intratubular

Intratubular is an anatomical and medical term describing something situated inside a tubule, a long, narrow, lumen-lined structure. Tubules are common in many organs, but the term is most frequently applied to the renal tubules of the kidney, where intratubular refers to the fluid within the tubular lumen and to forces and processes inside that lumen.

Renal intratubular fluid undergoes modification by epithelial transport; the composition and osmolarity of the fluid change along the proximal tubule, loop, distal tubule, and collecting duct. Intratubular pressure denotes the hydrostatic pressure inside the tubule; elevated intratubular pressure, such as from obstruction, can reduce glomerular filtration by increasing the back pressure on the ultrafiltration barrier. Intratubular pH and electrolyte concentrations are tightly regulated by transporters and channels.

In clinical settings, intratubular obstruction by crystals, sloughed cells, or casts can impair urine flow and contribute to kidney injury. The term is also used in other tubular structures, such as seminiferous tubules in the testis, to denote luminal contents or processes within the tubule lumen.

Origin: from intra- meaning within and tubulus meaning small tube.