Page 360 - Libro 2

340 PART 5 — ABDOMINAL
Duplex Sonographic Findings in Portal
Hypertension
Several sonographic findings are associated with portal hypertension. Pathology Box 22-1 lists the du- plex sonographic findings.10
With the development of portal hypertension, the main portal vein initially increases due to increasing portal venous pressure (Fig. 22-9). In cases of se- vere portal hypertension, the diameter of the portal vein may decrease (decompression) due to portosys- temic collaterals. An increased portal vein diameter 􏰁13 mm indicates portal hypertension with a high degree of specificity (100%) but with low sensitiv- ity (40%).11 Reversed or hepatofugal portal flow is generally associated with a significant reduction in the diameter of the portal vein because more blood is diverted to portosystemic collaterals. Hepatofugal flow in the MPV has been reported in the literature with an overall prevalence of 8.3% in patients.6 Other studies have reported hepatofugal flow in the portal venous system (portal, splenic, and superior mesenteric veins) in 3% to 23% of patients with cir- rhosis.12 In some patients with cirrhosis, hepatofugal flow is identified in isolated intrahepatic portal vein branches only. Hepatofugal flow can change to hepa- topetal flow after ingestion of a meal because of a postprandial increase in splanchnic venous flow. This phenomenon may be blunted in cirrhotic patients. Also, hepatofugal flow can revert to hepatopetal flow if the patient’s condition improves after medication.
With severe portal hypertension, flow velocity with- in the portal vein generally decreases due to increased
PATHOLOGY BOX 22-1
A portal vein with an increased diameter (1.63 cm) associated with portal hypertension.
resistance. Spectral Doppler demonstrates continuous (losing normal fluctuations), biphasic (to and fro in some patients), and eventually, reverse flow (hepatofu- gal) in patients with advanced disease (Fig. 22-10).
Although several studies advocate decreased por- tal vein flow as an indicator of portal hypertension, collateral pathways can augment portal vein hemo- dynamics. For example, a recanalized paraumbilical vein can increase portal vein velocity, whereas sple- norenal collaterals can reduce and reverse flow.
An increased splenic vein diameter 􏰁10 mm with reduced flow or retrograde (hepatofugal) flow and no detectable thrombus is an indicator for portal hypertension. In this situation, the mesenteric ve- nous blood is transported to the vena cava through
Figure 22-10 Abnormal hepatofugal Doppler waveforms from a portal vein in a patient with portal hypertension. The abnor- mal portal venous flow is displayed below the baseline and is color-coded in blue within the image. Normal antegrade he- patic artery flow is displayed above the baseline.
Figure 22-9
Duplex Sonographic Findings in Portal Hypertension
• Increased portal vein diameter (􏰁13 mm)
• Increased splenic vein and SMV diameters
(􏰁10 mm)
• 􏰂20% increase in SMV or splenic vein diameter,
quiet respiration to deep inspiration
• Decreased or absent respiratory variation (portal/
splenic veins)
• Diminished, static, altered pulsatility of portal and
hepatic venous flow
• Hepatofugal flow (portal/splenic veins)
• Portosystemic collaterals (varices)
• Ascites and splenomegaly
• Liver parenchymal pathology (cirrhosis, tumor,
Budd-Chiari syndrome)
• Portal vein obstruction (thrombus, tumor invasion)
• Increased hepatic artery flow (arterialization)