Secretin-stimulated MRI assessment of exocrine pancreatic function in patients with cystic fibrosis and healthy controls

Assessment of exocrine pancreatic function in children and adolescents with direct and indirect testing

The exocrine pancreas plays an important role in digestion. Understanding of the physiology and regulation of exocrine function provides insight into disease processes and basis of functional testing. Specifically, exocrine pancreatic insufficiency (EPI) can cause maldigestion and thus a proper assessment of exocrine pancreatic function is important. There are indirect and direct methods for evaluating pancreatic function. Indirect methods are varied and include stool, serum, urine, and breath tests. Fecal elastase is a commonly used indirect test today. Direct methods involve stimulated release of pancreatic fluid that is collected from the duodenum and analyzed for enzyme activity. The most used direct test today is the endoscopic pancreatic function test. Indirect pancreatic function testing is limited in identifying cases of mild to moderate EPI, and as such in these cases, direct testing has higher sensitivity and specificity in diagnosing EPI. This review provides a comprehensive guide to indirect and direct pancreatic function tests as well as an in-depth look at exocrine pancreatic function including anatomy, physiology, and regulatory mechanisms.

Correlation of Pancreatic T1 Values Using Modified Look-Locker Inversion Recovery Sequence (MOLLI) with Pancreatic Exocrine and Endocrine Function

Quantifying myocardial T1 values has been useful for detecting and characterizing fibrotic appearance in myocardial infarction, focal scars, and non-ischemic cardiomyopathies. Since pancreatic exocrine function decreases with chronic pancreatic fibrosis advancement, this study examined the correlation between pancreatic T1 values and pancreatic exocrine and endocrine insufficiency.

METHODS

Thirty-two patients underwent abdominal contrast-enhanced MRI in our department between October 2017 and February 2019. We evaluated the T1 values of the pancreas using a modified Look-Locker inversion recovery sequence (MOLLI), pancreatic exocrine insufficiency (PEI) by fecal elastase 1 (FE1) values, and pancreatic endocrine insufficiency using fasting insulin and blood glucose levels to calculate the HOMA-β. This trial is registered in the UMIN Clinical Trials Registry as UMIN 000030067.

RESULTS

The median cohort (9 males and 23 females) age was 71 (range: 49-84) years. Eighteen patients had pancreatic cysts, three had alcohol-induced chronic pancreatitis, three had pancreatic cancer, and eight possessed other pancreatic features (two patients each with autoimmune pancreatitis, acute pancreatitis, or a bile duct tumor, one with idiopathic chronic pancreatitis, and one healthy control with negative findings). The median pancreatic T1 value measured by the MOLLI was 857.5 ms (597-2569). A significant negative correlation was found between the T1 mapping and FE1 values (r = 0.69, p < 0.01), with none for the T1 with HOMA-β or serum albumin, triglycerides, or body mass index.

CONCLUSIONS

the pancreatic T1 values correlated significantly with pancreatic exocrine function and might be useful in PEI diagnosis.

Secretin-Stimulated Magnetic Resonance Imaging Reveals Variable Diagnostic Accuracy According to Etiology in Pancreatic Disease

OBJECTIVES

Secretin-stimulated magnetic resonance imaging (s-MRI) is the best validated radiological modality assessing pancreatic exocrine secretion. In this prospective observational study, we compare the diagnostic accuracy of s-MRI for exocrine pancreatic failure due to different pancreatic diseases and healthy controls.

METHODS

We performed s-MRI in 21 cystic fibrosis (CF) patients, 78 patients with chronic pancreatitis (CP) and 20 healthy controls. Exocrine failure was defined by fecal elastase-1 of less than 200 μg/g or bicarbonate concentration from endoscopic secretin test of less than 80 mmol/L.

RESULTS

Eleven CF and 61 CP patients were exocrine insufficient. Insufficient CF patients had lower s-MRI volume output compared with all other groups (P < 0.05). Insufficient CP patients had reduced volume output compared with controls and sufficient CF (P < 0.05). Secretin-stimulated MRI yielded overall accuracy of 0.78 (95% confidence interval [CI], 0.70-0.86) for exocrine failure. When divided according to etiology, the test yielded accuracy of 0.95 (95% CI, 0.90-1) in CF and 0.73 (95% CI, 0.64-0.82) in CP.

CONCLUSIONS

The accuracy of s-MRI volume output measures to diagnose exocrine failure was higher in CF than in CP. Differences in s-MRI volume output in patients with exocrine failure may be due to different etiological and pathogenic mechanisms in CF and CP.

Will MRI of gastrointestinal function parallel the clinical success of cine cardiac MRI?

Cine cardiac MRI is generally accepted as the "gold-standard" for functional myocardial assessment. It only took a few years after the development of commercial MRI systems for functional cardiac imaging to be developed, with electrocardiogram (ECG)-gated cine imaging first reported in 1988. The function of the gastrointestinal (GI) tract is more complex to study compared to the heart. However, the idea of having a non-invasive tool to study the GI function that also allows the concurrent assessment of different aspects of this function has become more and more attractive in the gastroenterological field. This review summarises key literature of the last 5 years to describe the current status of MRI in respect to the evaluation of GI function, highlighting the gaps and challenges and the future prospects. As the clinical application of a new technique requires that its clinical utility is confirmed by demonstration of its ability to enable clinicians to make a diagnosis and/or predict the treatment response, this review also considers whether or not this has been achieved, and how MRI has been validated against techniques currently recognised as the gold standard in clinical practice.

Guidelines for the Diagnostic Cross Sectional Imaging and Severity Scoring of Chronic Pancreatitis

The paper presents the international guidelines for imaging evaluation of chronic pancreatitis. The following consensus was obtained: Computed tomography (CT) is often the most appropriate initial imaging modality for evaluation of patients with suspected chronic pancreatitis (CP) depicting most changes in pancreatic morphology. CT is also indicated to exclude other potential intraabdominal pathologies presenting with symptoms similar to CP. However, CT cannot exclude a diagnosis of CP nor can it be used to exclusively diagnose early or mild disease. Here magnetic resonance imaging (MRI) and MR cholangiopancreatography (MRCP) is superior and is indicated especially in patients where no specific pathological changes are seen on CT. Secretin-stimulated MRCP is more accurate than standard MRCP in the depiction of subtle ductal changes. It should be performed after a negative MRCP, when there is still clinical suspicion of CP. Endoscopic ultrasound (EUS) can also be used to diagnose parenchymal and ductal changes mainly during the early stage of the disease. No validated radiological severity scoring systems for CP are available, although a modified Cambridge Classification has been used for MRCP. There is an unmet need for development of a new and validated radiological CP severity scoring system based on imaging criteria including glandular volume loss, ductal changes, parenchymal calcifications and parenchymal fibrosis based on CT and/or MRI. Secretin-stimulated MRCP in addition, can provide assessment of exocrine function and ductal compliance. An algorithm is presented, where these imaging parameters can be incorporated together with clinical findings in the classification and severity grading of CP.

Chronic pancreatitis: review and update of etiology, risk factors, and management

Chronic pancreatitis is a syndrome involving inflammation, fibrosis, and loss of acinar and islet cells which can manifest in unrelenting abdominal pain, malnutrition, and exocrine and endocrine insufficiency. The Toxic-Metabolic, Idiopathic, Genetic, Autoimmune, Recurrent and Severe Acute Pancreatitis, Obstructive (TIGAR-O) classification system categorizes known causes and factors that contribute to chronic pancreatitis. Although determining disease etiology provides a framework for focused and specific treatments, chronic pancreatitis remains a challenging condition to treat owing to the often refractory, centrally mediated pain and the lack of consensus regarding when endoscopic therapy and surgery are indicated. Further complications incurred include both exocrine and endocrine pancreatic insufficiency, pseudocyst formation, bile duct obstruction, and pancreatic cancer. Medical treatment of chronic pancreatitis involves controlling pain, addressing malnutrition via the treatment of vitamin and mineral deficiencies and recognizing the risk of osteoporosis, and administering appropriate pancreatic enzyme supplementation and diabetic agents. Cornerstones in treatment include the recognition of pancreatic exocrine insufficiency and administration of pancreatic enzyme replacement therapy, support to cease smoking and alcohol consumption, consultation with a dietitian, and a systematic follow-up to assure optimal treatment effect.

Secretin-stimulated ultrasound estimation of pancreatic secretion in cystic fibrosis validated by magnetic resonance imaging

OBJECTIVES

Secretin-stimulated magnetic resonance imaging (s-MRI) is the best validated radiological modality assessing pancreatic secretion. The purpose of this study was to compare volume output measures from secretin-stimulated transabdominal ultrasonography (s-US) to s-MRI for the diagnosis of exocrine pancreatic failure in cystic fibrosis (CF).

METHODS

We performed transabdominal ultrasonography and MRI before and at timed intervals during 15 minutes after secretin stimulation in 21 CF patients and 13 healthy controls. To clearly identify the subjects with reduced exocrine pancreatic function, we classified CF patients as pancreas-sufficient or -insufficient by secretin-stimulated endoscopic short test and faecal elastase.

RESULTS

Pancreas-insufficient CF patients had reduced pancreatic secretions compared to pancreas-sufficient subjects based on both imaging modalities (p < 0.001). Volume output estimates assessed by s-US correlated to that of s-MRI (r = 0.56-0.62; p < 0.001). Both s-US (AUC: 0.88) and s-MRI (AUC: 0.99) demonstrated good diagnostic accuracy for exocrine pancreatic failure.

CONCLUSIONS

Pancreatic volume-output estimated by s-US corresponds well to exocrine pancreatic function in CF patients and yields comparable results to that of s-MRI. s-US provides a simple and feasible tool in the assessment of pancreatic secretion.

KEY POINTS

• Cystic fibrosis patients with affected pancreas have reduced pancreatic secretions. • Secretin-stimulated sonography is a simple and feasible method to assess pancreatic output. • Secretin-simulated MRI is a more precise method to assess pancreatic secretions. • The sonographic and MRI methods yielded comparable pancreatic secretory output estimates.

Magnetic resonance elastography and T1 mapping for early diagnosis and classification of chronic pancreatitis

BACKGROUND

Early detection and classification of chronic pancreatitis (CP) are both important and challenging.

PURPOSE

To investigate the diagnostic performance of MR elastography (MRE) and T1 mapping of the pancreas for different stages of CP.

STUDY TYPE

Retrospective.

SUBJECTS

Clinical and imaging records of 81 patients (from 5/2015 to 7/2017) with suspected CP were analyzed. Patients were categorized into the normal control (n = 35), mild CP (n = 30), and moderate/severe CP groups (n = 16) according to the Cambridge Classification based on concordant endoscopic retrograde cholangiopancreatography or ultrasound endoscopy findings.

FIELD STRENGTH/SEQUENCE

3T pancreatic MRI, which included MRE and T1 mapping.

ASSESSMENT

T1 relaxation times, pancreatic stiffness values, the main pancreatic duct (MPD) diameter, and pancreatic thickness were measured in all patients. Statistical Tests: Cutoff values of T1 relaxation times and pancreatic stiffness values for diagnosis of CP were calculated using receiver operating characteristic analysis. Associations of imaging parameters with different stages of CP were assessed using logistic regression analysis.

RESULTS

Both T1 relaxation times (865 ± 220 msec vs. 1075 ± 221 msec vs. 1350 ± 139 msec) and pancreatic stiffness (1.21 ± 0.13 kPa vs. 1.50 ± 0.15 kPa vs. 1.90 ± 0.16 kPa) differed significantly (P < 0.001) among the control, mild CP, and moderate/severe CP groups. Pancreatic stiffness (>1.34 kPa) achieved significantly higher area under the curve (AUC) than T1 relaxation time (>908.4 msec) for detection of mild CP (AUC: 0.928 vs. 0.751, P = 0.011). Pancreatic stiffness values (>1.61 kPa) also achieved significantly higher AUC than T1 relaxation time (>1131.6 msec) (AUC: 0.981 vs. 0.910, P = 0.033) for diagnosing moderate/severe CP from the other two groups. Multiple regression analysis showed that T1 relaxation time and stiffness were the independent factors associated with mild CP (P = 0.025 and <0.001, respectively).

DATA CONCLUSION

Both MRE and T1 mapping are promising quantitative imaging methods for evaluation of CP; MRE slightly outperformed T1 mapping.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018.

MRI assessed pancreatic morphology and exocrine function are associated with disease burden in chronic pancreatitis

BACKGROUND AND AIM

The aim of this study was to explore the association between morphological and functional secretin-stimulated MRI parameters with hospitalization, quality of life (QOL), and pain in patients with chronic pancreatitis (CP).

PATIENTS AND METHODS

This prospective cohort study included 82 patients with CP. Data were obtained from clinical information, QOL, and pain as assessed by questionnaires (The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire and modified Brief Pain Inventory short form). Secretin-stimulated MRI morphological parameters included pancreatic gland volume, main pancreatic duct diameter, the modified Cambridge Classification of Duct Abnormality, apparent diffusion coefficient, fat signal fraction, and the pancreatic secretion volume as a functional parameter. The primary outcomes were time to first hospitalization related to the CP, as well as annual hospitalization frequency and duration. The secondary outcomes were pain severity, QOL, and pain interference scores.

RESULTS

A main pancreatic duct diameter below 5 mm was associated with reduced time to first hospitalization (hazard ratio=2.06; 95% confidence interval: 1.02-4.17; P=0.043). Pancreatic secretion volume was correlated with QOL (r=0.31; P=0.0072) and pain interference score (r=-0.27; P=0.032), and fecal elastase was also correlated with QOL (r=0.28; P=0.017). However, functional and morphological findings were not related to pain intensity.

CONCLUSION

Advanced pancreatic imaging techniques may be a highly sensitive tool for prognostication and monitoring of disease activity and its consequences.

Endocrine and exocrine pancreatic insufficiency after acute pancreatitis: long-term follow-up study

Background

Patients could develop endocrine and exocrine pancreatic insufficiency after acute pancreatitis (AP), but the morbidity, risk factors and outcome remain unclear. The aim of the present study was to evaluate the incidence of endocrine and exocrine pancreatic insufficiency after AP and the risk factors of endocrine pancreatic insufficiency through a long-term follow-up investigation.

Methods

Follow-up assessment of the endocrine and exocrine function was conducted for the discharged patients with AP episodes. Oral Glucose Tolerance Test (OGTT) and faecal elastase-1(FE-1) test were used as primary parameters. Fasting blood-glucose (FBG), fasting insulin (FINS), glycosylated hemoglobin HBA1c, 2-h postprandial blood glucose (2hPG), Homa beta cell function index (HOMA-β), homeostasis model assessment of insulin resistance (HOMA-IR) and FE-1 were collected. Abdominal contrast-enhanced computed tomography (CECT) was performed to investigate the pancreatic morphology and the other related data during hospitalization was also collected.

Results

One hundred thirteen patients were included in this study and 34 of whom (30.1%) developed diabetes mellitus (DM), 33 (29.2%) suffered impaired glucose tolerance (IGT). Moreover, 33 patients (29.2%) developed mild to moderate exocrine pancreatic insufficiency with 100μg/g<FE-1<200μg/g and 7 patients (6.2%) were diagnosed with severe exocrine pancreatic insufficiency with FE-1<100μg/g. The morbidity of DM and IGT in patients with pancreatic necrosis was significant higher than that in the non-pancreatic necrosis group (X² = 13.442,P = 0.001). The multiple logistic regression analysis showed that extent of pancreatic necrosis<30% (P = 0.012, OR = 0.061) were the protective factors of endocrine pancreatic insufficiency. HOMA-IR (P = 0.002, OR = 6.626), Wall-off necrosis (WON) (P = 0.013, OR = 184.772) were the risk factors.

Conclusion

The integrated morbidity of DM and IGT after AP was 59.25%, which was higher than exocrine pancreatic insufficiency. 6.2% and 29.2% of patients developed severe and mild to moderate exocrine pancreatic insufficiency, respectively. The extent of pancreatic necrosis>50%, WON and insulin resistance were the independent risk factors of new onset diabetes after AP.

Electronic supplementary material

The online version of this article (10.1186/s12876-017-0663-0) contains supplementary material, which is available to authorized users.