Appendicitis is an inflammation the blind ending worm like structure attached to the cecum or start of the colon. Appendicitis is caused by a blockage of this structure resulting in inflammation, potential perforation, abscess formation (pus pocket) and peritonitis or inflammation of the abdominal cavity.
Appendicitis often occurs in kids and young adults, but I have seen it occur at all ages. Appendicitis often presents with pain in the right lower abdomen, nausea, vomiting, and lab abnormalities. The clinical presentation can be varied. The appendix can have different positions extending upward from the cecum towards the liver and causing pain higher up, or lower down when it goes down into the pelvis. The clinical presentation can be confusing and mimic other conditions.
CT is most commonly ordered for diagnosis of appendicitis and other mimickers. Classically, CT will show a dilated fluid filled appendix with surrounding inflammatory changes. Inflammatory changes on CT look like dirty fat. In more advanced cases, there may be abscess or pus pocket formation, perforation with spillage of contents into the abdominal cavity, and peritonitis with inflamed abdominal cavity.
Early cases of Appendicitis on CT can be challenging and sometimes missed. Early appendicitis can simply be a slightly dilated or thickened appendix without any inflammatory changes. Often the radiologist may suggest a diagnosis but not be definitive. The patient may need observation in the hospital, a surgical evaluation and a repeat scan in some cases.
Appendicitis is usually treated with surgery. Complications such as perforation of the appendix and peritonitis make the mortality rate go up significantly. Usually perforated appendicitis is accompanied by fluid collections and possible free air. Peritonitis can follow which is an inflamed abdominal cavity. Sometimes an abscess can form far from the appendix in places like the liver. CT can also be done looking for complications. It is therefore very important to make an early and definitive diagnosis given the complications.