Surgical aspects of hepatic segmentation based on hepatic venographies

Venous hepatic segmentation in dogs (Canis lupus familiaris-L. 1758)

The external shape of the liver is varied and determines specific vascular arrangements. This morphological relationship is important to establish hepatic segmentation in different species submitted to surgeries that aim to preserve a larger area of liver parenchyma. After observing 60 livers injected with Neoprene Latex and three plastic moulds obtained by corrosion, eight hepatic venous segments were identified, drained by six hepatic veins agrouped into segmental veins, which drained one sector (segments I, VI, VII and VIII) and intersegmental veins, which drained more than one sector (segments II/III and IV/V). They were described as follows: left intersegmental vein, formed by a segmental vein from the papillary process (segment I), two to three lateral left segmental veins that drained the segment II, and one to five left paramedian segmental veins that drained the segment III; sagittal intersegmental vein, formed by the confluence between segmental vein of the quadrate lobe (segment IV) and the medial right paramedian segmental vein, which derived from the segment V; lateral right paramedian vein drained the dorsocranial sector of the segment VI; the lateral right segmental vein, formed by one to four vessels that drained segment VII, and the segmental vein of the caudate process, which drained the segment VIII. Understanding the number and disposition of the hepatic veins in lobate livers is essential to reduce bleeding risks in surgeries. The nomenclature based on segmentation analogy of non-lobate liver could be less confusing and, therefore, be more useful in the surgical approaches of lobate livers.

Intrahepatic venous anastomosis formation of the right liver in living donor liver transplantation: evaluations by Doppler ultrasonography and pulse-inversion ultrasonography with Levovist

BACKGROUND

Our aim was to investigate the development of intrahepatic venous anastomoses between the middle hepatic vein (MHV) and the right hepatic vein (RHV) in adult-to-adult, living donor, liver transplantation.

METHODS

Using Doppler ultrasonography, we studied the formation of venous anastomoses between the MHV tributaries for segments 5 and 8 (V5, V8) and the RHV in the liver remnants of 7 donors of a left liver, including the MHV, and in the liver grafts of 8 recipients of a right liver, without including the MHV. In 1 donor and 5 recipients, we performed pulse-inversion ultrasonography with a microbubble contrast agent to evaluate hepatic parenchymal perfusion in the drainage region of the MHV.

RESULTS

We observed 15 MHV tributaries of V5 and 13 of V8 among the 15 adult transplant patients. During the first postoperative week, we detected venous anastomosis between V5 and the RHV in 4 patients and in 10 patients between V8 and the RHV. After the 1st week, we observed the formation of anastomosis between V5 and the RHV in 10 patients, and between V8 and the RHV in 3. In both MHV tributaries, the mean flow velocities increased (P < .01). By the end of the 1st week, the formation rate in V8 was higher than in V5 (77% vs 27%, P < .03). In the parenchymal phase of the pulse-inversion ultrasonography with the microbubble contrast agent, the V5 drainage region had low intensities, while the V8 drainage territory revealed high intensities in 4 of 6 patients (66.7%).

CONCLUSIONS

Functional venous anastomoses between either V5 or V8 and the RHV developed in most of the donors of left hepatic lobes and in recipients of right hepatic lobes; however, anastomoses developed earlier in V8 than in V5. Furthermore, perfusion was decreased in the drainage area of V5, compared with V8.

Large inferior right hepatic vein. Clinical implications

The right middle and inferior hepatic vv. are very frequent, indeed constant, but usually of small caliber. The presence of an extra-wide right inferior hepatic v., usually solitary, produces a variation in the venous drainage of the right lobe of the liver. The right inferior hepatic vv. reaching or exceeding a caliber of 0.5 cm were investigated in 125 anatomic liver specimens: 70 injection-corrosion specimens, 32 formolised livers and frontal or frontal-oblique sections of the trunk made in 23 cadavers. The incidence of such vv. was estimated at 9% in the injection-corrosion specimens, 13% in the sections and 16% in the formolised livers. The incidence of these vv. in the literature varies from 10% to 24% according to the method used to demonstrate them. Usually, there is a balance between the right superior and inferior hepatic vv. Rarely, the right inferior hepatic v. predominates compared with the right superior hepatic v. The position of an extra-wide right inferior hepatic v. is constant, close to the visceral aspect of the liver. Its appropriate territory is segment VI, but it may encroach somewhat on adjacent segments. Clinically, the existence of an extrawide right inferior hepatic v. as detected by MRI and, especially, located by intraoperative ultrasonography, allows performance of a subtotal hepatectomy leaving only segment VI. In certain pathologic conditions, thanks to the development of anastomoses between the hepatic vv., an extra-wide right inferior hepatic v. may contribute to a compensatory circulation towards the right atrium.