Background: The urinary bladder requires a rich blood supply to mainta
in its functions, the storage and release of urine. Specialized proper
ties of the bladder vasculature might be anticipated to ensure the int
egrity of this blood supply, because it is known that blood flow is re
duced by distension during bladder filling. However, the bladder vascu
lature has been described in detail only at the gross level. A compreh
ensive, three-dimensional view of the blood supply to the bladder wall
is presented here. Methods: The microvasculature of the bladder of ma
le New Zealand white rabbits was described using the combination of va
scular corrosion casting, alkali digestion, light microscopy, and scan
ning and transmission electron microscopy. Following administration of
an anticoagulant and an overdose of anesthetic, the abdominal aorta w
as cannulated just above the inferior mesenteric artery to permit flus
hing of the distal vasculature. The bladder vasculature was cleared of
blood with buffered saline and then either perfuse-fixed with buffere
d 2% glutaraldehyde and sectioned, or filled with ''Mercox'' resin to
prepare vascular corrosion casts. Casts were cleaned with NaOH, formic
acid, and water. In some cases fixed bladders were partially digested
with NaOH to expose the mucosal capillary plexus. Results: The bladde
r is supplied with blood by single, left and right vesicular branches
of the internal or external iliac arteries. The serpentine vesicular a
rteries extend along the lateral borders of the bladder from base to a
pex just deep to the serosal surface and send dorsal and ventral branc
hes to supply the dorsal and ventral bladder walls. Veins accompany th
e arteries and exhibit numerous valves. A very dense complex of vessel
s at the apex of the bladder apparently serves to accommodate bladder
distension. The muscularis and submucosa contains few vessels, but the
mucosa is well vascularized. An especially dense capillary plexus is
present in the lamina propria at its junction with the transitional ep
ithelium. In the relaxed bladder these capillaries lie in grooves form
ed by the basal layers of the epithelium. The endothelial cells of the
se capillaries display few cytoplasmic vesicles and are continuous or
fenestrated. These capillaries are often invested with pericytes. The
mucosal capillary plexus may be associated with an epithelial transpor
t function or may be necessary for urothelial metabolism or maintenanc
e of the barrier function of the urothelium. Unusual capillary tufts,
possibly associated with vascular lymphatic tissue, are found associat
ed with the main vessels on the lateral walls in the basal half of the
bladder. Conclusions: These methods present a clear, comprehensive, t
hree-dimensional view of the microvasculature of the bladder wall. The
y also identify several unique features of this vasculature and provid
e a basis for studies of the response of this vasculature to pathologi
c states and experimental manipulation. (C) 1995 Wiley-Lies, Inc.