Nonpassage

Nonpassage is a term used in various disciplines to denote the absence or failure of passage of a substance, signal, or object through a boundary, channel, or process. It is formed from the prefix non- and the noun passage, and is used chiefly in technical writing to describe a state in which movement or transfer does not occur where it would be expected.

In medical contexts, nonpassage frequently refers to the failure to pass bodily materials such as stool or urine. It may indicate obstruction, ileus, or anatomic abnormality, and can influence clinical decisions, including the need for imaging, endoscopic intervention, or surgical treatment. Nonpassage is also used to describe the failure of contrast material to traverse a segment of the bowel during radiologic studies.

In physics, engineering, and biology, nonpassage describes resistance to transfer across a barrier. For membranes, nonpassage implies low permeability for a given solute. In fluid systems, it can refer to blocked flow in pipes or porous media, often tied to clogging, pressure differentials, or design limits.

In research contexts, nonpassage is sometimes noted as a negative result or as the absence of observed transfer under defined conditions. The term signals that an expected passage did not occur, rather than explaining the mechanism behind it. Related concepts include obstruction, blockage, permeability, and diffusion.