Right hepatic artery forming caterpillar hump, perforating Calot's triangle into the cystic plate and associated with a variant branching pattern of the parent vessel

Moynihan's hump of the right hepatic artery in Calot's triangle: a systematic review and meta-analysis of its incidence and surgical importance

INTRODUCTION

A rare variation known as "Moynihan's or caterpillar hump" of the right hepatic artery raises the danger of vascular and biliary injuries during hepatobiliary surgery. This research intends to carefully record every case (i.e., patients undergoing laparoscopic cholecystectomy or cadaver dissections) where the right hepatic artery received a caterpillar hump.

METHODS

The literature search was conducted with the medical subject headings (MeSH) and EMTREE (subject headings unique to Embase) keywords. The keywords with Boolean operators (OR, AND, and NOT) were used to create search strings in all possible combinations to retrieve bibliographic data. Two authors independently performed a risk of bias assessment and data extraction. The random effects model was used to conduct a meta-analysis.

RESULTS

Thirty studies with a total of 8418 subjects reported that Moynihan's hump was present in 3.81% of them, with a predictive interval of 0.88-16.45%. The incidence of the hump was 3.1% in surgical studies (7496 subjects) and 7.22% (95% CI 4.7-10.93%) in cadaveric data (625 cadavers). Only ten studies addressed the relationship between the caterpillar hump and the common bile duct.

CONCLUSION

A patient with an unusually "small cystic artery" or "large right hepatic artery" is likely to have a "caterpillar hump". The caterpillar's hump of the right hepatic artery is subject to rare anatomical variations in its course that increase the risk of incorrect vessel ligation or injury during laparoscopic cholecystectomy.

Moynihan's Lump as an unusual variant of right hepatic artery during a laparoscopic cholecystectomy approach. A case report

Introduction and importance

One of the most important measures during the cholecystectomy procedure is based on a “Culture for Safe Cholecystectomy (CSC)”. Vascular injury reports an open surgery conversion rate of 0 to 1.9% and a mortality of less than 0.02%. The caterpillar or Moynihan's hump configuration is characterized by a tortuous right hepatic artery (RHA) running proximal and/or parallel to the cystic duct and predisposes to a small and/or short cystic artery (CA).

Case presentation

A 65-year-old woman with no relevant clinical history underwent a laparoscopic cholecystectomy (LC) for cholelithiasis; during the procedure a caterpillar or Moynihan's hump was identified.

Clinical discussion

Anatomical variations represent 20-50% of all cases; therefore, CVS is required. The incidence of caterpillar or Moynihan's hump varies between 1% and 13% of all cases. To date, the scientific literature on this topic is limited. The most accepted etiology is related to embryological formation.

Conclusion

Biliary and arterial variations are more frequent than we think, so an anatomical knowledge, CSC and CVS represent a fundamental rule, increasing the safety of the surgical procedure.

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This is a reminder of how variant the anatomy of the biliary tree can be.

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Anatomical variations could increase the risk of inadvertent injury during LC.

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The certainty of a safe cholecystectomy is of great importance.

The unwanted third wheel in the Calot's triangle: Incidence and surgical significance of caterpillar hump of right hepatic artery with a systematic review of the literature

BACKGROUND

Caterpillar hump of the right hepatic artery is a rare variation increasing the risk of vascular and biliary injuries during hepatobiliary surgery. The aim of this study is to record the cases of the right hepatic artery forming caterpillar hump in a cohort of patients underwent laparoscopic cholecystectomy and to report a review of the literature systematically conducted.

METHODS

We reviewed clinical and surgical video data of 230 patients with symptomatic cholelithiasis treated with laparoscopic cholecystectomy between January 2016 and August 2017. A systematic literature search in PubMed, Medline, Cochrane and Ovid databases until 30th June 2017 was also performed in accordance with the PRISMA statement.

RESULTS

Our institutional data indicated that 1.3% of 230 patients presented caterpillar hump right hepatic artery. The systematic review included 16 studies reporting data from a total of 498 human cadavers and 579 patients submitted to cholecystectomy. The overall proportion of surgical patients with the caterpillar hump right hepatic artery was 6.9%.

CONCLUSIONS

Variations of the cystic artery are not just an anatomical dissertation, assuming a very crucial role in surgical strategies to avoid uncontrolled vascular lesions. A meticulous knowledge of the hepatobiliary triangle in association with all elements of 'Culture of Safety in Cholecystectomy' is mandatory for surgeons facing more than two structures within Calot's triangle.