Laparocopic Biliary Injuries (part one), classification and causes.

Introduction
Biliary injury is the most severe common complication of cholecystectomy.

It is always morbid, occasionally fatal, increases cost, and often results in litigation.

Bile duct injury has always been a risk of cholecystectomy but its incidence increased sharply when laparoscopic surgery for cholecystolithiasis was introduced.

• Not only has laparoscopic cholecystectomy led to more injuries, but certain types of injury, such as ductal lacerations, bile leaks, and aberrant duct injuries, are more common than they were previously.


• The causes of injury are becoming better understood and improved methods for preventing injury are available.


• When injury occurs, a high rate of permanent cure is possible using advanced techniques of reconstruction in specialized centers.

Classification of biliary injuries

Bismuth classified benign biliary strictures into five types based on the upper level of the stricture.

• This classification was used to stratify biliary injuries in the era of open cholecystectomy, but it became somewhat less useful as the injury pattern altered due to laparoscopic cholecystectomy.

In 1995, Steven M. Strasberg et al. introduced a classification that retained the essence of the Bismuth classification for major injuries, but broadened the classification to separately itemize injuries seen with increased frequency during laparoscopic cholecystectomy and this classification is based on anatomical location and on severity of injury and has found considerable acceptance. Other classification schemes not based on the Bismuth classification have been proposed by McMahon et al., Stewart and Way, and Schol et al.

Type A: bile leak from a minor duct retaining continuity with the common bile duct.

• These leaks are usually caused by a failure to adequately secure closure of the cystic duct or by an injury of a small bile duct in the liver bed.


• This type of biliary injury is the least serious, since major ducts are not involved and there is little chance of progression to a more serious form of injury.


• However, even these injuries can be quite morbid.


• They are usually lateral injuries to the biliary tract and therefore decreasing intrabiliary pressure by endoscopic sphincterotomy results in healing.

Types B and C: creation of a discontinuity of part of the biliary tree with occlusion (type B) or intraperitoneal leak (type C)

• These are end injuries which isolate a part of the biliary tree.


• They almost always result from injury to an aberrant right hepatic duct, although rarely an aberrant left ducts or a normally situated duct may be involved.


• About 2% of patients have an aberrant lowlying right duct which most commonly drains one or two segments of the right hemiliver.


• A key anatomical feature contributing to the likelihood of injury is that in some cases the cystic duct joins the aberrant duct, which then continues to join the main ductal system.


• The appearance of the junction of the aberrant duct with the hepatic duct may be identical to that of the junction of the cystic duct with the hepatic duct.


• As a result there is great potential for injury in these circumstances.
  When the injury is a ductal occlusion it is designated type B. When it is a transection without occlusion it is termed type C.


• The reason for the difference in classification is that presentation, management, and often prognosis are very different.

Occlusions are generally injuries of lesser severity.

• They are often asymptomatic, or if symptomatic may not cause symptoms such as cholangitis for months or years.


• The liver upstream from a type B injury atrophies and the remaining liver undergoes compensatory hyperplasia.

Transections without occlusion (type C) result in local intraperitoneal bile collections or bilious ascites and peritonitis.

• Type C injuries usually present in the early postoperative period and almost always require treatment.

Type D: lateral injury to major bile ducts

• D injuries are partial (<50%) transections of major bile ducts.


• When the transection involves >50% of the circumference of the duct, the injury should be considered an E type.


• Like the type A variant, they are lateral injuries and will often resolve after decompression by postoperative endoscopic sphincterotomy.


• Or if discovered at the time of surgery they may be corrected by simple suturing techniques and the placement of a t-tube.


• Type D injuries have the potential to evolve into more serious injuries, particularly if they are of thermal causation or associated with devascularization of the bile duct.


• Then they may progress to complete obstruction, that is a type E injury.


• Type D injuries may occur to other major ducts. Right hepatic duct injuries have been reported.


• Type C and type D injuries involving the right bile duct are very similar, but there are major therapeutic implications to complete transection (type C) versus lateral injury (type D).


• Inadvertent incision of the common bile duct instead of the cystic duct, when attempting to delineate ductal anatomy by operative cholangiography might be considered to be a type D injury.


• Cannulation of the bile duct, in order to protect it during abdominal surgery, is an accepted procedure and is not in itself considered a complication.

Type E: circumferential injury of major bile ducts (Bismuth class 1–5)

• These are circumferential injuries of major bile ducts.


• Sub classification into types E1 to E4 is based on the level of injury and, while type E5 is a combination of common hepatic duct and aberrant right duct injury.


• Type E injuries separate the hepatic parenchyma from the lower biliary tract, due to stenosis, simple occlusion, or transection.


• When occlusions or transections are present, resection of bile ducts may also have occurred.


• To classify the injury properly it must be stated which of these is present and if bile duct resection has occurred the length of excised duct should be given, for example “E2, simple total occlusion without resection” or “E3, 3-cm duct length excised, transection without proximal occlusion, distal occlusion present.” For purposes of repair the upper limit of injury is the key variable and this is given in the E type itself.

The incidence of laparoscopic biliary injury

• An increase in biliary injuries was an unforeseen accompaniment of laparoscopic cholecystectomy.


• The first indication of the problem was a sudden surge of referrals of biliary injuries to specialized hepatopancreaticobiliary units.


• To determine the true incidence of injury, large, accurate, representative studies were needed.


• Institutional or multi institutional studies, studies of fewer than several thousand cases, and studies with less than 100% reporting including mail surveys, fail to satisfy these conditions.


• Several excellent reports exist, including statewide evaluations from New York and Connecticut, a report from the armed services, and several from Europe.


• In all reports, an increase in the injury rate from 0.1% in the open era to 0.3 to 0.5% in the early laparoscopic era was noted.


• It is encouraging that two studies found that the injury rate is decreasing towards that in the open cholecystectomy era.


• All the early reports encompassed the period during which most surgeons were learning to perform the operation.


• As injury is more likely during the performance of the first fifty cholecystectomies, the injury rates reported in these studies are probably higher than current rates.


• Unfortunately, no study using reliable population techniques has defined the incidence in this decade and therefore it cannot be definitively stated whether injury rates remain above those before the introduction of laparoscopic cholecystectomy.


• However, based on available evidence, it seems that the incidence of the more serious type E injuries are moving towards rates seen in the open era but that type A to D injuries, which were rarely seen in the open era, are still more common today.

Risk factors for biliary injury Training and experience

• Early reports suggested that the high rate of injury was due mainly to inexperience in the procedure referred to as the “learning curve effect”.


• Unquestionably, experience did initially contribute to the high incidence of injury, but other factors are responsible for injury today.

Local operative risk factors

• As during open cholecystectomy, biliary injuries seem more likely to occur during difficult laparoscopic cholecystectomies.


• Russell, in a very large registry series from the State of Connecticut, reports that the incidence of injury when laparoscopic cholecystectomy is performed for acute cholecystitis (0.51%) is three time higher than that for elective laparoscopic cholecystectomy and twice as high as open cholecystectomy for acute cholecystitis.


• Thousand of patients are required to see this difference, and one should be wary of concluding that the procedure is as safe as elective cholecystectomy based on reports of a few hundred patients.


• Chronic inflammation with dense scarring, operative bleeding obscuring the field, or fat in the portal area are cited as contributing factors in 15 to 35% of injuries.


• Blood in the field hampers dissection more in laparoscopic than in open cholecystectomy, and gentle dissection is required, especially when inflammation is present, to avoid bleeding that then obscures vision.


• The role of obesity is difficult to evaluate, since it is so often present in patients with cholelithiasis.

Aberrant anatomy

• Aberrant anatomy is a well-described danger in biliary surgery.


• The aberrant right hepatic duct anomaly, referred to above under type B and type C injuries, is the most common anomaly associated with biliary injury.


• These injuries are probably under-reported since type B injuries may be asymptomatic.


• Isolated injuries to aberrant right ducts did occur before the advent of laparoscopic cholecystectomy, but such ducts appear to be particularly prone to injury during laparoscopic cholecystectomy.

Equipment

• Laparoscopic equipment must be well maintained.


• Thermal injuries to bile ducts or surrounding structures may occur due to focal loss of insulation on instruments used for cauterization.


• Also a charge may build up on laparoscopic instruments and cause arcing to surrounding structures.


• The incidence of such events must be extremely low, but specially shielded laparoscopic equipment and detectors are slowly becoming available to deal with the problem, although their use is not widespread.

Direct causes of laparoscopic biliary injury

• Biliary injury occurs either due to anatomical misidentification of the cystic duct or due to technical problems, especially the misuse of cautery.

Misidentification injuries

• Misidentification is the most common cause of serious injuries.

There are two scenarios.

In the first, the common duct is mistaken for the cystic duct, and is clipped and divided.

• To complete the excision of the gallbladder the bile ducts must be divided again.


• The type of injury produced varies from E1 to E4 and depends on the level of the second division of the biliary tree.


• Frequently, a “second cystic duct” or “accessory duct,” which is actually the common hepatic duct, is reported in the operative notes of these procedures, but just as often the second transection is not noted.


• High transections are probably associated with excessive traction on the gallbladder, an act which pulls the hepatic ducts down during transection of the biliary tree.


• Hepatic ducts may either be clipped or divided, resulting in either obstruction or bile leak.


• Injury of the bile duct is often associated with an injury to the right hepatic artery, with brisk bleeding that leads to conversion and diagnosis of biliary injury or simply to occlusion of the right hepatic duct.


• At the time of reconstruction there is often evidence of dissection on the left side of the common duct, even to the point of exposure of the portal vein.


• Sometimes one clip is placed on the cystic duct and the point of division is either the common duct or cystic duct.


• If the common duct is transected, bile drains from the cut end, sometimes leading to recognition of injury.


• However, equally often this is attributed, wishfully, to a second cystic duct and the full-blown injury evolves.


• The least harmful type of misidentification occurs when the cystic duct is divided, since if the injury is recognized by observation of bile in the field, the clip on the common bile duct may simply be removed.


• Bile leak will not occur if the cystic and common duct run in a common sheath and the clip is placed across both.


• Clip removal, balloon dilatation, or stenting of the clipped duct may occasionally resolve the injury even when the injury is recognized postoperatively but in other patients late stricture occurs after clip removal.

The second misidentification scenario leads to injury to an aberrant right hepatic duct, which is present in 2% of cases.

• The segment of the aberrant right hepatic duct, between where the cystic duct enters it and the point at which it joins the common hepatic, is thought to be the cystic duct.


• The misidentified segment is clipped and usually cut.


• In order to remove the gallbladder the aberrant duct must be cut again at a higher level.

Causes of misidentification injuries
The goal of dissection in laparoscopic cholecystectomy is positive identification of the cystic duct and artery as these are the structures to be divided. There are several methods used to identify the cystic duct –

1. intraoperative cholangiography,


2. the infundibular technique,


3. the critical view technique, and


4. identification by display of the cystic duct/common hepatic duct confluence to form the common bile duct.
   

The infundibular technique identifies the cystic duct by displaying the funnel-like (infundibulum = funnel) junction of the gallbladder and cystic duct.

• We have shown that the infundibular technique is prone to failure in the presence of severe acute or chronic infl ammation and when the cystic duct is hidden or effaced by a large stone, or hidden because of difficulty in retracting the gallbladder.


• These conditions tend to cause a visual deception when this technique is used.


• As a result, even when the technique is carried out properly, the common bile duct will be perceived as the cystic duct.


• This visual deception as a cause of injury in this operation has been focused in several reports .


• The approach to the problem by an analysis of operative notes came to the conclusion that a visual deception was most likely when the infundibular technique was used and the operative conditions listed above were present.
  


• Misidentification is also more common when adhesive bands tether the gallbladder to the common bile duct.


• Misidentification may lead to injury of the bile duct without division or clipping, since extensive dissection may cause devascularization especially if ductal arteries, thought to be the cystic artery, are divided.


• This type of injury may present later as a stricture.

Injuries due to technique

• The chief technical causes of laparoscopic ductal injury are failure to occlude the cystic duct securely, too deep a plane of dissection when taking the gallbladder off the liver bed, tenting injuries, and thermal injuries to the bile duct.


• The cystic duct is routinely occluded with clips.


• This method is less reliable than ligatures or suture ligatures, the standard methods of securing the cystic duct during open cholecystectomy.


• Retained stones in the bile duct may contribute to clip failure by raising biliary tract pressures, but the main cause is inappropriate use of clips instead of another occlusion device on a thick, rigid cystic duct.


• Clips may also “scissor” during application, resulting in faulty closure, or be loosened by subsequent dissection close to the clip.


• Injury to ducts in the liver bed is due to dissection in too deep a plane when excising the gallbladder.


• It usually occurs when the dissection is difficult such as when acute or severe chronic inflammation are present or when the gallbladder is intrahepatic.


• Tenting injury was well described in the open cholecystectomy era.


• There are few reports of this injury during laparoscopic cholecystectomy and it actually may be less common during laparoscopic cholecystectomy due to the excellent visualization of properly identified cystic ducts.


• In the tenting injury the junction of the common bile duct and hepatic bile duct is occluded when a clip is placed at the bottom end of the cystic duct while forcefully pulling up on the gallbladder.


• The tenting injury is more likely to occur when there is a parallel union of the cystic duct with the common bile duct, especially if ductal identification is attempted by dissection to the union of the cystic duct with the common hepatic duct.

Cautery-induced injuries are more likely to occur in the presence of severe inflammation, which may lead to the use of excessively high cautery settings to control hemorrhage.

• Misuse of cautery has led to some very serious bile duct injuries, characteristically type E injuries with loss of ductal tissue due to thermal necrosis.

Associated vascular injuries

• Vascular injuries may accompany ductal injuries, the commonest being injury to the right hepatic artery in association with an excisional injury of the common hepatic duct, due to the proximity of the artery to the duct.


• This association was noted by Meyers and his group in the early 1990s, and recent articles have expanded our knowledge of this complication.


• Vascular complications tend to be more common with higher levels of biliary injury.


• They are associated with a greater tendency to restricture, but this seems to be true only when bile ducts associated with vascular injuries are repaired in community hospitals rather than repaired after an interval in expert centers using the Hepp–Couinaud approach.


• There is a tendency to higher rates of mortality when an associated vascular injury has occurred.

Arterial injuries may involve the proper hepatic artery as well as the right hepatic artery, and portal vein thrombosis has also been reported.

• In severe vascular injuries the vascular component may become the predominant feature of the injury with necrosis of the intrahepatic biliary system, similar to that seen when the hepatic artery thromboses after liver transplantation, or even hepatic infarction.


• Infarction of the intrahepatic biliary tree requires transplantation, while hepatic infarction may lead to the need for hepatic resection or transplantation.


• Portal vein thrombosis may lead to cavernous transformation of the portal vein. This increases the difficulty of later repairs and may itself lead to bile duct compression.