Anatomy of Rouviere's Sulcus and Its Association with Complication of Laparoscopic Cholecystectomy

Methods This is a prospective observational study involving patients of age ≥16 years who underwent laparoscopic cholecystectomy for uncomplicated gall stone at BPKIHS between May and July 2019. Result 230 cases were analyzed, and RS was present in 90.4%. Open sulcus type was the commonest (54%), followed by scar type (22.9%), closed sulcus type (12.5%), and slit type (10.6%), respectively. In 59.1% of cases, it was oblique to the anterior, inferior, and external edge of the liver, while in the remaining cases, it was transverse. The mean ± SD values for operative time and duration of hospital stay in the RS visible and the RS not visible groups were 29.16 ± 8.736 and 42.9 ± 23.646 minutes, and 1.26 ± 0.440 and 1.90 ± 0.910 days, respectively (p value ≤0.001). One minor complication occurred in each group: RS initially visible group and RS visible on the adhesion release group, while 3 minor complications occurred in the RS not visible group. Only one major complication occurred in the RS not visible group. Conclusion Identification of RS by operating surgeons is a predictor of safe laparoscopic cholecystectomy.


Introduction
e Rouviere's sulcus (RS) represents a cleft, anterior to the traditionally described "segment 1 of liver" which has been recently described by Couinaud as segment IX [1]. Whatever is previously known about the sulcus came to us from some seminal studies on liver anatomy by Reynaud, Gans, and Couinaud who just noted that this sulcus was present in the majority [1][2][3].
Hugh et al. were the first to draw attention to its importance during laparoscopic cholecystectomy because it accurately indicates the plane of common bile duct (CBD) [4]. However, if one considers the anatomy of the RS, there are only limited studies in the literature. Its frequency and morphology are not well defined. is study was undertaken to describe the detail anatomy of RS in the population of our part of the world and to discuss the critical aspects of incorporating this useful landmark in safe cholecystectomy.
We believe that this study may increase awareness regarding variations in anatomy of Rouviere's sulcus and guide surgeons to perform safe laparoscopic cholecystectomy. close/slit/scar; oblique/transverse) in the population of our part of the world.

Secondary Objective.
Our secondary objective is to find the association of RS with incidence of complications (such as bile duct injury, port site infection/hematoma, and others, occurring within 2 weeks of surgery) and other morbidities such as operative time, conversion to open procedure, and duration of hospital stay.

Materials and Methods
is is a prospective observational study involving humans, with single institution-based setting and purposive sampling technique. e study period was 3 months (from May to July 2019).  [5]. erefore, we calculated the sample size using Cochran's formula (at 95% CI and 90% power) as follows: where Z-value � 1.96 at 95% confidence, p � 70, q � 30, and L � 10% of p � 7. By adding 20% to the sample size for nonresponse error, a total of 198 patients would have been adequate for the study.
However, during the study period, we encountered 230 patients fulfilling the inclusion criteria, and all were enrolled in the study.

Ethical Clearance.
e study was performed in accordance with the principle of the Declaration of Helsinki and was approved by the Institutional Review Board on 26 March 2019.

Conceptual Framework
4.3.1. Enrollment of Patients. All patients of age ≥16 years with uncomplicated gall stone disease who underwent laparoscopic cholecystectomy at BPKIHS from May to July 2019 were enrolled in the study. A detailed clinical history was recorded in a preset proforma. Ultrasonography of abdomen and pelvis and other relevant investigations as per protocol were performed. All patients were screened for exclusion criteria, and if any was present, they were excluded. After informed consent, they were posted for elective laparoscopic cholecystectomy.
Following general anesthesia, port placement, positioning, and proper gallbladder traction, RS whether initially visible to the operating surgeon or not was noted. If RS was not initially visible, the likely reason (such as omental/bowel adhesion, absence of RS, cirrhosis of liver) was noted, and, in case of adhesion, on release of adhesion whether RS became visible before dividing the cystic artery/duct or not was noted. In RS visible group (either initially or following adhesion release), RS characteristics (in terms of its type: open sulcus/closed sulcus/slit/scar; orientation: oblique/horizontal) were noted by the operating surgeon. e dimensions (width and depth) of the RS were measured intracorporeally by comparison with the standard distance between tips of two jaws of dissecting forceps. If the sulcus was deep and wide enough (centimetric), it was described as deep sulcus. Further, a note was made as to whether the deep sulcus was open or closed, depending on whether its medial end was open towards the porta hepatis making the portal structures visible or closed towards the porta hepatis. If the sulcus was too small in its depth and breadth (subcentimetric) so that only length was measurable, it was called slit sulcus. In case of invisible RS even on release of adhesion, the likely reason (such as absence of RS, cirrhosis of liver) was noted. In all cases, complications (recognized intraoperatively or within 2 weeks postoperatively) if any, operative time, and duration of hospital stay were noted. e data was then analyzed.

Operational Definitions.
e sulcus was categorized anatomically as either deep sulcus, narrow (slit), or scar. If the sulcus was deep and wide enough (centimetric), it was described as deep sulcus. Further, a note was made as to whether the deep sulcus was open ( Figure 1) or closed ( Figure 2), depending on whether its medial end was open towards the porta hepatis making the portal structures visible or closed towards the porta hepatis.
If the sulcus was too small in its depth and breadth (subcentimetric) so that only length was measurable, it was called slit sulcus ( Figure 3).
Sometimes the sulcus might have just appeared as a scar only and it may be even absent ( Figure 4).
We have considered bile duct injury (identified intraoperatively or postoperatively) as major complication, while other complications such as port site hematoma, port site SSI, and serous/serosanguinous collection in GB fossa were considered as minor complications.

Statistical
Analysis. Data was entered in Microsoft Excel and analyzed by SPSS 11. Data was analyzed using descriptive statistics for RS characteristics and patient data, chi square or Fisher exact test to compare categorical data, and Student's ttest (if data is normally distributed) or Mann-Whitney U test (if data is not normally distributed) for continuous data. A p value of less than 0.05 was considered statistically significant throughout.

Results
A total of 233 patients were enrolled in the study. 3 patients were excluded from the study. Figure 5 illustrates overall findings of the study.

Age Distribution.
e age of the patients enrolled in the study ranged from 16 to 80 years with a mean age of 41.56 ± 14.27 years. e majority were in the range of 26-35 years of age ( Figure 6).

Visibility of RS following Port Placement, Positioning, and
Proper Traction of Gallbladder. Following port placement, positioning, and proper traction of gallbladder, RS was initially visible to the operating surgeons in 162 (70%) cases, and in 68 (30%) cases, RS was not initially visible. e reasons for initial invisibility of RS were omental adhesion in 48 (70.6%) cases, absence of RS in 16 (23.5%) cases, and omentum-bowel adhesion in 4 (5.9%) cases. Out of 52 cases of initially invisible RS due to adhesion, on release of adhesion in 46 cases, RS became visible to the operating surgeon before dividing cystic artery/duct, while in 6 cases, RS was not visible because of its absence.

Intra/Postoperative Complications and RS. Only 2 cases
in RS visible before dividing cystic artery/duct group developed complications (port site hematoma: 1; serosanguineous collection in GB fossa: 1) as shown in Table 2. Port site hematoma was managed by evacuation, and serosanguineous collection in GB fossa was managed by image guided aspiration under antibiotic coverage. 4 cases in RS not visible before dividing cystic artery/duct group developed complications (port site hematoma: 1; port site SSI: 1; serosanguineous collection in GB fossa: 1; bile duct injury: 1) as shown in Table 2. Port site hematoma was managed by evacuation, port site SSI was managed by dressing and antibiotic coverage as per culture sensitivity, and serosanguineous collection in GB fossa was managed by image guided aspiration under antibiotic coverage. e one in which common bile duct (CBD) injury occurred was managed by conversion to open procedure by the experienced surgeon, and hepaticojejunostomy was performed.

Discussion
is Rouviere's sulcus is seen very clearly during laparoscopic cholecystectomy due to the pressure of CO 2 insufflation opening up the sulcus widely and due to the enhanced illumination and image quality of the laparoscopic camera.

Age Distribution.
e mean age of patients in our study was 41.56 ± 14.27 years, suggesting that uncomplicated gall stone is a disease of middle age population. is is in accordance with the study by Sachdeva et al. in which the mean age was 41.5 ± 15.4 years [6]. e majority in our study were in the range of 26-35 years of age. is suggests a shift in the trend of gall stone disease from middle to young age, and this is in accordance with the study by Gupta et al. [7].

Gender Distribution.
In our study, we observed that females had slightly higher preponderance of gall stone with female to male ratio of 2.43 : 1. In a study by Sachdeva et al., female had higher preponderance of gall stone with female to male ratio of 1.56 : 1 [6]. e sex hormones are believed to place females at higher risk. Estrogen increases biliary cholesterol secretion causing supersaturation of bile.  [2,4].

RS Characteristics
In our study, RS was oblique to the anterior, inferior, and external edge of the liver in 123 (59.1%) cases, while in 85 (40.9%) cases, it was transverse. In the study by Dahmane et al., the sulcus was oblique to the anterior, inferior, and external edge of the liver in 97% of cases and horizontal in 3% [5]. e orientation of RS as oblique or horizontal seen during laparoscopic cholecystectomy may change with orientation of camera and hence can be interpreted differently by different operating surgeons. Hence, this could be subject to bias.

Operative Time and RS.
e operative time in RS visible group was reduced by around 25% in comparison to RS not visible group. In RS visible group, no time would have been spent in adhesion release, and the operating surgeons might  Minimally Invasive Surgery not had any preoccupied hesitancy regarding chance of CBD injury as RS marks the plane of CBD.

Duration of Hospital Stay and RS.
e duration of hospital stay in the RS visible was significantly less than that in RS not visible group. e shorter hospital stay in RS visible group could be attributed to lesser operative time, lesser dissection, and lesser need to place drain in this group. Majority of patients with drain had tendency toward going home only after removal of drain. Even though this discrepancy on occurrence of complication in various groups was statistically not significant because of small sample size, it could be clinically significant and it can be concluded that recognition of RS before dividing cystic artery/duct during laparoscopic cholecystectomy avoids major complications.
Peti and Moser described a case where identification of the sulcus helped to prevent common bile duct injury [8]. Hugh et al. and Zubair et al. had shown minimal common bile duct injury during laparoscopic cholecystectomy by beginning the dissection ventral to the RS [4,9]. e overall incidence of bile duct injury (BDI) in our study was 1 in 230 cases, which amounts to 0.4%. Flum et al. reported that the incidence of bile duct injury increased from 0.2% in open cholecystectomy era to 0.5% after laparoscopic cholecystectomy [10].

Summary
e RS was present in 90.4% of the cases, and the open sulcus type was the commonest (54%), followed by the scar type (22.9%), the closed sulcus type (12.5%), and the slit type (10.6%), respectively. In 59.1% of the cases, it was oblique to the anterior, inferior, and external edge of the liver, and in 40.9% of the cases, it was transverse. e mean ± SD values for operative time and duration of hospital stay in the RS visible and the RS not visible groups were 29.16 ± 8.736 and 42.9 ± 23.646 minutes, and 1.26 ± 0.440 and 1.90 ± 0.910 days, respectively (p value ≤0.001). One minor complication occurred in each group: RS visible initially group and RS visible on adhesion release group. On the other hand, 3 minor complications occurred in RS not visible group. Only one major complication occurred in RS not visible group.

Conclusion
Rouviere's sulcus is present in majority of population in our part of the world, and open sulcus type is the commonest. Recognition of RS before dividing cystic artery/duct during laparoscopic cholecystectomy avoids major complications and is associated with short operative time as well as short duration of hospital stay.

Limitation.
is study had few limitations like small sample size, short term follow-up, observational bias, and being single center-based study.

Recommendation. Identification of RS is a predictor of safe laparoscopic cholecystectomy.
Data Availability e data used to support the findings of the study can be made available from the corresponding author upon request.

Additional Points
Highlights. Well established: Rouviere's sulcus is present in 70-80% of population and is an important anatomical landmark as the common bile duct lies below its level. Newly established: Rouviere's sulcus is present in 90% population in our part of world and open sulcus type is the commonest one. Recognition of RS before dividing cystic artery/duct during laparoscopic cholecystectomy avoids major complication and is associated with short operative time as well as short duration of hospital stay.

Conflicts of Interest
e authors declare that they have no conflicts of interest.