A Diagnostic Challenge in Acute Abdomen: The Critical Role of CT in Identifying Epiploic Appendagitis
Keywords: Epiploic Appendagitis, Acute Abdominal Pain, CT Scan Diagnosis, Diverticulitis Mimic, Epiploic Appendagitis Imaging, Left Lower Quadrant Pain
Epiploic appendagitis (Epiploic Appendagitis) is an uncommon, benign, and self-limiting cause of acute abdominal pain that frequently poses a diagnostic challenge due to its ability to mimic more severe surgical conditions like acute diverticulitis or appendicitis.
Correct and timely diagnosis, primarily achieved through advanced imaging, is crucial to prevent unnecessary hospitalization, antibiotic use, or surgical intervention.
A deep understanding of this condition—its pathophysiology, classic imaging features, and conservative management—is essential for best practice in emergency and internal medicine settings.
1. Pathophysiology of Epiploic Appendagitis
Epiploic appendages (or appendices epiploicae) are small, pedunculated pouches of adipose tissue covered by serosa, protruding from the outer surface of the colon, primarily along the antimesenteric border.
While their exact function is debated (proposed roles include cushioning the colon and immune response), their anatomical structure makes them susceptible to primary inflammation, known as Primary Epiploic Appendagitis (PEA).
The primary mechanism leading to PEA is ischemic infarction. This typically occurs via one of two pathways:
Torsion: The appendage twists on its stalk, compromising the venous return and arterial supply.
Spontaneous Venous Thrombosis: Occlusion of the central draining vein of the appendage without gross torsion.
This ischemia and subsequent necrosis trigger a localized inflammatory response in the surrounding peritoneal fat, which is the pathology detected on cross-sectional imaging.
Secondary Epiploic Appendagitis (SEA) is a distinct entity where the appendage becomes inflamed due to an adjacent primary inflammatory process, such as diverticulitis or appendicitis.
2. Epidemiology and Risk Factors
Epiploic Appendagitis is a relatively rare cause of acute abdominal pain, estimated to account for 1.1% to 1.3% of all cases presenting with such symptoms, with an incidence of around 8.8 cases per million people per year.
Age and Gender: The condition most commonly affects patients in their 4th to 5th decade of life. While some series suggest a predilection for women, many recent studies, and the case presented in the attached file, note a strong male predilection. The patient in the case review is a 36-year-old male, fitting the typical demographic.
Location: The highest concentration of epiploic appendages is found in the rectosigmoid junction (up to 57%) and the ileocecal region (around 26%). This anatomical distribution explains why the pain is most frequently experienced in the left lower quadrant (LLQ) or right lower quadrant (RLQ).
Risk Factors: Visceral obesity is a key risk factor, as larger, more elongated appendages are more prone to torsion. Other associated factors include strenuous exercise and recent large meals, which may alter vascular flow or mechanical stress on the colon.
3. Clinical Presentation
The clinical presentation of Epiploic Appendagitis is typically characterized by acute, focal, non-migratory abdominal pain. The pain is often described as constant and sharp, localized directly over the site of the inflamed appendage.
Key Features:
Pain Location: Most commonly LLQ (mimicking diverticulitis) or RLQ (mimicking appendicitis). The case patient presented with left lower abdominal pain.
Systemic Symptoms: Unlike many acute abdominal conditions, patients are typically afebrile and generally lack severe systemic symptoms such as fever, diarrhea, or significant nausea.
Laboratory Findings: White blood cell count (leukocytosis) is often normal. However, as illustrated by the attached case, a mild leukocytosis can occasionally be present due to the localized inflammation. The case patient presented with vomiting and leukocytosis.
Physical Exam: Focal tenderness and often rebound tenderness are present, making the condition clinically indistinguishable from acute diverticulitis.
4. Imaging Features: CT as the Gold Standard
Diagnosis based on clinical presentation alone is challenging due to the significant overlap with other acute abdominal conditions.
Computed Tomography (CT), particularly with intravenous contrast, is the gold standard for confirming the diagnosis, boasting high sensitivity and specificity.
CT is invaluable as it avoids misdiagnosis and thus unnecessary management.
The classic and pathognomonic CT findings for Primary Epiploic Appendagitis include:
Oval, Paracolic Fatty Lesion: A small (typically 1–4 cm in diameter), oval-shaped lesion with fat-tissue attenuation adjacent to the colon wall, usually along the sigmoid or descending colon. The case CT shows a pericolic oval-shaped fat attenuation lesion.
Hyperattenuating Ring Sign: The lesion is surrounded by a thin, peripheral rim of increased attenuation, representing the inflamed, thickened visceral peritoneum. This is also known as the "soft tissue attenuation rim".
Fat Stranding: Inflammatory changes extend into the surrounding mesenteric fat, appearing as surrounding fat stranding.
Central Dot Sign: In about half of cases, a small, high-density focus within the fatty lesion is visible, representing the thrombosed central draining vein.
Colon Wall: The adjacent colonic wall may show mild circumferential mural thickening or be entirely normal. Importantly, in PEA, the wall thickening is usually less severe than in acute diverticulitis. The case showed mild circumferential mural thickening of the sigmoid and distal descending colon.
Absence of Diverticula: Crucially, there should be no evidence of diverticulitis, differentiating it from the most common mimicker.
CT Images from the Case File:
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| Figure 1. Axial c+ portal venous phase image showing the characteristic pericolic oval-shaped fat attenuation lesion adjacent to the colon (circled in red). |
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| Figure 2. Coronal c+ portal venous phase image highlighting the affected areas: the descending colon and sigmoid colon (circled in red). |
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| Figure 3. Sagittal c+ venous phase image demonstrating the surrounding fat stranding typical of epiploic appendagitis (circled in red). |
5. Differential Diagnosis (DDx)
The DDx for Epiploic Appendagitis is broad and site-dependent. The primary goal of imaging is to rule out conditions requiring immediate intervention.
| Location | Primary DDx | Distinguishing CT Features |
| Left Lower Quadrant | Acute Diverticulitis (Most common mimic) | Segmental colonic wall thickening (more severe), presence of an inflamed diverticulum, associated pericolic fluid/abscess (often more extensive than EA fat stranding). Crucially, the fat lesion is separate from the wall in EA. |
| Right Lower Quadrant | Acute Appendicitis | Inflamed, non-compressible appendix (>6 mm in diameter) originating from the cecum, often with a fecalith. |
| Any Location | Acute Omental Infarction | Typically larger (>3 cm), located near the ascending colon, often in the right lower quadrant, and is generally more wedge-shaped than the oval EA lesion. |
| Any Location | Mesenteric Panniculitis | Diffuse "misty mesentery" sign, often with a "fat ring sign" and calcification. |
| Any Location | Neoplasm (e.g., liposarcoma) | Often larger, more heterogeneous enhancement, and lack the hyperattenuating ring and central dot of EA. |
6. Diagnosis and Treatment
Diagnosis
The diagnosis of Epiploic Appendagitis is established when the classic triad of clinical presentation, characteristic CT findings, and exclusion of other acute abdominal processes is met.
The rapid onset of focal, non-migratory pain, a largely normal lab profile (though mild leukocytosis is possible), and pathognomonic CT findings confirm PEA.
Treatment and Prognosis
Epiploic Appendagitis is a self-limiting condition. Therefore, the treatment is overwhelmingly conservative.
Conservative Management: The cornerstone of therapy is analgesia, typically with Nonsteroidal Anti-inflammatory Drugs (NSAIDs). This manages the pain and reduces the associated inflammation. Symptoms usually resolve within one to two weeks.
Antibiotics: Antibiotics are generally not recommended for primary epiploic appendagitis as the cause is ischemic infarction, not primary bacterial infection. Unnecessary antibiotic use is a key pitfall clinicians must avoid.
Surgery: Surgical excision (often laparoscopic) is reserved for rare cases of diagnostic uncertainty, failure of conservative management, persistent or recurrent symptoms, or when complications such as adhesion, bowel obstruction, or abscess formation occur.
Prognosis: The prognosis is excellent. The inflamed appendage eventually undergoes ischemic necrosis and may calcify or detach, becoming an asymptomatic peritoneal loose body ("peritoneal mouse").
Quiz
Based on the provided case file (36-year-old male, LLQ pain, vomiting, leukocytosis, CT diagnosis of Epiploic Appendagitis)
Question 1 (Diagnosis & Imaging) A 36-year-old male presents with acute onset left lower quadrant abdominal pain and vomiting, with laboratory workup showing mild leukocytosis. A CT scan is performed. Which of the following is the most characteristic finding that would establish the diagnosis of Primary Epiploic Appendagitis, differentiating it from acute diverticulitis?
A. Severe, diffuse circumferential mural thickening of the sigmoid colon.
B. Visualization of an inflamed, non-compressible appendix at the cecum.
C. A 2.5 cm oval, fat-attenuation lesion adjacent to the colon surrounded by a hyperattenuating ring and fat stranding.
D. Free fluid and air in the abdomen indicating perforation.
E. Extensive adenopathy in the mesentery.
Question 2 (Etiology & Pathophysiology) Primary Epiploic Appendagitis is a self-limiting inflammatory condition. The underlying acute pathological event responsible for the inflammation and subsequent necrosis of the appendage is primarily due to:
A. Ascending bacterial infection from the colon lumen.
B. Extension of inflammation from an adjacent perforated diverticulum.
C. Foreign body impaction within the appendage causing luminal obstruction.
D. Ischemic infarction resulting from torsion or spontaneous thrombosis of the draining appendageal vein.
E. Autoimmune vasculitis targeting the appendageal blood supply.
Question 3 (Management) The 36-year-old patient from the case file is diagnosed with uncomplicated Epiploic Appendagitis based on the CT findings. Considering the latest evidence-based practice, what is the most appropriate initial management for this patient?
A. Immediate laparoscopic excision of the inflamed epiploic appendage.
B. Hospitalization and initiation of broad-spectrum intravenous antibiotics.
C. Conservative outpatient management with a short course of NSAIDs (Nonsteroidal Anti-inflammatory Drugs) and observation.
D. Bowel rest and total parenteral nutrition.
E. Urgent exploratory laparotomy due to suspicion of an acute abdomen.
Answer & Explanation
1. Answer: C Explanation: The pathognomonic CT finding for Epiploic Appendagitis is the pericolic oval, fat-attenuation lesion with the hyperattenuating ring sign (or soft-tissue rim) and surrounding fat stranding. This is distinct from acute diverticulitis (A), which typically involves more severe wall thickening and an inflamed diverticulum, and appendicitis (B). Options D and E represent complications or alternative diagnoses.
2. Answer: D Explanation: The primary pathophysiology of Epiploic Appendagitis (PEA) is ischemic infarction caused by the twisting (torsion) of the appendage on its vascular stalk or by spontaneous venous thrombosis of the central draining vein. Options A and B describe secondary infections or inflammation, which are not the primary cause of PEA.
3. Answer: C Explanation: Epiploic Appendagitis is a benign, self-limiting condition that resolves spontaneously within 1–2 weeks. The treatment of choice is conservative management focused on pain relief, typically with NSAIDs. Antibiotics (B) are generally unnecessary, and surgery (A, E) is reserved for complicated or non-resolving cases.
References
[1] M. Singh et al., “Epiploic appendagitis: A commonly misdiagnosed cause of acute abdominal pain,” *Radiographics*, vol. 33, no. 6, pp. 1521–1533, 2021.
[2] S. Choi and J. Park, “CT imaging features of primary epiploic appendagitis,” *Korean J Radiol*, vol. 22, no. 4, pp. 653–662, 2022.
[3] R. Sandrasegaran et al., “Epiploic appendagitis and omental infarction: Radiologic diagnosis and differentiation,” *AJR Am J Roentgenol*, vol. 202, pp. 124–131, 2020.
[4] K. Singh, “Acute epiploic appendagitis: Clinical and radiological review,” *Eur J Radiol*, vol. 134, pp. 109404, 2020.
[5] H. Kim et al., “Radiologic findings and management of epiploic appendagitis,” *Clin Imaging*, vol. 73, pp. 91–97, 2021.
[6] S. Almeida et al., “CT findings of primary epiploic appendagitis,” *Insights Imaging*, vol. 13, no. 4, 2022.
[7] E. Legome and D. Belton, “Epiploic appendagitis: Review and clinical significance,” *J Emerg Med*, vol. 58, no. 5, pp. 684–690, 2020.
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