Demystifying The Triangle of Francois Calot
Authors: Ozobia Nathan Ibezimako 
Published: April 2020

The Triangle of Calot is a landmark in anatomy located in the right upper quadrant of the abdomen. Calot in his 1891 dissertation used the cystic artery as the upper boundary. This original monograph was in medieval French, which is no longer spoken, and no official English translation is currently available.

It is not clear who first used the term Triangle of Calot, but one wonders if that was when the under surface of the liver was introduced as the upper boundary, consequently introducing a new triangle, the Hepatocystic Triangle. This term is often used interchangeably with the Triangle of Calot, although their true borders differ.

Mystery #1: Who was Calot?

Jean‐Francois Calot [1861–1944] was born in a small farming community in the Hautes‐Pyrennes in France. He received his medical degree at the University of Paris and on graduation worked with Terrier, a surgeon, who Calot described in his publication as his mentor. Terrier had embraced the cholecystectomy as a surgical procedure after Langenbuch successfully performed the first cholecystectomy in 1882. Calot was intimately involved in caring for these patients and stated in his monograph that it was Terrier who encouraged him to study the hepatobiliary anatomy.

As a physician and prosector, Calot worked on cadavers at the Ecole Pratique in Paris and came up with the following description of his famed triangle: “The triangle is not equilateral exactly, but rather both upper and lower sides represented by the artery and the cystic duct being alone equal and a little longer than the portion of the liver bile duct entering the constitution of the triangle.” It is clear from this translation that Calot meant that the upper boundary of this near‐isosceles triangle should be the cystic artery, the lower boundary, the cystic duct and the medial boundary, the common hepatic duct.

Mystery #2: Who named the triangle?

It is unclear who first used the term, “Triangle of Calot,” as Calot himself did not use such a name in his dissertation. It is possible that someone at a later time, in not having access to a translation of Calot’s publication, incorrectly introduced the triangle with the undersurface of the liver as the upper boundary. While this difference may seem of little consequence, such a description does matter for the surgical approach during a cholecystectomy. The undersurface of the liver houses the soul of the liver, with the confluence of major biliary and vascular structures, and is an area most surgeons would be advised to avoid during routine cholecystectomies.

Conclusion

While we may never know who named Calot’s Triangle and who introduced the similar but distinct Hepatocystic Triangle, it is clear from our investigation that these two entities are not synonymous. Such knowledge is of great importance during difficult cholecystectomies, when the normal anatomy is distorted by inflammation and vital structures are at increased risk of injury. For the practicing surgeon, using the cystic artery as the upper boundary of Calot’s Triangle is much safer than the undersurface of the liver during a cholecystectomy.