DOI: 10.1148/rg.274065047
RadioGraphics 2007;27:1023-1038
© RSNA, 2007
CT Evaluation of the Bulging Papilla with Endoscopic Correlation1
Suk Kim, MD,
Nam Kyung Lee, MD,
Jun Woo Lee, MD,
Chang Won Kim, MD,
Suck Hong Lee, MD,
Gwang Ha Kim, MD, and
Dae Hwan Kang, MD
1 From the Departments of Diagnostic Radiology (S.K., N.K.L., J.W.L., C.W.K., S.H.L.) and Gastrointestinal Internal Medicine (G.H.K., D.H.K.), Pusan National University Hospital, Pusan National University School of Medicine, 1-10 Ami-Dong, Seo-gu, Busan 602-739, Republic of Korea; and the Medical Research Institute, Pusan National College of Medicine, Busan, Republic of Korea (S.K., J.W.L., G.H.K., D.H.K.). Recipient of a Cum Laude award for an education exhibit at the 2005 RSNA Annual Meeting. Received March 30, 2006; revision requested July 26 and received August 31; accepted September 1. Supported by Medical Research Institute grants from Pusan National University.
Address correspondence to J.W.L. (e-mail: junwlee{at}pusan.ac.kr).
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Abstract
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A variety of pathologic conditions can cause abnormalities of the ampulla of Vater. A bulging papilla is frequently encountered at computed tomography (CT) and can be seen in healthy individuals as well as in patients with various pathologic conditions such as papillitis, ampullary cancer, and intraductal papillary mucinous tumor. Mural thickening and certain attenuation patterns seen at contrast material–enhanced CT can help differentiate pathologic papilla from normal papilla. Increased targetlike enhancement of the papilla is likely to represent a benign condition such as papillitis, whereas an enhancing polypoid mass or focal asymmetric or irregular thickening with prolonged enhancement in the ampulla of Vater indicates a malignant condition such as ampullary or periampullary carcinoma. Although CT often does not clarify the exact cause of bulging, adequate duodenal distention may allow detection of an abnormal papilla, thereby providing additional information about other abnormalities in the pancreaticobiliary system. Thus, CT findings may prove useful for subsequent imaging studies such as magnetic resonance (MR) cholangiography or endoscopy. MR cholangiography may be equivalent to CT for identifying a bulging papilla and superior for distinguishing the underlying cause. However, endoscopy with or without biopsy is the best method for making a definitive diagnosis in patients with a bulging papilla. Familiarity with the normal imaging anatomy of the periampullary region and with the imaging features of the various pathologic causes of a bulging papilla may be useful in making the diagnosis.
© RSNA, 2007
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Introduction
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There are reports that enlargement and bulging of the papilla have been observed at duodenoscopy performed for various pathologic conditions such as intraductal papillary mucinous tumor (IPMT), papillitis, periampullary cancer, autoimmune pancreatitis, and choledochocele (Fig 1) (1,2). For example, the appearance of extruded mucin from a bulging patulous duodenal papilla at duodenoscopy performed at the time of endoscopic retrograde cholangiopancreatography (ERCP) is pathognomonic for IPMT (3).
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Figure 1a. (a) Drawing illustrates papillitis with a distal common bile duct (CBD) stone. Bulging of the papilla is due to inflammation in the ampulla of Vater, which is precipitated by mechanical irritation from choledocholithiasis. (b) Drawing illustrates branch duct type IPMT. Protrusion of the major papilla into the duodenal lumen, as well as mild and symmetric wall thickening, is frequently seen. (c) Drawing illustrates ampullary carcinoma (exposed type). Note the asymmetric and irregularly thickened wall at the distal margin of the pancreaticobiliary junction that obliterates the lumen, along with enlargement of the major duodenal papilla.
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Figure 1b. (a) Drawing illustrates papillitis with a distal common bile duct (CBD) stone. Bulging of the papilla is due to inflammation in the ampulla of Vater, which is precipitated by mechanical irritation from choledocholithiasis. (b) Drawing illustrates branch duct type IPMT. Protrusion of the major papilla into the duodenal lumen, as well as mild and symmetric wall thickening, is frequently seen. (c) Drawing illustrates ampullary carcinoma (exposed type). Note the asymmetric and irregularly thickened wall at the distal margin of the pancreaticobiliary junction that obliterates the lumen, along with enlargement of the major duodenal papilla.
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Figure 1c. (a) Drawing illustrates papillitis with a distal common bile duct (CBD) stone. Bulging of the papilla is due to inflammation in the ampulla of Vater, which is precipitated by mechanical irritation from choledocholithiasis. (b) Drawing illustrates branch duct type IPMT. Protrusion of the major papilla into the duodenal lumen, as well as mild and symmetric wall thickening, is frequently seen. (c) Drawing illustrates ampullary carcinoma (exposed type). Note the asymmetric and irregularly thickened wall at the distal margin of the pancreaticobiliary junction that obliterates the lumen, along with enlargement of the major duodenal papilla.
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Endoscopy not only allows direct visualization of lesions in or around the major duodenal papilla; it often allows a tissue diagnosis to be made as well, making it the most valuable of the available imaging methods for evaluating the papilla. However, the abnormal papilla is increasingly being discovered at computed tomography (CT) and magnetic resonance (MR) imaging because of the widespread use of these modalities for detecting various pathologic conditions.
As at endoscopy, a bulging papilla is seen at CT with a variety of pathologic conditions. The size of the major duodenal papilla, mural thickening of the papilla, and certain attenuation patterns seen at dynamic contrast material–enhanced CT can help differentiate pathologic papilla from normal papilla. Increased targetlike enhancement of the papilla is likely to represent a benign condition such as papillitis, whereas an enhancing polypoid mass or focal asymmetric or irregular thickening with delayed prolonged enhancement in the ampulla of Vater indicates a malignant condition such as ampullary or periampullary carcinoma. The findings of pneumobilia or intrapancreatic gas with a deformed papilla at CT are suggestive of a patulous papilla.
In this article, we review anatomic considerations, imaging technique, and normal findings in the evaluation of a bulging papilla. In addition, we discuss and illustrate the CT findings that help discriminate among various pathologic conditions that cause bulging of the papilla and correlate these findings with endoscopic findings.
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Anatomic Considerations
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The major duodenal papilla is a conic or cylindric protuberance at the medial aspect of the descending or horizontal duodenum (4). The ampulla of Vater consists of the bile duct, the main pancreatic duct (MPD), the ampulla, and the major duodenal papilla surrounded by the sphincter of Oddi (4). The ampulla of Vater is strictly defined as a slightly dilated conduit that results from the union of the bile duct and the pancreatic duct (4). Seventy-four percent of ampullae of Vater have a common channel, 19% have separate openings for the bile duct and the MPD, and 7% have an interposed septum (5). The location, size, and shape of the major duodenal papilla are variable. The major duodenal papilla is located either in the middle third of the descending duodenum (75% of cases) or in the horizontal portion of the duodenum (25%) (5). As the distal bile duct and the pancreatic duct approach the duodenal wall, they become invested by smooth muscle fiber, which is referred to as the sphincter of Oddi and regulates the passage of bile and pancreatic juice into the duodenum (4). An accessory pancreatic duct opens onto the minor duodenal papilla, which is situated about 2 cm anterosuperior to the major duodenal papilla and is distinguished by the absence of the specific mucosal folds that characterize the major papilla (5).
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Imaging Technique
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CT examinations were performed at our institution with either a four–detector row scanner (LightSpeed QX/i; GE Medical Systems, Milwaukee, Wis) or a 16–detector row scanner (Sensation 16; Siemens Medical Systems, Erlangen, Germany). All patients received 500 mL of water as an oral contrast agent approximately 30 minutes before the CT examination and an additional 500 mL immediately before the examination to distend the stomach and duodenum. All patients also received 120 mL of a nonionic contrast material containing 370 mg of iodine per milliliter (iopromide) (Ultravist 370; Schering Korea, Seoul, Korea) via an antecubital vein at a rate of 3 mL/sec. Parameters for CT performed on a four–detector row scanner were as follows: detector collimation, 1.25 mm; table speed, 7.5 mm per rotation; table pitch, 3; effective section thickness, 2.5 mm; reconstruction interval, 2.5 mm; 120 kVp; and 230 mAs. When a 16–detector row scanner was used, the parameters were as follows: detector collimation, 0.75 mm; table speed, 9 mm per rotation; effective section thickness, 3 mm; reconstruction interval, 3 mm; 120 kVp; and 230 mAs. Unenhanced and dual-phase contrast-enhanced scans were obtained. The scan delay time was determined with use of the bolus tracking technique. To obtain time-attenuation curves, a small region of interest was placed over the abdominal aorta. Arterial dominant phase CT was automatically initiated 10 seconds after contrast enhancement of the aorta reached the target level (100 HU). Portal venous phase CT was performed 20 seconds after completion of the earlier sequence. CT scans were routinely obtained during a single breath hold with the patient supine. As much as possible, two-dimensional multiplanar reformation was performed on a commercially available console.
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Normal Appearance of the Major Duodenal Papilla at Endoscopy and CT
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The major duodenal papilla is located at the intersection of a transverse mucosal fold that partially covers the papilla and a longitudinal mucosal fold that emanates from its inferior aspect; thus, a T configuration can be seen (Fig 2) (5).
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Figure 2. Endoscopic image shows the normal major duodenal papilla (arrow) as an oval protuberance at the intersection of a covering transverse mucosal fold (T) and the longitudinal folds (*).
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Fukukura et al (6) reported that the major duodenal papilla was identified on thin-section CT scans in 11 (21.6%) of 51 patients with a normal papilla, which was always less than 10 mm in diameter. Similarly, in our study, the normal papilla could barely be distinguished from the surrounding duodenal mucosal folds in most cases (Fig 3a). However, a normal papilla may appear as an oval protruding structure less than 5–10 mm in diameter (Fig 3b). An abnormal papilla may have one or both of the following features: (a) an increased diameter (10 mm); or (b) increased enhancement at contrast-enhanced CT, defined as enhancement that is greater than that of the surrounding duodenal mucosa. A normal papilla may demonstrate targetlike enhancement, a finding that reflects the enhancing inner mucosa of the ampulla surrounded by low-attenuation bile and the outer mucosa of the papilla (Fig 3). The enhancing mucosa seen at CT may be confused with stones in the case of a papilla with targetlike enhancement. To prevent this confusion, the use of unenhanced CT should be considered (7).
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Figure 3a. (a) On a contrast-enhanced CT scan, the normal major duodenal papilla (arrow) can barely be distinguished from the surrounding duodenal mucosal folds, which was true in most cases in our study. (b) Contrast-enhanced CT scan shows the papilla (arrow) as a protuberance less than 10 mm in diameter with enhancement comparable to that of the adjacent duodenal mucosa, a finding that is seen less frequently than that in a. The targetlike enhancement of the normal papilla may be confused with a stone surrounded by low-attenuation bile.
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Figure 3b. (a) On a contrast-enhanced CT scan, the normal major duodenal papilla (arrow) can barely be distinguished from the surrounding duodenal mucosal folds, which was true in most cases in our study. (b) Contrast-enhanced CT scan shows the papilla (arrow) as a protuberance less than 10 mm in diameter with enhancement comparable to that of the adjacent duodenal mucosa, a finding that is seen less frequently than that in a. The targetlike enhancement of the normal papilla may be confused with a stone surrounded by low-attenuation bile.
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Causes of a Bulging Papilla
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Papillitis
Endoscopic papillitis is an acute inflammatory disorder involving the mucosa overlying the major duodenal papilla. Because the major papilla corresponds anatomically to the junction of the CBD and the MPD, papillitis may reflect an underlying biliary or pancreatic disorder. The presence of a clinically acute inflammatory condition such as acute cholangitis, acute pancreatitis, or acute exacerbation of chronic pancreatitis is significantly associated with papillitis. Papillitis may also be caused by the passage of biliary stones, periampullary diverticulum, parasites, and infection (1).
Choledocholithiasis is the most common cause of acute cholangitis and the second most common cause of acute pancreatitis. The reported sensitivity of CT for the direct depiction (ie, excluding indirect signs such as ductal dilatation from the criteria) of CBD stones has not exceeded 75% because most hypo- or isoattenuating stones are less likely to be detected than are heavily calcified stones (7,8).
An inflamed papilla caused by choledocholithiasis, microlithiasis, or a recently passed stone usually measures more than 5–10 mm in diameter (Figs 4–7) (1). Symmetric thickening may also be present and is best demonstrated on images obtained with intravenous contrast material. The inflamed papilla usually displays homogeneously increased enhancement, although mural stratification in the form of targetlike enhancement may also be seen (Figs 4–7) (7,9). Bulging of the papilla may be due to edematous thickening at the ampulla of Vater, which is precipitated by mechanical irritation from choledocholithiasis (Fig 4) (10). An impacted stone within the ampulla can also cause bulging of the papilla (Fig 5). At contrast-enhanced CT, increased enhancement of the papilla that is greater than that of the duodenal mucosa reflects a hyperemic state that is classically seen with acute inflammation (10). The targetlike enhancement of the normal papilla at contrast-enhanced CT may be confused with that of papillitis; however, findings of wall thickening and more intense enhancement are more likely to indicate papillitis than a normal papilla (Figs 6, 7) (7). Bulging of the papilla with increased enhancement may be clues to the detection of an isoattenuating bile duct stone (Fig 6), microlithiasis, or a recently passed stone (Fig 7) (7,9). Symmetric wall thickening and increased contrast enhancement may help distinguish benign papillitis from hypovascular malignant conditions (7).
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Figure 4a. Bulging papilla from a distal CBD stone in a 48-year-old man. (a) Unenhanced CT scan shows a high-attenuation stone (arrow) in the intrapancreatic portion of the distal bile duct. (b) On a contrast-enhanced CT scan obtained at the same level, the stone is surrounded by inflammatory change in the ampulla of Vater, which causes bulging of the papilla with increased targetlike enhancement (arrow). (c) Endoscopic image obtained after stone removal shows pus leaking from the severely inflamed papilla.
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Figure 4b. Bulging papilla from a distal CBD stone in a 48-year-old man. (a) Unenhanced CT scan shows a high-attenuation stone (arrow) in the intrapancreatic portion of the distal bile duct. (b) On a contrast-enhanced CT scan obtained at the same level, the stone is surrounded by inflammatory change in the ampulla of Vater, which causes bulging of the papilla with increased targetlike enhancement (arrow). (c) Endoscopic image obtained after stone removal shows pus leaking from the severely inflamed papilla.
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Figure 4c. Bulging papilla from a distal CBD stone in a 48-year-old man. (a) Unenhanced CT scan shows a high-attenuation stone (arrow) in the intrapancreatic portion of the distal bile duct. (b) On a contrast-enhanced CT scan obtained at the same level, the stone is surrounded by inflammatory change in the ampulla of Vater, which causes bulging of the papilla with increased targetlike enhancement (arrow). (c) Endoscopic image obtained after stone removal shows pus leaking from the severely inflamed papilla.
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Figure 5a. Bulging papilla from an impacted stone in the ampulla of Vater in a 37-year-old woman. (a) Contrast-enhanced coronal reformatted CT image shows bulging of the papilla (arrow) caused by an impacted stone in the ampulla of Vater, along with upstream bile duct dilatation. (b) Endoscopic image also shows marked bulging of the papilla caused by the impacted stone in the ampulla of Vater.
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Figure 5b. Bulging papilla from an impacted stone in the ampulla of Vater in a 37-year-old woman. (a) Contrast-enhanced coronal reformatted CT image shows bulging of the papilla (arrow) caused by an impacted stone in the ampulla of Vater, along with upstream bile duct dilatation. (b) Endoscopic image also shows marked bulging of the papilla caused by the impacted stone in the ampulla of Vater.
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Figure 6a. Bulging papilla from an isoattenuating CBD stone in a 27-year-old woman. (a) Contrast-enhanced CT scan shows mild bulging of the papilla with increased targetlike enhancement (arrow). (b) ERCP image shows a filling defect (arrowhead) in the distal CBD. (c) Endoscopic image shows bulging of the papilla with erythema.
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Figure 6b. Bulging papilla from an isoattenuating CBD stone in a 27-year-old woman. (a) Contrast-enhanced CT scan shows mild bulging of the papilla with increased targetlike enhancement (arrow). (b) ERCP image shows a filling defect (arrowhead) in the distal CBD. (c) Endoscopic image shows bulging of the papilla with erythema.
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Figure 6c. Bulging papilla from an isoattenuating CBD stone in a 27-year-old woman. (a) Contrast-enhanced CT scan shows mild bulging of the papilla with increased targetlike enhancement (arrow). (b) ERCP image shows a filling defect (arrowhead) in the distal CBD. (c) Endoscopic image shows bulging of the papilla with erythema.
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Figure 7a. Bulging papilla from papillitis in a 35-year-old man. The papillitis may have been due to a recently passed stone. (a) Contrast-enhanced CT scan shows bulging of the papilla with intense mucosal enhancement (arrow), but there is no evidence of stones. (b) Endoscopic image shows the edematous papilla with petechia. As at CT, however, there was no evidence of stones at ERCP.
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Figure 7b. Bulging papilla from papillitis in a 35-year-old man. The papillitis may have been due to a recently passed stone. (a) Contrast-enhanced CT scan shows bulging of the papilla with intense mucosal enhancement (arrow), but there is no evidence of stones. (b) Endoscopic image shows the edematous papilla with petechia. As at CT, however, there was no evidence of stones at ERCP.
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A bulging papilla can be seen in cases of acute pancreatitis or acute exacerbation of chronic pancreatitis (1). For patients with a bulging papilla, CT features that can help distinguish pancreatitis from other diseases include (a) findings associated with acute pancreatitis such as enlargement of the pancreas, (b) a peripancreatic fluid collection, and (c) complications such as pseudocysts and abscesses (Fig 8).
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Figure 8. Bulging papilla from acute pancreatitis in a 46-year-old man. Contrast-enhanced CT scan shows bulging of the papilla with increased targetlike enhancement (arrow) and marked submucosal edema. A moderate amount of inflammatory fluid surrounding a mildly enlarged pancreas is indicative of acute pancreatitis.
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Periampullary diverticulum can also cause papillitis, even in the absence of stone (Fig 9). This phenomenon may be related to the mechanical pressure of the diverticula or to inflammation (11).
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Figure 9a. Bulging papilla from periampullary diverticulum in a 61-year-old man. Contrast-enhanced CT scans demonstrate a huge periampullary diverticulum (* in a) and bulging of the papilla (arrow in a). Mild dilatation of the upstream bile duct caused by papillary stenosis is also seen (arrowhead in b).
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Figure 9b. Bulging papilla from periampullary diverticulum in a 61-year-old man. Contrast-enhanced CT scans demonstrate a huge periampullary diverticulum (* in a) and bulging of the papilla (arrow in a). Mild dilatation of the upstream bile duct caused by papillary stenosis is also seen (arrowhead in b).
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Intraductal Papillary Mucinous Tumor
IPMTs are characterized by papillary epithelial proliferations ranging from benign lesions to atypical lesions to adenocarcinoma, with associated duct ectasia and excessive production of mucin. IPMT may involve only the MPD (main duct type), only a side branch (branch duct type), or both structures (combined type) (3).
Approximately two-thirds of affected persons are men, and the mean age at the time of diagnosis is approximately 60 years. These patients typically present with symptoms of acute or recurrent pancreatitis (12).
When mucin production is copious, marked distention of the entire ductal system due to mucin is often present. A widely patent papilla with mucin pouring out of it can be identified at ERCP (13). In one report, duodenoscopy revealed the extrusion of mucin through a bulging patulous papilla in 14 of 27 patients with IPMT, whereas CT showed a bulging papilla in only six patients (22.2%) (Fig 10) (6). Although a bulging papilla is depicted less frequently at CT than at duodenoscopy, this finding is important for differentiating IPMT from other pancreatic diseases (6).
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Figure 10a. Bulging patulous papilla from IPMT in a 52-year-old man. (a–c) Contrast-enhanced axial (a) and coronal reformatted (b, c) CT images show cystic dilated branch ducts (arrowhead in c), a dilated MPD (arrow in b), and bulging of the papilla with faint enhancement (arrow in a). (d) Endoscopic image reveals jellylike mucin leaking from the papilla.
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Figure 10b. Bulging patulous papilla from IPMT in a 52-year-old man. (a–c) Contrast-enhanced axial (a) and coronal reformatted (b, c) CT images show cystic dilated branch ducts (arrowhead in c), a dilated MPD (arrow in b), and bulging of the papilla with faint enhancement (arrow in a). (d) Endoscopic image reveals jellylike mucin leaking from the papilla.
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Figure 10c. Bulging patulous papilla from IPMT in a 52-year-old man. (a–c) Contrast-enhanced axial (a) and coronal reformatted (b, c) CT images show cystic dilated branch ducts (arrowhead in c), a dilated MPD (arrow in b), and bulging of the papilla with faint enhancement (arrow in a). (d) Endoscopic image reveals jellylike mucin leaking from the papilla.
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Figure 10d. Bulging patulous papilla from IPMT in a 52-year-old man. (a–c) Contrast-enhanced axial (a) and coronal reformatted (b, c) CT images show cystic dilated branch ducts (arrowhead in c), a dilated MPD (arrow in b), and bulging of the papilla with faint enhancement (arrow in a). (d) Endoscopic image reveals jellylike mucin leaking from the papilla.
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Thin-section CT can provide details that are useful for subsequent imaging studies of IPMT. These details include abnormal cystic structures (eg, lobulated multicystic dilatation of the branch ducts, diffuse dilatation of the MPD), the presence of a ductal communication, and the presence of mural nodules and a bulging papilla (Fig 10) (13–15). Contrast-enhanced CT may demonstrate a bulging papilla that exceeds 10 mm in diameter in patients with IPMT (Fig 10) (13–15).
Ampullary Adenoma and Carcinoma
Ampullary adenoma and adenocarcinoma are neoplasms that arise from the glandular epithelium of the ampulla of Vater. The progression from adenoma to carcinoma occurs in ampullary carcinoma much as it does in colon cancer (16).
Obstructive jaundice is present in most patients with ampullary carcinoma. Ampullary cancers can be divided into three types according to gross morphologic features: protruded, ulcerative, and mixed (Fig 11). The protruded type is subdivided into exposed (exophytic) and nonexposed (intramural) types according to whether the overlying mucosa is cancerous (Fig 11) (17).
Enlargement of the papilla with a nodular appearance of the overlying mucosa that is associated with erosion or an ulcer is a typical endoscopic finding in ampullary carcinoma (Fig 12). Intramural type ampullary carcinoma is one of the most difficult types to diagnose at endoscopy because the papilla is covered with normal duodenal mucosa (Fig 13) (1).
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Figure 12a. Bulging papilla from exposed (exophytic) type ampullary carcinoma in a 56-year-old woman. (a) Contrast-enhanced CT scan shows a polypoid lesion (arrow) at the ampulla of Vater. Note the bulging, irregularly contoured major duodenal papilla, findings that indicate tumoral invasion into the mucosa of the papilla. (b) Endoscopic image demonstrates the bulging papilla with coarse nodularity, a finding that suggests ampullary carcinoma. Adenocarcinoma was confirmed at biopsy.
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Figure 12b. Bulging papilla from exposed (exophytic) type ampullary carcinoma in a 56-year-old woman. (a) Contrast-enhanced CT scan shows a polypoid lesion (arrow) at the ampulla of Vater. Note the bulging, irregularly contoured major duodenal papilla, findings that indicate tumoral invasion into the mucosa of the papilla. (b) Endoscopic image demonstrates the bulging papilla with coarse nodularity, a finding that suggests ampullary carcinoma. Adenocarcinoma was confirmed at biopsy.
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Figure 13a. Bulging papilla from nonexposed (intramural) type ampullary adenocarcinoma in a 53-year-old man. (a) Contrast-enhanced coronal reformatted CT image shows irregularly thickened mucosa of the ampulla obliterating the lumen, but with the mucosa of the major duodenal papilla relatively intact (arrow). (b) Endoscopic image shows a bulging papilla with normal-looking overlying mucosa. Initial biopsy showed chronic inflammation. Repeat biopsy performed 1 month later revealed adenocarcinoma.
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Figure 13b. Bulging papilla from nonexposed (intramural) type ampullary adenocarcinoma in a 53-year-old man. (a) Contrast-enhanced coronal reformatted CT image shows irregularly thickened mucosa of the ampulla obliterating the lumen, but with the mucosa of the major duodenal papilla relatively intact (arrow). (b) Endoscopic image shows a bulging papilla with normal-looking overlying mucosa. Initial biopsy showed chronic inflammation. Repeat biopsy performed 1 month later revealed adenocarcinoma.
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Ampullary carcinomas typically manifest as small tumors at the time of diagnosis because of the relatively early onset of symptoms and because the mass itself is often not apparent at imaging (17). However, secondary findings such as marked bile duct dilatation, in association with mild to moderate dilatation of the pancreatic duct, can usually be seen at CT (18). Larger ampullary tumors usually manifest as an infiltrative or polypoid mass (Fig 12). An infiltrative mass manifests as an irregularly thickened ductal wall that obliterates the lumen and demonstrates delayed prolonged enhancement. A polypoid mass is seen as an intraductal soft-tissue mass that is hypoattenuating relative to the hepatic parenchyma (17). Small tumors may be difficult to distinguish at CT from other causes of ampullary obstruction such as papillitis, papillary stenosis, or dyskinesia of the sphincter of Oddi (19).
Periampullary Cancer
By definition, periampullary cancers arise within 2 cm of the major papilla in the duodenum. They include four different types of cancers: ampullary, biliary, pancreatic, and duodenal (19). Because ampullary cancer has a better prognosis than pancreatic or bile duct cancer, differentiation among the various types of periampullary tumors is important for treatment planning (20).
Pancreatic carcinoma usually manifests as a discrete and hypovascular pancreatic mass, whereas with ampullary and periampullary duodenal cancers there is no evident pancreatic mass (19). However, diffusely infiltrative periampullary cancers may make it rather difficult to determine the precise anatomic site of origin at CT, and the differential diagnosis may include adenocarcinoma of the distal CBD, the MPD, the ampulla of Vater, and the periampullary duodenal mucosa (19). Like ampullary cancer, periampullary cancers frequently involve the papilla, resulting in bulging of the papilla at CT (Fig 14).
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Figure 14a. Bulging papilla from periampullary cancer in a 65-year-old woman. (a) Contrast-enhanced coronal reformatted CT image reveals a periampullary mass (arrow) invading the distal CBD, resulting in upstream bile duct dilatation. (b) Endoscopic image shows an ulceroinfiltrative lesion in the periampullary region. The lesion was confirmed to be adenocarcinoma at biopsy.
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Figure 14b. Bulging papilla from periampullary cancer in a 65-year-old woman. (a) Contrast-enhanced coronal reformatted CT image reveals a periampullary mass (arrow) invading the distal CBD, resulting in upstream bile duct dilatation. (b) Endoscopic image shows an ulceroinfiltrative lesion in the periampullary region. The lesion was confirmed to be adenocarcinoma at biopsy.
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Autoimmune Pancreatitis
Autoimmune pancreatitis is a unique form of chronic pancreatitis with a pathogenesis that may involve autoimmune mechanisms. It is characterized morphologically by enlargement of the pancreas and irregular narrowing of the MPD, and is characterized serologically by elevation of the serum IgG level (especially the presence of high serum concentrations of IgG4) and, in some cases, the presence of autoantibodies that are associated with other autoimmune diseases such as Sjögren disease. Autoimmune pancreatitis is characterized clinically by its responsiveness to steroid therapy (21).
Pathologic analysis reveals dense lymphoplasmacytic infiltrates of the pancreas that are centered around the pancreatic ducts. A similar inflammatory process can also involve the biliary tree, gallbladder, and peripancreatic retroperitoneal tissue (22).
Reported CT findings that are suggestive of autoimmune pancreatitis include diffuse or focal enlargement of the pancreas with delayed enhancement at dynamic CT; a low-attenuation rim surrounding the pancreas, thought to correspond to an inflammatory process involving the peripancreatic tissues; the absence of atrophy of the pancreas; and the absence of significant pancreatic duct dilatation (Fig 15) (23). Thickening and contrast enhancement of the CBD and the gallbladder may be observed, findings that reflect the presence of inflammatory disease in these structures that is associated with autoimmune pancreatitis (23).
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Figure 15a. Bulging papilla from autoimmune pancreatitis in a 54-year-old woman. (a, b) Arterial phase (a) and equilibrium phase (b) CT scans demonstrate a bulging papilla with delayed enhancement (arrow) and diffuse enlargement of the pancreas. The pancreatic parenchyma shows delayed homogeneous enhancement, and a low-attenuation rim (arrowhead) is seen surrounding the pancreas. (c) Endoscopic image shows bulging of the papilla, which has a smooth surface. Lymphocytic infiltration of the papilla was revealed at biopsy.
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Figure 15b. Bulging papilla from autoimmune pancreatitis in a 54-year-old woman. (a, b) Arterial phase (a) and equilibrium phase (b) CT scans demonstrate a bulging papilla with delayed enhancement (arrow) and diffuse enlargement of the pancreas. The pancreatic parenchyma shows delayed homogeneous enhancement, and a low-attenuation rim (arrowhead) is seen surrounding the pancreas. (c) Endoscopic image shows bulging of the papilla, which has a smooth surface. Lymphocytic infiltration of the papilla was revealed at biopsy.
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Figure 15c. Bulging papilla from autoimmune pancreatitis in a 54-year-old woman. (a, b) Arterial phase (a) and equilibrium phase (b) CT scans demonstrate a bulging papilla with delayed enhancement (arrow) and diffuse enlargement of the pancreas. The pancreatic parenchyma shows delayed homogeneous enhancement, and a low-attenuation rim (arrowhead) is seen surrounding the pancreas. (c) Endoscopic image shows bulging of the papilla, which has a smooth surface. Lymphocytic infiltration of the papilla was revealed at biopsy.
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Unno et al (2) reported bulging of the papilla when T-lymphocyte infiltration was present, a characteristic endoscopic finding in patients with proved autoimmune pancreatitis (Fig 15). Dynamic CT shows bulging of the papilla with delayed enhancement similar to that described earlier for lymphoplasmacytic infiltration of the pancreatic parenchyma (Fig 15) (1,23).
Choledochocele
Choledochocele, or type III choledochal cyst, is a rare congenital anomaly of the hepatobiliary system. The choledochus duct terminates in a small, intramural cystic lesion that is lined by duodenal mucosa (24). Choledochocele alone can cause cholecystitis or cholangitis. There have been some recent reports that this entity is associated with biliary malignancy and with patients having a high amylase level in the bile (25). Although the pathogenesis of choledochocele is unknown, several possible causes have been proposed, including (a) dysfunction of the sphincter of Oddi, with or without weakness of the CBD; and (b) obstructive ballooning of the intramural portion of the CBD owing to inflammation at the papilla (24).
CT findings consist of spheric dilatation of the terminal bile duct that protrudes into the duodenal lumen (Fig 16a). Like MR cholangiopancreatography, thin-section CT has only a limited capacity to help detect a small choledochocele. A small choledochocele may become evident only at ERCP performed after contrast material has been injected under pressure (Fig 16b) (26). A bulging papilla caused by an impacted stone may also mimic a choledochocele (25).
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Figure 16a. Choledochocele in a 69-year-old woman. (a) Contrast-enhanced CT scan shows cystic dilatation of the terminal bile duct protruding into the duodenum (arrow). (b) ERCP image obtained after contrast material had been injected under pressure shows obvious cystic bulging of the papilla (arrowhead).
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Figure 16b. Choledochocele in a 69-year-old woman. (a) Contrast-enhanced CT scan shows cystic dilatation of the terminal bile duct protruding into the duodenum (arrow). (b) ERCP image obtained after contrast material had been injected under pressure shows obvious cystic bulging of the papilla (arrowhead).
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Unusual Primary Neoplasms
Primary benign tumors such as Brunner gland adenoma, lipoma, fibroma, lymphangioma, and paraganglioma can also occur in the periampullary region (27). Duodenal lipomas can be reliably diagnosed at CT as a smooth-margined mass with fat attenuation (28). Primary malignant tumors such as lymphomas and gastrointestinal stromal tumors (GISTs) with varying malignant potential and neuroendocrine tumors rarely arise from the periampullary region (27). Lymphoma involving the periampullary region may be a manifestation of systemic disease or primary tumor (28). Most gastrointestinal lymphomas are B-cell tumors, and they more commonly involve the small intestine than the large intestine. The CT appearance of lymphoma is variable and includes focal or segmental mural infiltration with or without aneurysmal dilatation, cavitating masses, and mesenteric or retroperitoneal lymphadenopathy (28).
Most GISTs of the duodenum are located in its second or third portion. At CT, GISTs may be seen as well-defined exoenteric masses that usually consist of an irregular central area of low attenuation surrounded by variably thickened soft-tissue-attenuation walls with or without ulceration (Fig 17) (29).
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Figure 17a. Bulging papilla from GIST (a high-grade malignancy). (a) Contrast-enhanced coronal reformatted CT image shows a slightly enhancing exoenteric mass with some necrotic areas (arrow) in the medial aspect of the third portion of the duodenum. (b) Endoscopic image shows an exophytic ulcerating mass in the proximal part of the third duodenal portion.
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Figure 17b. Bulging papilla from GIST (a high-grade malignancy). (a) Contrast-enhanced coronal reformatted CT image shows a slightly enhancing exoenteric mass with some necrotic areas (arrow) in the medial aspect of the third portion of the duodenum. (b) Endoscopic image shows an exophytic ulcerating mass in the proximal part of the third duodenal portion.
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Patulous Ampulla of Vater
Air in the bile duct or pancreatic duct almost always results from some type of communication between the pancreaticobiliary duct and the intestine (30). CT frequently demonstrates pneumobilia in patients who have undergone sphincterotomy. Unlike pneumobilia, air in the pancreas is seldom demonstrated at CT (Fig 18). Pancreatic and biliary sphincteric mechanisms play a major role in regulating secretory flow and preventing reflux, but patients who have undergone sphincterotomy or who have had papillitis may have altered sphincteric function and duodenal–pancreatic duct reflux. Clinical or laboratory evidence of pancreatitis or cholangitis is not seen in most patients. The infecting organisms may infrequently reach the hepatic parenchyma or the pancreatic bed as a result of the reflux of enteric organisms into the pancreatic duct or biliary tree via a patulous ampulla of Vater.
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Figure 18a. Bulging patulous papilla in a 62-year-old woman. (a) Contrast-enhanced CT scan demonstrates a low-attenuation masslike lesion in the uncinate process of the pancreas (arrow), with pneumobilia and air in the pancreatic duct (arrowhead) due to previous sphincterotomy. Pancreatic abscess was proved at sonographically guided core biopsy. (b) Endoscopic image shows two openings in the patulous papilla (*).
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Figure 18b. Bulging patulous papilla in a 62-year-old woman. (a) Contrast-enhanced CT scan demonstrates a low-attenuation masslike lesion in the uncinate process of the pancreas (arrow), with pneumobilia and air in the pancreatic duct (arrowhead) due to previous sphincterotomy. Pancreatic abscess was proved at sonographically guided core biopsy. (b) Endoscopic image shows two openings in the patulous papilla (*).
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Conclusions
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Endoscopy with or without biopsy is the best method for making a definitive diagnosis in patients with bulging of the papilla. Although CT often does not clarify the exact cause of bulging, especially if the tumor is small, CT performed with adequate duodenal distention may allow detection of an abnormal papilla, thereby providing additional information about other abnormalities in the pancreaticobiliary system such as dilatation of the bile duct or pancreatic duct. Thus, CT findings may prove useful for the next diagnostic or therapeutic modality such as MR cholangiography or endoscopy. MR cholangiography may be equivalent to CT in identifying a bulging papilla and superior in distinguishing the underlying cause (eg, a small impacted stone).
We have not presented any scientific data on the reliability of CT for helping detect a bulging papilla in this article. Nevertheless, we believe that familiarity with the normal CT anatomy of the periampullary region and with the imaging features of the various diseases that may cause bulging of the papilla will help the radiologist make a more confident diagnosis. Further studies will be required to demonstrate the accuracy and efficacy of CT and MR imaging in identifying a bulging papilla.
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Footnotes
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Abbreviations: CBD = common bile duct, ERCP = endoscopic retrograde cholangiopancreatography, GIST = gastrointestinal stromal tumor, IPMT = intraductal papillary mucinous tumor, MPD = main pancreatic duct
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References
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Abstract
Introduction
