Normal pancreatic parenchymal thickness by CT in healthy children

Pancreas volumes in pediatric patients following index acute pancreatitis and acute recurrent pancreatitis

BACKGROUND/OBJECTIVES

Pancreas volume derived from imaging may objectively reveal volume loss relevant to identifying sequelae of acute pancreatitis (AP) and ultimately diagnosing chronic pancreatitis (CP). The purposes of this study were to: (1) quantify pancreas volume by imaging in children with either (a) a single episode of AP or (b) acute recurrent pancreatitis (ARP), and (2) compare these volumes to normative volumes.

METHODS

This retrospective study was institutional review board approved. A single observer segmented the pancreas (3D Slicer; slicer.org) on n = 30 CT and MRI exams for 23 children selected from a prospective registry of patients with either an index attack of AP or with ARP after a known index attack date. Patients with CP were excluded. Segmented pancreas volumes were compared to published normal values.

RESULTS

Mean pancreas volumes normalized to body surface area (BSA) in the index AP and ARP groups were 38.2 mL/m2 (range: 11.8-73.5 mL/m2) and 27.9 mL/m2 (range: 8.0-69.2 mL/m2) respectively. 43 % (6/14) of patients post-AP had volumes below the 25th percentile, 1 (17 %) of which was below the 5th percentile (p = 0.3027 vs. a normal distribution). Post-ARP, 44 % (7/16) of patients had volumes below the 5th percentile (p < 0.001).

CONCLUSIONS

A significant fraction (40 %) of children with ARP have pancreas volumes <5th percentile for BSA even in the absence of CP. A similar, but not statistically significant, fraction have pancreas volumes <25th percentile after an index attack of AP. Pancreatic parenchymal volume deserves additional investigation as an objective marker of parenchymal damage from acute pancreatitis and of progressive pancreatitis in children.

Are the thickness and ADC values reliable to evaluate pancreas in children? A retrospective MRI study

PURPOSE

To define the pancreatic thickness on the transverse plane and apparent diffusion coefficient (ADC) values at multiple anatomical locations in the normal pancreas of children and to evaluate inter-rater and intra-rater reliability.

METHODS

Two reviewers measured the thickness and ADC values of the pancreas at four locations obtained from two different 1,5 Tesla MRI scanners [MAGNETOM Symphony (Siemens Medical Systems, Erlangen, Germany) and Signa HDxt(GE Healthcare, Milwaukee, WI, USA)]. Measurements were made based on 190 retrospective MRI examinations. Patients were distributed among ten age groups for thickness measurements and three age groups for ADC measurements between 0 and 18 years.

RESULTS

The thickness measurements from each segment of the pancreas were significantly correlated with patient age, height and weight (p < 0.01). Inter-rater agreement was excellent for pancreatic head (intraclass correlation coefficient (ICC): 0.837) and good for pancreatic neck, body and tail (ICC: 0.646, 0.632 and 0.678, respectively). We also defined the mean ADC values for three age groups. There was significant difference in the mean ADC value of the head and body by both the vendor and age group (p < 0.05). The mean ADC values and mean ranks of the Signa HDxt were significantly higher and the frequencies were lower than those of the MAGNETOM Symphony at all locations (p < 0.001).

CONCLUSION

The thickness of the pancreatic head is more reliable than that at other locations. Pancreatic body and tail measurements are not as reliable as head or neck measurements due to discrepancies between published studies and low interobserver agreement. ADC values of the normal pancreas can be significantly different among vendors; therefore, ADC comparison on follow-up should be performed using same MRI machine.

Inter- and intra-observer variability of computed tomography-based parenchymal- and ductal diameters in chronic pancreatitis: a multi-observer international study

PURPOSE

The need for incorporation of quantitative imaging biomarkers of pancreatic parenchymal and ductal structures has been highlighted in recent proposals for new scoring systems in chronic pancreatitis (CP). To quantify inter- and intra-observer variability in CT-based measurements of ductal- and gland diameters in CP patients.

MATERIALS AND METHODS

Prospectively acquired pancreatic CT examinations from 50 CP patients were reviewed by 12 radiologists and four pancreatologists from 10 institutions. Assessment entailed measuring maximum diameter in the axial plane of four structures: (1) pancreatic head (PDhead), (2) pancreatic body (PDbody), (3) main pancreatic duct in the pancreatic head (MPDhead), and (4) body (MPDbody). Agreement was assessed by the 95% limits of agreement with the mean (LOAM), representing how much a single measurement for a specific subject may plausibly deviate from the mean of all measurements on the specific subject. Bland-Altman limits of agreement (LoA) were generated for intra-observer pairs.

RESULTS

The 16 observers completed 6400 caliper placements comprising a first and second measurement session. The widest inter-observer LOAM was seen with PDhead (± 9.1 mm), followed by PDbody (± 5.1 mm), MPDhead (± 3.2 mm), and MPDbody (± 2.6 mm), whereas the mean intra-observer LoA width was ± 7.3, ± 5.1, ± 3.7, and ± 2.4 mm, respectively.

CONCLUSION

Substantial intra- and inter-observer variability was observed in pancreatic two-point measurements. This was especially pronounced for parenchymal and duct diameters of the pancreatic head. These findings challenge the implementation of two-point measurements as the foundation for quantitative imaging scoring systems in CP.

Pancreas volumes and predictive factors in healthy children

BACKGROUND

Pancreas volume might be a quantitative metric of pancreas health and function in children.

OBJECTIVE

To establish normative pancreas volumes and determine factors associated with pancreas volume.

MATERIALS AND METHODS

We conducted a retrospective study of 140 healthy children (balanced from 0 to 18 years, stratified by age and gender) who underwent contrast-enhanced CT of the abdomen. Pancreas volume was manually segmented by a single reviewer using 3D Slicer and corrected by a pediatric radiologist. We used Bland-Altman difference analysis to quantify differences in initial and refined segmented pancreas volume, and the Mann-Whitney U test to compare continuous variables. We used Pearson correlation for univariate associations. To determine predictors, we used multivariable regression. Finally, we generated quantile regression equations to determine pancreas volume based on age or body surface area (BSA).

RESULTS

Pancreas volume for the study sample ranged from 2 mL to 99 mL. Age (r=0.90, P<0.0001), body mass index (BMI) (r=0.66, P<0.0001), BSA (r=0.94, P<0.0001), height (r=0.91, P<0.0001) and weight (r=0.90, P<0.0001) were all positively correlated with pancreas volume on univariate analysis. On multivariable analysis, BSA (+36 mL/m², P<0.0001) and female gender (-2.8 mL, P=0.062) were significant independent predictors of pancreas volume. The mean difference between initial and refined segmentation was 0.80 mL (95% limits of agreement: -7.9 mL to 9.5 mL).

CONCLUSION

We report pancreas volumes for healthy children. We found that age, BMI, BSA, height and weight were each significantly, positively correlated with pancreas volume in univariate analyses, while BSA and female gender were significant independent predictive factors on multivariable analysis.

Interobserver Agreement for CT and MRI Findings of Chronic Pancreatitis in Children: A Multicenter Ancillary Study Under the INSPPIRE Consortium

BACKGROUND. Imaging findings represent key criteria for diagnosing chronic pancreatitis in children. Understanding radiologists' agreement for imaging findings is critical to standardizing and optimizing diagnostic criteria. OBJECTIVE. The purpose of this study is to evaluate the interobserver agreement among experienced pediatric radiologists for subjective, quantitative, and semiquantitative imaging findings of chronic pancreatitis in children. METHODS. In this retrospective study, CT or MRI examinations performed in children with chronic pancreatitis were submitted by six sites participating in the INSPPIRE (International Study Group of Pediatric Pancreatitis: In Search for a Cure) Consortium. One pediatric radiologist from each of the six sites reviewed examinations; three of the radiologists independently reviewed all CT examinations, and the other three radiologists independently reviewed all MRI examinations. Reviewers recorded 13 categoric imaging findings of chronic pancreatitis and measured pancreas thickness and pancreatic duct diameter. Agreement was assessed using kappa coefficients for the categoric variables and intraclass correlation coefficients (ICCs) for the continuous variables. RESULTS. A total of 76 CT and 80 MRI examinations performed in 110 children (65 girls and 45 boys; mean age, 11.3 ± 4.6 [SD] years) were reviewed. For CT, kappa coefficients for categoric findings ranged from -0.01 to 0.81, with relatively high kappa coefficients noted for parenchymal calcifications (κ = 0.81), main pancreatic duct dilatation (κ = 0.63), and atrophy (κ = 0.52). ICCs for parenchymal thickness measurements ranged from 0.57 in the pancreas head to 0.80 in the body and tail. The ICC for duct diameter was 0.85. For MRI, kappa coefficients for categoric findings ranged from -0.01 to 0.74, with relatively high kappa coefficients noted for main duct irregularity (κ = 0.74), side branch dilatation (κ = 0.70), number of dilated side branches (κ = 0.65), and main duct dilatation (κ = 0.64); kappa coefficient for atrophy was 0.52. ICCs for parenchymal thickness measurements ranged from 0.53 for the neck and body individually to 0.68 in the tail. ICC for duct diameter was 0.77. CONCLUSION. Interobserver agreement was fair to moderate for most CT and MRI findings of chronic pancreatitis in children. CLINICAL IMPACT. This study highlights challenges for the imaging diagnosis of pediatric chronic pancreatitis. Standardized and/or objective criteria are needed given the importance of imaging in diagnosis.

Magnetic resonance imaging glossary of findings of pediatric pancreatitis and the revised Atlanta classification

While still uncommon, the incidence of acute pancreatitis in children has been increasing over the last two decades. The Atlanta classification for acute pancreatitis, developed for adults, stratifies cases of acute pancreatitis based on imaging and clinical criteria. This classification scheme allows for standardized use of terminology to facilitate treatment and prognostication. Although US and CT should be used in critical or unstable patients, MRI is an ideal imaging modality in pediatric patients with acute pancreatitis because of its ability to characterize tissue without ionizing radiation. We review MRI examples specific to Atlanta classification terminology in pediatric patients. Chronic pancreatitis has also been increasingly diagnosed in children, and imaging plays a key role in the diagnosis and management of this insidious disease. MRI with magnetic resonance cholangiopancreatography is the optimal modality for assessing the pancreas in a child with known or suspected chronic pancreatitis because it provides tissue characterization and high-contrast imaging of the pancreatic duct without the use of invasive instrumentation or ionizing radiation. We also review and demonstrate accepted MRI findings of chronic pancreatitis.

Acute pancreatitis in children: a review with clinical perspectives to enhance imaging interpretation

Pediatric acute pancreatitis has distinct etiologic, clinical and prognostic characteristics in contrast to the adult form of the disease. This review offers a comprehensive imaging update that emphasizes the importance of recognizing specific findings that are relevant from the clinical standpoint. Knowledge of these features facilitates communication among multidisciplinary team members and ultimately could lead to the improved care of pediatric acute pancreatitis patients.

Comparison of the Balthazar score of acute pancreatitis between computed tomography and ultrasound in children: pitfalls of ultrasound in diagnosing and evaluating pancreatitis

PURPOSE

To demonstrate the utility of ultrasound for predicting the outcome of pancreatitis in pediatric patients using the Balthazar score.

METHODS

Twenty-four children diagnosed with pancreatitis, who underwent computed tomography (CT) followed by ultrasound within 24 h, were included. The Balthazar score was calculated using both modalities based on the appearance of the pancreas (score 0-4). The association between the Balthazar scores with CT and ultrasound was evaluated using single linear regression analysis. To evaluate the sonographic accuracy, the ultrasound severity index and findings were compared with those of CT. Presence or absence of abnormal pancreatic parenchymal change on ultrasound was compared to the presence or absence of pancreatic necrosis on CT. The CT and sonographic findings were evaluated in eight intra-abdominal segments.

RESULTS

The Balthazar scores yielded by CT (2.2 ± 1.1, range 0-4) and ultrasound (2.0 ± 1.1, range 0-4) showed a significantly strong correlation (r = 0.918, p < 0.001). The accuracy of ultrasound in determining the CT Balthazar scores was 91.7% (95% confidence interval 73.0-99.0%, 22/24 patients). In the two cases with pancreatic necrosis on CT, only one case was detected as abnormal pancreatic parenchymal change. Sonographic diagnostic accuracy in the pancreatic head was lower than that in the body and tail (accuracy of the pancreatic head, body, and tail enlargement/edema = 83.3%/75%, 100%/100%, and 100%/100%, respectively).

CONCLUSIONS

The total CT and ultrasound severity indices were significantly correlated. Ultrasound is a useful modality for evaluating not only the initial pancreatic condition but also the severity of pediatric pancreatitis.

Normal pancreatic thickness values in healthy children: an MRI study

INTRODUCTION

Normal pancreatic thickness values on ultrasound (US) have been defined in literature. However, there is insufficient information about normal pancreatic measurements acquired from computed tomography (CT) or magnetic resonance imaging (MRI). To define normal pancreatic thickness measurements acquired from different localizations in order to provide reference values for more objectively identified parenchymal thickness changes.

MATERIALS AND METHODS

A retrospective evaluation was made of the abdominal MRI examinations of 162 pediatric patients. Patients with any pancreatic disease, or chronic gastrointestinal inflammatory disease were excluded from the study. Measurements were taken from T2-weighted images.

RESULTS

Evaluation was made of 162 children, comprising 82 (50.6%) males and 80 (49.3%) females with a mean age of 9.8 ± 2.4 years. Mean pancreatic thickness was 18.3 ± 3.1 mm, 10.2 ± 2.9 mm, 14.9 ± 3 mm, 14.9 ± 3.3 mm in head, neck, body and tail localizations, accordingly. A positive correlation was determined between age, height, weight, body mass index (BMI) and pancreatic thickness in all the anatomic localizations (r > 0.55, p < 0.05). No significant difference was determined with gender. Interobserver agreement between two researchers was moderate and strong according to the different anatomic localizations.

CONCLUSIONS

The defined normal ranges are mostly consistent with previously published US and CT based values. Pancreatic thickness values were positively correlated with age, height, weight and BMI for all four anatomical regions of the pancreas. Knowledge of normal pancreatic thickness values will increase the diagnostic accuracy of radiologists in the assessment of pancreatic diseases and may aid in interpreting atrophy in the setting of chronic pancreatitis.

Current State of Imaging of Pediatric Pancreatitis: AJR Expert Panel Narrative Review

Pancreatitis is as common in children as it is in adults, though causes and accepted imaging strategies differ in children. In this narrative review we discuss the epidemiology of childhood pancreatitis and key imaging features for pediatric acute, acute recurrent, and chronic pancreatitis. We rely heavily on our collective experience in discussing advantages and disadvantages of different imaging modalities; practical tips for optimization of ultrasound, CT, and MRI with MRCP in children; and image interpretation pearls. Challenges and considerations unique to imaging pediatric pancreatitis are discussed, including timing of imaging, role of secretin-enhanced MRCP, utility of urgent MRI, severity prediction, autoimmune pancreatitis, and best methods for serial imaging. We suggest a methodical approach to pancreatic MRI interpretation in children and have included a sample structured report, and we provide consensus statements according to our experience imaging children with pancreatitis.

North American Society for Pediatric Gastroenterology, Hepatology and Nutrition and the Society for Pediatric Radiology Joint Position Paper on Noninvasive Imaging of Pediatric Pancreatitis: Literature Summary and Recommendations

ABSTRACT

The reported incidence of pediatric pancreatitis is increasing. Noninvasive imaging, including ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), play important roles in the diagnosis, staging, follow-up, and management of pancreatitis in children. In this position paper, generated by members of the Pancreas Committee of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) and the Abdominal Imaging Committee of The Society for Pediatric Radiology (SPR), we review the roles of noninvasive imaging in pediatric acute, acute recurrent, and chronic pancreatitis. We discuss available evidence related to noninvasive imaging, highlighting evidence specific to pediatric populations, and we make joint recommendations for use of noninvasive imaging. Further, we highlight the need for research to define the performance and role of noninvasive imaging in pediatric pancreatitis.

Ultrasound has limited diagnostic utility in children with acute lymphoblastic leukemia developing pancreatitis

PURPOSE

Acute pancreatitis (AP) due to chemotherapy-induced pancreatic injury is a common side effect of treatment for acute lymphoblastic leukemia (ALL), the most common childhood malignancy. The American College of Radiology recommends ultrasound (US) for initial imaging of AP in all populations to assess for ductal obstruction. However, US may be insensitive to diagnose and assess chemotherapy-associated AP.

METHODS AND MATERIALS

The institutional review board approved this retrospective study. Patients with ALL and AP were identified from protocol databases, using Common Terminology Criteria for Adverse Events (CTCAE) version 3. Chemotherapy dosing, amylase/lipase levels, clinical symptoms, and US/computed tomography (CT) reports within 10 days of diagnosis were recorded. All CT images were reviewed for revised Atlanta classification and CT severity index (CTSI).

RESULTS

Sixty-nine patients, aged 2-21 years, experienced 88 episodes of AP, undergoing 98 US and 44 CT. Seventy-two events (82%) occurred within 30 days of asparaginase administration. Sixty-nine episodes (78%) were initially diagnosed by the presence of abdominal pain and pancreatic enzyme elevation. Overall sensitivities for AP detection were 47% using US and 98% for CT. US sensitivity was greatest in CTCAE grade 4 (86%) and necrotizing pancreatitis (67%).

CONCLUSIONS

Most cases of AP in children with ALL can be diagnosed with clinical history and labs. US has limited sensitivity in detecting pancreatitis in this population. Imaging to diagnose AP in this patient population could be limited to clinically equivocal cases.

Validation of threshold values for pancreas thickness and T1-weighted signal intensity ratio in the pediatric pancreas

BACKGROUND

Pancreas atrophy and the loss of T1-weighted signal intensity by magnetic resonance imaging (MRI) are findings of chronic pancreatitis.

OBJECTIVE

The purpose of this study was to test published normal values and cutoffs for pancreas thickness and the pancreas:spleen T1-weighted signal intensity ratio in children without pancreatic disease.

MATERIALS AND METHODS

This was a secondary analysis of prospectively collected MRI data for 50 children (range: 6.3-15.9 years; 27 female) with no history of pancreatic disease. Two observers (R1, R2) measured linear pancreas thickness on axial T1-weighted, fat-saturated gradient recalled echo images and placed regions of interest in the pancreas and spleen to calculate the T1-weighted signal intensity ratio. Measurements were compared to published pediatric normal values (computed tomography [CT], ultrasound [US]) and adult cutoffs (CT, MRI).

RESULTS

Compared to published pediatric values for CT, 68% (R1: 34/50) or 40% (R2: 22/50) of participants had ≥1 pancreas segment with thickness below the normal range. No participant had a thickness value below the normal range published for US. Compared to cutoff values in adults, 84% (R1: 42/50) or 80% (R2: 40/50) of participants met the criteria for pancreas atrophy. Mean T1-weighted signal intensity ratio was 1.33±0.15 (R1) and 1.32±0.16 (R2). Twelve (R1: 24.5% of 49) or 11/49 (R2: 22.4%) participants had a T1-weighted signal intensity ratio below the threshold associated with exocrine insufficiency in adults.

CONCLUSION

Previously defined thresholds for pancreas thickness and pancreas:spleen T1-weighted signal intensity ratio appear too restrictive for a pediatric population. Further study is needed to define optimal quantitative metrics for findings of chronic pancreatitis in children.

Healthy pancreatic parenchymal volume and its relationship to exocrine function

BACKGROUND

Pancreatic atrophy as a finding of chronic pancreatitis has largely been a subjective finding. Cross-sectional imaging should provide a means to quantify pancreatic atrophy.

OBJECTIVE

The purposes of this study were to: (1) quantify pancreatic volume by magnetic resonance imaging (MRI) in a cohort of children without pancreatic disease, (2) define predictors of pancreatic volume and (3) assess the relationship between pancreatic volume and pancreatic fluid secretion.

MATERIALS AND METHODS

This study involved further analysis of data collected as part of an institutional review board-approved prospective study of secreted fluid volume in response to secretin in 50 healthy children ages 6-16 years. The pancreas was manually segmented on axial MR images to calculate pancreatic volume. Pearson correlation or the Student's t-test were used to define associations between pancreatic volume and patient characteristics and previously calculated secreted fluid volume. Quantile regression was used to define the 5th percentile for pancreatic volume based on body surface area (BSA) [1].

RESULTS

Mean pancreatic volume was 46.0±18.8 mL with no significant difference based on sex (boys: 42.4±19 mL, girls: 49.1±18.3 mL, P=0.21). Pancreatic volume was moderately correlated with age (r=0.51, P=0.002) and strongly correlated with BSA (r=0.75, P<0.0001), with the 5th percentile for pancreatic volume defined by: (24.66×BSA) - 4.97. Pancreatic volume was moderately correlated with volume of fluid secreted after secretin administration (r=0.51, P=0.0002).

CONCLUSION

We report increasing pancreatic volumes by MRI during childhood in a cohort of children without pancreatic disease. We have also shown that pancreatic volume is associated with secreted fluid volume as measured by MRI.