What term describes an abnormal channel connecting two surfaces?

The term that describes an abnormal channel connecting two surfaces is "fistula." A fistula is a pathological connection between two epithelial surfaces, which can occur between various structures in the body, such as between blood vessels, hollow organs, or even between an organ and the skin. This condition can result from various causes, including infection, inflammation, or surgery.

Understanding the nature of a fistula is important in clinical settings, as it often indicates the presence of underlying disease or injury and may necessitate medical or surgical intervention. Recognizing this term is crucial in pathology and medical practice, as it conveys important information about patient conditions and potential treatment strategies.

In contrast, an abscess refers to a localized collection of pus, typically caused by infection. A cyst is a sac-like structure that may contain fluid or semi-solid material and is not necessarily an abnormal channel. A pustule is a small, elevated lesion on the skin that contains pus, commonly associated with acne or infections. Thus, the unique definition and role of a fistula make it the correct term for an abnormal channel.