Frothy drainage fluid in the abdominal drain may be associated with infection, stones, and blood clots. 1. Infection: If there are a large number of stones in the bile duct, biliary drainage is performed after stone removal. When infection occurs, the bile duct epithelial cell necrosis may be shed and flow out with the bile, at this time, frothy bile duct drainage fluid may appear in the bile duct. 2. Stones: After removing larger stones, some small sediment-like stones may remain. When the bile duct is drained, the small sediment-like stones may be discharged through the surgically placed drainage tube and appear as froth. 3. Blood clots: If there is a small amount of bleeding from the bile ducts, the bleeding coalesces in the bile, which is then discharged through the drain and also forms a froth. In case of foamy drainage from the abdominal drain, it is recommended to notify your doctor in time, so that the cause can be clarified with the help of your doctor and targeted treatment or therapy can be carried out.