Sonographic detection of fluid in the cul-de-sac in children--a normal finding?

Fluid in the cul-de-sac was found in 6.7% of ultrasound examinations of the abdomen and pelvis in children aged one day to 20 years. The amount was graded as minimal (+), moderate (++), or abundant ( ). Excluding teenage girls and those clinical situations in which free intraperitoneal fluid was expected (48 children) or could be explained by clinical circumstances (71 children), there remained a group of 65 children in whom no explanation of the usually minimal amount of fluid in the cul-de-sac could be found. A small amount of such fluid is a normal finding in 1.5% to 2% of children of both genders. Follow-up examinations in 16 patients found to have minimal incidental fluid in the pelvis showed repeat findings only in two; in the others no free fluid was demonstrated. A moderate amount of incidental free fluid was not associated with any morbidity: two of seven having a follow-up examination were normal. A large amount of free pelvic fluid, even when found incidentally, should not be considered as normal.