Anatomical variations of the origin of the segment 4 hepatic artery and their clinical implications

Abstract

The threat of ischemic complications following massive resection, especially in living donor hepatectomy or split liver transplantation, has been haunting surgeons for many years. Postmortem dissections of 62 livers were performed to investigate anatomical variations of the principal artery for segment 4 (A4). The origin of A4 was examined separately in the liver with (n ϭ 46) or without (n ϭ 16) an aberrant left hepatic artery (abLHA). A4s were found to be extrahepatic or intrahepatic branches of the right hepatic artery (RHA), left hepatic artery, or proper hepatic artery and were categorized into 4 different types according to their origins. The RHA type, originating from the RHA or right anterior hepatic artery (RAHA), was the most common pattern in our series. The A4 roots had a strong tendency of stemming from the RHA (n ϭ 12) even in the livers with abLHA (n ϭ 16). Among the RHA-type A4s, the A4 arising from RAHA (n ϭ 2) is supposed to be the most dangerous variant because it can cause an ischemic change in the remaining part of the liver after right hepatectomy. In conclusion, in the era of living donor liver transplantation, paying particular attention to the point of origin of A4 is a prerequisite, especially when the lateral section is relatively small. Arterial injuries to A4 during split liver transplantation may also increase the risk of hepatic artery thrombosis and ischemic cholangiopathy. Liver Transpl 14:1180-1184, 2008. © 2008 AASLD. Received November 29, 2007 accepted February 22, 2008.The artery to segment 4 has been an area of debate in segmental liver anatomy. Unlike the other segments, segment 4 has a peculiar pattern of arterial supply (earlier branching for segment 4) in comparison with the portal vein supply.Embryologically, there are 3 lobes in the early stage of hepatic formation, each supplied by an embryonic artery of its own: the lateral sector (segment 2) by the embryonic left hepatic artery, the medial and anterior sectors (segments 3, 4, 5, and 8) by the embryonic middle hepatic artery, and the posterior sector (segments 6 and 7) by the embryonic right hepatic artery 1 (Fig. 1). In the adult liver, segment 4 is a part of the medial sector, and it has been called by various other names such as medial segment, left medial segment, and quadrate lobe. Likewise, the artery for segment 4Abbreviations: A2, segment 2 artery; A3, segment 3 artery; A4, segment 4 artery; A4*, dangerous type of segment 4 artery variation; abLHA, aberrant left hepatic artery; CA, celiac axis; CHA, common hepatic artery; eRHA, embryonic right hepatic artery; eLHA, embryonic left hepatic artery; eMHA, embryonic middle hepatic artery; LDLT, living donor liver transplantation; LGA, left gastric artery; LHA, left hepatic artery; LPV, left portal vein; MHV, middle hepatic vein; PHA, proper hepatic artery; RHA, right hepatic artery; RAHA, right anterior hepatic artery; PV, portal vein; SMA, superior mesenteric artery.

Arterial Blood Supply of Liver Segment IV and Its Possible Surgical Consequences

“…Azoulay et al reported in 2000 that in most cases the MHA originated from the left hepatic artery but could also originate from the RHA, especially in the presence of a replaced LHA 15. In contrast, Jin et al reported in 2008 that the arterial supply to segment IV was mainly via a branch of the RHA or the PHA 16.…”

Hepatic Arterial Configuration in Relation to the Segmental Anatomy of the Liver; Observations on MDCT and DSA Relevant to Radioembolization Treatment

“…In 1966, Michels introduced an internationally recognized classification of hepatic arterial variations, in which he described ten types of arterial configuration, based on his observations in 200 autopsy dissections [1]. Later, Hiatt et al introduced a reduced classification with six types, based on a review of operative RHA [7] aRHA [5,6,8] rLHA The segmental arterial vascularization patterns are summarized in this table. The main arterial branches are followed by their segmental territory of vascularization between brackets LHA left hepatic artery, RHA right hepatic artery, MHA middle hepatic artery, aRHA/aLHA accessory RHA/LHA, rRHA/LHA replaced RHA/ LHA a In one patient the rRHA originated from the aorta instead of the SMA reports of 1,000 patients who underwent liver harvesting for orthotopic transplantation.…”

“…2). Studies that previously investigated the origin of this arterial branch, often used different definitions, and terms, such as A4 and MHA were interchangeably used [8,12,18]. From an anatomical point of view, the term MHA refers to a hilar artery that originates from the CHA or PHA, between the origins of the LHA and RHA, whereas A4 also can refer to a small intrahepatic branch that originates from the distal LHA or RHA [12].…”

“…In the early stages of hepatic formation, an embryological left hepatic artery (eLHA) originates from the left gastric artery (LGA) and supplies S2, whilst an eRHA originates from the superior mesenteric artery (SMA) and vascularizes segments 6-7. The eMHA originates from the celiac axis and vascularizes the remaining S3, 4, 5, 8 of the liver [7,8]. Eventually, the eLHA and eRHA regress and the eMHA persists, resulting in a normal hepatic arterial configuration of the adult liver, in which the celiac axis gives rise to a left (LHA) and right hepatic artery (RHA).…”

Porción Hepática Izquierda (A05.8.01.037)

“…La rama segmentaria III nació de la rama izquierda en todos los casos. La rama segmentaria IV nació de la rama izquierda en 50 % y de la derecha en 20 % variación descrita también por Jin et al (2008). Panagouli et al (2011) reportaron que las arterias hepáticas accesorias pueden nacer de la gástrica izquierda o la mesentérica superior, para ambos lados, solo el ingreso a su territorio correspondiente las numera y clasifica.…”