Among the various emergency diseases in children, acute pulmonary and airway disease are common clinical conditions encountered by radiologists, and the first imaging modality is chest radiography. Therefore, it is important to be familiar with these diseases and their imaging findings. In this article, we review pneumonia and mimickers of acute pulmonary disease. For acute airway disease, we reviewed croup, acute epiglottitis, tracheomalacia, asthma, postinfectious bronchiolitis obliterans, and foreign body aspiration. We hope this review of special diseases can help the diagnosis and treatment in children.

Purpose: This study compared clinical and radiologic differences between cystic biliary atresia (cBA) and choledochal cyst (CC) type Ia/b. Methods: Infants (≤12 months old) who were diagnosed with cBA or CC type Ia/b from 2005 to 2019 were retrospectively reviewed. Imaging features on preoperative ultrasonography (US) and magnetic resonance imaging (MRI) were compared between the cBA and CC groups. Logistic regression and area under the receiver operating characteristic curve (AUC) analyses were performed for the diagnosis of cBA. Changes in cyst size were also evaluated when prenatal US exams were available. Results: Ten patients (5.5% of biliary atresia cases) with cBA (median age, 48 days) and 11 infants with CC type Ia/b (Ia:Ib=10:1; median age, 20 days) were included. Triangular cord thickness on US (cutoff, 4 mm) showed 100% sensitivity and 90.9% specificity (AUC, 0.964; 95% confidence interval [CI], 0.779 to 1.000) and cyst size on MRI (cutoff, 2.2 cm) had 70% sensitivity and 100% specificity (AUC, 0.900; 95% CI, 0.690 to 0.987) for diagnosing cBA. Gallbladder mucosal irregularity on US and an invisible distal common bile duct on MRI were only seen in the cBA group (10 of 10). Only the CC group showed prenatal cysts exceeding 1 cm with postnatal enlargement. Conclusion Small cyst size (<1 cm) on prenatal US, triangular cord thickening (≥4 mm) and gallbladder mucosal irregularity on postnatal US, and small cyst size (≤2.2 cm) and an invisible distal common bile duct on MRI can discriminate cBA from CC type Ia/b in infancy.

Purpose: To compare the Doppler sonographic findings of the left renal vein (LRV) of children diagnosed with nutcracker syndrome with and without orthostatic proteinuria. Methods: Fifty and 53 consecutive children with and without orthostatic proteinuria, respectively, underwent renal Doppler ultrasonography examinations. The peak velocity (PV) was measured at the hilar portion of the LRV and between the aorta and superior mesenteric artery. Renal Doppler ultrasonography findings and clinical data including urine protein-to-creatinine ratio (UPCR) were compared according to the presence or absence of orthostatic proteinuria. Results: Between the two groups, no significant differences were observed in terms of age or sex. The PV ratio between the aortomesenteric and hilar portions was 7.79±2.65 and 6.32±3.01 in children with and without orthostatic proteinuria, respectively (P=0.009). No significant differences were observed between the two groups in terms of the UPCR in the first morning urine sample. However, the UPCR in the afternoon urine sample was significantly higher in children with orthostatic proteinuria than in those without orthostatic proteinuria (0.49±0.46 vs. 0.11±0.04 mg/mg, P<0.001). Furthermore, the PV ratio between the aortomesenteric and hilar portions revealed a positive correlation with the ratio of UPCR of the afternoon and that of first morning urine samples (R=0.21, P=0.034). Conclusions This study suggests that there can be a significant correlation of the PV ratio between the aortomesenteric and hilar portion of the LRV with orthostatic proteinuria in pediatric patients with nutcracker syndrome.

Nipple discharge is a common symptom that is alarming for the patient since it can be a presenting symptom of breast cancer. Breast imaging is used to examine women with pathologic nipple discharge in order to detect any lesions that may be present and to assist in the differential diagnosis. The modalities of breast imaging include mammography, breast ultrasonography (US), and magnetic resonance imaging. Breast US is currently considered to be useful for the visualization of ductal structures and intraductal lesions that cause nipple discharge. In this review, we discuss US techniques that assist in the clear visualization of ductal structures and intraductal lesions in patients with nipple discharge. Controversy remains regarding the evaluation and management of patients with nipple discharge, and we summarize the results available in the currently published literature.
Breast ; Breast Diseases ; Breast Neoplasms ; Diagnosis, Differential ; Female ; Humans ; Magnetic Resonance Imaging ; Mammography ; Nipples* ; Ultrasonography ; Ultrasonography, Mammary

Background: Sarcopenia can be associated with the disease etiologies other than degenerative processes, such as neurologic disease including cerebral palsy, myelomeningocele, or Duchenne muscular dystrophy, even in children. Although the relationship between neurologic disease and scoliosis or ambulatory function is known, the mediators affecting scoliosis or gait function in these patients are unclear, an example might be sarcopenia. This study aimed to assess the degree of sarcopenia in young patients with neurologic diseases using computed tomography (CT), and analyze the correlation between sarcopenia and scoliosis or ambulatory function. Methods: Pediatric and young adult patients (≤ 25 years old) who underwent whole-spine or lower-extremity CT were retrospectively included. From bilateral psoas muscle areas (PMAs) at the L3 level, the psoas muscle z-score (PMz) and psoas muscle index [PMI = PMA/(L3 height) 2 ] were calculated. The t-test, Fisher’s exact test, and logistic regression analyses were performed. Results: A total of 121 patients (56 men, mean age 12.2 ± 3.7 years) were included with 79 neurologic and 42 non-neurologic diseases. Patients with neurologic diseases had lower PMz (P = 0.013) and PMI (P = 0.026) than patients without. In neurologic disease patients, severe scoliosis patients showed lower PMz (P < 0.001) and PMI (P = 0.001). Non-ambulatory patients (n = 42) showed lower BMI (β = 0.727, P < 0.001) and PMz (β = 0.547, P = 0.025). In non-ambulatory patients, patients with severe scoliosis also showed lower PMz (P < 0.001) and PMI (P = 0.004). Conclusion Patients with neurologic diseases could have sarcopenia even in young age.Psoas muscle volume was also associated with ambulatory function in these patients.Sarcopenia was more severe in severe scoliosis patients in the non-ambulatory subgroup.

Objective: To assess the feasibility of quantitatively assessing pancreatic steatosis using magnetic resonance imaging (MRI) and its correlation with obesity and metabolic risk factors in pediatric patients. Materials and Methods: Pediatric patients (≤ 18 years) who underwent liver fat quantification MRI between January 2016 and June 2019 were retrospectively included and divided into the obesity and control groups. Pancreatic proton density fat fraction (P-PDFF) was measured as the average value for three circular regions of interest (ROIs) drawn in the pancreatic head, body, and tail. Age, weight, laboratory results, and mean liver MRI values including liver PDFF (L-PDFF), stiffness on MR elastography, and T2* values were assessed for their correlation with P-PDFF using linear regression analysis. The associations between P-PDFF and metabolic risk factors, including obesity, hypertension, diabetes mellitus (DM), and dyslipidemia, were assessed using logistic regression analysis. Results: A total of 172 patients (male:female = 125:47; mean ± standard deviation [SD], 13.2 ± 3.1 years) were included. The mean P-PDFF was significantly higher in the obesity group than in the control group (mean ± SD, 4.2 ± 2.5% vs. 3.4 ± 2.4%; p = 0.037). L-PDFF and liver stiffness values showed no significant correlation with P-PDFF (p = 0.235 and p = 0.567, respectively). P-PDFF was significantly associated with obesity (odds ratio 1.146, 95% confidence interval 1.006–1.307, p = 0.041), but there was no significant association with hypertension, DM, and dyslipidemia. Conclusion MRI can be used to quantitatively measure pancreatic steatosis in children. P-PDFF is significantly associated with obesity in pediatric patients.

Purpose: This study aimed to analyze the renal growth slope in children with congenital and acquired solitary functioning kidneys. Methods: This retrospective study included all renal ultrasonography examinations performed in children in the agenesis, multicystic dysplastic kidney (MCDK), or nephrectomy group between September 2002 and February 2019. We reviewed the images and recorded the contralateral kidney size only when there was no focal lesion. Linear mixed model or piecewise linear mixed model analyses with a time point of 24 months of age were performed. Results: There were 132 patients, including 26 patients in the agenesis group, 35 in the MCDK group, and 71 in the nephrectomy group. The nephrectomy group showed the largest baseline kidney size (7.4 cm vs. 5.3 cm in the agenesis group [P<0.001] and 5.2 cm in the MCDK group [P<0.001]) and the smallest overall growth slope (0.04 cm/mo vs. 0.06 cm/mo in the agenesis group [P=0.004] and 0.07 cm/mo in the MCDK group [P<0.001]). However, considering the time point of 24 months for reaching adult renal function, there were significant changes in slope, from 0.1 cm/mo before 24 months of age to 0.03 cm/mo after 24 months of age in all three groups (P<0.001), without a significant difference among the groups. Conclusion Significant changes were found in the renal growth slope before and after 24 months of age, with no significant difference between congenital and acquired solitary functioning kidneys.

Background: Contrast-enhanced ultrasonography (CEUS) of the bowel wall has been suggested as an alternative imaging modality for the follow-up of children with Crohn’s disease. To demonstrate the feasibility and clinical usefulness of CEUS in the estimation of Crohn’s disease activity in children with endoscopy as the reference standard.Method: In this prospective study, 30 pediatric patients with Crohn’s disease (24 males and 6 females; median age 14 years) underwent CEUS from December 2020 to August 2021.The simple endoscopic score for Crohn’s disease, pediatric Crohn’s disease activity index, serologic inflammatory markers, fecal calprotectin and CEUS perfusion parameters were assessed and compared between the inactive and active group based on endoscopic findings. Results: CEUS was performed successfully in all 30 patients. Two patients showed mild adverse side effects such as temporary dysosmia. The active Crohn’s disease group showed higher erythrocyte sedimentation rate (mm/hr) (13.0 vs. 2.0, P = 0.003), C-reactive protein (mg/dL) (4.7 vs. 0.55, P = 0.018) and fecal calprotectin (mcg/g) (1,503 vs. 237.5, P = 0.005). Among the quantitative parameters for CEUS, the mean gradient to the peak value was higher in the active group (1.18 vs. 0.93, P = 0.034). The sensitivity and specificity of the mean gradient to the peak value for predicting active Crohn’s disease was 55.6% and 83.3%, respectively, with a cut-off of 1.09 (P = 0.015). Conclusion CEUS can be a safe and specific diagnostic modality for Crohn’s disease activity in children. Among quantitative CEUS parameters, the mean gradient to the peak value could be used to differentiate active and inactive Crohn’s disease.

Objective: Clear cell sarcoma of the kidney (CCSK) is the second-most common but extremely rare primary renal malignancy in children after Wilms’ tumor. The aims of this study were to evaluate the imaging features that could distinguish between CCSK and Wilms’ tumor and to assess the features with diagnostic value for identifying CCSK. Materials and Methods: We reviewed the initial contrast-enhanced abdominal-pelvic CT scans of children with CCSK and Wilms’ tumor between 2010 to 2019. Fifty-eight children (32 males and 26 females; age, 0.3–10 years), 7 with CCSK, and 51 with Wilms’ tumor, were included. The maximum tumor diameter, presence of engorged perinephric vessels, maximum density of the tumor (Tmax) of the enhancing solid portion, paraspinal muscle, contralateral renal vein density, and density ratios (Tmax/muscle and Tmax/vein) were analyzed on the renal parenchymal phase of contrast-enhanced CT. Fisher’s exact tests and Mann-Whitney U tests were conducted to analyze the categorical and continuous variables, respectively. Logistic regression and receiver operating characteristic curve analyses were also performed. Results: The age, sex, and tumor diameter did not differ between the two groups. Engorged perinephric vessels were more common in patients in the CCSK group (71% [5/7] vs. 16% [8/51], p = 0.005). Tmax (median, 148.0 vs. 111.0 Hounsfield unit, p = 0.004), Tmax/muscle (median, 2.64 vs. 1.67, p = 0.002), and Tmax/vein (median, 0.94 vs. 0.59, p = 0.002) were higher in the CCSK compared to the Wilms’ group. Multiple logistic regression revealed that engorged vessels (odds ratio 13.615; 95% confidence interval [CI], 1.770–104.730) and Tmax/muscle (odds ratio 5.881; 95% CI, 1.337–25.871) were significant predictors of CCSK. The cutoff values of Tmax/muscle (86% sensitivity, 77% specificity) and Tmax/vein (71% sensitivity, 86% specificity) for the diagnosis of CCSK were 1.97 and 0.76, respectively. Conclusion Perinephric vessel engorgement and greater tumor enhancement (Tmax/muscle > 1.97 or Tmax/vein > 0.76) are helpful for differentiating between CCSK and Wilms’ tumor in children aged below 10 years.

Objective: Clear cell sarcoma of the kidney (CCSK) is the second-most common but extremely rare primary renal malignancy in children after Wilms’ tumor. The aims of this study were to evaluate the imaging features that could distinguish between CCSK and Wilms’ tumor and to assess the features with diagnostic value for identifying CCSK. Materials and Methods: We reviewed the initial contrast-enhanced abdominal-pelvic CT scans of children with CCSK and Wilms’ tumor between 2010 to 2019. Fifty-eight children (32 males and 26 females; age, 0.3–10 years), 7 with CCSK, and 51 with Wilms’ tumor, were included. The maximum tumor diameter, presence of engorged perinephric vessels, maximum density of the tumor (Tmax) of the enhancing solid portion, paraspinal muscle, contralateral renal vein density, and density ratios (Tmax/muscle and Tmax/vein) were analyzed on the renal parenchymal phase of contrast-enhanced CT. Fisher’s exact tests and Mann-Whitney U tests were conducted to analyze the categorical and continuous variables, respectively. Logistic regression and receiver operating characteristic curve analyses were also performed. Results: The age, sex, and tumor diameter did not differ between the two groups. Engorged perinephric vessels were more common in patients in the CCSK group (71% [5/7] vs. 16% [8/51], p = 0.005). Tmax (median, 148.0 vs. 111.0 Hounsfield unit, p = 0.004), Tmax/muscle (median, 2.64 vs. 1.67, p = 0.002), and Tmax/vein (median, 0.94 vs. 0.59, p = 0.002) were higher in the CCSK compared to the Wilms’ group. Multiple logistic regression revealed that engorged vessels (odds ratio 13.615; 95% confidence interval [CI], 1.770–104.730) and Tmax/muscle (odds ratio 5.881; 95% CI, 1.337–25.871) were significant predictors of CCSK. The cutoff values of Tmax/muscle (86% sensitivity, 77% specificity) and Tmax/vein (71% sensitivity, 86% specificity) for the diagnosis of CCSK were 1.97 and 0.76, respectively. Conclusion Perinephric vessel engorgement and greater tumor enhancement (Tmax/muscle > 1.97 or Tmax/vein > 0.76) are helpful for differentiating between CCSK and Wilms’ tumor in children aged below 10 years.