Value of Periappendiceal Fat Sign on Ultrasound in Acute Appendicitis

Introduction Acute right lower quadrant abdominal pain is one of the most common surgical presentations to the emergency department with acute appendicitis being the topmost differential diagnosis. Although computed tomography (CT) is the gold standard in diagnosing appendicitis, in our setup ultrasound is often the initial imaging modality available in urgent care settings especially for children and pregnant females. On ultrasound, an inflamed appendix has a diameter of 6 mm or more and is non-compressible. Increased periappendiceal fat echogenicity is an important ancillary sign of acute appendicitis that supports the sonographic diagnosis of acute appendicitis. To determine the association of periappendiceal fat echo sign (PFES) on ultrasound in surgically proven cases of acute appendicitis. Methods This cross-sectional study was held at the Department of Radiology at the Aga Khan University Hospital in Karachi, Pakistan. Periappendiceal fat echogenicity was assessed and prospectively graded in 59 patients. These patients had sonographic features of acute appendicitis which was later confirmed by surgery. Data were collected on a proforma and later analyzed. Frequency of increased periappendiceal fat echogenicity in acute appendicitis was calculated. Association of PFES with gender and ascites was evaluated with Fischer's exact test and with patient's age and appendiceal diameter was assessed using analysis of variance (ANOVA). Results Increased periappendiceal fat echogenicity was seen in 89.8% of patients with acute appendicitis. 10.2% of patients had acute appendicitis with normal surrounding fat. Mean appendiceal diameter in patients with grade 3 PFES was significantly more than those with grade 2 or grade 1 PFES. PFES had no association with age and gender of the patient or with ascites. Conclusion Increased periappendiceal fat echogenicity is an important ancillary sign of acute appendicitis that helps support its sonographic diagnosis.