Liver Anatomy and Related Concepts – Study Notes

Borders and orientation of the liver

• Median approach and borders are key for boards-style questions.
• Medial borders (from the discussion of anterior view):
  • Stomach, duodenum, and part of the transverse colon lie medially to the liver.
  • The pancreas could also be more medial.
• Inferior border features:
  • Hepatic flexure as an indent in the liver where part of the colon sits against/into the liver.
  • The colon’s bend is accommodated by a small indentation in the liver tissue (the flexure), not a direct attachment.
  • The colon rests in this indent but is not attached to the liver.
• Inferior surface relationships include:
  • Hepatic flexure indentation supports the ascending colon turning into the transverse colon.
• Superior/lateral relationships:
  • Superiorly and laterally, the diaphragm surrounds/contacts the liver.
  • The right kidney lies posteriorly to the liver.
• Right lobe dominance:
  • In adults, the right lobe is larger than the left; in babies, the left lobe is relatively larger due to in utero circulatory changes.
• Falciform ligament as a landmark:
  • The falciform ligament divides the left and right lobes and is used to distinguish lobes on ultrasound.
  • Ligamentum teres lies within the falciform ligament and is a remnant of the umbilical vein.
• Practical test implications:
  • If a mass appears on the left side of the falciform ligament on ultrasound, it is in the left lobe; if on the right side it is in the right lobe.
• Visual orientation notes:
  • The first picture shows the liver from the front; the second picture shows the liver from the posterior view (reversed orientation).
  • The inferior border is observed in the frontal view; the posterior surface contains different landmarks (e.g., porta hepatis, IVC, etc.).

Posterior surface, impressions, and key landmarks

• Morrison's pouch:
  • The area between the right lobe of the liver and the right kidney where fluid can collect.
  • Specifically, Morrison's pouch is the hepatorenal recess on the posterior surface.
• Posterior liver impressions:
  • Renal impression: where the kidney sits against the liver.
  • Colic (colic/colic) impression: where the colon sits against the liver.
  • Gastric impression: on the left lobe where the stomach lays in a pocket.
• Gallbladder and biliary anatomy in posterior view:
  • The gallbladder and biliary tree are located near the porta hepatis on the posterior surface.
  • The porta hepatis is the entry/exit point for hepatic arteries, portal vein, and bile ducts into the liver.
• IVC and posterior liver relationship:
  • The IVC pierces the liver and creates an indentation on the posterior surface.
• Superiorly/posteriorly visible structures:
  • The liver’s posterior surface shows the diaphragm wrapping around superiorly.
  • The right kidney remains more posterior to the liver.

Ligaments, fissures, and lobar divisions

• Falciform ligament and ligamentum teres (umbilical):
  • Falciform ligament divides the liver into right and left lobes.
  • Ligamentum teres runs along the umbilicus upward within the falciform ligament; it marks the umbilical fissure.
  • Umbilical fissure (fissure for ligamentum teres) helps separate left medial and left lateral segments.
• Ligamentum venosum and caudate lobe:
  • Ligamentum venosum runs near the caudate lobe and helps separate the caudate lobe from the left lobe.
  • The caudate lobe sits adjacent to the IVC; the ligamentum venosum is a key landmark to distinguish the caudate from the left lobe.
• Fissures (general concept):
  • Fissures are creases or indentations that house ligaments; they help define segments and lobes.
• Transverse fissure (through the liver):
  • Runs transversely and houses the portal system as portal vein enters the liver.
  • It bisects both the left and right lobes transversely.
• Main (interlobar) fissure and gallbladder connection:
  • Interlobar fissure (main lobar fissure) connects the gallbladder area to the right portal vein area.
  • Helps separate portions of the right and left lobes at a different level than the falciform ligament.
• Ligamentum venosum and caudate-left relationship:
  • Ligamentum venosum separates the caudate lobe from the left lobe (not from the right lobe).
  • Anatomical views can be misleading depending on the angle of imaging; angle and orientation can make the venosum appear adjacent to the right lobe in some views.
• Caudate lobe and IVC relationship:
  • The caudate lobe lies near the IVC; the venosum is a landmark for this division.
• Practical imaging notes:
  • Expect to see the transverse fissure with portal vein traversing the hilum region.
  • The interlobar fissure visualization helps in orienting where the gallbladder, IVC, and middle hepatic vein lie relative to the lobes.
• Daily scan considerations:
  • People can image at different angles (coronal vs transverse) which can cause apparent misplacements of lobes; adjust by reorienting to a more standard plane and identify the fissures and venosum to confirm left vs right.

Capsule, peritoneum, and bare area

• Glisson's capsule (capsule of the liver):
  • Tough fibrous connective tissue that surrounds the liver and provides form and protection.
  • Adheres directly to the liver surface (outer surface of the liver parenchyma).
  • Plays a role during liver biopsies (core biopsy gun can puncture the capsule and pull tissue into the lab).
• Peritoneum layering around the liver:
  • Visceral peritoneum covers the liver externally, lying outside Glisson's capsule.
  • Parietal peritoneum lines the abdominal wall; a continuous layer is outside the visceral peritoneum.
• Bare area:
  • A small region on the liver surface that is not covered by peritoneum (bare area).
  • This area is near the superior/posterior surface and is clinically relevant for certain procedures.
• Gallbladder fossa and peritoneum:
  • The gallbladder sits in its fossa on the liver; this area is not fully covered by peritoneum because the peritoneum covers the gallbladder rather than the liver completely.
  • When the gallbladder is removed, a peritoneum-free space (fossa) remains where the gallbladder was.
• Practical notes on peritoneal coverage:
  • There is no peritoneal coverage in the bare area and in the gallbladder fossa.
  • The peritoneal layers surrounding the liver can influence surgical approach and imaging interpretation.

Liver structure in clinical and imaging context

• Ligamentous landmarks for lobe differentiation:
  • Falciform ligament divides left vs right lobes; the falciform region is used as a landmark in imaging and procedures.
  • Umbilical fissure marks the ligamentum teres position within the falciform ligament, aiding medial vs lateral segmentation.
  • Transverse fissure and portal vein location help orient left vs right lobes in cross-sectional images.
  • Main lobar (interlobar) fissure connects gallbladder region to the right portal vein and helps differentiate lobes at a different level.
  • Ligamentum venosum separates the caudate lobe from the left lobe; care is needed to distinguish this view from sometimes misinterpreting venosum as dividing the right lobe in certain angles.
• Segmentation implications:
  • The fissures help divide the liver into functional segments (e.g., left medial/lateral, caudate, etc.) and guide surgical planning for resections.
  • The venosum and the caudate lobe are key to understanding posterior anatomy and surgical margins.
• Imaging considerations and caveats:
  • Ultrasound imaging angles can alter apparent anatomy; use landmarks (falciform ligament, venosum, fissures, IVC, gallbladder) to confirm orientation.
  • The biliary tree, hepatic artery, and portal vein converge at the porta hepatis; proper identification is crucial for interpreting imaging and planning procedures.

Portal triad, porta hepatis, and intrahepatic relations

• Porta hepatis (hilum of the liver):
  • Entry/exit site for hepatic arteries, portal vein, and bile ducts.
  • Contains major vessels and ducts within the liver’s hilum region.
• Vascular and biliary components in imaging:
  • Hepatic artery, portal vein, and bile ducts are central to the porta hepatis as well as the biliary tree distribution.
• Intrahepatic relations:
  • The right portal vein lies near the interlobar fissure; the left portal vein lies closer to the falciform/umbilical fissure region.
  • The inferior surface shows the gallbladder fossa and the main lobar fissure; the IVC lies posteriorly near the caudate region.

Clinical relevance and exam strategy

• Why borders and landmarks matter:
  • Boards emphasize knowing borders to accurately identify which organ lies medial or lateral, especially near the liver where adjacent structures (stomach, duodenum, transverse colon, pancreas) meet.
• Typical exam tips from the lecture:
  • Use the falciform ligament and ligamentum teres to determine left vs right lobes on ultrasound.
  • Identify the fissures to orient left vs right lobes at different levels (gallbladder level vs hilum level).
  • Distinguish caudate lobe from left lobe using the ligamentum venosum near the IVC.
  • Be aware of the posterior surface impressions (renal, colic, gastric) to orient the liver in a posterior view.
• Practical biopsy note:
  • Glisson’s capsule is very tough; liver biopsy uses local anesthesia and a spring-loaded core biopsy gun to sample tissue through the capsule into the liver.
• Peritoneum and bare area considerations for procedures:
  • Bare area lacks peritoneal covering, which has implications for peritoneal reflections and surgical access.
• Common imaging pitfalls:
  • Different imaging angles can temporarily misrepresent where the right or left lobe is; rely on multiple landmarks (falciform ligament, venosum, fissures, IVC, portal vein) to confirm.

Quick reference: board-style specifics and exam logistics

• Board question structure and timing (as discussed):
  • Physics/diagnostic tests: 2 hours
  • Specialty exams: 3 hours
• Question format:
  • Multiple-choice; cannot go back to change answers during a given section.
  • No adaptive testing in the described format; the test has a fixed number of questions (specifics vary by exam type).
• Question counts and adaptive notes (as mentioned informally):
  • A common board format may have up to around 110 questions for physics and 170 for specialty (per the lecture).
  • Some boards (e.g., nursing boards) may cut off around 85 questions if performance is high or poor, but this is not the standard for the discussed exams.
• Post-exam feedback:
  • Immediate score reporting upon exit from the exam room.
• Practical lab/test-taking reminders:
  • The instructor emphasizes using diagrammatic landmarks (e.g., falciform ligament, Glisson’s capsule, fissures) for test questions and not panicking if a picture looks confusing due to angle.
  • Week-by-week scheduling notes indicate the current focus on liver and vascular anatomy, with abdominal topics upcoming later; next test planned for Thursday, with more content in following weeks.

Summary of key anatomical concepts to memorize

• Borders and relationships: Stomach, duodenum, transverse colon medially; hepatic flexure indentation; right kidney posteriorly; diaphragm superiorly.
• Lobes and landmarks: Right lobe larger in adults; falciform ligament and ligamentum teres divide left and right lobes; ligamentum venosum separates caudate from left lobe.
• Fissures and lobar division: Umbilical fissure (ligamentum teres); transverse fissure (portal vein path); interlobar (main lobar) fissure; caudate lobe proximity to IVC; venosum view caveats.
• Capsule and peritoneum: Glisson’s capsule adherent to liver; visceral peritoneum outside; bare area with no peritoneal covering; gallbladder fossa with limited peritoneal contact after gallbladder removal.
• Posterior surface impressions: Morrison’s pouch; renal impression; colic impression; gastric impression; porta hepatis and IVC relationships.
• Porta hepatis and hepatic inflow/outflow: Hepatic artery, portal vein, bile ducts at porta hepatis; gallbladder and biliary tree relation.
• Practical imaging orientation: Front vs back view differences; importance of angle in ultrasound imaging; use of multiple landmarks for accurate orientation.
• Clinical and biopsy relevance: Glisson’s capsule and biopsy considerations; bare area implications; importance of landmarks in planning resections or targeted therapies.