Taper: an important feature of Y-bifurcations in porcine renal arteries and human cerebral arteries.

The geometry of arterial bifurcations has been shown to alter fluid flow and the propagation of both pressure and flow waves. Here we provide a more complete description of the renal artery bifurcation geometry and show that the geometry of the bifurcation is more complex than was believed previously. The objective of this study was to quantify changes in cross-sectional luminal area in systemic arterial bifurcations using the method developed by Macfarlane [Ph.D. thesis, University of Western Ontario, Ontario (1985)] to study the geometry of human cerebral bifurcations. Porcine renal arterial bifurcations from seven young (6-14 weeks) and six old (greater than 52 weeks) animals were pressure-fixed (P = 140 mmHg) for 3 h with 10% formalin. Bifurcations were embedded in a block of frozen latex paint. Serial sections were cut at 20 microns (+/- 0.01 microns) using a sledge microtome while the block face was scanned with a video camera and the images were stored on a videotape. The luminal area was measured digitally upon playback. Bifurcations from the two age groups changed in cross-sectional area not only at the flow divider but also along the so-called straight regions. Proximal linear increases in cross-sectional area were observed proximal to the apex of the bifurcation in both young and old vessels, while linear luminal area decreases were measured in the daughter branches of both young and old porcine renals. Taper was defined as the change in luminal area per unit length of parent and daughter branches, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)