Contrast-Enhanced Dynamic Computed Tomography Does Not Aggravate the Clinical Severity of Patients With Severe Acute Pancreatitis: Reevaluation of the Effect of Intravenous Contrast Medium on the Severity of Acute Pancreatitis

Background  Contrast-enhanced abdominal computed tomography (CT) is useful in demonstrating pancreatitis necrosis, but the administration of contrast medium in animal models with acute pancreatitis may worsen the severity.

Hypothesis  The use of contrast-enhanced CT in clinical patients with acute pancreatitis may actually aggravate the severity of the disease.

Design  A randomized prospective study.

Setting  Chang Gung Memorial Hospital, Taipei, Taiwan.

Patients  Twenty patients with severe acute pancreatitis were randomly divided into 2 groups. Those in group A (n=10) underwent a CT examination with a contrast-enhanced medium, and those in group B (n=10) underwent a CT examination without a contrast-enhanced medium.

Main Outcome Measures  The patients' serum amylase, lipase, C-reactive protein, leukocyte, glutamic-oxaloacetic transaminase, creatinine, calcium, and phosphate levels were serially checked before the CT examination and at 2, 4, 6, 8, 12, and 24 hours after the examination was performed. The biochemical data between the 2 groups were compared. The morbidity, length of stay, and mortality were also compared.

Results  There were no significant changes in the level of pancreatic enzymes, C-reactive proteins, and leukocytes and in the biochemical data of either group before or after the CT examination. The difference in the previously examined values between the 2 groups was also not significant. There was also no difference in the morbidity, length of hospital stay, and mortality between the 2 groups.

Conclusion  Contrast-enhanced abdominal CT does not aggravate the severity of clinical patients with severe acute pancreatitis.

CONTRAST-ENHANCED abdominal computed tomography (CT) is frequently used for the diagnosis and prediction of the severity of acute pancreatitis. Several studies^1-4 have reported that the administration of a contrast medium in animal models with acute pancreatitis might worsen its severity. The contrast medium may cause significant additional reductions of capillary flow, especially in areas where flow is already impaired. Furthermore, it lowers pancreatic tissue oxygenation and increases acinar necrosis, trypsinogen activation peptide production, and mortality. However, another report⁵ observed that intravenous contrast medium does not increase the severity of acute necrotizing pancreatitis in the opossum. As the reported models used in those studies were all small animals, we believed that the response of acute pancreatitis after contrast-enhanced CT in clinical patients might be different. To our knowledge, reports on prospective studies of the effects of contrast-enhanced abdominal CT on patients with acute pancreatitis are rare. Therefore, the following prospective study was designed to compare the metabolic and functional changes of the pancreas after non–contrast- and contrast-enhanced CT in patients with severe acute pancreatitis.

This study was designed as a randomized trial. The institutional review board approved the project. Twenty patients with severe acute pancreatitis who were admitted into the Medical Intensive Care Unit of Chang Gung Memorial Hospital, Taipei, Taiwan, were included in this prospective study. The patients with an unstable hemodynamic condition or impaired nephric function were excluded. The average duration of the patients' symptoms before hospital admission was a few hours to half a day. Their diagnosis was based on symptoms and signs, elevated serum amylase and lipase levels, and the findings of abdominal CT scans. Furthermore, their Acute Physiology and Chronic Health Evaluation II score was 8 or higher or their Ranson score was 3 or higher (Table 1).

All of them underwent abdominal CT examinations on the first day of admission, when their hemodynamic status was stable. They were randomly divided into 2 groups. Group A (n=10) was composed of those patients whose abdominal CT scans were performed with an ionic contrast-enhanced medium. Group B (n=10) was composed of patients whose abdominal CT scans were performed without a contrast-enhanced medium. Ionized contrast medium, 100 mL, was injected into the patients at the speed of 2.5 mL/s. The patients' serum amylase, lipase, C-reactive protein, leukocyte, glutamic-oxaloacetic transaminase, creatinine, calcium, and phosphate levels were checked before and at 2, 4, 6, 8, 12, and 24 hours after the CT examination.

Serum amylase and lipase levels were determined by using a dry chemistry machine (Vitros E250; Johnson-Johnson Co, Rochester, NY); glutamic-oxaloacetic transaminase, creatinine, calcium, and phosphate levels were measured with the bromcresol green method, using an analyzer (model 736; Hitachi, Tokyo, Japan); and the C-reactive protein level was determined with the turbidity method, using a turbitimer (Dade Behring Marburg GmbH, Marburg, Germany).

The morbidity, need for surgery, length of hospital stay, and mortality were also compared between the 2 groups.

The t test was used for statistical analysis of the results, which are presented as the mean ± SEM. P<.05 was considered statistically significant.

Serial changes in amylase, lipase, C-reactive protein, and leukocyte levels in patients of both groups are listed in Table 2, Table 3, Table 4, and Table 5, respectively. There were no significant changes in amylase (P=.32), lipase (P=.01), C-reactive protein (P=.05), and leukocyte (P=.30) levels after either injection or noninjection of the contrast medium. The difference between the 2 groups was also not significant.

Serial changes in glutamic-oxaloacetic transaminase, creatinine, calcium, and phosphate levels in those patients who underwent contrast-enhanced CT are listed in Table 6. There were also no significant changes in these data after the contrast medium was injected.

Three patients in group A and 2 in group B needed to be operated on due to intra-abdominal infection. Three patients, 1 in group A and 2 in group B, died of sepsis and multiple organ failure after aggressive medical or surgical treatments. The difference in the morbidity and mortality rates between the 2 groups was not significant. The average length of hospital stay between the 2 groups (group A vs B, 30 ± 8 vs 32 ± 12 days) was also not different.

Contrast-enhanced dynamic CT has been reported to be able to demonstrate areas of reduced perfusion in patients with acute pancreatitis, and reduced contrast enhancement was found to correlate well with pancreatic necrosis.^6-11 But the radiographic contrast medium was also reported in recent years to impair microcirculation and increase acinar necrosis and mortality in experimental pancreatitis.^1-4

Foitzik et al¹ reported that ionic and nonionic contrast media can increase acinar cell necrosis and mortality early in the course of severe necrotizing acute pancreatitis in rats. They also explained that the contrast medium impairs the pancreatic microcirculation in necrotizing forms of acute pancreatitis.³ Since the contrast-enhanced abdominal CT scan is usually important for the early demonstration of ischemic areas and pancreatic necrosis in patients with acute pancreatitis, and if the pancreatic function and patients' metabolic and other vital organ functions, such as heart, liver, and kidney, are not impaired, the use of contrast-enhanced abdominal CT is still acceptable.

Our data demonstrate that, regardless of whether the contrast-enhanced medium was used, the severity of the pancreatitis did not show any change during the 24-hour serial follow-up period. The patients' liver and nephric functions and calcium and phosphate levels were also not affected after the enhanced contrast medium was injected. The final patient outcome between these 2 groups also showed no significant difference. The administration of this ionic contrast agent as we used it in our hospital did not worsen the severity of pancreatitis in clinical patients, although according to the reported animal studies, the microcirculation of the pancreas in patients with such a condition might have been affected. The difference between the present study and the reported results of the previous animal studies, therefore, may have been due to species difference.

These data may support us in allowing patients with acute pancreatitis to undergo an abdominal CT examination with an enhanced contrast medium. Although the magnetic resonance imaging contrast agent has been reported to be safe in patients with acute necrotizing pancreatitis in recent years,¹² the lower cost of an abdominal CT examination seems to be more acceptable if the intravenous contrast medium does not increase the severity of the disease, as we have reported in this study.

Reprints: Tsann-Long Hwang, MD, Department of Surgery, Chang Gung Memorial Hospital, 199, Tung-Hwa N Rd, Taipei, Taiwan (e-mail: hwangtl@adm.cgmh.com.tw).