MR imaging of hemorrhage associated with acute pancreatitis

Acute pancreatitis: A review of diagnosis, severity prediction and prognosis assessment from imaging technology, scoring system and artificial intelligence

Acute pancreatitis (AP) is a potentially life-threatening inflammatory disease of the pancreas, with clinical management determined by the severity of the disease. Diagnosis, severity prediction, and prognosis assessment of AP typically involve the use of imaging technologies, such as computed tomography, magnetic resonance imaging, and ultrasound, and scoring systems, including Ranson, Acute Physiology and Chronic Health Evaluation II, and Bedside Index for Severity in AP scores. Computed tomography is considered the gold standard imaging modality for AP due to its high sensitivity and specificity, while magnetic resonance imaging and ultrasound can provide additional information on biliary obstruction and vascular complications. Scoring systems utilize clinical and laboratory parameters to classify AP patients into mild, moderate, or severe categories, guiding treatment decisions, such as intensive care unit admission, early enteral feeding, and antibiotic use. Despite the central role of imaging technologies and scoring systems in AP management, these methods have limitations in terms of accuracy, reproducibility, practicality and economics. Recent advancements of artificial intelligence (AI) provide new opportunities to enhance their performance by analyzing vast amounts of clinical and imaging data. AI algorithms can analyze large amounts of clinical and imaging data, identify scoring system patterns, and predict the clinical course of disease. AI-based models have shown promising results in predicting the severity and mortality of AP, but further validation and standardization are required before widespread clinical application. In addition, understanding the correlation between these three technologies will aid in developing new methods that can accurately, sensitively, and specifically be used in the diagnosis, severity prediction, and prognosis assessment of AP through complementary advantages.

Acute pancreatitis: Structured report template of magnetic resonance imaging

Acute pancreatitis (AP) is a common acute abdomen disease of the digestive system. It has a potentially fatal risk because of its variable severity and various complications. With the widespread application of the Revised Atlanta Classification, new requirements for AP imaging reports are introduced. Experts in abdominal radiology and pancreatology in the United States published the first structured computed tomography reporting template for AP in 2020. However, there is no corresponding structured magnetic resonance imaging (MRI) reporting template globally. Therefore, this article focuses on the structured MRI report of AP images from our pancreatitis imaging center, which is intended to improve the systematic understanding of this disease and standardize the writing of MRI structured reports. In the meantime, we aim to promote the clinical diagnosis and assessment of MRI efficacy for AP and its multiple complications. It is further intended to facilitate academic exchanges and scientific research between different medical centers.

Basic pancreatic lesions: Radiologic-pathologic correlation

The basic pancreatic lesions include location, size, shape, number, capsule, calcification/calculi, hemorrhage, cystic degeneration, fibrosis, pancreatic duct alterations, and microvessel. One or more basic lesions form a kind of pancreatic disease. As recognizing the characteristic imaging features of pancreatic basic lesions and their relationships with pathology aids in differentiating the variety of pancreatic diseases. The purpose of this study is to review the pathological and imaging features of the basic pancreatic lesions.

Three-Dimensional Radiomics Features of Magnetic Resonance T2-Weighted Imaging Combined With Clinical Characteristics to Predict the Recurrence of Acute Pancreatitis

Objective

To explore the diagnostic value of radiomics model based on magnetic resonance T2-weighted imaging for predicting the recurrence of acute pancreatitis.

Methods

We retrospectively collected 190 patients with acute pancreatitis (AP), including 122 patients with initial acute pancreatitis (IAP) and 68 patients with recurrent acute pancreatitis (RAP). At the same time, the clinical characteristics of the two groups were collected. They were randomly divided into training group and validation group in the ratio of 7:3. One hundred thirty-four cases in the training group, including 86 cases of IAP and 48 cases of RAP. There were 56 cases in the validation group, including 36 cases of IAP and 20 cases of RAP. Least absolute shrinkage and selection operator (LASSO) were used for feature screening. Logistic regression was used to establish the radiomics model, clinical model and combined model for predicting AP recurrence. The predictive ability of the three models was evaluated by the area under the curve (AUC). The recurrence risk in patients with AP was assessed using the nomogram.

Results

The AUCs of radiomics model in training group and validation group were 0.804 and 0.788, respectively. The AUCs of the combined model in the training group and the validation group were 0.833 and 0.799, respectively. The AUCs of the clinical model in training group and validation group were 0.677 and 0.572, respectively. The sensitivities of the radiomics model, combined model, and clinical model were 0.646, 0.691, and 0.765, respectively. The specificities of the radiomics model, combined model, and clinical model were 0.791, 0.828, and 0.590, respectively. There was no significant difference in AUC between the radiomics model and the combined model for predicting RAP (p = 0.067). The AUCs of the radiomics model and combined model were greater than those of the clinical model (p = 0.008 and p = 0.007, respectively).

Conclusions

Radiomics features based on magnetic resonance T2WI could be used as biomarkers to predict the recurrence of AP, and radiomics model and combined model can provide new directions for predicting recurrence of acute pancreatitis.

MR Imaging for Early Extrapancreatic Necrosis in Acute Pancreatitis

RATIONALE AND OBJECTIVES

To study the MRI characteristics of early extrapancreatic necrosis and compare them with those of peripancreatic fluid collections in acute pancreatitis (AP).

MATERIALS AND METHODS

This retrospective study enrolled 70 AP patients who had extrapancreatic collections visible on MRI within 1 week of onset. Extrapancreatic collections were divided into extrapancreatic necrosis and peripancreatic fluid collections based on follow-up MRI, CT, or pathology. The number and area of extrapancreatic collections, extrapancreatic inflammation on MRI (EPIM) score, MR severity index score and clinical characteristics were evaluated and compared between the two groups.

RESULTS

Of the seventy AP patients, 32 (45.7%) had extrapancreatic necrosis, and 38 (54.3%) had peripancreatic fluid collections. The number and area of extrapancreatic collections, MR severity index score, EPIM score, and prevalence of associated hemorrhage were significantly higher in extrapancreatic necrosis patients than in those with peripancreatic fluid collections (p < 0.001). Among the single indicators, the accuracy of the area of extrapancreatic collections (AUC = 0.871) was comparable to that of the EPIM score for predicting extrapancreatic necrosis and was significantly higher than that of the other two indicators. The combination of all indicators showed the highest predictive accuracy (AUC = 0.949), and combinations of two or more indicators demonstrated significantly higher predictive accuracy for extrapancreatic necrosis than any single indicator (p < 0.05) except for the area of extrapancreatic collections (p > 0.05).

CONCLUSION

The MRI characteristics have the potential to differentiate early extrapancreatic necrosis from peripancreatic fluid collections and help indicate extrapancreatic necrosis.

Magnetic Resonance Imaging-Based Radiomics Models to Predict Early Extrapancreatic Necrosis in Acute Pancreatitis

OBJECTIVE

The aim of the study was to investigate radiomics models based on magnetic resonance imaging (MRI) for predicting early extrapancreatic necrosis (EXPN) in acute pancreatitis.

METHODS

Radiomics features were extracted from T2-weighted images of extrapancreatic collections and late arterial-phase images of the pancreatic parenchyma for 135 enrolled patients (94 in the primary cohort, including 47 EXPN patients and 41 in the validation cohort, including 20 EXPN patients). The optimal features after dimension reduction were used for radiomics modeling through a support vector machine. A clinical model, the MR severity index score, and extrapancreatic inflammation on MRI were evaluated.

RESULTS

Twelve optimal features from the extrapancreatic collection images and 10 from the pancreatic parenchyma images were selected for modeling. The pancreatic parenchyma-based and extrapancreatic collection-based radiomics models showed good predictive accuracy in both the training and validation cohorts. The areas under the curve of the extrapancreatic collection-based radiomics model (0.969 and 0.976) were consistent with those of the pancreatic parenchyma-based model (0.931 and 0.921) for both cohorts and better than those of the clinical model and imaging scores for both cohorts.

CONCLUSIONS

The MRI-based radiomics models of both the extrapancreatic collections and the pancreatic parenchyma had excellent predictive performance for early EXPN.

The role of imaging in acute pancreatitis

Acute pancreatitis is one of the most commonly encountered etiologies in the emergency setting, with a broad spectrum of findings that varies in severity from mild interstitial pancreas to severe forms with significant local and systemic complications that are associated with a substantial degree of morbidity and mortality. In this article the radiological aspect of the terminology and classification of acute pancreatitis are reviewed. The roles of ultrasound, computed tomography, and magnetic resonance imaging in the diagnosis and evaluation of acute pancreatitis and its complications are discussed. The authors present a practical image-rich guide, applying the revised Atlanta classification system, with the goal of facilitating radiologists to write a correct report, and reinforcing the radiologist’s role as a key member of a multidisciplinary team in treating patients with acute pancreatitis. Computed tomography is the most performed imaging test for acute pancreatitis. Nevertheless, MRI is useful in many specific situations, due to its superiority soft tissue contrast resolution and better assessment of biliary and pancreatic duct, for example in the ductal disconnection. The purpose if this article is to review recent advances in imaging acquisition and analytic techniques in the evaluation of AP.

Early-phase vascular involvement is associated with acute pancreatitis severity: a magnetic resonance imaging study

Background

Although a number of studies have reported on the vascular abnormalities detected by magnetic resonance imaging (MRI) in patients with late-phase acute pancreatitis (AP), few have studied those occurring in the early phase of the disease. The aim of this research was to investigate the MRI findings of early vascular abnormalities in AP and to analyze the correlation of the prevalence of vascular involvement with the severity of AP based on the MR severity index (MRSI) and Acute Physiology and Chronic Health Evaluation (APACHE) II scores.

Methods

A retrospective analysis was conducted of 301 consecutive AP patients who were admitted to our institution between March 2013 and June 2019. All patients underwent initial MRI during the early phase of pancreatitis and one or more repeat MRI scans in the late phase. Peripancreatic vascular conditions and pancreatitis were assessed using T1-/T2-weighted imaging and dynamic-enhanced MRI. The association between the prevalence of vascular involvement and AP severity graded according to the MRSI or APACHE II score was analyzed using Spearman's rank correlation.

Results

Among 301 AP patients, 75 (24.9%) had at least one MRI-detected vascular abnormality. Overall, vascular involvement on MRI was higher in necrotizing pancreatitis than in edematous pancreatitis [43.2% (54/125) vs. 11.9% (21/176), χ²=38.2, P<0.001]. In the early phase of AP, the prevalence of splenic vein phlebitis, portal vein phlebitis, and splenic arterial arteritis was 24.9% (75/301), 22.3% (67/301), and 19.9% (60/301), respectively. Splenic vein phlebitis was seen on initial MRI in 55.6% (15/27) of patients who had splenic vein thrombosis on repeat MRI. The MRSI scores showed that the prevalence of splenic vein phlebitis, portal vein phlebitis, and splenic arterial arteritis, respectively, was correlated with the severity of pancreatitis (r=0.532, 0.487, and 0.456; all P<0.01). The APACHE II scores showed that the prevalence of MRI-detected vascular involvement was significantly correlated with AP severity (r=0.335, P<0.05).

Conclusions

Vascular abnormalities, including splenic vein phlebitis and splenic arterial arteritis, are commonly seen on MRI in patients with early-phase AP, and they may be supplementary indicators that can reflect the severity of pancreatitis.

Magnetic resonance severity index assessed by T1-weighted imaging for acute pancreatitis: correlation with clinical outcomes and grading of the revised Atlanta classification-a narrative review

Acute pancreatitis (AP) is a common disease that may involve pancreas and peripancreatic tissues with a prevalence of up to 50 per 100,000 individuals for year. The Atlanta classification was assessed for the first time in 1992 and modified in 2012 in order to describe morphological features of AP and its complications. AP can be morphologically distinguished in two main types: interstitial edematous pancreatitis (IEP) and necrotizing pancreatitis (NEP). This classification is very important because the presence of necrosis is directly linked to local or systemic complications, hospital stays and death. Magnetic resonance (MR) is very useful to characterize morphological features in AP and its abdominal complications. Particularly we would like to underline the diagnostic, staging and prognostic role of T1-weighted images with fat suppression that could be significant to assess many features of the AP inflammatory process and its complications (detection of the pancreatic contour, pancreatic necrosis, presence of haemorrhage). Signs of inflammatory and edema are instead observed by T1-weighted images. MR cholangiopancreatography (MRCP) is necessary to study the main pancreatic duct and the extrahepatic biliary tract and contrast-enhancement magnetic resonance imaging (MRI) allows to assess the extent of necrosis and vascular injuries.

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.

Hemorrhage complicating the course of severe acute pancreatitis

Backgrounds/Aims

The course of severe acute pancreatitis (SAP) complicated by hemorrhage is associated with poor outcome.

Methods

Twenty-four (13%) out of 183 cases of SAP had hemorrhagic complications- 12 intraabdominal & 12 intraluminal, 13 had major & 11 had minor and 16 had de-novo & 8 post-surgical bleeding. The mean duration of pancreatitis prior to bleeding was 27±27.2 days.

Results

Predictors of haemorrhage on univariate analysis were delayed admission (0.037), more than one organ failure (p=0.008), presence of venous thrombosis (p=0.033), infective necrosis (0.001) and systemic sepsis – bacterial (0.037) & fungal (p=0.032). On multivariate analysis infected necrosis (OR=11.82) and presence of fungal sepsis (OR=3.73) were the significant factors. Patients presenting with more than one organ failure and bacterial sepsis had borderline significance on multivariate analysis. Need for surgery (50% vs. 12.6%), intensive care stay (7.4±7.9 vs. 5.4±5.2 days) and mortality (41.7% vs. 10.7%) were significantly higher in patients who suffered haemorrhage. Seven of the 13 with major bleeding had pseudoaneurysms-4 were embolized, 4 needed surgery including 1 embolization failure. Seven with intraabdominal bleeding required surgical intervention, 2 had successful embolization and 3 had expectant management. CT severity index and surgical intervention, were significantly associated with intraabdominal bleeding. Organ failure, presence of pseudoaneurysm and surgical intervention were associated with major bleeding.

Conclusions

Hemorrhage in SAP was associated with increased morbidity and mortality. Infected necrosis accentuated the degradation of the vessel wall, which predispose to hemorrhage. Luminal bleeding may be indicative of erosion into the adjacent viscera by the pseudoaneurysm.

Imaging guidelines for acute pancreatitis: when and when not to image

In patients with acute pancreatitis (AP), diagnostic imaging is performed for various reasons, including the detection of the etiology (e.g., biliary obstruction caused by gallstones), diagnosis of pancreatitis in an unclear clinical setting, assessment of the severity of the process, and evaluation of its complications. In spite of the potential benefits of these imaging studies in the setting of AP, especially economic consequences but also medical risks are associated with diagnostic imaging, including increase of the effective radiation dose received by patients with AP and rising health care costs, frequently without impact on management. The rising incidence of acute pancreatitis in the Western world is escalating its financial burden with national health care expenses of over 2.5 billion dollars annually. Despite evidence-based national recommendations on utilization of diagnostic imaging in patients with AP, unnecessary imaging studies are still frequently performed, especially in the early hospital course. The purpose of this article is, therefore, to review the imaging guidelines for acute pancreatitis with regards to when and when not to image, with the aim to minimize inappropriate utilization.

Acute Pancreatitis in Patients With a Medical History of Type 2 Diabetes Mellitus: Clinical Findings and Magnetic Resonance Imaging Characteristics

OBJECTIVE

To determine the characteristics of type 2 diabetes mellitus (T2DM)-related acute pancreatitis (AP) on magnetic resonance imaging (MRI).

METHODS

Retrospectively studied 262 patients with AP were admitted to our institution and underwent MRI. Diagnosis of T2DM-related AP was based on clinical manifestations, laboratory tests, and MRI. Pancreatic/peripancreatic changes were assessed on MRI.

RESULTS

Fifty-three (20.2%) patients with T2DM-related AP and 209 (79.8%) with nondiabetic AP were enrolled. On MRI, a higher prevalence of necrotizing pancreatitis (P < 0.001), pancreatic necrosis >30% (57.5% vs 29.2%; P = 0.006), hemorrhage (35.8% vs 19.1%; P = 0.009), abdominal wall edema (67.9% vs 46.8%; P = 0.006), walled-off necrosis (43.2% vs 14.6%; P < 0.001), and infected collections (P < 0.001) were registered in T2DM with AP. T2DM-related AP sustained greater magnetic resonance severity index (mean, 5.1 [range, 2-10] vs 3.4 [range, 1-10]; P < 0.001), higher incidence of moderate and severe pancreatitis (69.8% vs 40.2%; P < 0.001), higher organ failure (45.3% vs 22%; P = 0.001), and prolonged hospitalization (mean, 25.2 [range, 10-63] vs 16 [range, 5-48] days; P < 0.001).

CONCLUSIONS

Type 2 diabetes mellitus-related AP is more moderate-to-severe pancreatitis, and it correlates with MRI characteristics of the pancreas itself, hemorrhage, abdominal wall, and infected collections.

Current concepts for the diagnosis of acute pancreatitis by multiparametric magnetic resonance imaging

Acute pancreatitis is classically characterized by acute chemical inflammation of the pancreatic gland itself, peripancreatic tissues, and even remote organs. The newly revised Atlanta Classification 2012 redefined the patterns of pancreatic necrosis and local complications in acute pancreatitis. The Atlanta Classification's novelty was in emphasizing that extrapancreatic fat necrosis, which leads to walled-off necrosis, is associated with poor prognosis. Conversely, the free fluid liquid was considered to be less related to complications. The Atlanta's classification's main weakness is that it is mainly computed tomography (CT) based, as contrast-enhanced CT is the predominant imaging technique used for evaluating a wide range of pathological processes of acute pancreatitis. However, some local complications are difficult to distinguish accurately on CT. Recent advances, including significantly better soft-tissue contrast, favor multiparametric magnetic resonance imaging (mpMRI) for a more comprehensive assessment of acute pancreatitis pathology, particularly for small necrotic/fat debris within a collection. In addition, the MRI severity index (MRSI), which combines Balthazar's grade points and points of the extent of pancreatic necrosis, has been proven to be crucial for the initial evaluation, staging, and prognosis of acute pancreatitis. Other innovations, such as the recognition of important MRI features in acute pancreatitis and the utilization of newer, more effective terminology for imaging reporting assistance in the differentiation of the common local complications following this disease, have improved the treatment for acute pancreatitis. In this paper, with reference to the 2012 revised Atlanta classification, we review the strengths and limitations of MRI for identifying acute pancreatitis, the MRI findings of a spectrum of pathological entities, and the important local complications secondary to acute pancreatitis.

MR imaging for acute pancreatitis: the current status of clinical applications

Acute pancreatitis is a common clinical acute abdomen. Imaging examinations play an important role in the management of acute pancreatitis. MR imaging is a noninvasive examination with high tissue contrast and a variety of acquisition sequences that can help determine the diagnosis, complications and severity of acute pancreatitis. The acute pancreatitis classification working group modified the Atlanta classification in 2012 to improve clinical evaluations and standardize the radiologic nomenclature for acute pancreatitis. In particular, the redefinition of necrotizing pancreatitis offers a new understanding of this disease. In clinical practice, there is still a lack of unifying standards between radiologists and physicians, such as for the imaging features of pseudocysts, walled-off necrosis, peripancreatic necrosis and especially for the MR imaging features of acute pancreatitis. In this article, we review the 2012 revised Atlanta classification of acute pancreatitis and recent advances in the clinical applications of MR imaging (MRI) in acute pancreatitis by showing how MRI can provide more optimized information for clinical diagnosis and treatment plan.