Assessment of Renal Function; Clearance, the Renal Microcirculation, Renal Blood Flow, and Metabolic Balance

Abstract

Historically, tools to assess renal function have been developed to investigate the physiology of the kidney in an experimental setting, and certain of these techniques have utility in evaluating renal function in the clinical setting. The following work will survey a spectrum of these tools, their applications and limitations in four general sections. The first is clearance, including evaluation of exogenous and endogenous markers for determining glomerular filtration rate, the adaptation of estimated glomerular filtration rate in the clinical arena, and additional clearance techniques to assess various other parameters of renal function. The second section deals with in vivo and in vitro approaches to the study of the renal microvasculature. This section surveys a number of experimental techniques including corticotomy, the hydronephrotic kidney, vascular casting, intravital charge coupled device videomicroscopy, multiphoton fluorescent microscopy, synchrotron-based angiography, laser speckle contrast imaging, isolated renal microvessels, and the perfused juxtamedullary nephron microvasculature. The third section addresses in vivo and in vitro approaches to the study of renal blood flow. These include ultrasonic flowmetry, laser-Doppler flowmetry, magnetic resonance imaging (MRI), phase contrast MRI, cine phase contrast MRI, dynamic contrast-enhanced MRI, blood oxygen level dependent MRI, arterial spin labeling MRI, x-ray computed tomography, and positron emission tomography. The final section addresses the methodologies of metabolic balance studies. These are described for humans, large experimental animals as well as for rodents. Overall, the various in vitro and in vivo topics and applications to evaluate renal function should provide a guide for the investigator or physician to understand and to implement the techniques in the laboratory or clinic setting.

Rap1b in Smooth Muscle and Endothelium Is Required for Maintenance of Vascular Tone and Normal Blood Pressure

“…Here we show that Rap1b in kidney does not have a major function in that process, as we have observed normal gross kidney histology and no major changes in indices of renal function or plasma renin activity in Rap1b −/− mice. However, a number of additional studies would need to be performed to fully understand the role of Rap1b in kidney function 43 and in regulation of tissue renin-angiotensin system, which also contributes to BP regulation. Likewise, it is conceivable that Rap1b in the sympathetic nervous system contributes to the regulation of blood pressure.…”

Zwitterionic near infrared fluorescent agents for noninvasive real-time transcutaneous assessment of kidney function

“…Plasma endogenous creatinine concentration is commonly used to estimate the GFR, but it may result in erroneous estimates due to age, gender, muscle mass and many other anthropometric variables. 3 Determination of the plasma/urinary clearance of exogenous renal markers (such as 99m Tc-DTPA, inulin and iothalamate) is invasive and cumbersome, due to the requirement of multiple blood/urine sampling steps and tedious sample analysis by HPLC. 4 Moreover, many studies revealed that creatinine and iothalamate are secreted by proximal tubule cells, while cystatin C and 99m Tc-DTPA are reabsorbed by the tubular epithelial cells, leading to a bias in the GFR.…”

New insights in prevention and treatment of sepsis-induced acute kidney injury

“…[16] Therefore, monitoring limited to global evaluation of renal blood flow tells very little about the adequacy of oxygen supply to the kidneys. [17] As a consequence, renal Doppler is not a reliable tool to assess oxygen supply and its potential response to fluid loading.…”