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Usefulness of Computerized Tomography Scan for the Detection and Evaluation of Acute Pancreatitis

Introduction: Acute pancreatitis is one of the most common diseases of the gastrointestinal tract. Imaging by CT scan helps in diagnosing severity of acute pancreatitis including the presence of pancreatic necrosis as well as local and systemic complications. Current study aimed to study the use of CT scan for the detection and evaluation of acute pancreatitis. Material and Methods: A total of 110 patients diagnosed clinically with acute pancreatitis were studied for patient demographics, clinical presentation, etiology and CT scan findings. Results: A ttal of 110 patients with age ranging from 15 years to 60 years were studied. The male to female ratio was 2.1:1. Most (59%) of the cases were in the 41 to 50 years age. Epigastric pain and vomiting were the most common clinical features. Gall stones and alcoholism were the most common etiological factors for acute pancreatitis. CT findings showed diffuse enlargement in 43.6% cases, and irregular contour in 63.6% cases. Ascites and pleural effusion were noted in 31.8% cases. Balthazar’s CTSI system gave better results than the Ranson’s criteria. Conclusion: Acute pancreatitis commonly affects adult males. CT scan plays an important role in diagnosing acute pancreatitis and Balthazar’s CTSI system is advantageous over the Ranson’s criteria system. The CT modality gives information on the severity and extent of the inflammatory process and thereby helps in decision making for patient management.


INTRODUCTION
Acute pancreatitis is one of the most common diseases of gastrointestinal tract (GIT), leading to tremendous emotional, physical, and financial burden. 1 Acute pancreatitis (AP) is a complex clinical condition with majority of patients and in approximately 20% becomes clinically very severe with significant mortality. 2 Clinically severe patients require admission to intensive care unit (ICU), where close monitoring and treatment with aggressive fluid resuscitation are a must. 3 Clinically, acute pancreatitis is diagnosed in patients with two of the following three features: (a) sudden onset of upper abdominal pain, (b) serum amylase and/ or lipase levels more than three times the upper limit of normal, and/or (c) abdominal computed tomography (CT) scan or ultrasound scan having characteristic findings. 4,5 Diagnosis of acute pancreatitis is made by combination of clinical presentation, laboratory investigations and imaging. Serum amylase, lipase, liver function tests, serum electrolytes with blood gas analysis are the commonly performed laboratory investigations which help to grade the severity and prognosis of acute pancreatitis based on several clinical criteria including Ranson's criteria. 6 Imaging plays a major role in diagnosing severity of acute pancreatitis including the presence of pancreatic necrosis as well as local and systemic complications. It also serves as a guide for therapeutic intervention and response to therapy. 7 Modified CT severity index is used to detect extent of necrosis and various local and extra pancreatic complications. 8 Two commonly used CT scoring systems are the CT severity index (CTSI), and modified CT severity index (MCTSI), proposed by Mortele et al 9 and require the use of intravenous (IV) contrast agents to determine the presence and extent of pancreatic necrosis, as well as inflammatory changes and local and/or extrapancreatic complications. Modified Computed Tomography Severity Index (MCTSI) has been introduced which differs from the Computed Tomography Severity Index (CTSI) by including the presence of extra pancreatic complications and grading the peripancreatic fluid collection in terms of presence or absence instead of the number of fluid collections. The grading of necrosis is also different in this system. 9 In the cases with acute pancreatitis, CT examination should be performed if the clinical diagnosis is uncertain, clinical findings suggest severe acute pancreatitis (Ranson score ≥ 3, APACHE II score ≥ 8), or there is suspicion of necrotizing pancreatitis, and for patients who do not improve clinically within 72 hours of the initial conservative medical therapy or for patients who demonstrate improvement during the initial medical therapy but then manifest acute change in clinical status with fever, pain, decrease in hematocrit or hypotension, and also when any complication is suspected. 10,11 CT findings of acute pancreatitis depend on the severity and extent of the inflammatory process. A CT scan which is performed within the first 48 hours of the onset of symptoms may be completely normal. CT findings of acute pancreatitis include enlargement of the pancreas (localised or diffuse), ill defined parenchymal contours, decrease in density and inhomogeneity of the pancreatic parenchyma and there may also be fluid collections in the peripancreatic region. The inflammatory reaction can produce increased attenuation of the peripancreatic adipose tissue commonly described as ''stranding''. [12][13][14] Current study aimed to study the use of CT scan for the detection and evaluation of acute pancreatitis. given All the cases included in the study were from the out patient department of General Surgery and indoor admitted patients under department of General Surgery. Once the patients were clinically diagnosed as acute pancreatitis, then they were referred to department of Radiology for Imaging studies as part of patient work-up. A thorough clinical examination was done including history taking, onset of symptoms, past history of similar complaints, history of cholelithiasis, alcohol intake, or smoking. Local and systemic examination was done. Laboratory investigations were requested from the primary consulting physician and included hemogram, urine analysis, serum amylase, serum lipase, serum creatinine level, lipid profile (mainly triglyceride), and random blood glucose. All the patients were subjected to USG abdomen and findings were noted. All the patients were subjected to CT scan and the following points were noted: the pancreatic parenchyma affection (bulky, edematous, necrotic, focal, or diffuse); peripancreatic region (stranding, single peripancreatic collections, or pseudocysts); GB or common bile duct stones; biliary and pancreatic ducts; masses in the pancreas or ampulla; and extrapancreatic ascites, pleural effusion lung bases, and intestinal loops. In the department of Radiodiagnosis, the procedure was explained to the patients beforehand. The mean duration between onset of symptoms and CT scan procedure was 7 days (and within 15 days) as by that time necrosis can be detected very well.

Equipment used:
The CT machine that was used is Toshiba Aquilion (160 slices). The contrast used was water soluble and nonionic (Omnipaque) administered at 300 mg/ml through intravenous injection. After collecting all data from CT, we made grading of acute pancreatitis into five grades (A, B, C, D, and E), and this grading was done according to the texture of pancreas and peripancreatic fluid in the abdomen. Grading of Acute Pancreatitis with CT by Balthazar's system 9 as given below was done: Grade A Laboratory and clinical evidence of pancreatitis with normal pancreas (score 0). Grade B Showed bulky pancreas (focal or diffuse) with no peripancreatic changes (score 1). Grade C Showed peripancreatic stranding (score 2). Grade D Showed single peripancreatic fluid (score 3). Grade E Showed two or more than two pockets of fluid collection or gases on the retroperitoneal space (score 4). Ranson's clinical criteria were followed to categorize the cases and both systems of Ranson's criteria and Balthazar's CTSI grading were compared.

RESULTS
There were a total of 110 patients in the study. The male to female ratio was 2.1:1. The patient age ranged from 10 years to 60 years. The youngest patient was 15 years and the oldest patient was 60 years old ( In the present study, CT findings showed diffuse enlargement in 43.6% cases, and irregular contour in 63.6% cases. Ascites and pleural effusion were noted in 31.8% cases (table-4). In our study, amylase level was raised in 59% cases, whereas lipase level was raised in 80% cases (fig-1). In the present study, most common etiological factor was gall stones and was seen in 31.8% (35/110) cases, next common factor was alcoholism and was seen in 27.2% (30/110) cases (figure-5). A CT Severity index (CTSI) of less than 5 is taken as mild acute pancreatitis and CTSI of > 5 is considered as severe degree of acute pancreatitis (figure-6). In our study, there were 75 cases of mild acute pancreatitis as per Balthazar's CTSI system. Out of 75 cases, 64 cases (85.3%) correlated well for Ranson's criteria for mild severity. Remaining 11 (14.6%) cases were graded as severe as per Ranson's criteria but were actually mild category on CTSI score ( figure-7). In our study, 35 (31.8%) cases were in severe category as per Balthazar's CTSI system. Of these 35 cases, 29 (82.1%) correlated well with Ranson's criteria for severe disease process. The remaining 6 (17.1%) cases which were CT findings: In our study, the most common CT findings were of diffuse enlargement in 43.6% cases. In 63.6% cases there was irregular contour and focal hypodensity. Necrosis of <30% parenchyma was seen in 29% cases.
In Bader HA et al 15 study, the CT data classified acute pancreatitis into two types: interstitial edematous pancreatitis, which was recorded in 80 (80%) patients, and as necrotizing pancreatitis with or without peripancreatic necrotic fluid, which was recorded in 20 (20%) patients. Three patients with interstitial edematous acute pancreatitis changed to necrotic type in the follow-up. In Raghuwanshi S et al 19 study, most common CT findings were peri-pancreatic inflammatory changes in mesentery, greater omentum and transverse mesocolon (88%). Second most common CT finding was of pancreatic contour irregularity (80%). Twenty five patients (50%) had necrosis of the pancreas with 14 of them having more than 50% necrosis.

Etiology of acute pancreatitis:
In the present study, most common etiological factor was of gall stones and was seen in 31.8% (35/110), and the next common factor was alcoholism seen in 27.2% (30/110). In Bader HA et al 15 study, the first leading cause of acute pancreatitis was of gall bladder stones (biliary), found in 48 (48%) patients, and second cause was alcohol abuse in 25 (25%) patients, and the third cause was hyperlipidemia in 22 (22%) patients and post-endoscopic retrograde cholangiopancreatography (ERCP) in five (5%) patients. In Jeevangi BA et al 17 study, the most common cause of pancreatitis was attributed to chronic alcohol abuse in 32 cases. In Raghuwanshi S et al 19 study, most common etiological factors encountered were cholelithiasis (42%) and alcoholism (38%) followed by idiopathic (24%), trauma (2%) and drug induced (2%). In the study by Sahu B et al 20 chronic alcohol abuse was the most common cause of acute pancreatitis (n = 30, 50.0%), followed by gallstone disease (n = 15, 31%).
Biochemical investigations: In our study, amylase level was elevated in 59% cases, whereas, lipase level was elevated in 80%cases.
In Bader HA et al 15 study, amylase level less than or equal to 210 U/l was seen in 29 (29%) patients and more than 210 U/l in 71 (71%) patients, whereas lipase level less than or equal to 180 U/l in 20 (20%) patients and more than 180 U/l in 80 (80%) patients was seen. Sawarkar K et al 18 in their study observed elevated serum lipase and serum amylase levels in all the cases.