False-positive 111In-labeled leukocyte scan in cystic fibrosis.

A false-positive 111In-labeled leukocyte scan was obtained in a girl with cystic 
fibrosis and infection. There was focal accumulation of 111In activity in 
the abdomen and marked pulmonary uptake. Surgical exploration and postmortem examination 
revealed no abdominal abnormality. The abnormal activity was apparently due to 
swallowed sputum which contained labeled leukocytes. Broader clinical implications are discussed. 
