rEnal Blood supply and fluid thErapy

there are different underlying mechanisms of acute kidney injury (aKi) in various type of shock, but restoration of renal blood flow (rBf) is crucial in prevention of aKi. the first 24-48 hours of shock seem to be critical. monitoring of global rBf and its intrarenal distribution is not possible in current clinical practice. the only way for optimization of renal blood supply is optimization of macrohemodynamics. in volume-responsive aKi, fluid therapy restores kidney function. many clinical signs and parameters can be of use in determining the volume status. the accuracy of the assessment may be improved with the help of tools quantifying the clinical parameters (e.g. hypovolemic index – hvi). the basis of intravenous fluid therapy are crystalloids, and their effect is reported to be shorter than 120 min. Every form of hydroxyethyl starch has been shown to be harmful for patients at risk of impaired renal function. in sepsis, the boundary between volume-responsive and volume-unresponsive aKi is blurred. fluid responsiveness can be lost in the course of aKi as early as on the first day of sepsis. according to the results of the ards network study, the conservative approach in fluid therapy resulted in a shorter time of mechanical ventilation and did not affect the renal function, except for a slight increase of the serum creatinine level. fluid overload is to be avoided, as renal venous and lymphatic congestion can limit the urine filtration rate, further worsening edema.

A simple method to ensure homogeneous drug distribution during intrarenal infusion

Intrarenal drug infusion plays an important role in renal experimental research. Laminar flow of the blood can cause streaming and inhomogeneous intrarenal distribution of infused drugs. We suggest a simple method to achieve a homogeneous intravascular distribution of drugs infused into the renal artery of anesthetized rats. The method employs a multiple sidehole catheter inserted into the renal artery, which enables an efficient drug mixing with the arterial blood. To verify the efficiency of this method, we use laser speckle imaging and renal artery flowmetry. The results show that, compared with the conventional single-hole catheter, the multiple sidehole catheter provides a more uniform drug distribution and a homogenous vascular response on the surface of the kidney.

Measuring the intrarenal distribution of glomerular volumes from histological sections

Glomerular volume is an important metric reflecting glomerular filtration surface area within the kidney. Glomerular hypertrophy, or increased glomerular volume, may be an important marker for renal stress. Current stereological techniques report the average glomerular volume (AVglom) within the kidney. These techniques cannot assess the spatial or regional heterogeneity common in developing renal pathology. Here, we report a novel “unfolding” technique to measure the actual distribution of individual glomerular volumes in a kidney from the two-dimensional glomerulus profiles observed by optical microscopy. The unfolding technique was first developed and tested for accuracy with simulations and then applied to measure the number of glomeruli ( Nglom), AVglom, and intrarenal distribution of individual glomerular volume (IVglom) in the oligosyndactyl (Os/+) mouse model compared with wild-type (WT) controls. The Os/+ mice had fewer and larger glomeruli than WT mice: Nglom was 12,126 ± 1,658 (glomeruli/kidney) in the WT mice and 5,516 ± 899 in the Os/+ mice; AVglom was 2.01 ± 0.28 × 10−4 mm3 for the WT mice and 3.47 ± 0.35 × 10−4 mm3 for the Os/+ mice. Comparing the glomerular volume distributions in Os/+ and WT kidneys, we observed that the Os/+ distribution peaked at a higher value of IVglom than the WT distribution peak, and glomeruli with a radius greater than 55 μm were more prevalent in the Os/+ mice (3.4 ± 1.6% of total glomeruli vs. 0.6 ± 1.2% in WT). Finally, the largest profiles were more commonly found in the juxtamedullary region. Unfolding is a novel stereological technique that provides a new quantitative view of glomerular volume distribution in the individual kidney.