Teaching Case

A 22-month-old boy presented with intermittent lower abdominal pain for 2 days associated with 2 episodes of loose stool and fever. No vomiting, blood in stool or urinary symptoms were present. No risk factors were identified. The patient's weight is 10.5 kg.

The patient was referred for ultrasound.

Plain x-ray of the abdomen was performed and showed functional ileus.

Ultrasound of the abdomen showed a lentiform echogenic area located immediately beneath the anterior abdominal wall and anterior to the bowel in the right lower quadrant. The abnormality was tender, non-compressible, and demonstrated no vascularity on colour Doppler. Ultrasound also showed a small amount of free fluid in the right and left lower quadrants.

Exploratory laparoscopy was performed and showed a necrotic fatty mass connected to a twisted pedicle. Partial omentectomy was performed resulting in full relief of the patient’s symptoms with no postoperative complications. Omental necrosis was confirmed on histopathology.

Omental infarction is a rare cause of acute abdominal pain in children; more than 85% of reported cases occur in adults [1].

Approximately 0.1% of children undergoing laparotomy for suspected appendicitis have omental infarction associated with torsion at surgery [1].

The right epiploic vessels are involved in 90% of the known cases of infarction, explaining the predilection for right-sided omental infarctions [2]. Obesity associated with a heavily fat-laden omentum seems to be a major risk factor in the development of omental infarction in children [2].

Omental infarction can be classified as primary or secondary. The etiology of primary omental infarction is not clear. However, various risk factors may be relevant such as hypertrophic omentum with narrow pedicle; omental varicose veins, and raised intra-abdominal pressure caused by heavy exercise, sudden change of posture, or cough [3]. Precipitating factors for secondary omental infarction are previous surgery, trauma, inflammation, cysts, tumours, and hernias [3].

Ultrasound is the imaging technique of choice to investigate children with suspected omental infarctions as it is widely available, non-invasive. and does not involve ionizing radiation. Sonographically, omental infarction appears as a hyperechoic mass, most often oval or lentiform in shape, adjacent and sometimes adherent to the anterior abdominal wall. It is usually located on the right-side, anteromedial to the ascending colon, and appears avascular on Doppler, and a small volume of intra-abdominal free fluid may be present [4].

Although some surgeons advocate conservative treatment, many believe that laparoscopic excision is the treatment of choice as this prevents the possibility of abscess formation or other complications such as bowel obstruction which can be caused by adhesions [5].

In summary, omental infarction in children is a poorly understood entity that can mimic acute appendicitis and should be considered in all children with acute abdominal pain. It has typical appearances on ultrasound, which is considered the imaging modality of choice in the assessment of children presenting with acute abdominal pain [4].