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Replaced Right Hepatic ArteryEdit

Replaced right hepatic artery (RRHA) is an anatomical variant in which the arterial supply to the right lobe of the liver comes from the Superior mesenteric artery rather than from the Proper hepatic artery arising from the celiac trunk as in the classic pattern. When the right hepatic artery is “replaced,” the usual source is absent and the SMA becomes the primary arterial conduit to the right hepatic lobe. If an additional right hepatic artery from the SMA is present along with a normal right hepatic artery from the proper hepatic artery, the configuration is typically described as an “accessory” right hepatic artery rather than replaced.

RRHA is a well-recognized variation in hepatic arterial anatomy and is clinically important because it alters the vascular map surgeons and interventionalists rely on during hepatobiliary procedures. Its presence can influence decisions in liver resection, pancreaticoduodenectomy, liver transplantation, and regional oncologic strategies. The concept and terminology are covered in classic anatomy and surgical handbooks and are incorporated into modern cross-sectional imaging reports when relevant to clinical care.

Anatomy and variants

  • Origin and course

    • In RRHA, the artery originates from the Superior mesenteric artery and travels to the right lobe of the liver, supplying hepatic segments that would normally receive blood from the right hepatic artery from the proper hepatic artery. The course can vary, but a common pattern is that the artery enters the liver hilum and supplies the right lobe without crossing through the typical course of the proper hepatic artery. This arterial path has particular relevance for surgical approaches in the periampullary region and the right hepatic hilum.
    • In some individuals, the contralateral arterial supply is normal, whereas in others the right liver receives its arterial inflow exclusively from the SMA, with the typical right hepatic artery arising from the hepatic trunk being absent.

  • Types and classification

    • The most widely cited schemes for hepatic arterial variants include the classifications of Michels classification and Hiatt classification. In Hiatt’s system, a replaced right hepatic artery from the SMA is a recognized pattern and is typically categorized separately from a normal right hepatic artery. These classifications help surgeons anticipate potential vascular variations before planned interventions.
    • The term “RRHA” is used to distinguish when the SMA provides the sole arterial supply to the right lobe, while an “accessory” right hepatic artery refers to an additional arterial source to the right lobe in the presence of a normal right hepatic artery from the proper hepatic artery.

  • Prevalence

    • Estimates of RRHA prevalence vary by imaging modality and population, but it commonly occurs in roughly 10–15% of individuals, with some series reporting higher or lower rates depending on methodology. The coexistence of an RRHA with other arterial variants is part of the broader spectrum of hepatic arterial anatomy.

Embryology

  • The hepatic arterial system develops from ventral splanchnic arteries that supply the foregut. During embryogenesis, persistence or regression of these primitive channels shapes the adult arterial pattern. When arterial connections from the SMA persist and the usual connection to the celiac trunk regresses or fails to establish a robust connection to the right hepatic territory, a replaced right hepatic artery from the SMA can result. This embryologic plasticity underlies the spectrum of hepatic arterial variants encountered in adults.

  • The arrangement is sufficiently common that it is routinely considered in anatomical texts and radiologic reports prior to procedures that risk injuring hepatic arterial supply.

Imaging and diagnosis

  • Detection methods

    • Preoperative contrast-enhanced imaging, especially CT angiography and MR angiography, is the primary means of identifying a RRHA. These modalities provide three-dimensional vascular maps that are invaluable for surgical planning.
    • Intraoperative assessment and arterial palpation or direct visualization may supplement preoperative imaging, particularly in complex resections or when imaging is inconclusive.

  • Implications for reporting

    • Radiology reports for hepatobiliary surgery patients typically note the presence of a RRHA, its course relative to the portal vein and bile ducts, and its relationship to the pancreatic head if relevant. Accurate labeling of RRHA helps prevent inadvertent vessel injury during procedures such as Pancreaticoduodenectomy.

Clinical significance and surgical implications

  • Implications for hepatobiliary surgery

    • The RRHA can be at risk during a range of operations, including right hepatectomy, cholecystectomy, pancreatic surgery, and liver transplantation. Injury to a RRHA without adequate collateral supply can lead to right lobe ischemia and postoperative complications.
    • When the RRHA serves as the sole inflow to the right lobe, surgeons may need to plan arterial-preserving techniques or, in the setting of oncologic resection, consider arterial reconstruction to maintain hepatic perfusion.

  • Relevance to specific procedures

    • Pancreaticoduodenectomy (Whipple procedure): The close adjacency of the SMA, pancreas, and hepatic arterial tree makes variant arteries like the RRHA particularly important. Preserving or reconstructing the RRHA may be necessary to maintain right lobe viability.
    • Right-sided liver resections and donor hepatectomies: Knowledge of RRHA influences graft design and donor safety. Arterial anatomy dictates the feasibility of certain graft configurations and may require reconstruction.
    • Liver transplantation: In living-donor or cadaveric transplantation, arterial variants including RRHA must be matched with donor anatomy and recipient needs. Vascular reconstruction strategies may be influenced by the presence of a replaced artery.

  • Relationship to biliary system

    • While the RRHA primarily concerns arterial supply, its course can be related to the biliary tract, and inadvertent injury can contribute to bile duct complications if the arterial blood supply to the biliary tree is compromised. Comprehensive preoperative planning aims to mitigate these risks.

Controversies and debates

  • Preoperative imaging versus selective imaging

    • Supporters of routine preoperative vascular mapping argue that universal CT or MR angiography reduces intraoperative surprises, lowers complication rates, and improves planning for major hepatobiliary operations. Critics point to costs, resource use, and the notion that imaging may not change management in all cases, advocating a more selective approach based on tumor type, planned extent of resection, and surgeon experience.
    • In practice, decision-making often balances patient risk, tumor characteristics, and institutional protocols, with many high-volume centers adopting routine vascular mapping for complex liver or pancreatic resections.

  • Arterial preservation versus reconstruction

    • Some centers emphasize arterial preservation when a RRHA is involved in oncologic resection, aiming to minimize ischemic risk to the liver. Others may proceed with resection and rely on collateral circulation or staged reconstruction, depending on the case and available expertise.
    • The debate intersects with broader themes in surgical strategy, including the trade-off between achieving oncologic clearance and maintaining regional hepatic perfusion, and it is influenced by advances in microvascular reconstruction and perioperative management.

  • Classification and reporting standards

    • While multiple classification schemes exist, there is ongoing discussion about standardizing terms and reporting to improve communication across specialties. Consistent reporting of arterial variants, including RRHA, is essential for multicenter studies and comparative outcomes.

See also