Clinical History
A 30 year-old woman, with a history of endometriosis was admitted for diffuse abdominal pain, vomiting and also significant diarrhoea
Imaging Findings
A 30 year-old woman, with a history of endometriosis was admitted for diffuse abdominal pain, vomiting and also significant diarrhoea . At her admission, physical examination showed painful abdominal palpation in the inferior abdomen with fever of 37.8C. Rectal and vaginal revealed tenderness. Laboratory analysis revealed leucocytosis. The first diagnosis was gastroenteritis because of the presence of significant diarrhoea, with vomiting and abdominal pain. A sonography done at her admision was considered normal. Due to persisting abdominal pain, a helical CT scan was performed, with administration of contrast medium intravenously and rectally. A blind-ending holow tube, 3 cm in diameter, originating from the caecum and located behind the rigth psoas muscle was found (fig 1a). It showed a thichened wall, enhancing after intravenous contrast medium injection and associated with stranding of adjacent fat. Its distal part was surrounded by free air (fig 1b). A diagnosis of extraperitoneal appendicitis complicated by an abcess was made. The diagnosis was confirmed at surgery and histology.
Discussion
Typically the appendix is a small caliber blind-ending holow tube originating from the posteromedial aspect of caecum about two cm below the iliocecal junction[2]. Its relationship to the caecum can vary and relates to the mode of development in fetal life when the appendix formed the apex of the ceacum.[3] The free end of the appendix can occupy any position towards medially, caudaly laterally or retrocecally[2]. As the appendix is part of the ceacum it has no true mesentery. However, there is usually a peritoneal fold called the mesoappendix. There is sometimes a fold of peritoneum in front of the appendix called the bloodless fold of Treves[2].
In our patient, the appendix was located extraperitoneally between the right psoas and the the transverse apophysis of L5.
The unusual presentation could have delayed clinical diagnosis and surgical treatment. The sonography was normal. However CT allowed the corret diagnosis unaffected by the presence of meteorism,obesity and severe abdominal pain. Thanks to this exam, we could indicate the exact location of the inflamed appendix.This case understresses the valuable role CT plays in patients with acute abdominal pain (3,4).
To our knowledge, we report in this article the first case of an appendicitis located in the extraperitoneal space behind the psoas, and demonstrated by CT.
Two hypotheses may explain the unusual position of the appendix :
-A primarily extraperitoneal pelvic appendix with an unusual position behind the psoas as a rare normal variation.
-A primarily intraperitoneal appendix which has secondarily perforated into the extraperitoneal compartiment and formed an abscess behind the psoas.
Differential Diagnosis List
APPENDICITIS LOCATED BEHIND THE PSOAS
Final Diagnosis
APPENDICITIS LOCATED BEHIND THE PSOAS
