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E1989. Liver Anatomy Revisited: Variants and Their Clinical Significance
Authors
  1. Woon Tian Kai; Changi General Hospital
  2. Karen Fernandes; Changi General Hospital
  3. Ranu Taneja; Changi General Hospital
Background
Liver is a vital organ, often affected by pathology. A sound knowledge of hepatic anatomy and commonly encountered variants and their clinical significance is imperative to enable an accurate diagnosis and management of hepatic pathology. This exhibit aims to briefly discuss hepatic anatomy, common anatomic variants and their clinical significance.

Educational Goals / Teaching Points
1. To review salient features of hepatic lobar and segmental anatomy. 2. Familiarize with common anatomic variants. 3. Understand their clinical significance.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Hepatic anatomy can be described as morphological or functional. Morphological anatomy has been mostly replaced by functional anatomy, based largely on the work of Claude Couinaud [1], who divided the liver into 8 segments (I-VIII), each of which is an independent functional unit with its own hepatic arterial and portal venous supply and biliary drainage. This system has gained widespread acceptance as it facilitates lesion localization which can be adapted for surgical resection. Segment IV is subdivided into IVa and IVb subsegments [2]. Division of the liver into right and left lobes also follows a similar functional basis of vascular supply and biliary drainage. There are three major fissures which are constant anatomic features. The oblique fissure or fissure for the gallbladder lies in the inferior part of an imaginary line, first described by Cantlie, extends from gallbladder fossa to the junction of middle hepatic vein and inferior vena cava and divides the liver into right and left lobes. The fissure for ligamentum teres separates the left lobe into lateral and medial segments. The fissure for ligamentum venosum separates the caudate lobe from the more anterior medial and lateral segments of the left lobe. Accessory fissures [3], unlike the major fissures, are mostly limited to superior aspect of liver near the diaphragmatic dome. However, they may extend deeply into the liver substance creating pseudo lesions. Accessory liver lobes are defined as supernumerary lobes, composed of normal liver parenchyma in continuity with liver, in contrast to ectopic liver lobes that have no anatomical continuity with the liver. They are most often located in the right liver, attached by a pedicle containing vessels and biliary ducts. They can be sessile or pedunculated. “Riedel’s lobe” is the most well-known type of accessory liver lobe. Other anatomic variants such as “sliver of liver”, also known as “Beaver tail” where the left lobe extends laterally to contact and enclose the spleen [4], and “Papillary process” which is the inferior-medial extension of the caudate lobe [5] may also be encountered and cause diagnostic errors if not correctly identified.

Conclusion
Knowledge of hepatic anatomy and variants is imperative to guide surgical management and avoid diagnostic errors.