余田 篤

Atsushi YODEN

大阪医科大学泌尿生殖発達医学講座小児科

Department of Pediatrics, Osaka Medical College

キーワード : children, congenital anomalies of the kidney and urinary tract (CAKUT), urinary tract infection, vesico-ureteral reflux (VUR), ultrasound

小児科領域の腎尿路疾患では，腫瘍性疾患よりも尿路奇形の合併が多く，しばしばスクリーニングでも尿路奇形が超音波で診断される．また，乳幼児の尿路感染症では先天性尿路奇形を高率に合併しやすいことが知られている．尿路奇形で超音波が診断に有用な疾患は，水腎症，水尿管，低形成腎・片腎・萎縮腎，馬蹄腎，重複腎盂・重複尿管，嚢胞性腎疾患，膀胱憩室，尿管瘤などがある．一方，乳児の発熱性疾患の5％前後が尿路感染症によるものであり，尿路感染症では超音波検査をすることが勧められる．尿路感染症に特異的な超音波所見は得られにくく，超音波の感度も特異度も低い．それでも尿路感染症で超音波が推奨される理由は，上記の先天性尿路奇形を有する患児は腎機能障害に進展しやすく，それらの尿路奇形を早期に診断することで慢性の不可逆性の腎機能低下を防ぐことである．尿路感染症では腎盂腎炎，急性巣状細菌性腎炎，腎膿瘍，膀胱炎などがあげられる．腎盂腎炎と急性巣状細菌性腎炎では，腎盂腎炎が重症化すると急性巣状細菌性腎炎となり，さらに進行して腎膿瘍となるといわれている．腎尿路の直接的な感染症ではないが，病原性大腸菌感染症に伴う出血性腸炎に合併する溶血性尿毒症症候群の腎症も忘れてはならない．これらの腎尿路疾患を早期診断するために，小児の不明熱や尿路感染症では早期の超音波検査が勧められる．

In renal urinary tract diseases in children, there are more complications related to kidney and urinary tract malformations than tumor diseases, and urinary tract malformations are frequently diagnosed by ultrasonography in screening. It is also known that children with urinary tract infections tend to have a high rate of coexisting congenital anomalies of the kidney and urinary tract. Ultrasonography is useful for diagnosis of urinary tract malformations, such as hydronephrosis, megaureter, hypoplastic and atrophic kidney, horseshoe kidney, duplicated renal pelvis/duplicate ureter, cystic kidney disease, bladder diverticulum, and ureterocele. On the other hand, it is known that about 5% of febrile diseases are urinary tract infections in infants, and sonographic evaluation is recommended for urinary tract infections. Sonographic findings specific to urinary tract infections are difficult to obtain, and the sensitivity and specificity of ultrasound are low. Nevertheless, ultrasound is recommended for urinary tract infections, because children with congenital urinary tract malformation tend to develop renal dysfunction. By diagnosing those urinary tract malformations early, we are able to prevent chronic irreversible renal dysfunction. Examples of urinary tract infections include pyelonephritis, acute focal bacterial nephritis, renal abscess, and cystitis. In the case of pyelonephritis and acute focal bacterial nephritis, severe pyelonephritis can progress to acute focal bacterial nephritis, and it is said that further progression results in renal abscess. We should not forget nephropathy in hemolytic uremic syndrome, which is complicated by hemorrhagic enterocolitis associated with pathogenic Escherichia coli infection. For early diagnosis of these urinary tract malformations, early sonographic examination is recommended for pediatric unknown fever and/or urinary tract infections. Ultrasonography is the first imaging modality in all children suspected of any urinary tract abnormality.