Table 1 Methods of accessing microvessels in CKD

Synchrotron radiation (SR)

Visualizing proximal tubules, glomeruli and renal arterioles

Non-invasive method; visualizing the smaller arteriole

Can not fully reflect the three-dimensional structures within kidneys

[61]

Micro-computed tomography (μCT)

Quantitative monitoring for anatomical and functional changes of vascular alterations

Non-invasive method; user- friendliness; operator independence; quantitative assessment

X-ray exposure; the need for iodine- based contrast agents;

[30, 65]

FMA-method

Assessing the microvascular architecture of the kidney

Enabled the three-dimensional reconstruction; quantitative assessment

Sacrifice of the animals

[29, 67]

BOLD-MRI

Accessing tissue oxygen metabolism and indirectly evaluating the microcirculation

Noninvasive method; without exposure to radiation or exogenous contrast agents; high spatial resolution

The R2* value is easily affected; the absence of cortico- medullary differentiation

[74]

Electron microscopy

Visualizing subtle ultrastructure of the endothelium

Visualizing the very early changes to endothelium

Sacrifice of the animals; the potential sampling error

[9]

Intravital Multiphoton Microscopy (MPM)

Quantitative evaluations of numerous renal functions

Noninvasive; high-resolution

Motion artifact; endogenous autofluorescence; long time image collection

[77, 78]