Three-dimensional morphometric analysis of the renal vasculature

Abstract

Vascular topology and morphology are critical in the regulation of blood flow and the transport of small solutes, including oxygen, carbon dioxide, nitric oxide, and hydrogen sulfide. Renal vascular morphology is particularly challenging, since many arterial walls are partially wrapped by the walls of veins. In the absence of a precise characterization of three-dimensional branching vascular geometry, accurate computational modeling of the intrarenal transport of small diffusible molecules is impossible. An enormous manual effort was required to achieve a relatively precise characterization of rat renal vascular geometry, highlighting the need for an automated method for analysis of branched vasculature morphology to allow characterization of the renal vascular geometry of other species, including humans. We present a semisupervised method for three-dimensional morphometric analysis of renal vasculature images generated by computed tomography. We derive quantitative vascular attributes important to mass transport between arteries, veins, and the renal tissue and present methods for their computation for a three-dimensional vascular geometry. To validate the algorithm, we compare automated vascular estimates with subjective manual measurements for a portion of rabbit kidney. Although increased image resolution can improve outcomes, our results demonstrate that the method can quantify the morphological characteristics of artery-vein pairs, comparing favorably with manual measurements. Similar to the rat, we show that rabbit artery-vein pairs become less intimate along the course of the renal vasculature, but the total wrapped mass transfer coefficient increases and then decreases. This new method will facilitate new quantitative physiological models describing the transport of small molecules within the kidney.

Renal oxygenation: From data to insight

“…In the renal cortex arteries and veins run together in a counter‐current arrangement . Particularly in the case of larger vessels (interlobar and arcuate), the vein walls wrap the wall of the artery, providing a pathway for diffusion of oxygen from arterial to venous blood (AV oxygen shunting).…”

“…72 The extension of this proposal is that such mechanisms might In the renal cortex arteries and veins run together in a counter-current arrangement. [73][74][75] Particularly in the case of larger vessels (interlobar and arcuate), the vein walls wrap the wall of the artery, 74,76,77 providing a pathway for diffusion of oxygen from arterial to venous blood (AV oxygen shunting). There is considerable experimental evidence that oxygen can diffuse (or be shunted) from arteries to veins in the kidney (reviewed in 40 ), but because it cannot be measured experimentally, its quantity must be estimated from computational models.…”

“…Regarding criteria (i) and (ii), the starting point for all computational models of oxygen transport in the kidney must be accurate information about the geometry of the sources of oxygen (the vasculature) and the oxygen sinks (the tubules) and their relationships. Much progress has been made, including development of methods for automated analysis of the renal vasculature and development of exquisitely high resolution methods for imaging oxygenation of tubular and vascular structures in the kidney . The challenge is to adequately deploy these methods to determine typical arrangements, the variability in such arrangements under normal physiological conditions and how they are altered in CKD and AKI.…”

At last! Quantitative cortical vascular anatomy

“…To date, their use has been constrained by resolution and by datahandling procedures. Both of these points are addressed explicitly by Khan et al (7).…”

“…Segmentation is the process of extracting salient, three-dimensional features from an array of two-dimensional images and is central to anatomy. Anatomy today is thus made up of big data problems, such as the one addressed by Khan et al (7). As the increased resolution enabled by electron microscopy extended the insight provided by light microscopy into new levels of organization, so too have CT and X-ray microscopy begun to enhance and change our understanding of the renal circulations.…”