The metal is poured into the mold through a hollow channel called a sprue. Environmental enteropathy is a less severe, subclinical condition similar to tropical sprue. Diagnosis of tropical sprue can be complicated because many diseases have similar symptoms. The metal from the sprue and risers is cut from the rough casting. The design of the sprue gating and runner is also essential for casting. He built on his research on anemia and tropical sprue. Other conditions which can resemble tropical sprue need to be differentiated. He subsequently discovered folic acid as a cure for tropical sprue. The prognosis for tropical sprue may be excellent after treatment. The cause of tropical sprue is not known. Finally, the sprue is sawed off and the finished piece is polished. If they did develop tropical sprue, he could treat it with liver extract. The runner is a smaller channel from the sprue to the individual part. This casting method left only one sprue on the coins. Some moldmakers distinguish the sprue, the gate, and the runner.