*2.3.1 Biliary variations in hepatocystic triangle important for gallbladder surgery*

The right and left hepatic duct mostly joins at the level of the porta hepatis; however, in some individuals, this connection may be more distal eventually resulting in the absence of the common hepatic duct and potentially endangering the right hepatic duct during the surgical intervention (**Figure 3A**) [3]. Accessory hepatic duct can drain into the cystic duct or it may be mistaken for the cystic duct, and therefore, the surgeon has to be careful where to ligate the cystic duct during the surgery to preserve its function (**Figure 3C** and **D**) [3]. A similar problem arises with the duplication of the cystic duct, which may drain into the right hepatic duct, and therefore in the case of the omission of such anomaly leads to a biliary leak (**Figure 3E**) [3].

**Figure 3.**

*Schematic image of biliary tract variations: A: distal union of the right and left hepatic duct resulting in the absence of CHD; B: accessory hepatic duct joining left hepatic duct; C: accessory hepatic duct joining distal cystic duct; D: accessory hepatic duct joining proximal cystic duct; E: accessory cystic duct joining right hepatic duct.*

#### *2.3.2 Arterial variations in hepatocystic triangle important for gallbladder surgery*

The right hepatic artery (RHA) after originating from the proper hepatic artery crosses the common hepatic duct posteriorly in 85% of cases and in 15% either RHA or its branches passes anteriorly [3]. For a short distance, RHA runs parallel to the cystic artery before turning upward towards the liver and therefore can be mistaken for the cystic artery [3]. The general rule for minimising such a mistake is that no artery in the Calot's triangle with a diameter of more than 0.3 cm will be a cystic artery [3]. The superior mesenteric artery may give rise to an aberrant right hepatic artery entering the hepatocystic triangle from below and potentially giving rise to the cystic artery in the triangle [3]. In addition to the origins of the cystic artery from the right hepatic artery, there are reports describing the origins from the left hepatic artery with the course anterior to the common hepatic duct, while origins from the common hepatic artery or gastroduodenal artery mean the entry of the cystic artery to the hepatocystic triangle from below [3].

## **3. Indication for surgical therapy of gallstone disease**

#### **3.1 Uncomplicated gallstone disease**

Individuals with the gallstone disease have in the majority of cases asymptomatic course mostly continuing throughout their lives and often are diagnosed only incidentally [4].

Therefore, asymptomatic patients do not require surgical intervention and we wait for the symptom appearance [4]. However, cholecystectomy is recommended for asymptomatic patients with an increased risk of gallbladder cancer, like those with gallstones larger than 3 cm, porcelain gallbladder, or with the presence of gallbladder adenomas [4, 5]. In addition, the surgical therapy is recommended in patients suffering from sickle cell disease and spherocytosis, if abdominal surgery is performed due to other concerns, to prevent the formation of pigment gallstones [4].

For patients, who are surgical candidates with uncomplicated gallstone disease with imaging confirmation of gallstones and symptomatic course mostly with the biliary colic, there is a recommendation for an elective surgical therapy [4]. Patients who present themselves to the emergency ward with the acute aggravation of the biliary colic are treated conservatively with planned surgical intervention after resolution of symptoms due to a lesser risk of complication in elective surgery compared to emergency surgery [4].
