subsegmental

Subsegmental is an adjective used in anatomy and medicine to designate an area, structure, or process that lies within a segment of an organ but is smaller than that segment. The term is commonly applied where organs are divided into discrete segments for functional or surgical reasons, and it signals a finer level of localization than the segment itself.

In the lungs, for example, the bronchial tree and the pulmonary vasculature are organized into bronchopulmonary segments. Subsegmental bronchi and subsegmental arteries are subdivisions within a segment; radiologic findings may reference subsegmental involvement or pathology. A subsegmental pulmonary embolism, for instance, refers to a clot lodged in a subsegmental pulmonary artery, distal to the segmental arteries.

Subsegmentectomy, or subsegmental resection, describes a surgical procedure that removes only a subsegment, preserving as much healthy tissue as possible compared with a full segmentectomy or lobectomy. Similar concepts exist in other organs that utilize segmented anatomy, such as the liver, where subsegments have defined boundaries within hepatic segments.

Because the exact boundaries of subsegments can vary by organ and clinical convention, the term is descriptive rather than universally standardized. It is most informative when accompanied by the organ and segment designation.