Variations related to the liver are frequently encountered. This case reports the variant course of ligamentum teres present and its attachment along the inferior margin of falciform ligament which was embedded in a tunnel formed by the liver parenchyma. It also reports a complete absence of the quadrate lobe. This knowledge can be fruitfully utilised by anatomists, embryologists, radiologists and surgeons respectively for academic interest, to avoid possible errors in interpretation and subsequent misdiagnosis, and to assist in planing an appropriate surgical approach that is crucial for determining the patient outcome.
Study on the variations on the segmental anatomy of the liver are extensive, but morphological anatomy concerning the ligaments of liver are not commonly documented. In adults, cannulation of the upper part of the ligamentum teres has been achieved for a variety of therapeutic and diagnostic procedures, yet the indications for this remain limited1. The ligamentum teres also known as “round ligament of liver” is the fibrous remnant of the left umbilical vein that carries well-oxygenated and nutrient rich blood from the placenta to the fetus in vitro2. The liver is customarily apportioned by anatomists into a large right lobe and small left lobe by the line of attachment of falciform ligament anteriorly, and the fissure for ligamentum teres and ligamentum venosum on the inferior surface3. The ligamentum teres and small paraumbilical veins course in the inferior free margin of falciform ligament, which demarcates the anatomical right lobe from the left lobe on the diaphragmatic surface2. The fissure for ligamentum teres can be of variable depth and it ascends backwards from its notch on the inferior border to the left end of the fissure for the ligamentum venosum3.
Onitsuka et al reported that the falciform ligament and the ligamentum teres were considered as insignificant embryological remnants; however, the involvement in disease and significance in radiological imaging and therapeutic procedures should not be overlooked4. Elmar and Robert stated that after obliteration of umbilical vein over thenext several months after birth, it becomes the ligamentumteres hepatis, which usually measures 10 to 20 cms long5.
Quadrate lobe is distinguished physiologically as the medial segment of the left lobe. The fissure for ligamentum teres forms the left boundary of the quadrate lobe and may be partially bridged by a band of liver3. Aysin et al, Sanli et al and Abdullahi’s et al reported absence of the fissure for the round ligament on the visceral surface and the anatomic differentiation between the left and quadrate lobes could not be differentiated6-8. Sanli et al also noted the absence of fissure for ligamentum teres7. Abdullahi’s et al reported a complete absence of the left lobe of liver8.
Atkan et al studied cadaveric livers for the lobe and segmental anomalies; observed complete absence of quadrate lobe and anomalous quadrate lobes among the specimens9. In a study reported by Joshi et al in cadaveric livers, the quadrate lobe was found to be absent10. Albrech of Haller described Pons hepatis as a functionally insignificant, facultative bridge from liver fabric over the muzzle section of the ligamentum teres hepatis. Onitsuka et al reported metastatic liver carcinoma that develops from the pons hepatis, presents as an extrahepatic mass on ultrasonography and computed tomography4. Pathologies related to ligamentum teres such as stromal tumour and gangrene11 have been reported in few cases.
This case reports on the variation asscociated with ligamentum teres and the absence of the quadrate lobe. Precise knowledge on the morphological variations of the liver provides valuable information for anatomists, embryologists, operating surgeons12 and radiologists in this era of minimal invasive approaches.
On regular dissection of the formalin-fixed cadavers as part of medical training in the Department of Anatomy, Gulf Medical University, a variant course of the ligamentum teres with a complete absence of the quadrate lobe was found. No scar or any evidence of previous surgical operation nor any adhesions were noticed. On piecemeal dissection; ‘on going into the liver parenchyma’, of the specimen preserving the relevant structures, tributaries of portal vein and hepatic vein, branches of hepatic artery; we observed that the ligamentum teres joins with the left portal vein. Ligamentum teres (LT) was present on the inferior free margin of the falciform ligament, coursed deep through a tunnel within the liver substance and completely obscured the normal fissure for ligamentum teres present on the visceral surface of the liver (Figures 1 and 2). Complete absence of the quadrate lobe was noticed (Figure 3). The length of the LT was measured as 18.5 cm using a thread segment against a standard scale.
Variation of the anatomy of the ligamentum teres and the quadrate lobe is an uncommon anomaly of the liver development, usually noted during autopsies, surgeries13,14 and cadaveric dissections for routine medical training. The fissure for ligamentum teres can be of variable depth and ascends backwards from its notch on the inferior border to the left end of the fissure for the ligamentum venosum3. In this case the ligamentum teres was attached along the inferior margin of falciform ligament passing deep through a tunnel within the liver tissue reaching the left branch of the portal vein. Elma and Robert measured the mean length of the ligamentum teres to fall in the range of 10 to 20 cm and in our case the length was measured to be 18.5 cm5. Aysin et al reported an unsual ligamentum teres within the rectus sheath with the ventral component of the left sagittal fissure absent, and where the anatomic differentiation between the left and quadrate lobes could not be identified6. In our case the ligamentum teres was present within the liver parenchyma inside a tunnel and the ventral component of left sagittal fissure was absent. Sanli et al described the fissure for the round ligament on the visceral surface was absent, and was embedded inside the parenchyma on the diaphragmatic surface7 and also the findings go in favour with us and in our report there is a complete absence of quadrate lobe as well. Abdullahi et al reported the absence of the left lobe liver, with absence of fissure for ligamentum teres8. In our case we have noticed absence of fissure for ligamentum teres and quadrate lobe contrary to the classical observation of the lobation of the liver. The liver is separated into the left and right lobes by the falciform and round ligaments in the second month of gestation and Sato et al reported that lack of this separation might result in lobar fusion during the embryonic period. The present case goes in favour of Sato’s et al finding for the absence of quadrate lobe15. Quadrate lobe is physiologically considered as the medial segment of the left lobe, and the quadrate lobe was undistinguished anatomically in the present case3. Atkan et al reported 3.7% and 29.63% of livers studied had complete absence and anomalous quadrate lobe respectively; quadrate lobe could not be differentiated9. Joshi et al found notable variations: 66% rectangular, 6% narrow, 20% had fissured quadrate lobe; another 20% showed anomalous shapes viz: pear-shaped, triangular with the apex up, and presence of tongue-like processes in the quadrate lobe. Joshi et al also reported presence of pons hepatis bridging the fissure of ligamentum teres among 30%10; in the present case, it was a tunnel within the liver substance with complete absence of quadrate lobe.
In this case, we have noticed the complete absence of the fissure for ligamentum teres and instead it tunnelled deeply through the liver parenchyma thus completely obscuring the quadrate lobe. These findings may be utilised by anatomists, embryologists for academic interest, pathologists to identify a stromal tumor (15) and gangrene of ligamentum teres and by clinicians, radiologists and surgeons to avoid possible errors in interpretations and subsequent misdiagnosis, and to assist in planning appropriate surgical approaches related to liver pathology.
We wish to convey our sincere thanks to Mr. Kamal Hassan and Mr. Babu Panicker for their techinical assistance and for photographing the specimens
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