Human liver umbilical fissure variants: pons hepatis (ligamentum teres tunnel)

In the classical description of normal liver anatomy, the umbilical fissure is a long, narrow groove that receives the ligamentum teres hepatis. The pons hepatis is an anatomic variant, where the umbilical fissure is converted into a tunnel by an overlying bridge of liver parenchyma. We carried out a study to evaluate the existing variations of the umbilical fissure in a Caribbean population.

We observed all consecutive autopsies performed at a facility in Jamaica and selected cadavers with a pons hepatis for detailed study. A pons hepatis was considered present when the umbilical fissure was covered by hepatic parenchyma. We recognized two variants: an open-type (incomplete) pons hepatis in which the umbilical fissure was incompletely covered by parenchyma ≤ 2 cm in length and a closed type (complete) pons hepatis in which the umbilical fissure was covered by a parenchymal bridge > 2 cm and thus converted into a tunnel. We measured the length (distance from transverse fissure to anterior margin of the parenchymatous bridge), width (extension across the umbilical fissure in a coronal plane) and thickness (distance from the visceral surface to the hepatic surface measured at the mid-point of the parenchymal bridge in a sagittal plane) of each pons hepatis. A systematic literature review was also performed to retrieve data from relevant studies. The raw data from these retrieved studies was used to calculate the global point prevalence of pons hepatis and compared the prevalence in our population.

Of 66 autopsies observed, a pons hepatis was present in 27 (40.9%) cadavers. There were 15 complete variants, with a mean length of 34.66 mm, mean width of 16.98 mm and mean thickness of 10.98 mm. There were 12 incomplete variants, with a mean length of 17.02 mm, width of 17.03 mm and thickness of 9.56 mm. The global point prevalence of the pons hepatis (190/5515) was calculated to be or 3.45% of the global population.

We have proposed a classification of the pons hepatis that is reproducible and clinically relevant. This allowed us to identify a high prevalence of pons hepatis (41%) in this Afro-Caribbean population that is significantly greater than the global prevalence (3.45%; P < 0.0001).