Which term is defined as an abnormal opening or passage between organs?

The term that describes an abnormal opening or passage between organs is "fistula." This condition can occur between various structures in the body, such as between the intestines, bladder, or blood vessels. Fistulas can develop due to injury, surgery, or an underlying disease process, and may present challenges in medical management due to the abnormal communication that bypasses normal anatomical barriers.

Fissure refers to a split or crack, often seen in the context of the skin or mucous membranes, but it does not imply a passage between organs. Edema describes an accumulation of fluid in tissues, leading to swelling; it is not related to the concept of abnormal openings. Otomy refers to a surgical incision into a part of the body, such as a surgical opening, but does not refer to a communication between two organs. Thus, "fistula" is the precise term for an abnormal connection between two bodily structures.