Imaging of Vesicoureteral Reflux: AJR Expert Panel Narrative Review.

Vesicoureteral reflux (VUR) is a common congenital anomaly of the urinary tract that can present with collecting system dilation or as a febrile infection. VUR can lead to permanent renal sequela requiring surgery but can also spontaneously resolve without complication. Therefore, it is important to recognize those patient populations who warrant imaging for screening, confirmation, or ongoing surveillance for VUR, while avoiding overdiagnosis. In the appropriate patient populations, an accurate diagnosis of VUR allows early treatment and prevention of pyelonephritis and scarring. Various imaging modalities are available to diagnose and grade VUR, including voiding cystourethrogram (VCUG), radionucleotide cystography (RNC), and contrast-enhanced voiding urosonography (ceVUS). The objective of this article is to summarize the current understanding of VUR diagnosis and management and to discuss these imaging modalities' strengths and pitfalls. Considerations include indications for VUR imaging, patient preparation, conduct of the examination, issues related to radiologic reporting, and cost-effectiveness. An emphasis is placed on ceVUS, which is the most recently introduced of the three imaging modalities and is receiving growing support among pediatric radiologists.

Prevalence of intrarenal reflux in pediatric patients on contrast-enhanced voiding urosonography.

BACKGROUND: Intrarenal reflux may be seen with vesicoureteral reflux (VUR) when contrast from the pelvocalyceal system extends into tubules in the parenchyma. Because intrarenal reflux has been associated with scarring, detecting intrarenal reflux may influence management to avoid renal damage. OBJECTIVE: Our objective was to evaluate the prevalence of intrarenal reflux identified on contrast-enhanced voiding urosonography (ceVUS) and its association with sex, age, grade of VUR, location in kidney and stage of bladder filling or voiding. MATERIALS AND METHODS: CeVUS studies performed from August 2019 through July 2020 with VUR were retrospectively reviewed by two pediatric radiologists. They independently graded VUR and assessed for intrarenal reflux, noting its location and stage of bladder filling or voiding during which it occurred. The presence and location of scarring was also recorded. RESULTS: One hundred and six ceVUS exams were reviewed with 211 kidneys evaluated (one solitary kidney). Patients were ages 2 weeks to 12 years (mean: 1.8 years) with 71 females (67%) and 35 males (33%). Grades 2 to 5 VUR were detected in 165 kidneys with intrarenal reflux seen in 42 (25.4%). Intrarenal reflux was present in 1 of 40 kidneys (2.5%) with grade 2, 10 of 67 (14.9%) with grade 3, 25 of 47 (53.2%) with grade 4 and 6 of 11 (54.5%) with grade 5 VUR. Intrarenal reflux occurred during voiding in 31 of 42 kidneys (73.8%) and was seen most often in the lower pole (71.4%) with significant association between intrarenal reflux and interpolar renal scarring (odds ration [OR] 3.92; 95% confidence interval [CI] 1.49, 10.32; P-value 0.01). CONCLUSION: Intrarenal reflux was often seen on ceVUS, with the highest frequency occurring in young patients with grades 4 and 5 VUR and during voiding. Radiologists should have a high index of suspicion for intrarenal reflux on ceVUS, especially in young children with high-grade VUR.

Assessment of distal ureteral and ureterovesical junction visualization on contrast-enhanced voiding urosonography.

BACKGROUND: Contrast-enhanced voiding urosonography (CEVUS) uses intravesically administered microbubble contrast to detect vesicoureteral reflux (VUR) and urethral anomalies with ultrasound. Multiple studies have suggested CEVUS can replace voiding cystourethrogram (VCUG) as a radiation-free alternative. Analysis of the ureterovesical junction and ureters on VCUG documenting the ureterovesical junction position, ureteral duplication, periureteral diverticula and ureteroceles is important as anatomical variations may affect management and surgical approach. OBJECTIVE: Our purpose was to assess distal ureteral and ureterovesical junction region visualization in children with VUR detected on CEVUS. MATERIALS AND METHODS: CEVUS studies performed between June 2018 and March 2019 with reported VUR were retrospectively reviewed by two pediatric radiologists to confirm VUR and to qualitatively assess the ureterovesical junction region for each renal moiety using a 3-point scale for clear, limited or absent visualization of the distal ureter, ureterovesical junction, ureteral duplication, periureteral diverticula and ureteroceles. RESULTS: Thirty-four studies with VUR on CEVUS were identified. Sixty-seven renal moieties were evaluated including a solitary kidney in one child. VUR was detected in 52 moieties by reader 1 and in 53 by reader 2. A single moiety with discrepancy between readers regarding VUR was excluded from statistical analysis. No diverticula were detected by either reader and one ureterocele was detected by both readers. Visualization of the ureterovesical junction was described as clear in 5/52, limited in 14/52 and absent in 33/52 refluxing renal moieties by reader 1 and as clear in 12/52, limited in 20/52 and absent in 20/52 by reader 2. The ureterovesical junction was clearly visualized in 5/52 (9.6%) by reader 1 and 12/52 (23.1%) by reader 2. The Kappa value of -0.29 (confidence interval [CI] -0.25, 0.21) reveals a lack of agreement between the readers for clear versus limited or absent ureterovesical junction visualization. Distal ureteral visualization was described as clear in 14/52, limited in 16/52 and absent in 22/52 refluxing renal moieties by reader 1 and as clear in 27/52, limited in 7/52 and absent in 18/52 by reader 2. The distal ureter was clearly visualized in 14/52 (26.9%) by reader 1 and 27/52 (51.9%) by reader 2. The Kappa of 0.43 (CI 0.22, 0.64) reveals moderate agreement between the readers for clear versus limited or absent distal ureteral visualization. Duplication of the renal collecting system was identified in 13/52 refluxing kidneys by reader 1 and 11/52 refluxing kidneys by reader 2. Visualization of ureteral duplication was described as clear in 9, limited in 4 and absent in 39 of 52 refluxing renal moieties by reader 1 and as clear in 9, limited in 2 and absent in 41 by reader 2. Ureteral duplication was clearly visualized in 9/52 (17.3%) by reader 1 and 9/52 (17.3%) by reader 2. Kappa of 0.87 (CI 0.68, 1) reveals high agreement between the readers for clear versus limited or absent identification of ureteral duplication. CONCLUSION: The distal ureter and ureterovesical junction region frequently are not clearly visualized in refluxing renal moieties on CEVUS. Awareness of this limitation is important as there may be implications when evaluating patients for surgical management of VUR.

Physeal separation in pediatric osteomyelitis.

In children, acute osteomyelitis, an infection of the bone, is most commonly hematogeneous in origin. Osteomyelitis is most often diagnosed with magnetic resonance imaging (MRI) and findings may include marrow signal changes on T1 and T2, with abnormal enhancement after gadolinium. Imaging helps detect any associated intraosseous or subperiosteal abscesses, which may require orthopedic drainage. In this pictorial essay, we demonstrate the association of acute pediatric osteomyelitis with physeal separation, resulting in what may be confused for simple trauma, although there was no known history of trauma in any of the cases we researched. All of the cases had a large subperiosteal fluid collection with marked separation of the epiphysis from the metaphysis. It is important to recognize this potential association in osteomyelitis, as it is readily visible by radiographs and may lead to diagnostic uncertainty.

Evaluation of a pediatric fluoroscopy training module to improve performance of upper gastrointestinal procedures in neonates with bilious emesis.

BACKGROUND: Life-threatening midgut volvulus usually occurs in infants with malrotation and requires rapid diagnosis and surgical treatment to prevent bowel necrosis and death. However, because of the low frequency of upper gastrointestinal studies performed in infants younger than 1 month, many diagnostic radiology residents finish their residency training having limited or no opportunity to perform or observe an upper gastrointestinal (GI) series for evaluation of bilious emesis in a neonate. OBJECTIVE: To determine whether adding simulated upper GI series on neonates with bilious emesis to the curriculum improves residents' skill and accuracy in diagnosing midgut volvulus. MATERIALS AND METHODS: We assessed the performance of 12 residents in training whose curriculum included simulated upper GI series (study group) and 10 traditionally trained residents (control group) using a multiple-choice test, checklist procedure evaluation and diagnostic accuracy scores for 3 randomly selected simulated upper GI series. We then compared the results from the study group that had simulation curriculum to the scores for the control group using the Mann-Whitney test. We also analyzed the scores for the study group obtained prior to and after simulation curriculum using Wilcoxon signed rank test. RESULTS: There was a significant difference in test scores (study group median = 84.5%, control group median = 67.2%, P=0.001), overall diagnostic accuracy (study group median = 100%, control group median = 50%, P=0.011) and checklist evaluation (study group median = 83.3%, control group median = 70.8%, P=0.025) for the residents in the study group who completed simulation curriculum compared with the control group. There was also a significant difference in multiple-choice test scores for the study group before and after completion of simulation curriculum (before simulation curriculum median = 56.9%, after simulation curriculum median = 84.5%, P=0.002), checklist evaluation (before simulation curriculum median = 58.3%, after simulation curriculum median = 83.3%, P=0.002) and overall diagnostic accuracy scores (before simulation curriculum median = 50%, after simulation curriculum median = 100%, P=0.024). CONCLUSION: Radiology residents had significantly higher scores on a multiple-choice test, checklist procedure evaluation and overall diagnostic accuracy after completing a structured pediatric fluoroscopy curriculum that included simulated neonatal upper GI series and when compared to a control group of traditionally trained residents.

Upper gastrointestinal fluoroscopic simulator for neonates with bilious emesis.

Prompt diagnosis of malrotation and midgut volvulus in infants with bilious emesis is critical. However because of the limited frequency of pediatric upper gastrointestinal (UGI) fluoroscopic procedures in neonates, many diagnostic radiology residents complete their training never having seen or performed a UGI on a baby for evaluation of malrotation and midgut volvulus. A UGI simulation model for infants with bilious emesis was created to supplement the hands-on fluoroscopic experience of residents in training. We are now studying the addition of simulated UGI studies to our pediatric radiology curriculum.

Utility of the computed tomography severity index (Balthazar score) in children with acute pancreatitis.

BACKGROUND: Previous studies in children with acute pancreatitis have demonstrated that clinical scoring systems such as the Ranson, modified Glasgow, and pediatric acute pancreatitis scores are of value in predicting severity of the disease. The aim of this study was to determine the predictive value of the computed tomography severity index (CTSI or Balthazar score) in pediatric patients. METHODS: All children (≤ 18 years) admitted to our institution with acute pancreatitis from 2000 through 2009 were reviewed. Contrast-enhanced computed tomographic (CT) images at presentation were retrospectively reviewed by 2 pediatric radiologists. Peripancreatic fluid and the extent of necrosis were assessed to determine the CTSI. The predictive value of the CTSI was calculated and compared with clinical scoring systems. RESULTS: Of 211 children with acute pancreatitis, 64 underwent contrast-enhanced CT at presentation. The median age was 12.3 years. Etiology of pancreatitis was idiopathic (35.9%), gallstone (17.2%), medication-induced (20.3%), posttransplant (9.4%), traumatic (6.3%), structural (1.6%), and other (9.4%). The sensitivity, specificity, positive predictive value, and negative predictive value of the CTSI (using a cutoff score of 4+) were 81%, 76%, 62%, and 90%, respectively, which compared favorably to the results of the pediatric acute pancreatitis (53%, 72%, 41%, 80%), Ranson (71%, 87%, 67%, 89%), and modified Glasgow (71%, 87%, 67%, 89%) scores. CONCLUSION: The CTSI is superior to clinical scoring systems for identifying children with acute pancreatitis at heightened risk for developing serious complications.

A rare case of thymoma in a 15-month-old girl.

We report a case of thymoma in a 15-month-old girl successfully treated with thymectomy. This case is unique due to the very young age of the child and a family history of thymoma in the father, who was treated with resection at age 10. Radiographic and CT findings mimicked thymic hyperplasia, and highlight the difficulty of distinguishing between these two conditions, since the latter is more common in children. The case is followed by a discussion of thymic hyperplasia and thymoma.

Evaluation of pediatric bone lesions.

The radiologist is commonly confronted with bone lesions in children. Knowledge of the age of the patient, the lesion location, and various imaging characteristics are all important in making an accurate diagnosis, and determining benign from malignant etiologies should be a primary goal. Various imaging features seen on cross-sectional imaging, including marrow edema, periosteal reaction patterns, and fluid-fluid levels, are discussed. The advantages of different imaging modalities, including CT and MRI, are reviewed.

Anatomical location of the bifurcation of the sciatic nerve in the posterior thigh in infants and children: a formula derived from MRI imaging for nerve localization.

BACKGROUND AND OBJECTIVES: Sciatic nerve block is performed at the popliteal fossa for various surgical procedures in infants and children. The aim of this study is to review magnetic resonance imaging scans in children of various ages to assess the location of the division of the nerve in the posterior thigh. METHODS: After Institutional Review Board approval was obtained, measurements of the bifurcation of the sciatic nerve in the posterior thigh were recorded from magnetic resonance images that were previously obtained in children of various ages. Data were recorded in a database and parametric and nonparametric statistical analysis was performed. RESULTS: Measurements were recorded from 59 patient images. Using a linear regression model, we were able to arrive at a formula for determining the point of bifurcation of the sciatic nerve at the posterior thigh. The mathematical formula derived from the linear regression equation was: CONCLUSIONS: We speculate that this knowledge will assist practitioners who use nerve stimulation techniques for sciatic nerve blocks in children of all ages.

MRI characterization of the glenohumeral joint in Apert syndrome.

The features of craniosynostosis, facial dysmorphism, and distal extremity syndactyly in Apert syndrome are well known. However, there have been limited descriptions of the associated glenohumeral joint findings. We report the radiographic and MRI abnormalities of the glenohumeral joints in a 10-month-old girl with Apert syndrome. The MRI findings in the girl support the hypothesis that the pathogenesis of Apert syndrome is caused by defective cartilage segmentation with premature and abnormal ossification of a cartilage bar within a joint space. The resultant shoulder joint deformity is related to glenoid hypoplasia and growth arrest of the medial aspect of the humeral head.

Safety and efficacy of pressure-limited power injection of iodinated contrast medium through central lines in children.

OBJECTIVE: The purpose of this study was to evaluate the safety and efficacy of pressure-limited power injection of contrast medium through central lines for pediatric body CT examinations. SUBJECTS AND METHODS: All patients with a central line who were referred for body CT examinations requiring an i.v. contrast agent were prospectively evaluated. The power injector was pressure limited to 25 psi (172 kPa). A standard dose of 2 mL/kg of iodinated contrast medium was power-injected through the central line. Two pediatric radiologists scored all examinations on a scale of 1 (poor) to 5 (superior) for adequacy of contrast enhancement. Regression and receiver operating characteristic analyses were performed. RESULTS: The subjects were 63 patients 0.3-22 years old. Nineteen of these patients had tunneled lines, 18 had ports, and 26 had peripherally inserted central catheters. There were no complications related to power injection. Regression analysis showed a significant association between patient weight and contrast enhancement adequacy score (p < 0.001), higher patient weights yielding lower contrast enhancement adequacy scores. Receiver operating characteristic analysis showed a weight cutoff of 30 kg as a reasonable predictor of adequacy of contrast enhancement. For patients weighing 30 kg or more, the average contrast enhancement score was 2.4 (suboptimal to adequate). For patients weighing less than 30 kg, the average contrast enhancement score was 3.4 (adequate to good). CONCLUSION: Pressure-limited power injection through central lines in children is safe. The contrast enhancement obtained with 25 psi (172 kPa) pressure-limited injection is acceptable only for patients who weigh less than 30 kg.

Umbilical artery catheter use complicated by pseudoaneurysm of the aorta.

We report a case of a large aortic mycotic pseudoaneurysm in a premature infant, a rare but serious complication associated with sepsis and umbilical artery catheter (UAC) use. Sonography is an appropriate first-line imaging modality for detection of aortic pseudoaneurysms. Increased awareness of this rare complication may lead to earlier diagnosis in the high-risk premature infant with a history of a UAC and sepsis.