DOI: 10.1148/radiol.2292020446
(Radiology 2003;229:421-422.)
© RSNA, 2003
The Antral Pad Sign1
Ashwin Vasudev Asrani, MBBS
1 From the Department of Radiology, Seth G. S. Medical College and KEM Hospital, Parei, Mumbai 400012, India. Received May 7, 2002; revision requested July 15; revision received November 7; accepted November 14. Address correspondence to the author (e-mail: ashwinasrani@yahoo.com).
Index terms: Gastrointestinal tract, neoplasms, 723.364, 723.365 • Pancreas, neoplasms, 770.30 • Pancreatitis, 770.291 • Signs in Imaging
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APPEARANCE
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The antral pad sign is seen on a radiograph of the upper gastrointestinal tract obtained with orally administered contrast material. The sign refers to an extrinsic impression or indentation on the posteroinferior aspect of the antrum. The impression is generally arcuate and smooth, and it may or may not be associated with an impression on the medial aspect of the duodenum (1–3) (Figs 1, 2).
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Figure 1. Frontal radiograph of upper gastrointestinal tract obtained with orally administered barium shows the arcuate impression (arrow) being caused on the antrum by an adenocarcinoma of the pancreatic head.
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Figure 2. Frontal radiograph of the upper gastrointestinal tract obtained with orally administered barium shows large smooth extrinsic impression on the antrum caused by pancreatic pseudocyst (arrows).
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EXPLANATION
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The impression is typically caused by a lesion in the region of the head or body of the pancreas. This is because the anterior surface of the body of the pancreas is directed anteriorly and cephalad. It is covered by the posteroinferior surface of the stomach, which rests on it, and the two organs are separated by the omental bursa. The pancreas forms part of the stomach bed structures (4). Though the head of the pancreas is not directly posterior to the gastric antrum, it lies in close proximity to the antrum. Thus, lesions in the head and body of the pancreas will cause the antral pad sign (Fig 3).
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Figure 3. Contrast-enhanced transverse computed tomographic section of the abdomen shows how the antral pad sign is produced by a pancreatic pseudocyst (single arrow). Double arrows indicate the antrum.
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A similar impression may be caused by a normal or distended gallbladder, which lies ventrolateral to the duodenal bulb. The gastric antrum is mobile, and since the anterior abdominal wall is pliant, the liver and gallbladder move to the left when the patient is in the right anterior oblique position. Thus, an impression is produced on the posteroinferior aspect of the antrum (1).
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DISCUSSION
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The antral pad sign originally referred to splaying of antral rugal folds because of a mass in that region, posterior to the stomach (3). However, it has been shown that the antral pad sign can be caused by a normal gallbladder or by pancreatitis, pseudocyst of the pancreas, or neoplasms of the head and body of the pancreas (1,2,5). In a series of 222 consecutive combined upper gastrointestinal and cholecystography examinations, 18 cases (8.1%) demonstrated a definite indentation on the posteroinferior aspect of the antrum (1).
Patients with pancreatitis present with pain in the epigastric region that radiates to the back or chest (6). There are two major causes of acute pancreatitis: biliary calculi in 50%–70% of patients and alcohol use in 25% of patients (6). Pleural effusion occurs in 10%–20% of patients (6). Acute abdominal fluid collection occurs early in the course and is often located near the head of the pancreas and has a poorly defined wall (6). It is likely that it is this fluid collection or just the edematous head and body of the pancreas that cause the antral pad sign in patients with acute pancreatitis.
Patients with pseudocyst of the pancreas usually have a history of one or more episodes of pancreatitis with acute pain due to infection or hemorrhage into the cyst. Pseudocyst of the pancreas is a complication of pancreatitis that results when a collection of pancreatic fluid is walled off by granulation or fibrous tissue to form a cyst but does not have a true epithelium-lined wall (7). Pseudocysts less than 4 cm in diameter may resolve spontaneously, but larger ones (>7 cm) need to be treated, as hemorrhage may occur or they may get infected or rupture into the hollow viscera. Persistent pseudocysts generally communicate with the pancreatic duct (7). It may take 4 weeks or more after the onset of disease for pseudocysts to form (6). Hence, in a known case of pancreatitis that has developed more than 4 weeks previously, visualization of the antral pad sign may indicate this complication (Fig 2).
Pancreatic neoplasms have been classified as epithelial and nonepithelial tumors; the majority are epithelial tumors, of which 90% are ductal cell adenocarcinoma and its variants (8). Approximately 60%–70% arise in the head of the pancreas, and about 10% arise in the body of the pancreas (8). The prognosis of malignant neoplasm of the pancreas is not very favorable, because by the time it is diagnosed it is at an advanced stage. This is partly because the initial symptoms and signs of the disease are vague and nonspecific; symptoms include weight loss, jaundice, vomiting, and pain (8). A combination of abdominal pain with acute onset diabetes mellitus is suggestive of malignancy (8). Patients may also have spontaneous venous thrombosis (Trousseau syndrome) (8). Painless jaundice occurs in 25% of patients (8). The antral pad sign is generally seen rather late in the clinical course of pancreatic neoplasms and does not serve as an early marker for pancreatic neoplasms.
In conclusion, the antral pad sign may be produced by pancreatic abnormality or by a normal or distended gallbladder (1). The sign is less useful today than in the past, as cross-sectional imaging modalities such as computed tomography and magnetic resonance imaging are used in the evaluation of the disorders mentioned here.
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ACKNOWLEDGMENTS
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I am grateful to Govind Chavhan, MD, and Arpit Nagar, DMRD, for their invaluable guidance and support in the preparation of this article.
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FOOTNOTES
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A trainee (resident or fellow) wishing to submit a manuscript for Signs in Imaging should first write to the Editor for approval of the sign to be prepared, to avoid duplicate preparation of the same sign.
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REFERENCES
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- Smeets R, Odo Op Den Orth J. Gallbladder: common cause of antral pad sign. AJR Am J Roentgenol 1979; 132:571-573.[Abstract]
- Eisenberg RL. Miscellaneous abnormalities. In: Gore RM, Levine MS, Laufer I, eds. Textbook of gastrointestinal radiology. Philadelphia, Pa: Saunders, 1994; 731-732.
- Eisenberg RL. Antral pad sign. In: Eisenberg RL, eds. Atlas of signs in radiology. Philadelphia, Pa: Lippincott, 1984; 11.
- Bannister HL. Alimentary system. In: Williams PL, eds. Gray’s anatomy. 38th ed. Edinburgh, Scotland: Harcourt, 2000; 1754-1755, 1790.
- Eisenberg RL. Widening of the duodenal sweep. In: Eisenberg RL, eds. Gastrointestinal radiology. Philadelphia, Pa: Lippincott, 1983; 348-349.
- Russell RCG. The pancreas. In: Russell RCG, eds. Bailey and Love’s short practice of general surgery. 23rd ed. London, England: Arnold, 2000; 996-999.
- Balthazar EJ. Pancreatitis. In: Gore RM, Levine MS, Laufer I, eds. Textbook of gastrointestinal radiology. Philadelphia, Pa: Saunders, 1994; 2132-2134.
- Friedman AC. Pancreatic neoplasms Gore RM, Levine MS, Laufer I, eds. Textbook of gastrointestinal radiology. Philadelphia, Pa: Saunders, 1994; 2161-2172.
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