Portal hypertension in alcoholic liver disease has been attributed to an increased resistance to blood flow either of sinusoidal or of postsinusoidal origin. The former should be accompanied by sinusoidal compression while the latter is expected to result in an increased or a normal sinusoidal diameter. Patients with alcoholic liver disease showed a marked reduction (p less than 0.001) in relative sinusoidal area (995 +/- 135 micron 2; n = 19) when compared to nonalcoholic patients with normal liver histology (5,100 +/- 389 micron 2; n = 6), or to patients with nonalcoholic liver disease (6,242 +/- 467 micron 2; n = 19). Hepatocyte surface area was significantly increased in patients with alcoholic liver disease when compared to hepatocytes from normal biopsies (563 +/- 32 micron 2 vs. 301 +/- 26 micron 2; p less than 0.001). Patients with nonalcoholic liver disease had hepatocyte surface areas within the normal range (327 +/- 14 micron 2). There was a significant inverse correlation between hepatocyte size and sinusoidal area (r = -0.63; p less than 10(-6); n = 44), indicating that larger hepatocytes were associated with sinusoidal compression. In the alcoholic patients, portal pressure correlated inversely (r = -0.77; p less than 0.01) with sinusoidal area only after the sinusoidal area was markedly reduced to areas below 20% of normal. Such a threshold was not reached in patients with nonalcoholic liver disease, in whom no correlation between sinusoidal area and portal pressure was observed.(ABSTRACT TRUNCATED AT 250 WORDS)