Page 357 - Libro 2

22 — The Hepatoportal System
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Figure 22-3 Normal portal vein Doppler waveforms with flow directed toward the liver.
trans-sinusoidal transmission of atrial pulsations, the respiratory cycle, and the transmission of vena cava, hepatic arterial, or splanchnic pulsations.
SPLENIC VEIN
In normal patients, the diameter of the splenic vein (in the transverse view at the level of the superior mesenteric artery [SMA]) measures up to 10 mm (inner wall to inner wall) and increases by 20% to 100% from quiet respiration to deep inspiration. An increase in caliber of less than 20% indicates por- tal hypertension with 80% sensitivity and 100% specificity.6
Normal splenic vein flow direction is hepatopetal (toward the liver). As seen in the portal vein, res- piration and cardiac activity can also affect splenic vein velocity. Flow velocity decreases during inspira- tion and increases during expiration. Peak systolic velocity in the splenic vein normally ranges from 9 to 30 cm/s. The mean velocity ranges from 5 to 12 cm/s. The Doppler spectral waveforms of the nor- mal splenic vein display a monophasic waveform with slight pulsatility (Fig. 22-4).
SUPERIOR MESENTERIC VEIN
In normal patients, the diameter of the SMV can measure up to 10 mm at the trunk (inner wall to in- ner wall) and increases by 20% to 100% from quiet respiration to deep inspiration. As with the splenic vein, an increase in caliber of less than 20% indi- cates portal hypertension.6
Normal SMV flow is hepatopetal (toward the liver). Peak systolic velocity in the SMV normally ranges between 8 and 40 cm/s. The mean velocity range is 9 to 18 cm/s. Doppler spectral analysis of
Figure 22-4 Normal splenic vein Doppler waveforms.
the SMV shows a monophasic waveform with slight pulsatility (Fig. 22-5). Flow in the portal confluence is turbulent as the splenic vein joins the SMV to form the portal vein. Respiratory maneuvers and ingestion of food affect flow velocity. Flow velocity decreases during inspiration and increases with expiration, similar to that of the portal and splenic veins. Post- prandially, SMV velocity increases 50% to 100%.
HEPATIC VEINS
The normal diameter of the RHV is less than 6 mm. The thin walls of the hepatic veins are less reflec- tive as compared to the portal veins. In patients with congestive heart failure, the RHV diameter increases to a mean diameter of 9 mm or greater.7
The hepatic veins normally exhibit a pulsatile tri- phasic waveform with both antegrade and retrograde flow (Fig. 22-6). This waveform corresponds to cy- clic pressure changes within the heart. The initial wave is termed the S wave and is directed toward the
Figure 22-5 Normal superior mesenteric vein Doppler wave- forms.