DOI: 10.1148/radiol.2371031627
(Radiology 2005;237:301-302.)
© RSNA, 2005
The Ring Sign1
Arumugam Rajesh, MD, FRCR
1 From the Department of Abdominal Imaging, Indiana University Hospitals, Indianapolis, Ind. Received October 7, 2003; revision requested December 18; revision received December 22; accepted January 30, 2004.
Address correspondence to the author, Department of Radiology, University Hospitals of Leicester, Leicester General Hospital, Gwendolen Rd, Leicester LE4 5PW, United Kingdom (e-mail: arajesh27{at}hotmail.com).
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APPEARANCE
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The ring sign is seen on transverse computed tomographic (CT) scans of the abdomen or pelvis. The characteristic features of the sign are a round or oval pericolonic lesion with attenuation that is either the same as or higher than that of normal peritoneal fat and a thickened hyperattenuating rim that represents the ring (1–4).
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EXPLANATION
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The ring (Figs 1, 2) is caused by the thickening of a rim of visceral peritoneum around the epiploic appendages in the absence of surrounding pathologic abnormalities and can be seen in patients with primary epiploic appendagitis (PEA). A central dot or line of increased attenuation may also be seen and is thought to represent a thrombosed vessel, fibrous tissue, or hemorrhage (3,4). Perilesional stranding and fascial thickening, which may be caused by edema or inflammation, are frequently encountered (3–7). Mass effect and focal wall thickening of the adjacent colon may also be present (3). PEA is caused by torsion or spontaneous venous thrombosis, with subsequent ischemic or hemorrhagic infarction of the appendages (3,4).
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Figure 1. Transverse contrast material–enhanced CT scan of patient presenting with abdominal pain. Scan demonstrates thickening of visceral peritoneum (arrow) around epiploic appendage of sigmoid colon.
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Figure 2. Transverse contrast-enhanced CT scan of patient presenting with abdominal pain. Scan demonstrates thickening of visceral peritoneum around epiploic appendage (arrow) of sigmoid colon and increased attenuation of fat (*) resulting from edema, inflammation, or hemorrhage.
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DISCUSSION
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Epiploic appendages are visceral peritoneal outpouchings that contain fat and blood vessels. There are approximately 50–100 appendages that are located on the serosal surface of the colon and are distributed from the cecum to the rectosigmoid junction (8). These appendages are 2–5 cm long and 1–2 cm thick and are arranged in two rows along the tenia libera and tenia omentalis; in the transverse colon, only one row is present (2). Most cases of PEA are thought to occur in the region of the sigmoid colon that is located at the level of the anterior superior iliac spine on the left side of the patient (2,8,9). PEA is thought to occur in this area because of the transition from the more mobile sigmoid colon to the fixed retroperitoneal descending colon at this level. The appendages are also larger and more pedunculated in the upper sigmoid colon than in the lower sigmoid colon (2).
Clinically, PEA mimics acute appendicitis or diverticulitis, depending on the side of manifestation. Obesity, heavy exercise, and vigorous stretching are reported to be possible predisposing factors for epiploic appendagitis (4). Most patients present with acute onset of abdominal pain and localized tenderness but no rigidity. Patients with PEA are not seriously ill, unlike other patients who experience more common and severe causes of acute abdomen (10). Nausea, vomiting, and loss of appetite are rare symptoms. White blood cell count is normal or slightly elevated in most of the cases. The pain may be exacerbated by coughing, deep breathing, or stretching because the infarcted appendage is adherent to the parietal peritoneum. Signs and symptoms are self-limiting and rarely last more than 1 week (4,5). Because PEA is a self-limiting disease, conservative treatment with analgesics is usually sufficient (5,11). Follow-up imaging may show a complete resolution of findings, a residual fibrous band, or a calcified appendage (2,4).
The differential diagnosis based on CT findings includes omental infarction and secondary epiploic appendagitis. Omental infarction may manifest with clinical signs that are identical to those of PEA, but omental infarction is unlikely to be confused with PEA except in the transverse colon. When compared with PEA, omental infarction is considerably larger in size (3–15 cm) and does not demonstrate thickening of the visceral peritoneum (3). Secondary epiploic appendagitis is an inflammation of the epiploic appendage that is caused by the presence of diverticulitis or appendicitis. Patients with secondary epiploic appendagitis may demonstrate the ring sign at CT but have associated features of diverticulitis or appendicitis.
PEA is a condition with characteristic CT appearances. Radiologists should be aware of the ring sign for diagnosis.
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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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- McClure MJ, Khalili K, Sarrazin J, Hanbidge A. Radiological features of epiploic appendagitis and segmental omental infarction. Clin Radiol 2001;56:819–827.[CrossRef][Medline]
- Hollerweger A, Macheiner P, Rettenbacher T, Gritzmann N. Primary epiploic appendagitis: sonographic findings with CT correlation. J Clin Ultrasound 2002;30:481–495.[CrossRef][Medline]
- Rao PM, Wittenberg J, Lawrason JN. Primary epiploic appendagitis: evolutionary changes in CT appearance. Radiology 1997;204:713–717.[Abstract/Free Full Text]
- Rioux M, Langis P. Primary epiploic appendagitis: clinical US, and CT findings in 14 cases. Radiology 1994;191:523–526.[Abstract/Free Full Text]
- Molla E, Ripolles T, Martinez MJ, Morote V, Rosello-Sastre E. Primary epiploic appendagitis: US and CT findings. Eur Radiol 1998;8:435–438.[CrossRef][Medline]
- Rao PM. CT of diverticulitis and alternative conditions. Semin Ultrasound CT MR 1999;20:86–93.[CrossRef][Medline]
- Torres GM, Abbitt PL, Weeks M. CT manifestations of infarcted epiploic appendages of the colon. Abdom Imaging 1994;19:449–450.[CrossRef][Medline]
- Ghahremani GG, White EM, Hoff FL, Gore RM, Miller JW, Christ ML. Appendixes epiploicae of the colon: radiologic and pathological features. RadioGraphics 1992;12:59–77.[Abstract]
- Carmichael DH, Organ CH. Epiploic disorders. Conditions of the epiploic appendages. Arch Surg 1985;120:1167–1172.
- Sirvanci M, Tekelioglu MH, Duran C, Yardimci H, Onat L, Ozer K. Primary epiploic appendagitis: CT manifestations. Clin Imaging 2000;24:357–361.[CrossRef][Medline]
- Rao PM, Rhea JT, Wittenberg J, Warshaw AL. Misdiagnosis of primary epiploic appendagitis. Am J Surg 1998;176:81–85.[CrossRef][Medline]
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