**3. Liver functional anatomy – Couinaud classification system**

The Couinaud classification is the most widely used classification for functional liver anatomy [11]. It divides the liver into eight functionally independent segments, which have their own individual vascular supply and biliary drainage (**Figure 1**) [12]. A branch of the portal vein, hepatic artery, and bile duct are centrally located in each segment, while the vascular outflow to hepatic veins is located peripherally. Due to their functional independence, each segment can be safely resected without damaging the remaining liver parenchyma [13]. Nevertheless, the Couinaud classification system does not take into account the influence of vascular variations and does not provide liver surface landmarks for segment separation [14].

**39**

**Table 1.**

*Damage Control Surgery for Liver Trauma DOI: http://dx.doi.org/10.5772/intechopen.94109*

lateral to the right hepatic vein.

**4. Liver trauma classification**

**AAST grade Injury description**

I Subcapsular hematoma <10% of surface

diameter

*Advance one grade for multiple injuries up to grade III.*

injury (**Table 2**) [2, 20].

The liver segments are divided by portal vein branches and hepatic veins and are numbered clockwise [12]. The portal vein bifurcates at hepatic hilum into the left and right branches, which separate the liver into upper and lower segments. The right and left lobes are divided by middle hepatic vein, which runs along the Cantlie's line from the inferior vena cava to the gallbladder fossa [15] Furthermore, the right hepatic vein divides the right lobe into anterior and posterior segments and

The Caudate lobe (segment 1) is located posteriorly and often drains directly to inferior vena cava, while it can be supplied by both the right and the left portal vein branches, while segments II (superiorly) and III (inferiorly) are located medial to the left hepatic vein [16]. Segment IV (quadrate lobe) is located between the left and middle hepatic veins and is further divided by Bismuth into IVa (superiorly) and IVb (inferiorly) [17]. The anterior segments of the right hemiliver, V (inferiorly) and VIII (superiorly) lie between the middle and right hepatic veins, while the posterior right hemiliver segments, VI (inferiorly) and VII (superiorly), are located

The American Association for the Surgery of Trauma (AAST) grading scale is widely utilized for the classification of liver injury severity (**Table 1**) [18, 19]. However, it does not take into consideration the hemodynamic status of patients and the associated injuries. Thus, the World Society of Emergency Surgery (WSES) proposed a novel classification for the proper management of hepatic injuries involving AAST grade (1994 revision), hemodynamic stability, and mechanism of

Minor (WSES grade I) and moderate (WSES grade II) liver injuries concern hemodynamically stable patients after either blunt or penetrating trauma with AAST grade I-II or III lesions, respectively. Severe hepatic injuries include

Parenchymal laceration or capsular tear <1 cm depth

Parenchymal laceration >3 cm in depth

IV Parenchymal disruption 25–75% of hepatic lobe

V Parenchymal disruption >75% of hepatic lobe

II Subcapsular hematoma 10–50% of surface area; intraparenchymal hematoma, <10 cm

Any liver vascular injury or active bleeding contained within liver parenchyma

Active bleeding extending beyond the liver parenchyma into the peritoneum

Juxtahepatic venous injury including retroheaptic vena cava and major hepatic veins

Parenchymal laceration 1–3 cm in depth or < 10 cm in length III Subcapsular hematoma >50% of surface area or expanding; ruptured subcapsular or parenchymal hematoma; intraparenchymal hematoma >10 cm in diameter

*Grade is based on highest grade assessment made during imaging, intraoperatively or pathologic specimen.*

*The American Association for the Surgery of Trauma (AAST) liver injury scale (2018 revision).*

left hepatic vein divides the left lobe into medial and lateral parts.

**Figure 1.** *Liver functional anatomy – Couinaud classification system.*

#### *Damage Control Surgery for Liver Trauma DOI: http://dx.doi.org/10.5772/intechopen.94109*

*Trauma and Emergency Surgery - The Role of Damage Control Surgery*

this setting.

**2. Liver anatomy**

In this chapter, we aimed to describe the classification and appropriate investigations of liver injuries and elaborate on the use of damage control surgery (DCS) in

The liver is a wedge-shaped abdominal organ and is located in the right hypochondrium and epigastrium and may extend into the left hypochondrium [9, 10]. It is covered by fibrous Glisson's capsule and is attached to the surrounding structures and the abdominal wall by several ligaments (falciform, coronary, triangular, hepatoduodenal and hepatogastric ligaments). It is divided into two lobes (right and left) by the falciform ligament, while two "accessory" lobes, the caudate and quadrate lobe, arise from the right lobe. The liver has unique double blood supply from the proper hepatic artery (25%) and portal vein (75%). Venous drainage is achieved through hepatic veins (right, middle, left) to the inferior vena cava.

The Couinaud classification is the most widely used classification for functional liver anatomy [11]. It divides the liver into eight functionally independent segments, which have their own individual vascular supply and biliary drainage (**Figure 1**) [12]. A branch of the portal vein, hepatic artery, and bile duct are centrally located in each segment, while the vascular outflow to hepatic veins is located peripherally. Due to their functional independence, each segment can be safely resected without damaging the remaining liver parenchyma [13]. Nevertheless, the Couinaud classification system does not take into account the influence of vascular variations and

**3. Liver functional anatomy – Couinaud classification system**

does not provide liver surface landmarks for segment separation [14].

**38**

**Figure 1.**

*Liver functional anatomy – Couinaud classification system.*

The liver segments are divided by portal vein branches and hepatic veins and are numbered clockwise [12]. The portal vein bifurcates at hepatic hilum into the left and right branches, which separate the liver into upper and lower segments. The right and left lobes are divided by middle hepatic vein, which runs along the Cantlie's line from the inferior vena cava to the gallbladder fossa [15] Furthermore, the right hepatic vein divides the right lobe into anterior and posterior segments and left hepatic vein divides the left lobe into medial and lateral parts.

The Caudate lobe (segment 1) is located posteriorly and often drains directly to inferior vena cava, while it can be supplied by both the right and the left portal vein branches, while segments II (superiorly) and III (inferiorly) are located medial to the left hepatic vein [16]. Segment IV (quadrate lobe) is located between the left and middle hepatic veins and is further divided by Bismuth into IVa (superiorly) and IVb (inferiorly) [17]. The anterior segments of the right hemiliver, V (inferiorly) and VIII (superiorly) lie between the middle and right hepatic veins, while the posterior right hemiliver segments, VI (inferiorly) and VII (superiorly), are located lateral to the right hepatic vein.
