in the structure or function of primary cilia may lead to the development of various cystic renal disease including ARPKD, ADPKD, juvenile nephronophthisis, and congenital nephrotic syndrome. In general, imaging starts with ultrasound. The ultrasonographic findings of MCDK include multicystic structure with big and some smaller cysts that do not communicate and possibly some central echogenic, nondifferentiated tissue components. In ARPKD, ultrasound shows bilaterally enlarged cysts with increased echogenicity of renal parenchyma and small cysts (<3 mm). Histology demonstrates a fusiform dilatation of the collecting ducts and ductal plated malformation at the level of the liver resulting in hepatic fibrosis and Caroli disease. ARPKD has mutations identified in the PKHD1 gene. ADPKD is a ciliopathy that affects not only the kidneys and liver but also the pancreas. ADPKD has mutations identified in the PKD1 and PKD2 genes. Ultrasound shows multiple renal cysts without kidney enlargement. Ultrasound is useful for diagnosis of cystic renal disease. Familial and clinical inquiry will further help towards the diagnosis.