Background — The hemodynamical effect of the collateral portosystemic circulation upon the portal system has not yet been fully understood. The US-Doppler made possible the non-invasive study of the portal system by evaluating the parameters: flow direction, diameter and flow velocity in it's vessels. Aims - To study the paraumbilical vein as a collateral portosystemic pathway and identify patterns for appraising its hemodynamic importance to the portal system. Method - US-Doppler study of the portal system of 24 patients with Mansoni's hepatosplenic schistosomic portal hypertension, previous esophagic variceal bleeding and patent paraumbilical vein with hepatofugal flow. The diameter and the mean flow velocity were measured in the paraumbilical vein and so were the mean flow velocity in the portal vein, right and left portal branches. The Pearson test (linear correlation) was applied to the portal vein's mean flow velocity and the paraumbilical vein's diameter and mean flow velocity. The patients were divided in four groups: D1 - paraumbilical vein with diameter <0.68 cm (n = 14), D2 - paraumbilical vein with diameter <FONT FACE=Symbol>³</FONT>0.68 cm (n = 10), V1 - paraumbilical vein with mean flow velocity <18.41 cm/seg (n = 13) and V2 - paraumbilical vein with mean flow velocity <FONT FACE=Symbol>³</FONT> 18.41 cm/seg (n = 11). The mean flow velocity in the portal vein, right and left portal branches of the four groups were compared. Results - The paraumbilical vein diameter was 0.68 ± 0.33 cm (range: 0.15 - 1.30 cm) and the mean flow velocity was 18.41 ± 11.51 cm/seg (range: 5.73 - 38.20 cm/seg). The linear correlation between the portal vein's mean flow velocity / paraumbilical vein diameter and the paraumbilical vein's mean flow velocity showed r = 0.504 and r = 0.735, respectively. In the group D2 there was an increase in the mean flow velocity in the portal vein (17.80 ± 3.42 / 22.30 ± 7.67 cm/seg) and in the left portal branch (16.00 ± 4.73 / 22.40 ± 7.90 cm/seg). In the group V2 there was an increase in the mean flow velocity in the portal vein (16.31 ± 3.49 / 21.96 ± 5.89 cm/seg) and in the left portal branch (14.22 ± 4.41 / 21.94 ± 7.20 cm/seg). There was no change in the right portal branch (13.67 ± 5.74 / 15.43 ± 3.43 cm/seg). Conclusions - In portal hypertension due to hepatosplenic schistosomiasis, the patent paraumbilical vein, with hepatofugal flow, diameter <FONT FACE=Symbol>³</FONT> 0.68 cm and mean flow velocity <FONT FACE=Symbol>³</FONT> 18.41 cm/seg causes an increase of the mean flow velocity in the portal vein and left portal branch. The best US-Doppler parameter to appraise the paraumbilical vein influence upon the portal system is the mean flow velocity. The correlation between the increase in portal vein's mean flow velocity is stronger with the paraumbilical vein's mean flow velocity than with its diameter. The increase in the portal vein's and left portal branch's mean flow velocity may be understood as the paraumbilical vein's hemodynamic influence upon the portal system. An active portosystemic collateral pathway increases the mean flow velocity in the vein's segment proximal to its point of origin.
Paraumbilical vein; Portal system; Hypertension, portal; Schistosomiasis mansoni; Ultrasonography, Doppler
