*18-year-old male with right lower quadrant pain.
What is the most likely diagnosis?
Answer
Answer: Acute appendicitis
Case Discussion:
US and Doppler US images revealed aperistaltic, noncompressible, dilated appendix, and hyperemia within the thickened wall. Delayed phase MDCT showed dilated appendix with thickened and enhancing wall (green arrows).
Acute appendicitis is a very common situation in general radiology practice and is a major cause of abdominal surgery in children and young adults. Appendicitis is inflammation of the vermiform appendix (1).
Appendicitis is caused by a blockage of the lumen of the appendix. Obstruction can be caused by (2):
• lymphoid hyperplasia (~60%)
• appendicolith (~33%)
• foreign bodies (~4%)
• Crohn disease or other rare causes, e.g. stricture, tumour, parasite
Imaging Features
Plain radiography can show an appendicolith in 7-15% of cases (2).
Ultrasound findings (3):
• aperistaltic, noncompressible, dilated appendix ( >6 mm outer diameter)
• appendicolith
• distinct appendiceal wall layers
• echogenic prominent pericaecal fat
• periappendiceal fluid collection
• target appearance (axial section)
CT findings (2, 4, 5):
CT is the most sensitive modality to detect appendicitis.
• dilated appendix with distended lumen ( >6 mm diameter)
• thickened and enhancing wall
• thickening of the caecal apex (~80%): caecal bar sign, arrowhead sign
• periappendiceal inflammation
• extraluminal fluid
• inflammatory phlegmon
• abscess formation
• appendicolith
Complications
• Perforation (~13-30%)
• Abscess formation
• Generalized peritonitis
Differential diagnosis
• mesenteric adenitis (most common)
• inflammatory bowel disease (especially Crohn disease)
• pelvic inflammatory disease (PID)
• Right sided diverticulitis
• Meckel’s diverticulitis
• Acute epiploic appendagitis
• Omental infarction
References:
1. MerriamWebster definition.
2. Weissleder R, Wittenberg J, Harisinghani MG et-al. Primer of diagnostic imaging. Mosby Inc. (2007).
3. Puylaert JB. Acute appendicitis: US evaluation using graded compression. Radiology. 1986;158 (2): 355-60.
4. Callahan MJ, Rodriguez DP, Taylor GA. CT of appendicitis in children. Radiology. 2002;224 (2): 325-32.
5. Pereira JM, Sirlin CB, Pinto PS et-al. Disproportionate fat stranding: a helpful CT sign in patients with acute abdominal pain