ObjectiveTo identify portal segmentation and a portal fissure in the caudate lobe of the human liver in relation to the hepatic venous system and the external notch at the caudal edge of the caudate lobe. Summary Background DataAlthough the anatomy of the caudate lobe has been studied, the detailed anatomy has not yet been clarified; this is necessary to develop safe procedures for caudate lobe resection. MethodsA total of 88 formalin-fixed human livers were dissected to visualize the portal vein and hepatic vein systems of the caudate lobe in relation to the external notch. ResultsThe patterns of portal branching were classified into two types. In 58 livers (67.4%), the territories of the first-order portal branches were clearly divided into two areas (the Spiegel lobe and the paracaval portion). In the remaining 28 livers (32.6%), the territories of the second-order portal branches were clearly divided into two areas. These two areas were distinctly separated by an internal plane, which was coincident with the external notch. The caudate lobe had a systematized hepatic venous system that consisted of one (87.5%) or two (11.4%) proper hepatic veins and plural accessory hepatic veins. The proper hepatic veins laid along the internal plane between these two portal areas. ConclusionsThe caudate lobe exhibited distinct portal segmentation with a portal fissure that was indicated internally by the proper hepatic vein and externally by the notch at the caudal edge of the caudate lobe.

To compare the fundamental structure of the human liver, in relation to that of the rat a comparative study was performed, in which 20 rat livers and 78 human cadaver livers were examined. The rat livers had four lobes (left, middle, right, and caudate). The left and middle lobes formed a single lobe but the middle lobe had a deep notch to which the round ligament attached. The right lobe was split into two sub-lobes and the caudate lobe was divided into the paracaval portion and the Spiegel lobe, which was split into two sub-lobes. The left, right, and caudate lobes had one primary portal branch, whereas the middle lobe had two portal branches. The left and the right sub- and caudate lobes had one large hepatic vein each, whereas three large hepatic veins were observed in the middle lobe. Based on the ramifying patterns of the portal and hepatic veins, the rat middle lobe possessed left and right hepatic components and a main portal fissure. The following rat hepatic lobes were equivalent to the following human liver segments: the left lobe to segment II; the middle lobe to segments III, IV, V, and VIII; and the right lobe to segments VI and VII. The fundamental structures of rat and human livers were similar, and the findings demonstrated a new interpretation of the anatomy of the human liver.

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The present study was conducted to assess the role of activin(s) in the regulatory mechanism to maintain constant liver mass. To this end, we infused follistatin, an activin antagonist, into the portal vein of the rat. Follistatin induced DNA synthesis, as assessed by bromodeoxy uridine labeling, in intact livers. Small peaks of bromodeoxy uridine labeling were observed after 3 and 18 hours of infusion, and a large peak was observed after 48 hours. In follistatin-treated rats, the DNA content of the liver was significantly elevated after 72 hours and returned to the basal value within 120 hours. Likewise, liver weight increased significantly after 60 and 72 hours, but returned to the control value within 120 hours. Apoptosis of hepatocytes, assessed by the Tdt-mediated, dUTP-biotin nick end labeling method was observed after 72 hours or later. Messenger RNA (mRNA) expression of hepatocyte growth factor, transforming growth factor-␣ ␣, tumor necrosis factor-␣, and interleukin-6 did not increase after the addition of follistatin. The mRNA expression and immunoreativity of transforming growth factor-␤ ␤ increased after the administration of follistatin. These results suggest that the blockade of activin action leads to the initiation of DNA synthesis in the intact liver. Activins may tonically inhibit hepatocyte growth in the intact liver. Transforming growth factor-␤ ␤ may also act to maintain constant liver mass when activin action is blocked. (HEPATOLOGY 2000;31: 916-921.)Liver mass is carefully regulated in mammals, 1 and the ratio of liver mass and body weight is maintained within a narrow range under normal conditions. When the effective liver mass is reduced by partial hepatectomy, the remnant liver tissue, comprising parenchymal and nonparenchymal cells, starts growing. 2-4 Parenchymal cells eventually initiate DNA replication, which is followed by DNA replication of nonparenchymal cells. Within a few days after hepatectomy, the liver mass is restored, and liver regeneration stops when the liver mass reaches the optimal level for body size.

Background: A minimum, but necessary amount, of cancer-containing liver tissue is to be excised in patients who have poor liver function. To achieve that goal of excision, a limited hepatic resection has been carried out. However, performing subsegmentectomy of the anterior segment according to the conventional segmental anatomy introduced by Healey and Schroy or Couinaud is difficult. Because the transverse border between segments 5 and 8 was drawn as an imaginary line through the right portal vein, there is no anatomical structure indicating this border. Hypothesis: Hjortsjo divided the anterior segment into 2 vertical segments according to the fissure in which a hepatic vein coursed. By including Hjortsjo's concept of segmental anatomy, new procedures will be added to hepatic surgery. Design: Sixty-five cadaveric livers were dissected to confirm Hjortsjo's concept of segmental anatomy by inves

Objective:To propose an algorithm for resecting hepatocellular carcinoma (HCC) in the caudate lobe.Background:Owing to a deep location, resection of HCC originating in the caudate lobe is challenging, but a plausible guideline enabling safe, curable resection remains unknown.Methods:We developed an algorithm based on sublocation or size of the tumor and liver function to guide the optimal procedure for resecting HCC in the caudate lobe, consisting of 3 portions (Spiegel, process, and caval). Partial resection was prioritized to remove Spiegel or process HCC, while total resection was aimed to remove caval HCC depending on liver function.Results:According to the algorithm, we performed total (n = 43) or partial (n = 158) resections of the caudate lobe for HCC in 174 of 201 patients (compliance rate, 86.6%), with a median blood loss of 400 (10–4530) mL. Postoperative morbidity (Clavien grade ≥III b) and mortality rates were 3.0% and 0%, respectively. After a median follow-up of 2.6 years (range, 0.5–14.3), the 5-year overall and recurrence-free survival rates were 57.3% and 15.3%, respectively. Total and partial resection showed no significant difference in overall survival (71.2% vs 54.0% at 5 yr; P = 0.213), but a significant factor in survival was surgical margin (58.0% vs 45.6%, P = 0.034). The major determinant for survival was vascular invasion (hazard ratio 1.7, 95% CI 1.0–3.1, P = 0.026).Conclusions:Our algorithm-oriented strategy is appropriate for the resection of HCC originating in the caudate lobe because of the acceptable surgical safety and curability.

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