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Difficulty: HardInterpreting Imaging Results

A previously healthy individual in their early forties presents to the urgent care clinic complaining of sudden-onset, sharp left lower quadrant abdominal pain that started 24 hours ago. The pain is localized and exacerbates with movement. Vital signs are within normal limits, and the patient is afebrile. Physical examination reveals focal tenderness in the left lower quadrant without guarding or rebound tenderness. Laboratory studies, including a complete blood count and basic metabolic panel, are unremarkable. A computed tomography (CT) scan of the abdomen and pelvis with intravenous contrast is performed. The radiologist notes an isolated, 2.5-cm, oval-shaped, fat-attenuating lesion abutting the anterior serosal surface of the sigmoid colon. The lesion features a hyperdense peripheral rim and a central high-attenuation dot. The adjacent colonic wall thickness is normal, and there is no free fluid or significant lymphadenopathy. Based on these imaging findings, which of the following best describes the underlying pathophysiology of this patient's acute presentation?

  1. Ischemic necrosis of an adipose appendage of the colonAnswer
  2. B
    Microperforation of a colonic mucosal herniation
  3. C
    Infarction of the right-sided greater omentum
  4. D
    Walled-off collection of polymicrobial purulent exudate
  5. E
    Inflammatory infiltration of the transmural colonic wall

Answer

Ischemic necrosis of an adipose appendage of the colon
The correct answer accurately describes the pathophysiology of epiploic appendagitis. Epiploic appendages are small, fat-filled pouches of visceral peritoneum that line the colon. When one of these appendages undergoes torsion, it leads to venous thrombosis and subsequent ischemic necrosis. The CT findings described in the vignette are pathognomonic for this condition: the oval, fat-attenuating lesion represents the infarcted appendage, the hyperdense rim represents the inflamed surrounding visceral peritoneum, and the central high-attenuation dot represents the thrombosed central draining vein. Recognizing this specific imaging pattern is crucial because epiploic appendagitis is a benign, self-limiting condition managed conservatively with pain control, avoiding unnecessary antibiotics or surgery.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has acute left lower quadrant pain but lacks systemic inflammatory signs (normal vital signs, afebrile, normal leukocyte count), suggesting a localized, possibly non-infectious etiology.
Establishing the clinical severity and systemic involvement helps differentiate between inflammatory, infectious, and ischemic causes of abdominal pain.
2
Interpret the specific computed tomography (CT) imaging findings.
The CT shows an oval, fat-attenuating lesion with a hyperdense peripheral rim and a central high-attenuation dot adjacent to a normal-thickness colon.
Imaging is the definitive diagnostic modality for this presentation. The specific combination of radiological signs must be correlated with a structural pathology.
3
Synthesize the clinical and radiologic data to determine the pathophysiology.
The radiologic pattern is pathognomonic for epiploic appendagitis, which occurs due to torsion and subsequent ischemic necrosis of an epiploic appendage.
Recognizing this classic radiologic signature prevents misdiagnosis of conditions requiring surgical or antibiotic intervention, as epiploic appendagitis is treated conservatively with NSAIDs.

Key Concept

Radiologic identification of epiploic appendagitis
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Topics

Interpreting Imaging Results

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