Table 1 Definitions of the various types of capillary morphologies [12, 13, 26,27,28]

Normal

Capillaries with a hairpin shape or a once crossing shape, on the condition that the apex is convex

Multiple crossings

The capillary limbs cross at least twice

Tortuous

Curled capillary limb without crossing of the limb

Ramified

Branched capillary limb, like a tree without leaves

Bushy

Capillary loop with limbs originating from small and multiple buds instead of branches

Nonconvex

The form of the apex is not curved like the exterior of a circle or sphere (convex)

Bizarre

Atypical morphology, distinct from the other described morphologies