Primary Epiploic Appendagitis: A Rare but Crucial Mimicker of Acute Abdomen

원발성 복강내 충수염: 급성 복부의 드물지만 중요한 유사 증상

Keywords: Epiploic appendagitis, hyperattenuating ring sign, CT diagnosis, acute abdominal pain, omental infarction mimics, lower quadrant pain, epiploic appendage torsion

Introduction

Acute abdominal pain is one of the most common presentations in emergency departments and is often attributed to conditions like appendicitis or diverticulitis. However, Primary Epiploic Appendagitis (PEA)—a rare, self-limiting inflammatory condition of the epiploic appendages—remains an under-recognized entity. Despite its benign nature, misdiagnosis may lead to unnecessary surgical interventions. This article presents a case study of a 20-year-old male with lower abdominal pain diagnosed with epiploic appendagitis via contrast-enhanced CT and provides a comprehensive review of the condition's imaging characteristics, pathophysiology, and clinical management.

Case Presentation

A 20-year-old man presented to the emergency room with three days of progressive abdominal pain. The discomfort, initially localized to the left lower quadrant (LLQ), became more generalized and was accompanied by localized tenderness on physical examination.

Contrast-enhanced CT of the abdomen and pelvis was performed, revealing hallmark signs of epiploic appendagitis.

Imaging Findings

Figure 1: Axial CT with IV contrast shows a small (<5 cm) oval-shaped lesion of fat attenuation adjacent to the distal descending colon, surrounded by subtle fat stranding and a thin hyperattenuating rim.

Figure 1. Axial CT showing a fat-attenuated lesion with hyperattenuating ring sign near the sigmoid colon.

Figure 2: The lesion demonstrates a central dot sign with mild surrounding colonic wall thickening, which is likely reactive.

Figure 2. Coronal reformatted CT images in a 20-year-old male demonstrate an oval-shaped, fat-attenuated lesion adjacent to the descending colon (left panel) with a hyperattenuating peripheral rim and surrounding mild fat stranding. The right panel also shows the same lesion located near the anterior peritoneal reflection, consistent with an inflamed epiploic appendage. These findings are characteristic of epiploic appendagitis and help distinguish it from diverticulitis or appendicitis.

These features are classic for epiploic appendagitis and help differentiate it from other causes of acute abdomen.

Pathophysiology of Epiploic Appendagitis

Epiploic appendages are small, fat-filled peritoneal outpouchings along the colon, each supplied by one or two small arterioles and drained by a single vein. Torsion or spontaneous venous thrombosis of these appendages leads to ischemia and localized inflammation, resulting in the radiological and clinical syndrome of epiploic appendagitis.

The hyperattenuating ring sign, as seen in our case, is due to surrounding inflammatory changes and thrombosed vessels.

Epidemiology and Risk Factors

Occurs across all age groups, peaks in the 4th to 5th decade.
Mild male predominance.
Precipitated by obesity, strenuous exercise, and abdominal hernia.
Frequently misdiagnosed as diverticulitis (left-sided) or appendicitis (right-sided).
Incidence in patients with suspected diverticulitis: 2.3%–7.1%.

Clinical Presentation

Patients typically present with:

Sudden-onset localized pain, most commonly in the LLQ or RLQ.
Absence of fever, leukocytosis, or systemic signs.
No associated nausea, vomiting, or altered bowel habits.

In contrast to appendicitis, systemic inflammatory signs are usually absent.

Radiologic Features

On CT, classic signs include:

Oval-shaped fat-attenuated lesion (<5 cm) adjacent to the colon.
Surrounded by a hyperdense rim (hyperattenuating ring sign).
May show a central dot sign indicating a thrombosed draining vein.
Minimal adjacent bowel wall thickening, often reactive.

Differential Diagnosis

Condition	Key Differentiating Features
Diverticulitis	Segmental colonic wall thickening, pericolonic stranding, possible abscess
Omental infarction	Larger lesion (>5 cm), more centrally located
Appendicitis	RLQ pain with enlarged, inflamed appendix and periappendiceal fat stranding
Sclerosing mesenteritis	Fibrosis and calcification, often involving the mesentery diffusely

Management and Prognosis

Treatment is conservative, focusing on:

NSAIDs for symptom relief
Avoidance of unnecessary antibiotics or surgery
Symptoms typically resolve in within 1–2 weeks

Misdiagnosis may lead to unwarranted appendectomy or colectomy.

Conclusion

Epiploic appendagitis, although rare, is an important mimicker of other acute abdominal conditions. Accurate diagnosis via CT is essential to avoid unnecessary interventions. Radiologists and clinicians must maintain a high index of suspicion in young adults presenting with localized abdominal pain and benign laboratory findings.

Quiz

1. What is the most likely radiologic abnormality in this patient?

(1) Swirling mesentery
(2) Localized fat stranding
(3) Peritoneal thickening
(4) Mesenteric desmoplastic reaction

2. Which radiologic sign is characteristic of epiploic appendagitis?

(1) Hyperattenuating ring sign
(2) Central scar sign
(3) Comb sign
(4) Target sign

3. The lesion in epiploic appendagitis is fat-attenuated.

(1) True
(2) False

4. What is the most likely diagnosis based on the CT findings?

(1) Crohn’s disease
(2) Appendicitis
(3) Peritoneal implant
(4) Epiploic appendagitis

5. What is a likely cause of the CT findings?

(1) Colitis
(2) Dysplasia
(3) Infarction
(4) Lymphangitis

Answer & Explanation

1. Answer: (2) Localized fat stranding. Explanation: The key CT sign in epiploic appendagitis is pericolic fat stranding around a small fat-attenuated lesion.

2. Answer: (1) Hyperattenuating ring sign. Explanation: A hallmark of epiploic appendagitis on CT is the hyperdense rim surrounding the infarcted appendage.

3. Answer: (1) True. Explanation: The infarcted appendage retains its fat composition, which is distinguishable on CT imaging.

4. Answer: (4) Epiploic appendagitis. Explanation: The location, CT morphology, and absence of systemic signs point to epiploic appendagitis.

5. Answer: (3) Infarction. Explanation: The pathogenesis involves infarction due to torsion or venous thrombosis of the appendage.

References

[1] P. M. Rao, J. Wittenberg, and J. N. Lawrason, “Primary epiploic appendagitis: Evolutionary changes in CT appearance,” Radiology, vol. 204, no. 3, pp. 713–717, 1997.

[2] A. K. Singh et al., “Acute epiploic appendagitis and its mimics,” Radiographics, vol. 25, no. 6, pp. 1521–1534, 2005.

[3] A. C. Van Breda Vriesman, “The hyperattenuating ring sign,” Radiology, vol. 226, no. 2, pp. 556–557, 2003.

[4] C. L. Almeida et al., “CT features of epiploic appendagitis: an overlooked cause of acute abdominal pain,” Insights Imaging, vol. 9, pp. 347–354, 2018.

[5] A. E. Sandrasegaran and R. L. Maglinte, “Colon: CT of common and uncommon conditions,” Clin Radiol, vol. 70, no. 1, pp. 1–11, 2015.

[6] D. Horton et al., “Epiploic appendagitis: a review,” AJR Am J Roentgenol, vol. 195, no. 4, pp. 861–867, 2010.

[7] H. El-Matary, “Clinical clues to epiploic appendagitis,” World J Gastroenterol, vol. 13, no. 5, pp. 753–756, 2007.

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