Observations on the rare association between portal and pulmonary hypertension

Pulmonary arterial hypertension with severe pulmonary vascular disease is a rare association of portal hypertension in man, be it the result of cirrhosis of the liver or obstruction of the portal vein. We induced portal hypertension in 23 rats by partially ligating the portal vein or by totally occluding it in two stages. The rats were killed between one and 15 months after operation. A collateral circulation of varicose, anastomotic vessels was established, and in six animals well-marked oesophageal varices developed. Despite this evidence of sustained portal hypertension, hypertrophy did not develop in the right ventricle or in the media of the pulmonary trunk or muscular pulmonary arteries in any of the animals. This suggests that mechanical obstruction of the portal vein per se is not responsible for the development of pulmonary hypertension. Other factors, perhaps of a humoral nature, appear to be required to induce this rare association of portal hypertension but we have been unable to identify these. In particular, blood levels of oestrogen were not raised after ligation of the portal vein.