Medical Terminology Daily (MTD) is a blog sponsored by Clinical Anatomy Associates, Inc. as a service to the medical community. We post anatomical, medical or surgical terms, their meaning and usage, as well as biographical notes on anatomists, surgeons, and researchers through the ages. Be warned that some of the images used depict human anatomical specimens.

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A Moment in History

Jean-Louis Petit

Jean Louis Petit
(1674 – 1750)

French surgeon and anatomist, Jean Louis Petit was born in Paris in on March 13, 1674.  His family rented an apartment at his house to Alexis Littre (1658 – 1726), a French anatomist. Petit became an apprentice of Littre at seven years of age, helping him in the dissections for his lectures and at an early age became the assistant in charge of the anatomic amphitheater.

Because of Petit’s dedication to anatomy and medicine, in 1690 at the age of sixteen, became a disciple of a famous Paris surgeon, Castel.

In 1692, Petit entered the French army and performed surgery in two military campaigns. By 1693 he started delivering lectures and was accepted as a great surgeon, being invited to the most difficult operations.  In 1700 he was appointed Chief Surgeon of the Military School in Paris and in the same year he received the degree of Master of Surgery from the Faculty of Paris.

In 1715 he was made a member of the Royal Academy of Sciences and an honorary member of the Royal Society of London. He was appointed by the King as the first Director General of the Royal Academy of Surgery when it was founded in 1731.

Petit’s written works are of historical importance.  “Traite des Maladies des Os” ( A Treatise on Bone Diseases);  “Traite des Maladies Chirurgicales et des Operation” (A Treatise on Surgical Diseases and their Operations” This last book was published posthumously in 1774. He also published a monograph on hemorrhage, another on lachrymal fistula, and others.

He was one of the first to perform choIecystotomy and mastoidotomy. His original tourniquet design for amputations saved many in the battlefield and the design of the same surgical instrument today has not changed much since its invention by him.

His name is remembered in the lumbar triangle, also called the "triangle of Petit", and the abdominal hernia that can ensue through that area of weakness, the lumbar hernia or "Petit's hernia".

Sources:
1. “Jean Louis Petit – A Sketch of his Life, Character, and Writings” Hayne, AP San Fran Western Lancet 1875 4: 446-454
2. “Oeuvres compl?tes de Jean-Louis Petit” 1837 Imprimerie de F. Chapoulaud
3. Extraits de l'eloge de Jean-Louis Petit Ius dans Ia seance publique de I' Academie royale de chirurgie du 26 mai 1750” Louis A. Chirurgie 2001: 126 : 475- 81


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Triangle of Calot

Triangle of Calot 
Image modified from the original
(Singh and Ohri, 2006

The [triangle of Calot], also known as the “cystohepatic triangle” is a triangular region found within the lesser omentum connecting the duodenum, stomach, and liver. It is an area bound superiorly by the inferior surface of the liver, laterally by the cystic duct and the medial border of the gallbladder, and medially by the common hepatic duct.

The surgical importance of this area is for a cholecystectomy. It is within this area that the surgeon will usually find the cystic artery, a critical structure that needs to be ligated in this procedure.  I stress the term “usually” as the hepatobiliary tree is one of the areas in the human body that has the most anatomical variations. In fact, the anatomy in this region is considered to be “normal” only in 64% of the cases. The cystic artery may not be found in the triangle of Calot therefore careful dissection and identification of the structures is needed in every surgery.

The above description of the triangle of Calot is what some refer to as the “modern triangle of Calot”, as the original triangle described by Dr. Jean-Francois Calot (1861 – 1944) is different.

Calot’s original description of this triangle is: “Le triangle n’est pas exactement équilatéral, mais plutôt isocéle, les deux cotés supérieur et inférieur, représente par l’artére et le conduit cystique, étant seuls égaux, et un peu plus longs que la partie du canal hépatique qui entre dans la constitution du triangle’’ , which can be translated as: “ The triangle is not exactly equilateral, but rather an isosceles triangle. The superior and inferior sides, represented by the cystic artery and cystic duct, are equal and a little longer than the part of the hepatic duct, which enters into the formation of the triangle. (Abdalla, 2013).

In the accompanying image Calot’s original triangle is shown by horizontal blue lines while the modern version of the triangle of Calot is shown with vertical red lines.

Sources:
1. “Calot's triangle” Abdalla S, Pierre S, Ellis H. Clin Anat. 2013 May;26 (4):493-501
2. “Anatomic landmarks: their usefulness in safe laparoscopic cholecystectomy” Singh, K; Ohri, A. Surg Endosc (2006) 20: 1754–1758
3. “Surgical Anatomy” Deaver, J P. Blakiston's Son & Co. Philadelphia, 1901
4. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
Image modified from the original (Singh and Ohri, 2006. Pastel sketch by Dr. E. Miranda