The role of ascitic fluid viscosity in the differential diagnosis of ascites.
BACKGROUND
Ascites is defined as the pathological accumulation of fluid in the peritoneal cavity. It is the most common complication of cirrhosis, which is also the most common cause of ascites. Viscosity is a measure of the resistance of a fluid to deform under shear stress. Plasma viscosity is influenced by the concentration of plasma proteins and lipoproteins, with the major contribution from fibrinogen. To our knowledge, the viscosity of ascitic fluid has not yet been studied.


OBJECTIVE
To evaluate the role of ascitic fluid viscosity in discriminating between ascites due to portal hypertension-related and nonportal hypertension-related causes, and to compare results with the serum-ascites albumin gradient (SAAG).


METHODS
The present study involved 142 patients with ascites presenting with diverse medical problems. Serum total protein, albumin, glucose, lactate dehydrogenase (LDH) levels and complete blood count were obtained for all subjects. Paracentesis was performed routinely on admission and all ascitic fluid samples were evaluated by manual cell count with differential, ascitic fluid culture and biochemistry (total protein, albumin, glucose and LDH). Cultures of ascitic fluid were performed at bedside in all patients using blood culture bottles. Ascitic fluid viscosity was measured in a commercially available cone and plate viscometer.


RESULTS
Of the 142 patients studied, 34 (24%) had an SAAG of 11 gL or less, whereas 108 (76%) had an SAAG of greater than 11 gL. Sex and mean age did not differ significantly between the two groups (P>0.05). Serum total protein, albumin, glucose, LDH levels, leukocyte count, ascitic fluid glucose levels and ascitic fluid leukocyte counts were similar in both groups, with no statistically significant relationship detected (P>0.05). However, the mean (+/-SD) ascitic fluid total protein (0.0172+/-0.1104 gL versus 0.043+/-0.011 gL), albumin (0.0104+/-0.0064 gL versus 0.0276+/-0.0069 gL) and LDH (102.76+/-80.95 UL versus 885.71+/-199.93 UL) were found to be higher in patients with an SAAG of 11 gL or less than in those with an SAAG of greater than 11 gL (P<0.001). The mean ascitic fluid viscosities were 0.86+/-0.12 centipoise (cP) and 1.22+/-0.25 cP in patients with an SAAG greater than 11 gL and an SAAG of 11 gL or less, respectively (P<0.001). Although ascitic fluid infection was detected in 35 patients (24.6%) (19 patients with spontaneous bacterial peritonitis, seven patients with culture-negative neutrocytic ascites, three patients with monobacterial non-neutrocytic bacterascites and six patients with secondary bacterial peritonitis), no significant effect on ascitic fluid viscosity was detected. Multiple linear regression analysis revealed that ascitic fluid total protein, albumin and LDH levels were independent predictors of ascitic fluid viscosity (P<0.001). The sensitivity, specificity, and positive and negative predictive values of ascitic fluid viscosity for the discrimination between ascites due to portal hypertension-related and nonportal hypertension-related causes according to the SAAG were determined by receiver operating characteristic analysis. Regarding the cut-off value of 1.03 cP, ascitic fluid viscosity measurement had a high sensitivity, specificity (98% and 80%, respectively), and positive and negative predictive value (79% and 94%, respectively) for the etiological discrimination of ascites.


CONCLUSIONS
The measurement of ascitic fluid viscosity correlates significantly with SAAG values. In view of its simplicity, low cost, small sample volume requirement and allowance for measurement in previously frozen samples, measurement of ascites viscosity could be useful for the accurate and rapid classification of ascites.
Gokturk
Huseyin Savas
HS
Department of Gastroenterology, Baskent University Faculty of Medicine, Adana, Turkey. savasgokturk@yahoo.com
Demir
Mehmet
M
Ozturk
Nevin Akcaer
NA
Unler
Gulhan Kanat
GK
Kulaksizoglu
Sevsen
S
Kozanoglu
Ilknur
I
Serin
Ender
E
Yilmaz
Ugur
U
D000418:Albumins / Q000032:analysis; D001201:Ascites / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism; D001202:Ascitic Fluid / Q000737:chemistry*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006975:Hypertension, Portal / Q000150:complications* / Q000378:metabolism; D008103:Liver Cirrhosis / Q000150:complications* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014783:Viscosity
D000418:Albumins