Omental Infarction

Omental infarction is ischemic necrosis of part of the greater omentum, from torsion of its pedicle or from venous thrombosis. It is a rare, usually benign cause of acute abdominal pain, accounting for under 1% of cases that mimic appendicitis. Adults aged 30 to 50 are most affected (men more than women), with about 15% of cases in children.

Types

• Primary (idiopathic): unexplained torsion or thrombosis, favored by obesity, a bifid or elongated omental segment, a sudden change in position, cough, and hypercoagulable states
• Secondary: torsion around a hernia, adhesions, a cyst or a tumor, after abdominal surgery, trauma or inflammation

The right side is involved in about 90%, because the right omental segment is longer and more mobile. The usual size is 3 to 5 cm, and can be up to 15 cm. The natural history is of spontaneous resolution over 1 to 4 weeks. Complications are abscess, adhesion formation with obstruction, and rarely peritonitis, and a few patients have a chronic pain syndrome.

• Sudden or gradual onset right-sided abdominal pain, often well localized, with tenderness in the right iliac fossa or upper quadrant
• Low-grade or no fever, mild nausea, and little vomiting or anorexia
• A tender mass or localized peritonism, with no marked guarding
• Normal or mildly raised white cell count
• Red flags: generalized peritonitis, high fever, hemodynamic instability, a hernia sac with tenderness, and a mass in a patient with cancer

1. Ultrasound: a non-compressible, hyperechoic, ovoid mass in the area of maximum tenderness, with no blood flow on Doppler.
2. CT with intravenous contrast is the investigation of choice: a focal, heterogeneous fatty mass of 3 to 5 cm lying between the anterior abdominal wall and the colon, with hyperattenuating strands, a whirl of omental vessels at the torsion site, and no abnormal bowel wall or appendix.
3. Blood tests: white cell count, CRP, and amylase and lipase, mainly to exclude other diagnoses.
4. Diagnostic laparoscopy when imaging is equivocal and the patient is deteriorating.

Differentials: acute appendicitis, epiploic appendagitis, acute cholecystitis, diverticulitis, mesenteric panniculitis, omental tumor or metastasis, Crohn disease, ovarian torsion.

Conservative treatment (stable patient, clear CT diagnosis)

• Analgesia: paracetamol 1 g orally every 6 hours (maximum 4 g a day), with ibuprofen 400 mg orally every 8 hours with food for 5 to 7 days (avoid in peptic ulcer disease, renal impairment and anticoagulation).
• Children: paracetamol 15 mg/kg orally every 6 hours and ibuprofen 10 mg/kg orally every 8 hours.
• Review within 48 to 72 hours, with a clear safety-net on fever, vomiting or worsening pain.
• Antibiotics are not needed.
• Resolution of symptoms in 1 to 2 weeks and imaging changes at 4 to 8 weeks.

Surgery (laparoscopic omentectomy of the infarcted segment)

• Uncertain diagnosis, failing conservative treatment, persistent or worsening pain, abscess, fever or peritonitis, and large infarcts.
• Cefazolin 2 g IV 30 to 60 minutes before incision (children 30 mg/kg).
• Ligate the pedicle, remove the necrotic omentum in a retrieval bag, irrigate, and evaluate the appendix.
• Symptoms resolve within 24 to 48 hours, with discharge in 1 to 2 days and a return to activity in 1 to 2 weeks.

Complications of surgery: wound infection, bleeding, adhesions and port-site hernia.

Weight reduction lowers recurrence risk. Counsel on the benign course and on returning for increasing pain or fever.