Pathophysiology of elevated ascites fluid cholesterol in malignant ascites

The existence of marked elevations of ascitic fluid cholesterol has
been observed in patients with peritoneal carcinomatosis compared
to patients with cirrhosis and has been found useful in
differential diagnosis. This finding could be caused by an enhanced
movement of plasma lipoproteins into the peritoneal cavity. To test
this hypothesis we determined the fasting concentrations of total,
high density lipoprotein (HDL)- and low density lipoprotein
(LDL)-cholesterol, apolipoprotein-A1 (apo-A1) and apolipoprotein-B
(apo-B) in serum and ascites of 17 patients with cirrhosis and 16
patients with peritoneal carcinomatosis. The movement of proteins
from plasma to ascites was calculated from the ascites/serum
concentration ratios of six different sized proteins with a
molecular mass ranging from 54 kDa to 971 kDa. Mean values (mg/dl)
for total cholesterol (92.6 vs. 21.0), HDL-cholesterol (15.6 vs.
1.8), LDL-cholesterol (63.4 vs. 16.1), apo-A1 (50.2 vs. 13.6) and
apo-B (41.2 vs. 12.9) in ascites were significantly higher in
peritoneal carcinomatosis than in cirrhosis. These differences
could only partially be explained by the higher serum
concentrations of these parameters in peritoneal carcinomatosis,
but were mainly due to a lower selectivity for the movement of
plasma proteins and lipoproteins into ascites (mean ascites/serum
(A/S) ratio: 0.30–0.77) in peritoneal carcinomatosis as compared to
cirrhosis (mean ascites/serum ratio: 0.11–0.21). In both groups
about 85% of the total cholesterol in serum and ascites consisted
of HDL- and LDL-cholesterol. These findings support the hypothesis
that elevations in ascitic cholesterol in peritoneal carcinomatosis
compared to cirrhosis are mainly caused by the increased movement
of plasma HDL and LDL into the peritoneal cavity.