The true incidence of Mirizzi syndrome is unknown, as most of the cases are diagnosed in symptomatic patients undergoing biliary surgery, while asymptomatic cases may go undetected [3]. Most of the large patient series estimate the incidence of types I and II Mirizzi syndrome between 0.05 and 2.7% among patients with symptomatic gallstone disease in western developed countries [8, 24]. However, in Asia, Central and South America the incidence of Mirizzi syndrome is higher (4.7–5.7% of symptomatic gallstone disease) [6, 11, 12]. Mirizzi syndrome is more frequent in women than men with mean age of presentation 44–68 years (range 22–95 years) [4, 11, 17]. The incidence of type II Mirizzi syndrome is estimated in 0.1–0.5% of all patients submitted to surgery for symptomatic gallstones [3]. To the best of our knowledge, the incidence of type II Mirizzi syndrome in patients undergoing LCBDE for proven or suspected choledocholithiasis is not known. In our series of laparoscopic CBD exploration, the incidence of type II Mirizzi syndrome was 2.6%. The probability of an unsuspecting surgeon discovering type II Mirizzi syndrome intra-operatively during cholecystectomy is about 1 per 1250–2500 cases [3, 12]. In the UK, national guidelines advocate LCBDE at the time of laparoscopic cholecystectomy for the management of choledocholithiasis and concomitant gallstones [25]. As LCBDE becomes more widely adopted, surgeons should be aware that approximately 1 in 40 cases of LCBDE may result in uncovering type II Mirizzi syndrome intra-operatively.

There is an increased incidence of gallbladder cancer in Mirizzi syndrome compared with isolated cholelithiasis [7]. Gallbladder carcinoma has been associated with various degrees of Mirizzi syndrome [6]. Six to 24% of patients diagnosed pre-operatively with Mirizzi syndrome (mainly type II) are associated with gallbladder cancer. Patients with Mirizzi syndrome and biliary-enteric fistulas associated with gallbladder cancer have been reported. The main risk factors for gallbladder cancer are longstanding gallstone disease and stasis, which are also present in Mirizzi syndrome [5, 6, 13, 17]. There are no clinical features that help differentiate between a Mirizzi syndrome and a gallbladder cancer. Levels of CA 19-9 are highly elevated in gallbladder cancer (> 800 UI/mL), while they are only moderately elevated in benign disease associated with obstruction of the CBD. This could help to distinguish between them. When suspected pre-operatively, patients should undergo extensive studies including CT and MRCP [6]. One patient (9%) was diagnosed with gallbladder cancer within our series, who underwent further resection of the CBD and hepatectomy.

Pre-operative diagnosis of Mirizzi syndrome is challenging because of the absence of pathognomonic signs and symptoms, and low sensitivity rates of imaging tests. It is only achieved in 8–62.5% of cases [6]. In our series the preoperative diagnosis rate was 27%. ERCP has the highest sensitivity for the diagnosis of Mirizzi syndrome, ranging between 55 and 90% [6, 8, 13, 26]. It is considered a gold standard diagnostic tool, as it defines the cause, level and extent of biliary obstruction, as well as ductal abnormalities, including fistula [14, 18]. In our series four patients underwent pre-operative ERCP, none of which were diagnostic of Mirizzi syndrome. This may have been due to incomplete assessment of the CBD as there was difficulty in cannulating, clearing or imaging the CBD. Ultrasonography is the most commonly used imaging procedure in the diagnosis of gallstones. The sensitivity of US for the diagnosis of Mirizzi syndrome ranges 8.3–62.7% [6, 8, 13, 26]. However, in our series, none of the pre-operative US scans performed yielded a positive diagnosis. MRCP is commonly used as it is non invasive and has a high sensitivity, similar to ERCP (50–90%) [6, 26]. MRCP also delineates the cause, level and extent of biliary obstruction, as well as ductal abnormalities, including fistula [14]. In our series MRCP was the pre-operative diagnostic tool with highest sensitivity (50%). CT scan is useful in differentiating Mirizzi syndrome from a malignancy, especially when a cholecystobiliary fistula is present [14]. Pre-operative diagnosis improves outcomes of surgery, allowing better planning [5, 6, 8, 27–29] and referral to the appropriate surgeon. If pre-operative diagnosis is not achieved, intra-operative recognition and proper management are essential to improve outcomes, reduce morbidity (up to 17% bile duct injury) and mortality [5, 13]. Furthermore, the intra-operative diagnosis of type II Mirizzi syndrome is challenging due to two main reasons. Firstly, Mirizzi syndrome implies longstanding chronically inflamed tissue that is difficult to manipulate and dissect. As a consequence, the gallbladder is fibrosed and adhered to the bile duct making visualization of the anatomy of the fistula and bile duct difficult [6]. Secondly, there is no standard measure to establish the difference between a dilated cystic duct and type II Mirizzi syndrome (as a consequence of longstanding impacted stones that erode into the CBD) if a transinfundibular approach of the fistula is chosen. Perhaps a dilated cystic duct is the initial stage of an evolving cholecysto-biliary fistula. This is demonstrated in our series by the last two cases (cases 10 and 11) where the stone was impacted within the CBD at the site of the junction with the cystic duct (Fig. 6). This is in comparison with the complete destruction of the CBD between the proximal and distal duct in case 8 which was repaired over a T-tube (Fig. 3).

There is no standard treatment for Mirizzi syndrome. Treatment is often dependent on the available surgical expertise and intra-operative findings [5, 12, 29] but ultimately aims to reconstruct the anatomy by recruiting the infundibular part of the fistula. The traditional approach for type II Mirizzi syndrome included a subtotal cholecystectomy leaving a 10 mm flap of gallbladder around the fistula for the reconstruction of the destroyed bile duct protected by a T-Tube to avoid post-operative strictures or bile leakages. In cases with large defects (> 50% of the circumference of the CBD) when the surrounding tissues cannot be recruited to reconstruct the CBD bilioenteric anastomosis may be required [3, 5, 28] (Fig. 3). Moreover, some authors have reported successful treatment of complex bile duct stones in selected patients with and without Mirizzi syndrome using peroral cholangioscopy-directed lithotripsy. However, the rate of stone recurrence was high (16%) [13]. We described the TIA for accessing the bile duct in cases of a frozen hilum secondary to severe inflammation and/or fibrosis [12]. Chuang et al. described a similar approached to the bile duct but named it differently (transfistulous approach) [17]. As demonstrated by the last two cases in our series, we believe that a TIA or trans-infundibulo-fistulous approach (TIFA) augmented with the LABEL technique (when necessary) can avoid a fistulotomy or choledochotomy. Through an infundibular longitudinal incision (Fig. 1), this technique allows the removal of impacted gallstones and a more complete assessment of Hartmann’s pouch, the cystic duct area and the CBD. The reflux of bile indicates the presence of a fistula between the gallbladder/infundibulum/dilated cystic duct and the bile duct, as the cystic duct is usually occluded [5]. IOC and choledochoscopy will also help to identify the anomalous fistula anatomy and perform a safer dissection within the hepatic hilum, aided by the LABEL technique in cases with large stones [5, 19, 20, 22]. Since the introduction of the transinfundibular approach at our institution, we have noticed a decrease in the cases labelled as type II Mirizzi syndrome. However, there was no statistical difference in the incidence of type II Mirizzi syndrome in our series before and after implementation of TIA. Series of type II Mirizzi syndrome from Asian countries report a higher incidence when compared to our series: 11/425 in our series vs. 11/103 in Chuang et al. series [17]. Is this because the incidence of Mirizzi syndrome is higher in Asia or because patients within our series that had CBD exploration via TIA/transcystic route were labelled as dilated cystic ducts rather than Mirizzi syndrome [12]. Moreover, the difference between type II Mirizzi syndrome and a dilated cystic duct is not clearly defined when TIA is used as the impacted stones can be removed through the infundibulum. It is therefore not necessary to dissect the hilum, expose the fistula and perform a choledochotomy or fistulotomy when the procedure is completed by TIA. Impacted stones produce local inflammatory changes that distort the hilar and cystic duct anatomy. As a consequence, when exploring the CBD via TIA the choledochoscope directly accesses the stones lodged in the CBD without recognizing the anatomical features of the fistula/dilated cystic duct (Fig. 7). Due to this, intra-operative diagnosis of type II Mirizzi syndrome can be challenging as we experienced with the last two patients of the series. In our usual clinical practice, over 90% of patients undergo CBD exploration through the transcystic route, sometimes allowed by TIA when the dissection of the cystic duct is hazardous. Finally, when possible, a retrograde subtotal cholecystectomy is performed, and the closure of the CBD is performed with the flap of the infundibulum over a T-tube, a cholangiocatheter placed through the fistula or a stent to avoid post-operative bile leakages and strictures (Fig. 4). If patients were referred following preoperative ERCP with stent placement, closure of the CBD was performed over the pre-existing stent. In patients that did not undergo preoperative ERCP or a stent could not be placed during ERCP, the CBD was closed over a T-tube, a transcystic stent or a cholangiocatheter. The TIA approach has the advantage of not requiring choledochotomy or fistulotomy, thereby avoiding post-operative complications associated with bile leaks. However, in these cases we recommend leaving a transcystic drain to decompress the CBD which also allows post-operative cholangiography to assess that the anatomy has been restored [12]. An intra-abdominal drain is always left in the subhepatic region unless the infundibulum/dilated cystic duct can be closed with an Endoloop as we did in the last case.

Laparoscopy has traditionally not been recommended for the treatment of complex Mirizzi syndromes (McSherry type II) due to high risk of biliary injury (up to 22%) during dissection of the cystic duct and artery in an inflamed, distorted hilum and high conversion rates to open surgery (11.1–80%) [4–7, 13, 17, 18, 24, 27, 29–34]. Some groups advocate that laparoscopy is only feasible in type I Mirizzi syndrome [13, 14, 16]. In our experience laparoscopy is no longer a contraindication for the treatment of Mirizzi syndromes with a cholecystobiliary fistula. It is not strictly necessary to obtain a “critical view” of Calot’s triangle or perform a choledochotomy for exploring the CBD [5, 10, 18, 19, 24], avoiding hazardous dissection and further biliary tract injuries. There were no conversions to open surgery in our series. Two patients had a bile leak during the post-operative period that resolved with conservative management (Clavien–Dindo grade 2). We therefore advocate that a laparoscopic TIFA is a safe and feasible technique when performed by experienced surgeons. It provides the advantages of laparoscopy in terms of post-operative outcomes with reduced morbidity and shorter hospital stay whilst providing appropriate treatment for type II Mirizzi syndrome.