Ultrasonography of abdominal fluid collections.

Ultrasonic examination of abdominal fluid collections sometimes allows identification of the nature of the contained fluid. Abscesses, hematomas, and lymphoceles tend to be ellipsoidal unless confined by particularly resistant structures. Abscesses often contain fine debris. Hematomas develop coarse clumps of strongly echoing material as they age. Lymphoceles have sharp walls and are echo-free. Ascites has an irregular outline, a sharply defined wall, and is echo-free. There may be bowel loops floating in it. Pseudocysts have a widely variable appearance. Bowel loopes that are distended with fluid often show peristalsis. Ultrasonically directed fine needle puncture allows confirmation of the nature of the fluid.