Radiologic diagnosis of pseudoaneurysms complicating pancreatitis

102

EURRAD

0

1993 Elsevier Scientific

Publishers

European Journal of Radiology, 16 ( 1993) 102- 106 Ireland Ltd. All rights reserved. 0720-048X/93/$06.00

00328

Radiologic diagnosis of pseudoaneurysms complicating pancreatitis C. PQez, J. Llauger, Y. Pallard6,

E. Sanchis, J.M. Sabat6

Radiology Dept., Hospital de Sant Pau. Barcelona, Spain

(Received 1 June 1992; accepted 22 July 1992)

Key words: Pancreatitis,

complication;

Pancreas, CT; Pancreas, angiography; Intestine, hemorrhage;

Computed tomography, pancreas

Abstract Angiographic and computed tomographic (CT) examinations in five patients with arterial pseudoaneurysms complicating pancreatitis were evaluated retrospectively. Selective arteriography was superior to CT imaging in demonstrating pseudoaneurysm formation. However, angiography was performed in four patients after a CT study considered suspicious for a pseudoaneurysm; none of these four patients had clinical evidence of bleeding. Correlation with surgical findings was established in four patients, indicating that pseudoaneurysms complicating pancreatitis were not located within a pancreatic pseudocyst. Some thrombus-containing pseudoaneurysms may present with a pseudocyst appearance on CT images.

Introduction Pseudoaneurysm formation secondary to arterial erosion is a rare complication of chronic or acute pancreatitis. Pancreatic pseudoaneurysms may result in massive hemorrhage in any stage of pancreatitis, or may be the cause of fatal complications during surgical or percutaneous procedures. Patients with pancreatitis and clinical evidence of bleeding should undergo immediate arteriography. This technique is highly sensitive in the demonstration of pseudoaneurysms or extravasation of contrast. Additionally, transcatheter embolization is the treatment method of choice, allowing for reduction of morbidity and mortality in these patients. Computed tomography (CT) has demonstrated itself to be useful in the noninvasive diagnosis of pancreatic pseudoaneurysm, particularly in patients without clinical evidence of hemorrhage. This study reviews the CT and angiographic manifestations of pseudoaneurysms complicating pancreati-

Correspondence

to: C. Perez, M.D., Radiology Dept., Hospital De Sant Pau, Av. S. Antoni M. Claret, 167, 08025 Barcelona, Spain.

tis in five patients, and correlates radiologic and pathologic findings. Patients and methods We retrospectively evaluated the CT images, angiograms, and clinical and operative records of five patients with pseudoaneurysms complicating chronic (4 cases) or acute (1 case) pancreatitis that were examined at our hospital between January 1988 and October 1990. The group consisted of five men, who ranged in age from 48 to 70 years (mean, 58 years). The etiology of pancreatitis was alcohol abuse in four cases and gallstones in one. All patients were examined with CT and angiography, with selective celiac and superior mesenteric artery injections. CT was performed on a Somaton DR2 (Siemens Medical Systems, Erlangen, Germany). Usually, 8-mmthick images were obtained every 1 cm over the upper abdomen. All patients were given diluted oral contrast. This was followed by intravenous administration of 80-100 ml of a 60% iodinated contrast while scans were obtained at 1 cm intervals over the pancreas. Conventional angiography was performed via a 6F catheter inserted into the celiac artery and the superior mesenteric artery.

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Results The clinical findings and diagnostic procedures for each patient are summarized in Table 1. Pancreatic pseudoaneurysm was demonstrated on CT in 4 patients and on arteriography in all 5 patients. Two patients (cases 1 and 2) showed pancreatic calcifications, Wirsung dilation, atrophy of the pancreatic tail, and enlargement of the head. Extrapancreatic fluid collections were not seen. In both patients, an irregular, 3 cm low-attenuation mass was observed within the pancreatic head. In one of these patients, small peripheral linear calcifications were detected. CT after bolus injection of contrast material revealed, in both patients, an enhancing eccentric lesion within the previously described low-attenuation masses. It was surrounded by a hypodense area, giving a typical appearance of a pseudoaneurysm. In both cases, selective angiography demonstrated a pseudoaneurysm arising from the inferior pancreatoduodenal branches of the superior mesenteric artery (Fig. 1). Another patient (case 3) showed CT features of chronic pancreatitis with an atrophic gland and an intrasplenic fluid collection. Hyperdense areas indicative of hemorrhage could be identified within the intrasplenic pseudocyst. Additionally, a rounded, 3 cm mass with marked post-contrast enhancement was observed in the left paraortic area (Fig. 2). In this patient, celiac

TABLE

angiography demonstrated a pseudoaneurysm arising from the middle portion of the splenic artery. One patient with acute pancreatitis (case 4) showed a large extrapancreatic fluid collection occuping the left pararenal space. High-density areas within this collection could be observed, and small air bubbles indicating abscess formation. Post-contrast CT scans showed an enhancing lesion, surrounded by a hypodense rim, in continuity with the splenic artery. In this case, celiac injection revealed a pseudoaneurysm involving the proximal splenic artery. In the remaining patient (case 5) who had previously been diagnosed of chronic pancreatitis, CT demonstrated a large subcapsular splenic collection. In postcontrast CT scans pseudoaneurysms were not identified. Splenic arteriography showed two small pseudoaneurysms arising from distal branches of the splenic artery. The diagnosis of pseudoaneurysms complicating chronic pancreatitis was corroborated by surgery in four of the five patients. Surgical treatment consisted either of distal pancreatectomy and splenectomy (cases 3 and 5) or dissection and inferior pancreatoduodenal arteries ligation (cases 1 and 2). One patient with splenic pseudoaneurysm complicating acute pancreatitis (case 4) was treated by selective transcatheter embolization with Gelfoam particles, without evidences of recurrent hemorrhage.

1

Clinical and radiological findings Case No. (Age:

Etiology

History

CT

Angiography

1 (62)

Chronic alcohol abuse

Abdominal pain

Chronic calcific pancreatitis. Enhancing mass in pancreatic head.

SMA pesudoaneurysm (2.5 cm)

2 (57)

Chronic alcohol abuse

Abdominal pain

Chronic calcilic pancreatitis. Enhancing mass in pancreatic head.

SMA pseudoaneurysm (3.8 cm)

3 (70)

Chronic alcohol abuse

Abdominal pain

Splenic pseudocyst. Atrophic gland. Left paraaortic enhancing mass.

SA pseudoaneurysm (2.5 cm)

4 (54)

Acute cholelithiasis

Anemia. Leukocytosis. Fever.

Extrapancreatic fluid collections with high-density areas. Enharming mass in pancreatic tail.

SA pseudoaneurysm

Chronic calcific pancreatitis. Subcapsular splenic collection.

SA pseudoaneurysms (
years)

5 (48)

Chronic alcohol abuse

Pain. Left abdominal mass. Anemia.

SMA = superior mesenteric artery; SA = splenic artery.

(3 cm)

b

d Fig. 1. Pseudoaneurysm complicating chronic pancreatitis in a 57-year-old man (case 2). a; CT image at the level of the uncinate process of the pancreas shows a 4 cm mass displacing mesenteric vessels and containing a high attenuation area surrounded by a low-density zone. b; After intravenous bolus of contrast, CT scan shows an area of intense enhancement corresponding to a pseudoaneurysm. The low-density periphery represents thrombus. There are small calcifications at the periphery of the lesion c, d; Superior mesenteric angiography demonstrates a 4 cm pseudoaneurysm involving the inferior pancreatoduodenal arteries.

b

a

Fig. 2. Splenic artery pseudoaneurysm and intrasplenic pseudocyst complicating chronic pancreatitis. a; Non-contrast-enhanced CT scan demonstrates an intrasplenic fluid collection, containing high-density areas, and a 3 cm homogeneous mass in the left paraaortic region. b; Post-contrast image shows enhancement of this mass to the same degree as the aorta, thus establishing its vascular nature. Splenic angiogram confirmed the diagnosis.

At surgical exploration, pseudoaneurysms found within a pancreatic pseudocyst.

were not

Discussion Splenic vessels thrombosis, vascular erosion, and pseudoaneurysm formation are the major vascular complications of pancreatitis. Arterial changes - erosion, thrombosis, or pseudoaneurysms - are related to inflammatory changes that produce necrosis of adjacent structures, and are the cause of hemorrhagic complications of severe pancreatitis, occurring in 1.5-7.5% of patients [l-3]. Hemorrhage may occur in the abdominal cavity, pseudocysts, retroperitoneum, or gastrointestinal tract. Gastrointestinal bleeding may be secondary to associated causes (gastritis, gastric or duodenal ulcers, diverticulosis, and esophageal varices), or may be due to hemorrhage directly into the gastrointestinal tract, pancreatic duct (hemoductal pancreatitis), or biliary tract (hemobilia). The vast majority of pseudoaneurysms complicating pancreatitis occur in men, whereas true splenic aneurysms are more prevalent in women [ 41 and only 65 % of cases of true hepatic artery aneurysms occur in males [ 51. Hemorrhagic complications of pancreatitis are clinically suspected in cases of gastrointestinal bleeding, sudden decrease in hematocrit, or enlargement of a previously present pseudocyst. Hemoductal pancreatitis is usually accompanied by epigastric pain and hemobilia may be associated with jaundice. Selective angiography has long been the procedure

of choice for evaluating hemorrhagic complications of pancreatitis. Endoscopic procedures and technetium99 m studies have been used to localize the source of bleeding, but their specificity is low. The major advantages of arteriography is its ability to identify small pseudoaneurysms (case 5; Fig. 4) and the vessel of origin, usually the splenic artery or the gastroduodenal branches. Moreover, transcatheter embolization is often the optimal treatment in many of these patients, due to the high surgical morbidity and mortality reported [ 61. In our patients, selective angiography was the most sensitive method for pseudoaneurysms and also identified the vessel of origin. In one patient, two small pseudoaneurysms arising from distal splenic artery not found by CT were evidenced by arteriography. Although conventional angiography remains the gold standard in the diagnosis work up of pseudoaneurysms, it is not performed unless the patient is symptomatic, or another imaging study appeared suspicious for a pseudoaneurysm. Recently, cross-sectional methods such as CT, ultrasonography (US), and Doppler US have proven useful in the noninvasive diagnosis of pseudoaneurysms [ 7-91. Contrast-enhanced CT has become the examination of choice for the initial evaluation and follow-up of patients with severe acute pancreatitis and chronic pancreatitis. In cases of pseudoaneurysms, diagnostic accuracy of CT using dynamic techniques may be comparable with the accuracy of selective angiography. However, most reports of CT studies describe single or

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a few cases, and the exact ability of CT to define asymptomatic pseudoaneurysms is difficult to determine. The detection rate may be affected by aneurysm size, timing since injection of contrast, and resolution of the system. Several articles, mostly case reports, have described the CT appearance of pancreatic pseudoaneurysms. Usually, large intraglandular or peripancreatic cysticlike lesions, considered as pseudocysts, with eccentric enhancing areas have been observed. These features were also noted in three of our cases. However, when surgery was performed (cases 1 and 2), pseudocyst containing pseudoaneurysms were not demonstrated. In both cases, only thrombus-containing pseudoaneurysms arising from gastroduodenal branches were observed. This pseudopseudocyst appearance has been previously reported in hepatic artery aneurysms located in the pancreatic head (replaced right hepatic artery) [ lo]. In one of our cases (Fig. 1) small peripheral calcifications also suggested the true exclusively vascular nature of the lesion. The radiologic differentiation between pseudocysts and thrombus-containing pseudoaneurysms is very important to prevent hemorrhagic complications and to avoid catastrophic consequences of drainage procedures [ 111. In a patient with splenic pseudoaneurysm complicating chronic pancreatitis (case 3), CT scans demonstrated a 3 cm left paraaortic mass, with intense and uniform postcontrast enhancement corresponding to an arterial lesion. In this case, absence of thrombosis within the pseudoaneurysm avoided confusion with a pseudocyst. In summary, pseudoaneurysm formation is the most common vascular complication of chronic and, less usually, severe acute pancreatitis. CT has proved to be an accurate method of evaluating this condition. However, rapid contrast administration is necessary, particularly if cystic-like lesions are identified in the pancreas or peripancreatic area. With this technique diagnosis may be stablished in asymptomatic patients,

without clinical evidence of bleeding. Only one (20%) of our patients had clinical and radiological evidence of bleeding. In the other patients, angiographic demonstration of pseudoaneurysms was obtained after a CT study was considered suspicious. We think that most lesions may not be located within pseudocysts, and thrombus-containing pseudoaneurysms may present with a pseudoseudocyst appearance. Although CT advantages are clear, selective angiography is required to accurately assess the vessel involved, as well as to identify small pseudoaneurysm, and to undergo percutaneous treatment. References

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