Right anterior subphrenic space: an important site for the early detection of intraperitoneal fluid on abdominal CT

Abstract

Small rinds of free fluid are frequently seen in the right anterior subphrenic space. Therefore, we investigated patients undergoing abdominal computed tomography (CT) to see whether early fluid collections are seen preferentially at this or any other site. CT examinations of 59 randomly selected patients with minor or moderate quantities of free intraperitoneal fluid were analyzed. The location of the fluid was determined [subphrenic spaces, the right hepatorenal fossa (Morison's pouch), paracolic gutters, pelvis (pouch of Douglas)]. The amount of fluid in each location was subjectively quantified (none, trace, small, or moderate). Free fluid was seen most frequently in the right anterior subphrenic space (44/59 patients, 75%) and pelvis (43/59 patients, 73%). Eight patients had intraperitoneal fluid at an isolated location (three in the pelvis alone, two in the left subphrenic space, one in the right subphrenic space, and one in each of the right and left paracolic spaces). Contrary to popular belief, intraperitoneal fluid is not always seen first in the pelvis when the patient is in the supine position. Although fluid is not consistently seen first in any specific location, the subphrenic space (especially the right anterior) is a common site where small quantities of fluid may be identified.