Development of collateral circulation following distal embolization of hepatic artery in pigs.

The distal hepatic artery was embolized with black polystyrene microspheres (diameters of 50 +/- 10 mu and 200 +/- 25 mu) in 12 pigs. The animals were reexamined from 1 h to 2 weeks after embolization via hepatic angiography and subsequent injection of Microfil, a silicone rubber compound, into the arterial and portal vascular systems of the liver. Dissection of dehydrated and cleared liver specimens under the stereomicroscope demonstrated the presence of arterial collaterals bypassing embolized vessels within 2-3 days after embolization. Collaterals were noted to develop around occlusions in arteries with inner diameters as small as 100 mu.