The hydrochloride salt of an anthracycline antineoplastic antibiotic with therapeutic effects similar to those of doxorubicin. Daunorubicin exhibits cytotoxic activity through topoisomerase-mediated interaction with DNA, thereby inhibiting DNA replication and repair and RNA and protein synthesis. OR A procedure used to look at the inside of the small intestine. A special instrument made up of two tubes (one inside the other) is inserted through the mouth or rectum and into the small intestine. The inside tube, which is an endoscope with a light and lens for viewing, is moved through part of the small intestine, and a balloon at the end of it is inflated to keep the endoscope in place. Next, the outer tube is moved through the small intestine to reach the end of the endoscope, and a balloon at the end of the outer tube is inflated to keep it in place. Then, the balloon at the end of the endoscope is deflated, and the endoscope is moved through the next part of the small intestine. These steps are repeated many times as the tubes move through the whole small intestine. This allows the doctor to see all of the small intestine. Tissue samples may be removed so they can be checked under a microscope for signs of disease. Also called double balloon endoscopy and double balloon enteroscopy.