Cystic renal disease is divided into two categories: non-hereditary and hereditary disease. The most common type of non-hereditary 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, non-differentiated 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.

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Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common causes of advanced chronic kidney disease (CKD) in children. CAKUT should be diagnosed as early as possible to prevent the renal damage caused by urinary tract obstruction, vesicoureteral reflux, and/or febrile urinary tract infection. As such, ultrasonography is the most useful and minimally invasive tool for diagnosing CAKUT, and also essential for assessing treatment efficacy and evaluating outcomes in those children. Furthermore, we discuss the clinical guidelines on ureteropelvic junction obstruction (UPJo) and vesicoureteral reflux (VUR) published simultaneously by the Japanese Society of Pediatric Urology in 2016.

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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.

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This report summarizes the role of ultrasonography in the diagnosis of commonly encountered disorders in the field of pediatric urology, and outlines the surgical treatments provided by pediatric urologists. Transvesical laparoscopic surgery for vesicoureteral reflux and ureterovesical junction obstruction, and reduced port surgery for ureteropelvic junction obstruction, are described. Surgical procedures for diseases of the scrotum and how to determine when they are indicated are also outlined.

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Purpose: The application of elastography in breast ultrasound is expanding. However, optimal cutoff values are not known for Elasticity Index (E-Index) and Elasticity Ratio (E-Ratio) on the LOGIQ E9 (GE Healthcare). The purpose of this study is to determine appropriate cutoff values. Subjects and Method: We retrospectively evaluated values for 50 consecutive benign lesions and 50 invasive cancers dating from March 2015. The Youden index was estimated for both E-Index and E-Ratio. Results and Discussion: The optimum cutoff value for E-Index was 3.15. The optimum cutoff value for E-Ratio was between 2.95 and 3.1. We think it reasonable to set the E-Index and E-Ratio to 3 for routine clinical examinations. The optimal cutoff value of fat-to-lesion strain ratio (FLR) (Hitachi) has been suggested to be 4.3 to 5. Although both FLR and E-Ratio are values that reflect the difference in elasticity between fat and lesions, the results of E-Ratio in this study are different from FLR. Conclusion: Users should be aware that optimal cutoff values vary by device.

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Background and purpose: Chronic kidney disease is a risk factor for cardiovascular disease (CVD). Renal resistive index (RI) measured by Doppler ultrasonography is associated with renal impairment. We investigated the relationship between RI and cardiac function, and evaluated the utility of RI for predicting cardiac events in patients with CVD. Methods and results: Renal Doppler ultrasonography and echocardiography were performed in a total of 452 patients with CVD. Correlations of RI with serum creatinine and estimated glomerular filtration rate (eGFR) were significant but not strong (r=0.37, p⟨0.001; r=-0.42, p⟨0.001, respectively). RI correlated positively with age, left atrial volume index, left ventricular mass index, and early transmitral velocity to mitral annular early diastolic velocity (e′) ratio (E/e′), and showed significant negative correlations with e′ and diastolic blood pressure. Between two subgroups-112 patients hospitalized with cardiovascular events (Group A) and 200 age- and eGFR-matched controls (Group B)-RI was significantly higher in Group A than in Group B, although age and eGFR were similar. Conclusions: RI reflects the impairment of intrarenal hemodynamics that cannot be adequately elucidated by eGFR alone. Assessment of renal RI may be useful in conjunction with prognostic estimates for patients with CVD.

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