Anatomical mapping of the biliary tree during laparoscopic cholecystectomy by using indocyanine green dye.

Background: Fluorescent cholangiography using intravenous indocyanine green (ICG) is a noninvasive technique that enables real-time intraoperative imaging of biliary anatomy. The objective of this study was to visualise the biliary anatomy in routine and complicated cases of laparoscopic cholecystectomy (LC).
Methods: This was a prospective observational study of patients undergoing LC for various indications. After obtaining consent, 5 mg/1 ml of ICG dye was administered intravenously in each patient, 2 h before the incision time. LC was performed by standard critical view of the safety technique. The biliary tree was visualised using near-infrared (NIR) view before clipping any structure. Intra-operative findings, visibility of ducts in the NIR view, conversion, adverse reactions to ICG and post-operative outcomes in all patients were recorded.
Results: Out of 43 patients undergoing LC, 24 had cholelithiasis, 10 had acute cholecystitis, 3 had chronic cholecystitis, 1 had mucocele of the gall bladder, 1 had gall bladder polyp and 4 cases had common bile duct (CBD) stone clearance with endoscopic retrograde cholangiopancreatography. Cystic duct (CD) and CBD were visualised in 100% of cases among all groups except for those with acute cholecystitis where CD and CBD were visualised in 90% and 80% of cases, respectively, and in chronic cholecystitis CD and CBD were visualised in 66.6% and 80% of patients, respectively. There was one elective conversion in the chronic cholecystitis group due to dense adhesions and non-progression. Only the CBD was visualised in this case. There were no cases of CBD injury or any allergic reactions to the dye. Conclusions: Fluorescent cholangiography during LC is a safe and non-invasive method, allowing superior anatomical visualisation of the biliary tree in comparison to simple laparoscopy. This method can correct misinterpretation errors and detect aberrant duct anatomy, thus increasing the confidence of the operating surgeon enabling safe dissection. This simple technique has the potential to become standard practice to avoid bile duct injury during LC.

INTRODUCTION

Laparoscopic cholecystectomy (LC) is the most commonly performed surgical procedure for cholelithiasis and is considered the gold standard technique. However, the biliary tree often shows variant anatomy and knowledge about anatomical variations is important to prevent complications during the cholecystectomy. Injury to the bile duct is among the complications of the LC, with an overall prevalence of 0.4%. It is also observed that the chances of bile duct injury increase in acute cholecystitis cases, which is up to 4%.[12] A patient with bile duct injury has to undergo additional procedures based on the type of injury, which affects his or her quality of life and also increases the expenditure, for which the operating surgeon might be held responsible.

Intra-operative cholangiography (IOC) is considered to be the standard procedure for biliary imaging,[3] which can help in preventing the common bile duct (CBD) injuries during the LC. Its routine use is debatable as IOC is a time-consuming procedure and the catheterization process involves the risk of injury to the bile duct. This intervention also carries the risk of radiation exposure to both the patient and the operation theatre staff. The cystic duct (CD) should be delineated before injecting the dye and this procedure may fail if there are dense adhesions in the cysto-hepatic triangle. It is believed that the disadvantages of IOC can be overcome with a non-invasive method. In this context, the present study aims to visualize the anatomy of the biliary tree by using indocyanine green (ICG) dye, followed by using the near-infrared (NIR) camera (at 823 nm) for the fluorescent documentation of biliary mapping, during the LC. The objectives are accurate delineation and safe clipping of CD.

MATERIALS AND METHODS

Patients

This was a prospective study of patients who underwent LC from September 2019 to March 2021. Inclusion criteria consisted of patients older than 15 years of age, patients with symptomatic gallstone disease, acute cholecystitis with or without empyema, perforation or gangrenous changes and also patients with choledocholithiasis and biliary pancreatitis. Pregnant women, nursing mothers, patients <15 years of age, patients with known liver disease and kidney disease, those with allergies to iodine or ICG, and patients with known or suspected gall bladder cancer were excluded from the study. All the patients underwent pre-operative blood investigations and radiological workup, which consisted of complete blood count, liver function tests, blood urea, serum creatinine, serum electrolytes, serum lipase, serum amylase and ultrasound of the abdomen. Magnetic resonance cholangiopancreatographywas done in patients with suspicion of CBD calculi. endoscopic retrograde cholangiopancreatography (ERCP) and stone clearance were done in patients with CBD calculi. These patients underwent LC either after 48–72 h or after 6 weeks post-procedure.

Written informed consent was obtained from all patients. All surgeries were conducted in the department of general surgery of our institution. Patient demographics, operative findings, post-operative course and outcomes were collected from patient records.

Indocyanine green dye

Initial experimental applications of ICG mainly focused on the dilutional methods of assessing cardiac perfusion and retinal angiography. ICG dye is a tricarbocyanine florescent dye with the peak emission at NIR light with a wavelength of 830 nm. It is administered through the intravenous route and basically, it binds to proteins. ICG is excreted exclusively by the liver in the bile secretion and it is possible to map the extrahepatic biliary tree by using the NIR laparoscopic camera at 830 nm with the help of this dye.[4] ICG is safely used and considered as being pharmacologically inert and not metabolised.

Near infrared laparoscopic camera

The NIR camera used in this study is the STYKER 1588 laparoscopy system (Stryker Endoscopy, San Jose, CA). This imaging system has its own infrared light source, light cables, camera control unit, 0 and 30 degree laparoscopes. This camera detects light of 823 nm wavelength. By pressing a button on the camera head, the image on the display system can be toggled between NIR mode and visible light. All the structures with ICG dye are visualised in green against the black background in the NIR mode.

Procedure

The ICG dye (Aurogreen, Aurolab, Madurai, India) consists of 25 mg of dye in a powdered form, with 5 ml distilled water for reconstitution. The dye was reconstituted and 5 mg i.e. 1 ml of reconstituted ICG was given to the patients intravenously 2 h before the incision time of LC. LC was performed according to standard surgical techniques. All the procedures were performed by senior consultant surgeons of our institution. The critical view of safety technique with Calot's first approach was the technique most commonly employed.[5] However, in difficult cases, the fundus first approach was used. NIR visualization [Figure 1] was done at first before the start of dissection and then as required by the operating surgeon. After completion of dissection, the critical view of safety [Figure 2] was displayed and the NIR mode was turned on. Visualisation of the CD and CBD was done before clipping any structure. Following this, the procedure was completed by dividing the clipped cystic artery and CD, haemostasis and specimen retrieval through the epigastric port. The procedure was recorded and the video was reviewed by the consultant surgeons.

Figure 1

Showing CD and gall bladder in (a) normal mode and (b) near-infrared mode

Figure 2

Critical view of safety in (a) normal mode and (b) near infrared mode

RESULTS

A total of 43 LCs were performed in our institution by fluorescence biliary mapping from September 2019 to March 2021. These 43 patients include 19 males and 24 females with a mean age of 41.67 years. The patient characteristics of this study including the ASA score are given in Table 1.

Table 1

Patient characteristics of this study (n = 43)

Patients description	Frequency
Male: female	19:24
Mean age	41.67
ASA score 1	26
ASA score 2	16
ASA score 3	1

ASA: American Society of Anesthesiologists

Patients were categorised into six groups [Table 2] based on the history and intra-operative findings. Out of 43 cases, 24 were symptomatic cholelithiasis, 10 were acute cholecystitis with inflamed gall bladder and early adhesions, 3 were chronic cholecystitis with contracted gall bladders, 1 was mucocele of the gall bladder, 1 was gall bladder polyp and 4 cases presented with CBD calculi who underwent ERCP and CBD stone removal before the LC and were included in post-ERCP group. There were no cases of gangrenous gall bladder or perforation of the gall bladder. None of the patients presented with biliary pancreatitis.

Table 2

Indications of cholecystectomy in the present study (n=43)

Indication	Number of cases
Symptomatic gall stone disease	24
Acute cholecystitis	10
Chronic cholecystitis	3
Post-ERCP	4
Mucocele gall bladder	1
Gall bladder polyp	1
Perforated gall bladder	0
Gangrenous gall bladder	0

ERCP: Endoscopic retrograde cholangiopancreatography

Each group was individually assessed for the visualisation of CD and CBD both before and after the complete dissection at calot's triangle in the NIR view [Figure 1] before clipping of the CD. CD was visualised before the dissection in 60.4% of cases and in 95.3% of cases before clipping, whereas, CBD was noted in 53.4% of cases before dissection and in 93% of cases after the dissection at Calot's triangle [Table 3].

Table 3

Frequency of overall biliary visualization in this study

Ducts	Before dissection (%)	After dissection (%)
CD	26 (60.4)	41 (95.3)
CBD	23 (53.4)	40 (93)

CD: Cystic duct, CBD: Common bile duct

In symptomatic gall stone disease group, mucocele, gall bladder polyp and post-ERCP group CD and CBD were visualised in 100% of patients [Table 4] before clipping whereas, in acute cholecystitis group CD and CBD is visualised in 90% and 80% of cases, respectively, before clipping. In the chronic cholecystitis group, CD and CBD are visualised in 66.6% and 80% of cases, respectively, before clipping [Table 4].

Table 4

Frequency of biliary visualization by pathology

Group	CD		CBD
	Before dissection (%)	After dissection (%)	Before dissection (%)	After dissection (%)
Symptomatic cholelithiasis (24)	19 (79.1)	24 (100)	18 (75)	24 (100)
Acute cholecystitis (10)	2 (20)	9 (90)	1 (10)	8 (80)
Chronic cholecystitis (3)	1 (33.3)	2 (66.6)	1 (33.3)	2 (80)
Mucocele gall bladder (1)	1 (100)	0	1 (100)	0
Gall bladder polyp (1)	1 (100)	1 (100)	1 (100)	1 (100)
Post-ERCP (4)	3 (75)	4 (100)	2 (50)	4 (100)

CD: Cystic duct, CBD: Common bile duct, ERCP: Endoscopic retrograde cholangiopancreatography

There was one elective conversion in a patient with chronic cholecystitis. The gallbladder was contracted with dense adhesions to the omentum. There was dense fibrosis in the Calot's triangle (frozen Calot's triangle) with non-visualisation of CD and cystic artery [Figure 3]. A tubular structure could be made out which showed faint fluorescence in the NIR view [Figure 3]. A decision was made in favour of elective conversion due to non-progression of dissection for around 30 min. This structure was later identified as CBD. No anomalies of the anatomy were noted in the current group [Table 5]. None of the patients developed allergic reactions to ICG. There were no bile duct injuries or any kind of post-operative complications in the current study group. No mortality was noted [Table 5].

Figure 3

Showing (a) frozen Calot's triangle with ambiguous anatomy, (b) near infrared mode image showing a duct with uncertain anatomy and non-progression for more than 30 min hence this case was converted to open procedure

Table 5

Patient outcomes in this study (n=1)

Outcome	Frequency
Open conversion	1 (2.3%)
Bile duct injury	0
Allergies to ICG	0
Biliary pancreatitis	0
Retained CBD stone	0
Mortality	0

ICG: Indocyanine green, CBD: Common bile duct

DISCUSSION

LC was performed for the first time in 1987 and has now dramatically replaced the open cholecystectomy procedure. LC is preferred over the open cholecystectomy, because of its lesser hospital stay, lesser post-operative pain and morbidity.[6] The problems faced during a difficult LC may include difficulty in achieving the pneumo-peritoneum, releasing the adhesions, dissecting the structures of the extrahepatic biliary apparatus and its anatomical variations.[7] Cholecystectomy can become difficult due to the obscure biliary anatomy due to the inflammation and prior operative exposure. A difficult gallbladder can also be due to rare causes like cirrhosis of the liver and Mirizzi syndrome. The risk of CBD injury following the LC for cholelithiasis without acute inflammation is about 0.4%.[8] Bile duct injury puts the patient at risk for additional procedures and increased health-care costs depending on the magnitude of the injury. The purpose of minimally invasive surgery is defeated, patient quality of life impaired and ensuing malpractice claims can lead to significant physician distress.[9]

Misinterpretation of biliary anatomy is considered as the commonest cause of bile duct injury where the CBD is mistaken for the CD and partially resected, resulting in the classic laparoscopic bile duct injury.[1011] This implies that major duct injuries can occur even in routine cases. Since the introduction of LC, multiple strategies to reduce bile duct injury have been proposed. According to Strasberg et al., proper dissection has to be performed at the cysto-hepatic triangle and a critical view of safety is necessary before clipping any tubular structure.[5] In patients, where the anatomy of the biliary tree is not clear and the critical view of safety is not accomplished, the LC needs to be changed to laparotomy and this happens in about 5% of patients.[12]

Fluorescent cholangiography using an ICG-NIR camera has possible benefits in comparison to the routine IOC. The ICG method prevents iatrogenic injury to the bile duct during the placement of cannula while injecting the contrast to get the imaging of the biliary tree. The biliary mapping using ICG dye is a noninvasive method as the dye is injected through the intravenous route and act in real-time enabling the surgeon to view the biliary map during the operative procedure, without the aid of radiology. The fluorescence cholangiogram is safe, as there is no radiation exposure, and the risk of allergic reaction is negligible with the ICG.[13] NIR cholangiography does not require C-arm and other radiological assistance. This method allows the surgeon to toggle to NIR view at any point in surgery and any number of times making it surgeon friendly.[1415]

ICG remains the only fluorophore to be used in humans, due to its established safety and availability.[1415] Visualisation of the ducts in the NIR view has the potential to re orient the surgeon to the correct anatomy, provided the biliary tree is seen well in every routine case. Anomalies of the biliary tree, although rare become immediately apparent, making the surgeon dissect safely and with confidence.

The present study observed that ICG fluorescence is decreased in complicated cases mainly pertaining to the acute cholecystitis group [Figure 4], where the CD is identified in only 20% of cases, before the dissection and in 90% of cases after the dissection at the Calot's triangle. The results of the current study are in consistent with the previous pioneer studies. A study by Ishizawa et al.[13] has visualised the CD in 100% of patients and CBD in 96.2% of patients. In a study by Kaneko et al.[16] in 28 patients for biliary mapping by using the ICG, CD was visualised in 92.9% of the patients. A study by Spinoglio et al.[17] on biliary mapping by using the ICG in single incision robotic cholecystectomy, showed similar results, where CD was visualised in 93% of patients. The acute cholecystitis group did not exhibit the bile ducts clearly, even with the ICG-NIR in this study. This may be because of the adhesions and oedema, due to the process of acute inflammation.[418] The depth of penetration of ICG is narrow (±10 mm) and can be insufficient to visualise the bile ducts, when there is a thickened tissue around it. The fluorescence decreases in the tissue oedema and when the Calot's triangle is not exposed properly. However, the fluorescence cholangiogram can still be helpful in guiding the biliary map and the CD can be securely reached.[13]

Figure 4

Decreased indocyanine green fluorescence in acute cholecystitis

The present study did not include the comparison of the LC with the study group of robotic surgeries. This is due to increased costs of robotic cholecystectomy and non-availability of the firefly robotic platform in our institution. The other limitation of ICG cholangiography is that it cannot be used in the case of choledocholithiasis. The CBD calculi were extracted by the ERCP before the cholecystectomy in this present study. We did not encounter any case of the variant anatomy of the extrahepatic biliary tree. This was because of the small sample size. We believe that further study with a large number of patients is required to evaluate NIR cholangiography in more challenging situations like empyema, gangrenous and perforated gallbladders and in patients with Mirizzi syndrome.

CONCLUSIONS

Fluorescent cholangiography during LC is a safe and non-invasive method, allowing superior anatomical visualisation of the biliary tree in comparison to simple laparoscopy. This method can correct misinterpretation errors and detect aberrant duct anatomy, thus increasing the confidence of the operating surgeon enabling safe dissection. This simple technique has the potential to become standard practice to avoid bile duct injury during LC.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.