CASE 4436 Published on 05.02.2006

US FINDING FOR APPENDICEAL PHLEGMON

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Antonio Gligorievski

Patient

25 years, male

Clinical History
US examinations shows enlarged (diameter 9,2 mm) noncompressible, appendix with periappendiceal inflammation.
Imaging Findings
A previously healthy 25 year old man presents to the emergency department with acute abdominal pain in the right lower quadrant of 24 hours' duration. He has no fever, and his examination is remarkable only for right lower quadrant tenderness without peritoneal signs. The three factors with the highest predictive value for acute appendicitis are right lower quadrant pain, abdominal rigidity, and migration of pain from the periumbilical region to the right lower quadrant. US examinations with linear 7,5 Mhz probe, shows enlarged (diameter 9,2 mm) noncompressible, appendix with periappendiceal inflammation. Enlargement of the appendix is a sign of suppurative or gangrenous appendicitis. The inflamed appendix can usually be identified medial and inferior to the cecum. It appears as a sausage-shaped, blind-ending structure on longitudinal, or as a target lesion on transverse sections. In addition, an irregular hypoechoic mass is identified surrounding the appendix, this represents periappendiceal inflammation.
Discussion
Acute appendicitis is the most common indication for emergency laparotomy especialy in children. Perforation, although still uncommon, occurs with a much greater frequency (approximately 25-35%) in the pediatric and oldery population. The pathogenesis generally begins with luminal obstruction. The usual initial symptoms are vague visceral abdominal pain secondary to the distention of the appendix. After 4 to 6 hours, as the inflammation spreads to the parietal peritoneum, the pain increases in intensity and becomes somatic in nature localized at "McBurney's Point" in the RLQ. Nausea, vomiting, and anorexia are frequently associated. The typical historical and physical findings are found in approximately 2/3 of patients eventually determined to have appendicitis. The clinical diagnosis is not always entirely straightforward especially in children who may not be able to communicate their symptoms adequately. Imaging methods must be used in patients with indeterminate clinical findings to avoid unnecessary laparotomies. On the US exam the mucosa, if seen, will appear as a thin hyperechoic line surrounding the lumen. The wall of the appendix is hypoechoic and is usually <2 mm in thickness with an overall cross-sectional diameter of less than or equal to 6mm. A recent study has shown that any appendix measuring >6 mm at its greatest point will be inflamed 93% of the time. Enlargement of the appendix is a sign of suppurative or gangrenous appendicitis. A cross-sectional diameter measurement of greater than 6 mm along with noncompressibility in a patient with persistent RLQ pain is considered reliable evidence of appendicitis. It is extremely important that the entire appendix is visualized because inflammation may be localized to the distal tip. Associated findings include loss of the echogenic submucosal layer which may reflect extension of the inflammation through the muscularis propria. There may be a fluid-filled lumen which will be anechoic and/or a hyper echoic appendicolith with acoustic shadowing. There may also be associated periappendiceal fluid collections or mass which may displace adjacent structures. These latter findings are more likely to be seen in association with perforation. The lumen of the appendix may be hyperechoic or, if fluid filled, anechoic. An appendicolith, gas, or inspissated feces can be seen as an intraluminal hyperechoic structure with or without shadow. The diameter of the lumen is between 3 and 10 mm. When an appendicolith is detected, the thickness and compressibility are not important in making the diagnosis of appendicitis. If, in addition, an irregular hypoechoic mass is identified surrounding the appendix, this represents periappendiceal inflammation.
Differential Diagnosis List
Acute Phlegmonous Appendicitis
Final Diagnosis
Acute Phlegmonous Appendicitis
Case information
URL: https://www.eurorad.org/case/4436
DOI: 10.1594/EURORAD/CASE.4436
ISSN: 1563-4086