Choledochoscopy: An update

Table 1 Technical specifications of commonly discussed choledochoscopes

Type of choledochoscope	Fibreoptic or digital-based imaging systems1	Outer diameter (mm)	Accessory working channel diameter (mm)	Tip deflections
Percutaneous
CHF-CB30 L/S (Olympus Medical Systems, Tokyo, Japan)[13]	Digital	2.8	1.2	2-way (up-down)
Peroral – dual-operator
Mother-baby[4]	Fibreoptic	“Mother”: 12.6 mm “Baby”: 2.8–3.4 mm	0.8 – 1.2	2-way (up-down)
Short-access-mother-baby (Karl Storz, Tuttlingen, Germany)[4]	Fibreoptic	“Mother”: 12.6 mm “Baby”: 3.4 mm	1.5	2-way (up-down)
Videocholangioscope (CHF-B290; Olympus Medical Systems, Tokyo, Japan )[6]	Digital	3.3	1.3	2-way (up-down)
Peroral – Single-Operator
SpyGlass Legacy 2007 (Boston Scientific Corporation, Natick, MA, United States)[5]	Fibreoptic	3.3	1.2	4-way (up-down, left-right)
SpyGlass Direct Visualisation 2015 (Boston Scientific Corporation, Natick, MA, United States)[5]	Digital	3.6	1.2	4-way (up-down, left-right)
SpyGlass Direct Visualisation II 2018 (Boston Scientific Corporation, Natick, MA, United States)	Digital	Data has not been published yet
Direct peroral choledochoscopy using variety of ultra-thin endoscopes[5]	Digital	5.0 – 5.9	2.0	4-way (up-down, left-right)

Fibreoptic and digital catheters differ in the modality used to illuminate, acquire and transmit endoscopic images back to the camera. Fibreoptic catheters utlitise multiple individual fibre-optic bundles to reflect light off cable walls and into a camera. Digital catheters use imaging chips to convert reflected light into a digital signal, to produce a higher resolution digital image.

Table 2 Types of choledochoscopy

Type of choledochoscopy	Advantages	Disadvantages
Peroral (endoscopic)	Natural orifice	(1) Technical expertise; (2) Sedation or anesthesia; and (3) Not possible in patients with previous gastric resections or Roux-en-Y gastric bypass
Percutaneous transhepatic (interventional radiology)	(1) Shorter scope length; (2) Repeated with ease; and (3) Therapeutic interventions	(1) Need dilated intra-hepatic ducts; and (2) Risk of bleeding, bile leak, tumor seeding, biliary fistula and skin excoriation
Percutaneous transenteric via access loop (interventional radiology, surgical)	(1) Shorter scope length; (2) Repeated with ease; (3)Therapeutic interventions; (4) Ductal dilatation not necessary; and (5) In patients with RPC	(1) Previous access loop creation; and (2) Risk of small bowel injury, peritonitis, biliary fistula and skin excoriation
Intra-operative transcystic (surgical)	(1) Avoid CBD incision; (2) Therapeutic interventions; (3) Can document CBD clearance; and (4) It can be done laparoscopically	(1) The spiral valve of Heister; (2) Anatomy of the cystic duct; (3) Size of the cystic duct; (4) Need thin scopes (3 mm); (5) Technical expertise; and (6) Risks of bleeding, bile leak
Intra-operative transcholedochal (surgical)	Most direct access	(1) Need dilated extra-hepatic biliary system; (2) Risk of bleeding, bile leak; (3) Can put an internal stent; and (4) Can put T tube

RPC: Recurrent pyogenic cholangitis; CBD: Common bile duct.

Table 3 Diagnostic and therapeutic indications for choledochoscopy

Diagnostic indications	Therapeutic indications
Visual impression and visually-guided biopsies of: (1) Indeterminate biliary strictures (IBS); (2) Dominant strictures in primary sclerosing cholangitis (PSC); and (3) IgG4-related sclerosing cholangitis (IgG4-SC)	Stone fragmentation: (1) Electrohydraulic lithotripsy (EHL); and (2) Laser lithotripsy (LL)
Precise preoperative mapping of the extent of tumor involvement in CCA	Ablative therapies in cholangiocarcinoma (CCA): (1) Radiofrequency ablation; (2) Photodynamic therapy; (3) Nd:YAG laser ablation; and (4) Argon plasma coagulation
Choledochal cysts	Cystic duct stent placement
Intraductal papillary neoplasms of the bile duct	Guidewire passage through strictures, surgically altered anatomy
Cholangioadenoma	Resection of ductal masses
Biliary papillomatosis	Retrieval of migrated ductal stents
Eosinophilic cholangitis	Gallbladder stenting and drainage
Biliary varices
Right Hepatic Artery Syndrome
Congenital pancreaticobiliary maljunction
Post-liver transplant ductal ischemia
Tissue sampling and visual evaluation for infections: (1) Cytomegalovirus; and (2) HIV
Evaluation of intrahepatic biliary tracts during minimally invasive surgery

HIV: Human immunodeficiency virus.