European Journal of Cardiovascular Medicine

The liver is the most massive of the viscera, occupying a substantial portion of the abdominal cavity1. It occupies whole of the right hypochondrium, upper part of the epigastrium and part of the left hypochondrium up to the left lateral plane2. It presents five surfaces - superior, anterior, right lateral, posterior and inferior surfaces. It is anatomically divided into larger right and a smaller left lobes by the attachment of falciform ligament on the anterior surface, the fissure for ligamentum venosum on the posterior surface and the fissure for ligamentum teres on the inferior surface in the 2nd month of intrauterine life. Failure of such separation into lobes may result in the fusion of lobes of the liver. The fissure for ligamentum teres is a deep cleft that usually extends from a notch on the inferior border of the liver to the left end of porta hepatis. The floor of this fissure lodges ligamentum teres hepatis, that is a remnant of obliterated left umbilical vein and extends up to the left branch of portal vein at the porta hepatis2. During the intrauterine life, it supplies oxygenated and nutrient rich blood from the placenta to the foetus3.

Clinically, the ligamentum teres is used for cannulation in various diagnostic and therapeutic procedures. Rarely, this fissure for ligamentum teres may be completely bridged by liver tissue converting the fissure into a tunnel or may be partially bridged leaving an incomplete fissure for the ligamentum teres. Such variation has been given different names – Pons hepatis4, Absent fissure for ligamentum teres5, Absent quadrate lobe6, Tunnel for ligamentum teres6,7. Shamir O. Cawich, et al have classified the anatomical variants of the fissure for Ligamentum teres into following types:

                                                            Table-1

Though some anomalies of liver such as presence of accessory lobes, etc. are occasionally seen, but the above-mentioned variations in the fissure for Ligamentum teres are rare, having clinical significance.  In the present study, we have identified such variations in the fissure for Ligamentum teres among the selected sample of liver specimens, which we have documented and reported with photographs.

The present study was carried out in 40 formalin fixed liver specimens in the department of Anatomy, Rangaraya Medical College, Kakinada which were removed from the adult human cadavers during routine dissection classes for the First year MBBS students and preserved in 10% formalin. Fissure for ligamentum teres was studied in these specimens and the identified variations were noted and reported. Photographs of the specimens with variations were captured during the course of the study.

We have observed 40 liver specimens that were removed from the cadavers during routine dissection for the Undergraduate students and preserved in 10% formalin. Out of these 40 specimens, 12 showed different variations in the fissure for Ligamentum teres hepatis. Remaining 28 specimens had normal, anatomical fissure for Ligamentum teres.

                                                                                          Table-2

Chart-1

Chart-2

In 1743, Von Haller first described the Pons hepatis, which is the segment of hepatic tissue connecting the left lobe with the quadrate lobe over the fissure for Ligamentum teres. The prevalence of Pons hepatis throughout the world is 3.45%8. Development of liver is a complex process controlled by various growth factors9. During the developmental process of liver, lack of separation might often result in the fusion of the lobes of liver10. The present study aims to present various variations in the fissure for Ligamentum teres hepatis. According to Shamir O.  Cawich, et al ’s classification of the anatomical variants of fissure for Ligamentum teres (Table.1), Type I:  refers to the normal anatomical pattern of the fissure for Ligamentum teres, in which the fissure extends from the inferior border of the liver to the left end of Porta hepatis. Type II: the fissure for Ligamentum teres is covered by a fibrotic band devoid of liver tissue. Type III:  the liver tissue projects from the lateral wall of the fissure for Ligamentum teres, making the fissure narrow but not completely covering it. Type IV: a bridge of liver tissue (Pons hepatis) covers the fissure for Ligamentum teres. Depending on the Length of this bridge and the portion of the fissure that  is  covered by the bridge, the following subtypes were  described: Open type: in which, the bridge of liver tissue is < 2 cm in length, Closed type: in which, the bridge of liver tissue is > 2 cm in length

In the present study, normal anatomical pattern of the fissure for Ligamentum teres was observed in 70% (28 specimens) of the total liver specimens. 30% (12 specimens) of the total liver specimens showed Type – IV variation in the fissure for Ligamentum teres.

Table-3 Out of the 12 specimens: 7.5% (3 specimens) showed Type IV - Open type:

Table-4 Out of the 12 specimens: 22.5% (9 specimens) showed Type IV – Closed type:

In a study by Ebby, et al., a case of liver with the presence of complete tunnel instead of fissure for ligamentum teres has been reported11.  In the present study, out of 40 specimens, 12 showed variations in the fissure for Ligamentum teres with bridging of the fissure by liver tissue (Type – IV variant). Based on the length of the bridging tissue, we have identified Open and Closed varieties in Type – IV. Shamir O. Cawich et al., have reported two variants of pons hepatis, an open-type in which the umbilical fissure was incompletely covered by parenchyma ≤ 2 cm in length and a closed type in which the umbilical fissure was covered by a parenchymal bridge > 2 cm and thus converted into a tunnel8.

Table-5 Correlating the present study with other studies

In a study by Onitsuka, et al, 2003., out of 125 liver specimens, 31 specimens (25%) showed the presence of Pons hepatis. Donmez, et al, 2009., out of 2 liver specimens that were studied, Pons hepatis was observed in both the specimens, of which, 1 specimen showed Open type and in the other, it was of Closed type  Nune GKR, et al, 2015., out of 2 liver specimens, Pons hepatis was reported in 1 specimen. In 2017, Chaudhari, et al., have carried out a study in 80 liver specimens, and found that the Pons hepatis was present in 10 (12.5%) specimens, of which 9 specimens (11.2%) showed Open type and 1 specimen (1.25%) showed Closed type. In 2018, Singh, et al., carried out a study in 40 liver specimens, and observed that the Pons hepatis was present in 1 specimen (2.5%) which was of Closed type. In 2018, Chin, et al., carried out a study in 33 liver specimens, of which, 12 specimens (36.4%) showed the presence of Pons hepatis. In 2020, Anbumani, et al., carried out a study in 30 liver specimens, and found that the Pons hepatis was present in 5 specimens (16.7%), of which, 2 specimens (6.7%) showed Open type and 3 specimens (10%) showed Closed type. In the present study out of 12 (chart 2), (Table 3 & Table 4) specimens showing type IV Variation 3 specimens i.e., 7.5% showing open type IV, and 9 specimens i.e. 22.5% showing closed type IV which is correlating with the study by Chin, et al (2018).                                                      

The knowledge of the variations in fissure for ligamentum teres hepatis is essential for hepatobiliary surgeons as the fissure for ligamentum teres is considered as landmark to plan liver resections. Surgical oncologists must be able to recognise pons hepatis if present as the cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC) is an important procedure to treat patients with peritoneal malignancies.In this procedure it has been recognised that the tunnel created under complete pons hepatis can hide malignant cells,which may be a focus for recurrence. The knowledge of these variations is also essential for radiologists,as the tunnel might be confused for a pathological cavity formed in the liver parenchyma or in case of Pneumoperitoneum, the air trapped in the tunnel may not be seen as hyperlucency in the radiograph, which may lead to misinterpretation and misdiagnosis. So, the knowledge of the variations in the fissure for Ligamentum teres is  important  for the clinicians to avoid misdiagnosis and provide an efficient healthcare to the patients.

1. Henry Gray: Gray’s Anatomy, 38th edition., Pg.no: 1795.
2. K. Datta: Essentials of Human Anatomy, 10th edition., Pg.no: 202  Keith LM, Arthur FD: Clinically oriented anatomy, 5th ed. Philadelphia: Lippincot Williams & Wilkins; 2006. Pg.no: 291.
3. Chin J, O’Toole P, Lin J, Velavan SS - Hepatic morphology: variations and its clinical importance., Eur J Anat 22(3): 195–201.
4. Chaudhari HJ, Ravat MK, Vania VH, Bhedi AN: Morphological study of human liver an its surgical importance., J Clin Diagn Res 11(6): 9–12..
5. Ebby S, Ambike MV: Anatomical variation of ligamentum teres of liver - a case report.,Webmed Cent Anat 3(5): WMC003389.
6. Nune GKR, Mohanty SR, Patra M - Tunnel for ligamentum teres: a rare variation of th liver seen in 2 cadaveric livers - a case report., Indian J Res 4(6): 239–240.
7. Cawich SO, Gardner MT, Shetty R. et al. Human liver umbilical fissure variants: pons hepatis (ligamentum teres tunnel). SurgRadiol Anat 2021; 43:795– 803.
8. Gray’s Anatomy, 39th edition: the anatomical basis of clinical practice. AJNR Am J Neuroradiol. 2005, 26:2703-4.
9. Sato S, Watanabe M, Nagasawa S, Niigaki M, Sakai S, Akagi S. Laparoscopic observations of congenital anomalies of the liver. Gastrointest Endosc.1998;47(2):136-40.
10. Ebby S, Ambike MV. Anatomical variation of ligamentum teres of liver—a case report. Webmed Cent 2012; 3(5):WMC003389.
11. Onitsuka A, Katagiri Y, Miyauchi T et al (2003) Metastatic hepatoma originating from the pons hepatis  presenting extrahepatic growth - classification of different patterns covering REX’s recesses. Hepatogastroenterology 50(49):235–237.
12. Donmez BO, Sarikcioglu L, Gokhan G, Elpik GO, Ucar Y (2009) Pons hepatis: report of two cases. Acta Gastroenterol Belg 72(2):279–280.
13. Singh H, Diwan RK, Rani A, Rani A, Sehgal G, Singh R (2018) Tunnel for ligamentum teres hepatis – a case report. EJMR 6(1):1–7.
14. Chin J, O’Toole P, Lin J, Velavan SS (2018) Hepatic morphology: variations and its clinical importance. Eur J Anat 22(3):195–201.
15. Anbumani L, Pavazhakkurinji TN, Thamaraiselvi A (2020) Morphological study on variation of external surface of liver. Int J Anat Res 8(2.2):7481–7485.