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Correlation of Modified Computed Tomography Severity Index with Ranson’s Criteria in Assessing Severity of Acute Pancreatitis |
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S Mangalanandan, Divya Ann Thomas, Geena Benjamin 1. Associate Professor, Department of Radiology, Pushpagiri Institute of Medical Science, Thiruvalla, Pathanamthitta, Kerala, India. 2. Resident, Department of Radiology, Pushpagiri Institute of Medical Science, Thiruvalla, Pathanamthitta, Kerala, India. 3. Professor, Department of Radiology, Pushpagiri Institute of Medical Science, Thiruvalla, Pathanamthitta, Kerala, India |
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Correspondence Address : Dr. S Mangalanandan, Pushpagiri Institute of Medical Science Thiruvalla, Pathanamthitta-689101, Kerala, India. E-mail: anand.mangal443@gmail.com |
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| ABSTRACT |  | |||||||||||||||||||||||||||||||||||||||||||||||||
: Introduction: Acute Pancreatitis (AP) is an illness which results in increase in morbidity and mortality when there is a delay in diagnosis and there are false results. Various scales help in making early and accurate diagnosis of AP and predict prognosis. Validity of these scales needs to be studied and compared. Balthazar score and Ranson’s criteria have been commonly used. Modified CT score’s usefulness need to be studied as it involves only CT and their early detection will help in reducing the morbidity (reducing the residual damage) and mortality. Aim: To determine validity of modified Computed Tomography Severity Index (CTSI) and Ranson’s score in assessing severity of AP and study their correlation. Materials and Methods: This is an observational study among 39 patients with AP. Ranson’s score and Modified CT index was calculated and actual outcome of the disease was observed. Results: Ranson’s Score and Modified CTSI were strongly correlated with rho value of 0.912 and p-value of <0.001. Sensitivity and specificity of Ranson’s criteria in predicting the actual outcome of the disease is 80% and 83.3%, respectively. Sensitivity and specificity of Modified CT criteria in predicting the actual outcome of the disease is 93.33% and 54.17%, respectively. Conclusion: From the results of this study, it is evident that Modified CT index is more sensitive than Ranson’s score, but less specific. | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Keywords : Computed tomography, Diagnosis, Pancreatitis | ||||||||||||||||||||||||||||||||||||||||||||||||||
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DOI and Others :
DOI: 10.7860/IJARS/2021/44831:2595
Date of Submission: Apr 26, 2020 Date of Peer Review: Jun 10, 2020 Date of Acceptance: Jul 01, 2020 Date of Publishing: Jan 01, 2021 b#bAuthor Declaration:b?b • Financial or Other Competing Interests: None • Was Ethics Committee Approval obtained for this study? Yes • Was informed consent obtained from the subjects involved in the study? Yes • For any images presented appropriate consent has been obtained from the subjects. Yes |
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| INTRODUCTION |
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Clinically the presentation of AP varies from oedematous mild AP to severe AP, and is commonly seen with necrosis of the pancreas, a protracted clinical course, failure of organ, a high incidence of local complications, and a high mortality rate (1). Severe AP occurs in nearly one-fourth of patients with AP. The 1992 Atlanta classification defined severe AP “as the presence of organ failure or local complications such as pancreatic necrosis”. Revision on Atlanta classification described interstitial and necrotising pancreatitis based on CT scan and included peripancreatic necrosis (2). Various clinical scales including the Ranson and Acute Physiology and Chronic Health Evaluation (APACHE II) systems have been used for assessing the severity of AP since the 1970s (3),(4). Balthazar CTSI was used from 1990 (5). Computed tomography with intravenous contrast medium injection is widely accepted as the imaging procedure of choice: primarily to document the extent of pancreatic and extrapancreatic acute fluid collections and, secondarily to detect pancreatic necrosis. These two parameters have been widely used as prognostic indicators in assessing the severity of AP. Modified CTSI uses combined assessment of degree and extent of pancreatic involvement, pancreatic necrosis and fluid collections to improve prognostic accuracy (6). The present study was conducted to evaluate the outcome of AP by Ranson’s criteria and modified CTSI. Severity Classification Organ failure, local complications (fluid collections and necrosis) and systemic complications (7) are used to stratify disease severity. Mild disease lacks organ failure and local or systemic complications and is associated with rare mortality (1-2%) (8). Moderately severe disease have transient organ failure (resolves within 48 hours) or local or systemic complications and is associated with a low mortality rate of approximately 2% (9). Severe disease has persistent organ failure (persists beyond 48 hours), a mortality rate of approximately 20-30% (10),(11) and typically also presents with local complications. Severity Assessment A prognostic method to identify patients likely to develop severe AP would allow clinicians to triage into an intensive care setting and initiate outcome improving measures, such as aggressive fluid resuscitation (12). Radiologic grading systems developed to help predict disease severity (13) are CTSI and modified CTSI. Both the CTSI and modified CTSI assign points on the basis of the presence and extent of pancreatic inflammation, parenchymal necrosis, and extrapancreatic complications (modified CTSI only) observed on CT, up to a maximum of 10 points. The score correlates with mortality and indexes of patient morbidity, including occurrence of pancreatic infection, length of hospital stay, and need for invasive intervention (13). For severity assessment MRI can be comparably used (14). A major drawback of imaging for severity assessment is its reliance on necrosis characterisation, which as discussed previously is difficult within 72 hours of disease onset. Therefore, imaging solely for severity assessment at admission is not recommended. There are several clinically-based scoring systems for predicting the severity of AP. The Ranson score, APACHE II and Bedside Index for Severity in AP are three of the most prevalent. However, these clinical scoring systems provide limited additional information, because they typically require 24-48 hours of clinical data to become accurate, and severe disease is often apparent regardless of score. Clinically-based systems for severity assessment are of limited efficacy, similar to imaging-based systems (15). Ranson’s criteria: At admission/diagnosis: i. Age >55 years ii. WBC >16,000/mm3 iii. Blood Glucose >200 mg/dlL iv. Serum LDH >350 U/L v. AST >250 U/L During initial 48 hours: vi. Hematocrit decrease >10% vii. Blood Urea Nitrogen increase >5 mg/dL viii. Serum Calcium <8 mg/dL ix. Base deficit >4 mmol/L x. Fluid Sequestration >6000 mL xi. PaO2 <60 mm Hg Scoring: 1 point for each criterion met. Criteria (Mortality rate): 0-2 (~2%), 3-4 (~15%), 5-6 (40%), 7-8 (100%) Modified CT Severity Index (CT SI) a. Pancreatic inflammation score: Normal pancreas (0 points)/Intrinsic pancreatic abnormalities with or without inflammatory changes in peripancreatic fat (2 points)/Pancreatic or peripancreatic fluid collection or peripancreatic fat necrosis (4 points) b. Pancreatic necrosis score: None (0 points)/<30% (2 points)/>30% (4 points) c. Extrapancreatic complications: 1/> pleural effusion, ascites, vascular complication, parenchymal or GIT involvement)=2 points CT Grade: Mild-0-2, Moderate-4-6, Severe-8-10 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Material and Methods |
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This is an observational study (hospital-based) done in our institute involving the Department of Radiodiagnonis and the Department of General Surgery February 2016-August 2017. The sample size worked out to be 39 i.e., 39 people satisfied inclusion, exclusion criteria and undergoing a contrast-enhanced CT after clearance obtained from Institutional Ethical Committee (16). Inclusion Criteria i. All patients referred for CT with positive laboratory findings (serum amylase and serum lipase) for AP. ii. All patients referred for CT who are diagnosed with AP on ultrasonography. Exclusion Criteria i. Chronic Pancreatitis. ii. Pancreatitis associated with pancreatic carcinoma and metastasis ii. Pancreatitis secondary to trauma. iv. Acute on chronic pancreatitis Study Procedure Imaging: A MDCT (GE OPTIMA 128 SLICE) using 120 KVp and 160 MAS was used. The patients were scanned in supine position with suspended respiration. Noncontrast-enhanced scans were obtained from the diaphragm to the level of the pubic symphysis. Then oral mannitol (100 mL) and rectal gastrograffin (40 mL), both diluted with water upto one litre was given. It was followed by intravenous contrasts study using 80 mL of Iopamidol (370 mg/mL) because the pancreas has essentially the same attenuation coefficient as unopacified bowel and blood vessels. Following i.v., contrast by pressure injector scan acquisition was done in three phases. First phase (pancreatic parenchymal phase) images were acquired after a delay of 40-45 seconds. Contrast enhancement is best during this arterial phase and therefore it is the best phase to study pancreas. Thinner slices were obtained to avoid partial volume averaging when trying to obtain a more accurate density reading of a small lesion and at any time greater spatial resolution was required and for virtualisation of pancreatic duct. The Second phase (portal venous phase) images of the entire abdomen and pelvis after a delay of about 70 seconds were acquired. The Third phase (delayed phase) images of the entire abdomen and pelvis were taken after a delay of about 15 minutes after administration of i.v., contrast. All images were viewed in a range of standard window settings (Table/Fig 1),(Table/Fig 2),(Table/Fig 3),(Table/Fig 4),(Table/Fig 5). | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Results |
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Variables Related to Severity of AP Out of the study population, about 22 (56.4%) had decreased PCV, 5 (12.8%) were having increased blood urea nitrogen, 7 (18%) were having base deficit, 22 (56.4%) were having fluid sequestration and 8 (20.5%) were having PaO2 level less than 60. In the study population, Ranson’s Severity score is graphically represented as the following (Table/Fig 6) Ranson’s Score is further categorised into Mild (≤3) and Severe (>3) based on the scores for Ranson’s Criteria. Out of the study population, 23 (59%) were falling into mild category and rest 16 (41%) were falling into severe category according to Ranson’s Criteria. This is shown in (Table/Fig 7). Modified CT score: In the study population, Modified CT score is graphically represented in the following (Table/Fig 8). The score is maximum contributed by the ascites and pancreatic inflammation. Modified CT Score is further categorised into Mild (0-2); (Table/Fig 1), Moderate (4-6); [Table/Fig-2,3] and Severe (8-10); (Table/Fig 5) based on the scores for Modified CT scoring criteria. Out of the study population, 14 (36%) were falling into mild category, 17 (43.6%) were falling into moderate category and rest 8 (20.5%) were falling into severe category according to Modified CT severity criteria. This is shown in (Table/Fig 9). Outcome of Acute Pancreatitis In the present study, among 17 patients in moderate category of modified CTSI, nine patients had ascites of which four underwent ascitic tapping and five were managed conservatively. Among eight patients in severe category of modified CTSI, all had ascites of which five underwent ascitic tapping and three were managed conservatively. Five patients had pleural effusion in moderate and five in severe category of modified CTSI, of which three underwent pleural tapping in each of these categories. Two patients with pleural effusion were managed conservatively in both categories. One patient in moderate category had pancreatic abscess, for him needle aspiration was done. Five patients in severe category had vascular complications of which, three had thrombosis and two had pseudoaneurysm. All were under follow-up. All patients among severe category had necrosis. Among 17 patients in moderate category, five had necrosis. They were all managed conservatively with follow-up. Among 39 patients in our study, three patients had pseudocyst (Table/Fig 4), one each in mild, moderate and severe category. They were managed conservatively due to their small size (<4 cm). Out of the 39 patients studied, majority 24 (61.5%) were completely cured from the disease. And rest 15 (38.5%) had residual damage with the disease. None of the patient died in the present study. This is represented in (Table/Fig 10). Cross Tabulation of Categories of Ranson’s Score and Modified CT Score The following (Table/Fig 11) represents the cross tabulation between categories of Ranson’s score and Modified CT Score. Mild and severe are agreed 100% same as the other criteria. The 17 participants present in moderate in modified CT score were distributed equally in mild and severe category of Ranson’s Criteria as 9 and 8, respectively. (Chi-square value 21.5, p-value=<0.001). Correlation between Ranson’s score and Modified CT severity score: Correlation test (Spearman’s rho) was done between the two ordinal variables (Ranson’s Score and Modified CT Severity Score) and the two variables were strongly correlated with rho value of 0.912 and p-value of <0.001. This is represented in the following (Table/Fig 12). Cross Tabulation between Ranson’s Score Severity and Outcome The following (Table/Fig 13) represents the cross tabulation between categories of Ranson’s score and outcome of the disease. There is a significant association between the prediction of severity by Ranson’s criteria with the actual outcome of the disease with sensitivity and specificity being 80% and 83.3%, respectively. Calculations for accuracy of Ranson’s score with the outcome of disease are represented in the following (Table/Fig 14). Cross Tabulation between Modified CT Score and Outcome The following (Table/Fig 15) represents the cross tabulation between categories of Modified CT Score and outcome of the disease. There is a significant association between the prediction of severity by Modified CT Score with the actual outcome of the disease with p-value <0.001. For the purpose of calculation of accuracy indicators the moderate and severe categories of modified CT index have been clubbed together and represented in the following (Table/Fig 16). Calculations for accuracy of Modified CT score with the outcome of disease are represented in the following (Table/Fig 17). There is a significant association between the prediction of severity by Modified CT criteria with the actual outcome of the disease with sensitivity and specificity being 93.33% and 54.17%, respectively. | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Discussion |
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The study population comprised of 33 males (85%) and 6 females (15%). The prevalence of the biochemical markers needed for the calculation of Ranson’s Score was as follows: About 22 (56.4%) had decreased PCV, 5 (12.8%) were having increased blood urea nitrogen, 7 (18%) were having base deficit, 22 (56.4%) were having fluid sequestration and 8 (20.5%) were having PaO2 level <60. Out of the study population, 23 (59%) were falling into mild category and rest 16 (41%) were falling into severe category according to Ranson’s Criteria. Out of the study population, 14 (36%) were falling into mild category, 17 (43.6%) were falling into moderate category and rest 8 (20.5%) were falling into severe category according to Modified CTSI. In the present study, out of the 39 patients, majority 14 (35.9%) were having AP due to cholelithiasis, followed by aetiologies including alcohol (12, 30.8%), idiopathic (11, 28.2%) and post ERCP (2, 5.1%). Out of the 39 patients studied majority 24 (61.5%) were completely cured from the disease. And rest 15 (38.5%) had residual damage with the disease. Ranson’s score is calculated by biochemical parameters and needs time, whereas modified CT criteria need CT equipment and manpower in the form of radiologist to interpret the imaging findings. When comparing the categories of Ranson’s score and Modified CT Score, mild and severe forms showed 100% agreement with each other. But moderate category in Modified CT Score has disagreeing results. Since Ranson’s criteria has only mild and severe category, moderate category among participants cannot be studied for agreement. Correlation test (Spearman’s rho) between the two ordinal variables (Ranson’s Score and Modified CT Severity Score) showed strong correlation between the two variables with rho value of 0.912 and p-value of <0.001. Chand P et al., showed lack of statistical significant difference between Ranson’s criteria and Modified CTSI in evaluation of the outcome of AP amongst the systemic complications (16). Even though the local complications were seen in patients with higher Ranson’s score, the statistical difference was not significant. Kumar et al., demonstrated lack of significant difference between Ranson’s score and Modified CTSI in predicting pancreatic necrosis, organ failure and ICU admission in patients with AP with a p-value of 0.10, 0.22, and 0.10, respectively (17). The present findings are of strong correlation between Ranson’s score and Modified CTSI and in line with previous studies. When comparing categories of Ranson’s score and outcome of the disease, there was a significant association between the prediction of severity by Ranson’s criteria with the actual outcome of the disease with sensitivity and specificity being 80% and 83.3%, respectively. There is a significant association between the prediction of severity by Modified CT criteria with the actual outcome of the disease with sensitivity and specificity being 93.33% and 54.17%, respectively. Hence, it is evident that Modified CT index is more sensitive than Ranson’s score, but less specific. In the present study, results of higher sensitivity and lower specificity of Modified CTSI in comparison to Ranson’s score is comparable to previous published studies. Though Modified CTSI has higher sensitivity, the lower specificity could be due to one-time evaluation of imaging findings performed about 72 hours after symptom onset in comparison to Ranson’s score which includes follow-up of the biochemical parameters at admission and after 48 hours postadmission enabling assessment of disease progression. Limitation(s) Studies with large sample size are recommended to explore more about the usefulness of Modified CT Index. | ||||||||||||||||||||||||||||||||||||||||||||||||||
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