PELVIC EXTENSION OF RETROPERITONEAL FLUID - ANALYSIS IN-VIVO

OBJECTIVE, The purposes of this study were to describe the pathway of fluid flow from the retroperitoneal space into the pelvic extraperiton eal space on CT in vivo, to clarify the relation between its occurrenc e and the site or amount of retroperitoneal fluid, and to delineate th e anatomic relation between the retroperitoneal spaces and the pelvic extraperitoneal space. MATERIALS AND METHODS. We reviewed the CT scans of 37 patients with retroperitoneal fluid collections. Patients who h ad undergone pelvic laparotomy and patients who had either fascial thi ckening alone or fluid within muscle (such as the psoas muscle or ilia c muscle) alone were excluded. RESULTS. Fluid extension into the pelvi c extraperitoneal space was seen in six patients (16%), Extension by t he infrarenal extraperitoneal space was seen in all six of these patie nts, but extension by properitoneal fat was seen in only one of the si x patients. In patients with large amounts of fluid in the infrarenal extraperitoneal space, we frequently saw extension into the pelvic ext raperitoneal space. Extension of pancreatic fluid into the infrarenal extraperitoneal space occurred in only 15% of the 37 patients. However , it occurred in both patients with ruptured abdominal aortic aneurysm s. Three pathways from the infrarenal extraperitoneal space into the p elvic extraperitoneal space were seen: extension dorsally medial to th e iliac vessels (n = 6), extension dorsally lateral to the iliac vesse ls (n = 1), and extension medially into the prevesical space (n = 2). Coexistence of two of these three pathways was seen in three patients. CONCLUSION. In vivo, extension of retroperitoneal fluid into the pelv ic extraperitoneal space is not rare and occurs more often by the infr arenal extraperitoneal space than by properitoneal fat. Extension of r etroperitoneal fluid to the infrarenal extraperitoneal space can be at tributed less frequently to sources distant to the pelvic cavity such as pancreatic fluid. Such extension often derives from sources that ca n produce large amounts of retroperitoneal fluid such as ruptured abdo minal aortic aneurysms. Of the three pathways from the infrarenal extr aperitoneal space to the pelvic extraperitoneal space, dorsal extensio n medial to the iliac vessels is the most common, and multiple pathway s often coexist.