[Ultrasonic diagnosis of intraperitoneal fluid in Morrison's pouch (and in the splenoperitoneal recess): the moon crescent sign (author's transl)].

Morrison's pouch, and, accessorily, the spleno-peritoneal recess, constitute specific indicators of the presence of intraperitoneal fluid. Intraperitoneal fluid gives rise to sonolucent atraip between the reflectivity of mean intensity of the liver and spleen, and the intense reflectivity of the perirenal fat. That image, which the authors term the "moon crescent sign", is displayed even when the fluid volume is as small as 30 to 40 ml. It is encountered in presence of ascites, but also in presence of fluid of inflammatory origin, of fluid due to pancreatic autolysis, or of blood. Hence the display of a moon crescent sign is of particular interest in the radiologic evaluation of an acute abdomen.