Omental Infarction

Sudden Pain
Didn't play the corresponding interactive case or want to try it again? Click here to do so.

Diagnosis and reasoning

The pediatric patient with an acute abdomen is one of the most common presentations encountered in clinical practice. In the majority of cases, the pain is due to benign and self-limiting disease; however, in a significant minority, it may herald a serious surgical or medical condition. A careful history and examination is key towards differentiating between the above; one should also appreciate that there are several important differences between the clinical evaluation of a pediatric patient, vis-a-vis that of an adult. The first clinical point to keep in mind is that the differential diagnosis of acute abdominal pain varies significantly by age; in patients between 6 to 11 years old, the most common pathologies include appendicitis, gastroenteritis, urinary tract infections, mesenteric lymphadenitis, constipation, and functional pain. The second key point is that the location of the pain is perhaps the strongest pointer towards the likely etiology; in particular, right lower quadrant pain (as in this patient) is strongly suspicious of acute appendicitis (which is also the commonest surgical cause of an acute abdomen in children). Note also the presence of fever; this is the single most useful sign associated with appendicitis, increasing the likelihood of this diagnosis. The Alvarado score is a very useful clinical tool for objectively determining the probability of acute appendicitis; this uses 3 symptoms (anorexia, nausea and vomiting, migration of pain to the right lower quadrant), 3 signs (right lower quadrant tenderness, rebound tenderness, elevated temperature) and 2 laboratory measurements (leukocytosis > 10,000/mm3, leukocyte left shift) to generate a score of between 0 to 10. Note that a score of between 5 to 6 indicates possible appendicitis; a score of 7 to 8 indicates probable appendicitis; and a score of 9 to 10, definite appendicitis. The Alvarado score in this patient is 7, indicating that this is probably appendicitis; thus, follow up imaging should be performed to confirm this diagnosis. While Computerized Tomography (CT) of the abdomen is the most sensitive investigation for diagnosis of acute appendicitis, many clinicians prefer to use ultrasonography in children, to avoid exposure to ionizing radiation. One caveat in this patient is that she is obese, which will reduce the sensitivity of ultrasound; nevertheless, it can be argued that sonography should still be attempted first, as confirmation will avoid the need for a CT. However, the ultrasound scan reveals an unexpected finding: a hyperechoic, relatively superficial mass in the right iliac fossa. This finding is strongly suggestive of a rare entity: omental infarction (OI); note that obese individuals are at increased risk for this condition. Further imaging via a CT is mandatory now; the findings seen there confirm the presence of OI. OI is a benign, self limiting condition; conservative management with analgesics is usually all that is necessary. IV antibiotics should be commenced to prevent secondary infection. Laxatives are not indicated in her current management.


Discussion

Omental infarction (OI) is a rare cause of acute abdominal pain, being encountered in approximately 0.1% of all laparotomies performed for an acute abdomen; the overall incidence is estimated to be between 0.0016% to 0.37% in patients with acute abdominal pain. The condition is more common in adults; children only account for 15% of reported cases. Boys are more frequently affected than girls, in a ratio of 2 : 1. OI can be an idiopathic event, or more often, associated with omental torsion. This is clinically irrelevant because the treatment is identical in either case. The pathogenesis is unknown, but anomalous arterial supply to the omentum, kinking of veins associated with increased intra abdominal pressure, and vascular congestion after large meals are thought to be causes. Predisposing factors include a bifid omentum and obesity. The increasing rate of childhood obesity may result in an increasing prevalence of OI in children. Patients typically present with acute right-sided abdominal pain (90%) and tenderness, which is mostly localized; this is often confused with acute appendicitis. The preponderance of right side abdominal pain can be explained by the increased length and mobility of the right sided omentum than the left, leading to a high possibility of torsion and infarction. Increased fatty accumulation in the omentum in individuals with high BMI may outstrip the blood supply to the developing omentum, causing relative ischemia, or the increased omental weight may predispose to torsion; this makes OI more prevalent in the obese. OI is easily diagnosed via abdominal imaging; characteristic findings include a triangular mass located between the abdominal wall and the transverse or ascending colon (this corresponds to the greater omentum). Both computerized tomography (CT) and ultrasound show an ovoid or cakelike soft-tissue mass; however ultrasound is less specific, and can lead to misinterpretation. A contrast enhanced CT may show a heterogeneous fatty mass, concentric linear strands, and hyperattenuated streaky infiltration. OI is thought to be a self-limiting, benign condition with an excellent prognosis. It may resolve spontaneously and often only requires conservative management. Thus, exclusion of other mimicking diseases (especially the ones requiring surgery) is very important. Definitive differentiation between idiopathic OI and omental torsion related infarction can only be made surgically. However, this is of little clinical relevance as the management is the same regardless. Most clinicians prefer to manage OI conservatively with analgesics, anti-inflammatory medications, antibiotics and optimal fluid management; surgery is reserved for the few patients who deteriorate clinically. However, some experts prefer to proceed immediately to surgery; laparoscopic omental necrosectomy and thorough abdominal exploration is considered to be the best surgical option. Both approaches have their individual pros and cons; while immediate surgery will result in speedy symptomatic relief, the patient is at risk of surgical complications; conversely, conservative management has the advantage of avoiding anaesthetic and surgical risks. However both options have shown satisfactory results and no comparative study has yet demonstrated a significant difference in outcomes between the two.


Take home messages

  1. The differential diagnosis of abdominal pain in children varies significantly by age.
  2. The Alvarado score is of help in stratifying patients with suspected appendicitis.
  3. The possibility of OI should be considered in patients with acute abdominal pain, particularly if obese.
  4. Imaging of the abdomen is key to diagnosing OI; the radiological findings are usually characteristic.
  5. OI is self-limiting and benign; conservative management is usually sufficient.

Insightful, fun cases to improve your diagnostic skills

Use your detective skills, strengthen fundamentals faster, and access a wealth of knowledge.

  1. AJR Am J Roentgenol. 2002 Jun;178(6):1537-9: Omental infarction in pediatric patients: sonographic and CT findings: Grattan-Smith JD, Blews DE, Brand T.
  2. Am Fam Physician. 2003 Jun 1;67(11):2321-2327: Acute Abdominal Pain in Children: Alexander K.C, David L.
  3. BMC Med. 2011 Dec 28;9:139. doi: 10.1186/1741-7015-9-139. The Alvarado score for predicting acute appendicitis: a systematic review. Ohle R, O'Reilly F, O'Brien KK, Fahey T, Dimitrov BD.
  4. BMJ. 1996 Feb 24;312(7029):498-501. Acute abdominal pain in children. Davenport M.
  5. Indian J Surg. 2010 August; 72(4): 290–293. Published online 2010 November 18. doi: 10.1007/s12262-010-0190-5 PMCID: PMC3002776 Alvarado Scoring in Acute Appendicitis—A Clinicopathological Correlation Subhajeet Dey,corresponding author Pradip K. Mohanta, Anil K. Baruah, Bikram Kharga, Kincho L. Bhutia, and Varun K. Singh
  6. J Pediatr Surg. 2009 May;44(5):953-6. doi: 10.1016/j.jpedsurg.2009.01.032: Primary omental infarct: conservative vs operative management in the era of ultrasound, computerized tomography, and laparoscopy: Nubi A, McBride W, Stringel G.
  7. J R Soc Med. 1992 February; 85(2): 87–88. PMCID: PMC1294889 Evaluation of the Alvarado score in acute appendicitis. T D Owen, H Williams, G Stiff, L R Jenkinson, and B I Rees
  8. JAMA. 2007 Jul 25;298(4):438-51. Does this child have appendicitis? Bundy DG, Byerley JS, Liles EA, Perrin EM, Katznelson J, Rice HE.