Perforated Appendix with Abscess

Patient was subjected to laparotomy which revealed a perforated oedematous retrocaecal infrahepatic appendix having an appendicolith with abscess in the subhepatic area (which on CT scan [Figure - 2][Figure - 3] gave a false impression of liver abscess with air fluid level) and extending inferiorly with inflammatory features for 8-10 cm into the medial part of right paracolic gutter (These findings are depicted on CT [Figure - 4][Figure - 5][Figure - 6] around the inflamed appendix, over 120 ml of pus was removed. The base of appendix appeared normal. Patient responded to appropriate antibiotics and the post operative period was uneventful.

Appendicitis generally presents with typical and diagnostic clinical features and is managed effectively without the need for radiologic studies. In some patients, however, the clinical presentation is at typical and confusing as was seen in this case. This is true for patients in whom the appendix lies in a subhepatic or other unusual location.It also applies to patients receiving corticosteroid therapy, which lessens their inflammatory response to appendicaeal obstruction, which may lead to perforation. IN these circumstances, CT can play avital role in establishing the diagnosis of appendicitis and its severity [1].

It is important to look carefully at the appendix on CT in every patient with abdominal pain having no prior appendectomy. The normal wall of appendix has a thickness of 3 mm or less and a diameter 6 mm or less [2]. The finding of a normal appendix with no fluid in its lumen, normal periappendiceal fat, and no calcified appendicolith indicates that the appendix is not inflamed. In early or mild appendicitis, the appendiceal wall appears thickened and the fat immediately surrounding the appendix shows a hazy, ill defined increase in its CT attenuation [2]. When the terminal ileum is in contact with the inflamed appendix it is usually thickened as well.

An abscess is identifiable in about 45% of patients with appendicitis, and a calcified appendicolith is seen in about 25% [3]. In patient with appendiceal perforation and abscess, extraluminal gas is seen near appendix. A periappendiceal collection of fluid is present and may contain an air fluid level or an appendicolith. If the abscess is small, it invariably lies in direct contact with the thickened appendix. Larger abscesses may fill much of the right lower abdomen or extend upto the subhepatic region. In this case the abscess was seen extending from infrahepatic to subhepatic area giving a false impression on CT of rupture of a liver abscess. It can be seen from the serial CT section [Figure - 2][Figure - 3][Figure - 4][Figure - 5] that the extrahepatic component with entrapped air is much larger than the apparent hepatic component and the clinical data should suggest the likely diagnosis of perforated appendix with abscess. Patients with large or poorly localized abscesses generally are treated surgically, whereas those with well localized abscesses may be managed with CT guided percutaneous catheter drainage [3].

CT findings of appendicitis can be mimicked by those of caecal diverticulitis, tubo-ovarian abscesses, hemorrhagic ovarian cyst, septic thrombosis of the ovarian cyst, septic thrombosis of the ovarian vein [4], or infection with  Yersinia ^{More Details} enterocolitica [5]. The visualization of normal appendix can sometimes prevent confusion with these conditions.