DTI of the kidney in children: comparison between normal kidneys and those with ureteropelvic junction (UPJ) obstruction.

OBJECTIVE: To compare renal diffusion tensor imaging (DTI) parameters in patients with or without ureteropelvic junction (UPJ) obstruction. METHODS: Patients that underwent functional MR urography (MRU) with renal DTI were retrospectively selected. Kidneys deemed normal on T2-weighted images and functional parameters were used as controls and compared to those kidneys with morphologic and functional findings of UPJ obstruction. DTI included a 20-direction DTI with b values of b = 0 s/mm2 and b = 400 s/mm2. Diffusion Toolkit was used for analysis and segmentation. TrackVis was used to draw regions of interest (ROI) covering the entire volume of the renal parenchyma, excluding the collecting system. Fibers were reconstructed using a deterministic fiber tracking algorithm. Whole kidney ROI-based analysis was performed to obtain cortico-medullary measurements (FA, ADC and track length) for each kidney. T tests were performed to compare means and statistical significance was defined at p < 0.05. RESULTS: 118 normal kidneys from 102 patients (median age 7 years, IQR 6-15 years; 58 males and 44 females) were compared to 22 kidneys from 16 patients (median age 13 years, IQR 3-15 years; 9 males and 7 females) with UPJ obstruction. Mean FA values were significantly lower (0.31 ± 0.07; n = 22) in kidneys with UPJ obstruction than normal kidneys (0.40 ± 0.08; n = 118) (p < 0.001). ADC was marginally significantly increased (p = 0.01) and track length was not significantly different (p = 0.24). CONCLUSION: Our results suggest that DTI-derived metrics including FA and ADC are potential biomarkers to differentiate kidneys with UPJ obstruction and assess renal parenchymal damage.

Supine versus prone positioning for ultrasound evaluation of postnatal urinary tract dilation in children.

BACKGROUND: Ultrasound (US) is used in the initial evaluation and surveillance of urinary tract dilation in children. Urinary tract dilation is diagnosed in 1-2% of all pregnancies during routine prenatal sonography with technological advances in US imaging. Urinary tract dilation classification systems, including the 2014 multidisciplinary consensus, assess anterior-posterior renal pelvic diameter and calyceal dilation. There is no consensus regarding optimal patient positioning - supine versus prone - during US assessment of urinary tract dilation. OBJECTIVE: We performed this study to determine whether there is a significant difference in the measurement of the anterior-posterior renal pelvic diameter, presence of calyceal dilation, or resulting urinary tract dilation consensus score obtained between supine and prone positions. MATERIALS AND METHODS: Two raters retrospectively reviewed renal bladder US exams of children with urinary tract dilation of one or both kidneys. We included technically adequate US examinations of orthotopic kidneys that were imaged in both supine and prone positions; we excluded children with renal anomalies or prior surgery. Anterior-posterior renal pelvic diameter measurements as well as central and peripheral calyceal dilation were documented in both supine and prone positions. A postnatal urinary tract dilation consensus score was assigned to each kidney based only on these features. RESULTS: Urinary tract dilation in either the supine or prone position was performed in 146 kidneys (69 right, 77 left) in 89 children. Median age was 0.26 years (interquartile ratio [IQR] 0.08-0.61 years). Female-to-male ratio was 1:3 (21/89). The interclass correlations of the anterior-posterior renal pelvic diameter were 0.88 and 0.87 in the supine and prone positions, respectively, without significant differences (P=0.1). When comparing all kidneys together, the mean anterior-posterior renal pelvic diameter was 7.1 mm (95% confidence interval [CI] 6.4-7.8) in supine and 7.9 (95% CI 7.1-8.7) in prone, with a mean difference between the measurements of 0.83 mm (95% CI 0.3-1.4; P=0.16). Central calyceal and peripheral calyceal dilation were more commonly found in the prone position versus the supine position in both kidneys. Central calyceal dilation was observed in 15 cases in the prone but not in the supine position. In one kidney, it was seen only in the supine but not in the prone position. Overall the urinary tract dilation score differed between positions in 10.3% (15/146) of cases, most of them (14/15) with a higher score in prone compared to the supine position. CONCLUSION: Scanning in prone position tends to more frequently show calyceal dilation and a greater size of the anterior-posterior renal pelvic diameter, resulting in higher urinary tract dilation classification scores, with almost perfect interobserver agreement.

Assessment of normal jejunum with diffusion-weighted imaging on MRE in children.

BACKGROUND: Diffusion restriction has been utilized as a marker for bowel inflammation on magnetic resonance enterography (MRE). However, diffusion restriction has been seen in otherwise normal appearing small bowel in patients without active inflammation, with little published data on this subject. OBJECTIVE: Assess diffusion restriction in normal loops of jejunum and to determine if there is a correlation to luminal distention, age, magnet field strength, slice thickness, and bowel segment location. MATERIALS AND METHODS: A retrospective analysis of subjects with a normal MRE and clinical work-up was performed. The abdomen was divided into four quadrants. If available, two loops of jejunum were randomly chosen in each quadrant. Two radiologists evaluated the loops of jejunum for distension, wall thickness, enhancement and diffusion restriction. Disagreement was resolved by consensus. Presence of diffusion restriction was correlated with luminal distension, age, magnet field strength, slice thickness and abdominal quadrant. RESULTS: One hundred ninety-seven loops of jejunum were evaluated in 39 subjects. Fifteen subjects (38.5%) had jejunal loops with diffusion restriction for a total of 28 loops. There was no correlation between diffusion restriction and luminal distension, age, magnet field strength or quadrant location (P>0.05, Pearson chi-squared test or Student's t-tests). Of the 15 subjects with a loop demonstrating diffusion restriction, additional loops with diffusion restriction were found in 40%. There was a very weak trend observed for greater slice thickness in patients with jejunal diffusion restriction (Student's t-test, P=0.10). CONCLUSION: Jejunal diffusion restriction is a common finding in children with no clinical evidence of bowel pathology, irrespective of patient age, luminal distension, location of bowel loop and magnetic field strength. Further studies may be valuable in assessing the impact of slice thickness on subjective diffusion restriction in the jejunum.

Emergent ultrasound evaluation of the pediatric female pelvis.

Ultrasound is the primary imaging modality of the pediatric female pelvis and is often requested to evaluate girls with pelvic or abdominal pain or abnormal bleeding. The US interpretation can help guide the clinician toward medical or surgical management. Here we discuss the normal US anatomy of the female pelvis and illustrate, through case examples, conditions encountered when performing emergent pelvic US for common and uncommon clinical scenarios.

Ultrasound of congenital and inherited disorders of the pediatric hepatobiliary system, pancreas and spleen.

Ultrasound is often the initial imaging examination performed of the solid organs of the pediatric abdomen. The sonographic appearance of the hepatobiliary system, pancreas and spleen changes with growth and development. This article reviews the normal US appearance of these organs in children and illustrates, through case examples, congenital and inherited conditions that affect them.

Ultrasound shear wave elastography cannot discriminate between low- and high-pressure neurogenic bladders.

BACKGROUND: Patients with neurogenic bladders are monitored with renal bladder ultrasounds and video urodynamics studies (VUDS) to assess upper urinary tract injury. Ultrasound shear wave elastography (US-SWE) can assess tissue stiffness. If bladder compliance is affected by bladder wall fibrosis and stiffening, then high-pressure bladders may be detectable by US-SWE therefore reducing the need for VUDS in some patients. OBJECTIVE: To determine if US-SWE can differentiate between low- and high-pressure bladders and hence be used for noninvasive assessment of neurogenic bladder in children. STUDY DESIGN: Prospective study of patients with neurogenic bladder undergoing clinically indicated VUDS between February and July of 2017. During VUDS, bladder wall US-SWE was measured at different filling percentages of estimated bladder capacity (EBC). The bladders were divided into cohorts according to the detrusor muscle pressure (Pdet) reached at the maximum bladder capacity: normal (1 to <15 cmH2O) and abnormal (≥15 cmH2O) pressure. T-test was used to compare elastography values at different bladder volumes and Pdet; (statistical significance set at p < 0.05). RESULTS: 30/31 enrolled children completed the protocol. With an empty bladder, as well as at all other bladder volumes, no relationship was observed between Pdet and mean SWE of the anterior or posterior bladder wall. At maximum bladder capacity, there was no difference between mean SWE values of the anterior or posterior bladder walls in those with normal pressure, 2.97 m/s (SD ± 0.82) and 1.96 m/s (SD ± 0.75), compared to those with abnormal pressures 3.08 m/s (SD ± 0.84) and 2.39 m/s (SD ± 0.96), p = 0.75 and p = 0.2, respectively. DISCUSSION: We found no difference between SWE values of either the anterior or posterior bladder wall in neurogenic bladders with normal and abnormal filling pressures measured during VUDS. Our study differs from previously reported studies with more positive results in that our cut-off for abnormal bladder pressure was (Pdet ≥15 cmH2O). This is lower than the more commonly used leak point pressure of 40 cmH2O because our practice is to intervene earlier. Moreover, SWE would be most useful if it can identify changes before the bladder has reached such severe conditions, to allow for early intervention. Additional differences between ours and other studies include US manufacturer and younger age of the participating children. CONCLUSIONS: US-SWE, while feasible, was not able to discriminate between low- and high-pressure bladders. Moreover, US-SWE did not show significant correlation with the current gold standard, VUDS.

Morphologic and functional evaluation of duplicated renal collecting systems with MR urography: A descriptive analysis.

PURPOSE: To describe the morphology and function of duplicated collecting systems in pediatric patients undergoing functional MR urography (fMRU). METHODS: This is a HIPAA compliant IRB approved retrospective study of all patients with duplicated renal collecting systems undergoing fMRU at our institution between 2010 and 2017. Two pediatric radiologists evaluated the studies to determine the presence, morphology and function of duplicated collecting systems using both T2-weighted and dynamic post-contrast fat saturated T1-weighted images. Assessed morphologic features included pelvic and calyceal dilation, partial or complete ureteral duplication, ureteral dilation, ectopic ureteral insertion and ureteroceles. Functional analysis was carried out per moiety. RESULTS: A total of 86 examinations (63 girls; 23 boys), median age 2.6 years (Standard Deviation 6.4 years, interquartile range: 0.4-10.3 years) and 107 kidneys (39 right; 30 left and 19 bilateral), which yielded 214 evaluable moieties, were included in the final sample. One hundred and sixty-three (76.1%) of the moieties had normal morphological features and normal functional results (average calyceal transit time and renal transit time of 2 min 28 s and 3 min 16 s, respectively). The remaining 51 moieties (23.8%) were hypoplastic or dysplastic. Seventy-seven (35.9%) had pelvic and calyceal dilation. Slightly more than half of the kidneys had complete ureteral duplication (60/107; 56%); 50 (50/107, 46.7%) had ectopic ureters (23 intra- and 27 extravesical) and 9 (9/107, 8.4%) had ureteroceles. CONCLUSION: fMRU provides comprehensive information regarding the morphology and function of duplicated renal collecting systems in children. In particular, fMRU is useful for assessing barely or non-functioning renal poles and ectopic ureters.