Preoperative evaluation of accessory hepatic ducts by drip infusion cholangiography with CT

Laparoscopic cholecystectomy (LC) has become the gold standard procedure for patients with cholecystolithiasis or gallbladder polyps; however, the incidence of bile duct injuries during LC has been reported to be about 0.5–1.7% [1, 2]. Anatomical anomalies of the biliary tree are considered to be a risk factor for bile duct injuries, and it was previously reported that the frequency of bile duct injuries is higher in patients with bile duct anomalies than in patients without them [3]. Therefore, it is important to evaluate the anatomy of the biliary tree, especially those of the cystic duct and any accessory hepatic ducts, preoperatively. Usually, drip infusion cholangiography with computed tomography (DIC-CT) or magnetic resonance cholangiopancreatography (MRCP) is performed to evaluate choledocholithiasis and the anatomy of the biliary tree before LC in Japan.

It was reported that accessory hepatic ducts exhibit an incidence rate of 2–11% [1, 4‐7]; however, there are few reports about the drainage areas of accessory hepatic ducts.

The aims of this retrospective study are to investigate the incidence, type, and drainage area of accessory hepatic ducts using DIC-CT.

Of a total of 738 consecutive patients who underwent LC, DIC-CT was performed in 569 patients, MRCP was conducted in 94 patients, endoscopic retrograde cholangiography was carried out in 34 patients, cholangiography was performed using a percutaneous transhepatic gallbladder drainage tube in 3 patients, and no examination of the biliary tree was conducted in 38 patients. Of the 569 patients that underwent DIC-CT, 11 belonged to the poor study group.

Fifty (9%) of the 558 patients that did not belong to the poor study group had accessory hepatic ducts (Table 1). Type I, II, III, IV, and V accessory hepatic ducts were observed in 32 (64%) (Fig. 2), 3 (6%) (Fig. 3), 1 (2%) (Fig. 4), 11 (22%) (Fig. 5), and 3 patients (6%) (Figs. 6, 7), respectively. The accessory hepatic ducts were classified as the posterior branch type in 22 patients (44%) (Figs. 3, 5), the anterior branch type in 9 patients (18%) (Fig. 4), the combined posterior and anterior branch type in 16 patients (32%) (Fig. 2), the left-sided branch type in 2 patients (4%) (Fig. 6), and the caudate branch type in 1 patient (2%) (Fig. 7). Following the separation of the gallbladder from the liver bed, the cystic duct was clipped and divided to prevent bile duct injuries in the patients with type IV accessory hepatic ducts.

Although bile duct injuries occurred in 4 (0.7%) of the 569 patients that underwent LC, none of the patients with accessory hepatic ducts suffered bile duct injuries. All of the bile duct injuries were noticed during the operation, and primary repair of the injuries was performed via conversion to open laparotomy. Two patients underwent cholangioduodenostomy, and two patients underwent simple closure of their bile duct injuries. LC was converted to open cholecystectomy in 23 patients (4%) due to severe adhesion in 15 patients, bile duct injuries in 4 patients, uncontrolled bleeding in one patient, and other reasons in 3 patients. Conversion to open cholecystectomy was necessary in one of the 50 patients with accessory hepatic ducts due to severe adhesion.

DIC-CT or MRCP is usually performed preoperatively in patients who undergo cholecystectomy to evaluate choledocholithiasis and the anatomy of the biliary tree in Japan. Although MRCP is the most widely used non-invasive means of evaluating biliary disease, DIC-CT depicts small bile ducts (e.g., accessory hepatic ducts, the cystic duct, or the caudate branch) than MRCP [7, 8]. Because only 11 patients (1.9%) were classified in the poor study group in this study, DIC-CT is successful in assessing the biliary tree anatomy. Therefore, DIC-CT is performed routinely at our institution except in patients who exhibit adverse reactions to contrast media or severe thyroid disease. We consider that the radiation during DIC-CT does not affect the patient’s health because the radiation dose during DIC-CT is about 8 mGy. The side effects of meglumine iotroxate have been reported, however, severe side effects such as anaphylactic shock did not occur in this study.

The incidence of accessory hepatic ducts was reported to range from 2 to 11% in previous studies [1, 4‐7], whereas it was 9% in this study. The incidence rates of type I, II, III, IV, and V accessory hepatic ducts were previously reported to range from 35 to 66.7%, 2–19%, 0–21.6%, 13–25%, and 0–7.7%, respectively [1, 4‐7]. In this study, type I accessory hepatic ducts exhibited the highest frequency, followed by type IV ducts. Types II, III, and V were less common, as was found in previous studies. On the other hand, there have been few reports about the drainage areas of accessory hepatic ducts. It was reported that most accessory hepatic ducts (86.7–100%) are right posterior bile ducts [1, 6]. Hirao et al. [7] found that of 13 patients with accessory hepatic ducts 9 (69%) had posterior ducts, two had anterior ducts (15%), one had an anteroinferior branch (8%), and a caudate branch was seen in the remaining patient (8%). In our study, we investigated the drainage areas of accessory hepatic ducts in detail. Although the posterior branch type exhibited the highest incidence (44%), several other types of accessory hepatic ducts, such as the combined posterior and anterior branch type (32%), anterior branch type (18%), left-sided branch type (4%), and caudate branch type (2%) were also seen. This information is important not only for cholecystectomy, but also for surgery for cholangiocarcinoma [9, 10], pancreatic head tumors [11] and for transplant procedures involving living liver donors [12‐14].

The causes of bile duct injuries during LC can be divided into anatomical [3, 15], inflammatory [16], and technical factors. The critical view of safety [17] is the important technique for preventing bile duct injuries during LC. Several authors have reported that intraoperative cholangiography reduces bile duct injury [18, 19], on the other hand, it has been done that intraoperative cholangiography does not reduce bile duct injury [20], and that injuries to accessory hepatic ducts or anomalous cystic ducts cannot be prevented by intraoperative cholangiography because anomalous bile ducts sometimes cannot be found with intraoperative cholangiography [4]. It has been reported that fluorescence cholangiography is a safe and effective procedure that enables real-time visualization of the biliary tree, and this novel procedure may become standard practice in order to prevent bile duct injury [21]. In our study, all of the bile duct injuries occurred in patients with severe inflammatory adhesion due to chronic cholecystitis. Thus, even in patients with accessory hepatic ducts, precise preoperative diagnosis and the meticulous performance of surgical procedures might prevent bile duct injuries. Of the various types of accessory hepatic ducts, type I, II, III, and IV ducts, which were observed in 32 (5.7%), 3 (0.5%), 1 (0.2%), and 11 patients (2.0%), respectively in this study, are at risk of bile duct injuries during the Calot triangle dissection. Especially, type IV ducts carry the greatest risk of bile duct injuries [1, 5, 6]. Noji et al. [4] suggested that the installation of an endoscopic nasobiliary drainage tube prior to LC in cases involving predictable bile duct anomalies might reduce the incidence of complications, and Kurata et al. [6] did that bile duct injuries can be avoided by using a surgical technique that exposes the inner layer of the subserosal layer of the gallbladder wall. We consider that intraoperative fluorescence cholangiography may be useful procedure to avoid bile duct injuries when patients with type I, II, III, or IV accessory hepatic ducts have severe inflammatory adhesion due to chronic cholecystitis. Furthermore, we recommend the dome down technique, in which the cystic duct is divided following the separation of the gallbladder from the liver bed, to prevent bile duct injuries in patients with type IV accessory hepatic ducts. Type V accessory hepatic ducts do not usually cause problem during LC; however, surgeons should take special care to prevent injuries to accessory hepatic ducts in segment 2 (type V) in patients with true left-sided gallbladders [22].

There are a number of variants of the accessory hepatic duct. Surgeons should pay special attention to accessory hepatic ducts to prevent bile duct injuries during LC. Furthermore, the knowledge of the variations in accessory hepatic ducts is important for hepatobiliarypancreatic surgery.