Upper abdominal cross-sections

Axial Slice @ T12/L1 - The Celiac Trunk Show

• Landmarks: T12/L1 vertebral body, crus of the diaphragm.
• Great Vessels: Aorta gives rise to the celiac trunk; IVC is to the right.
• Viscera:
  • Liver: Right lobe occupies the right upper quadrant.
  • Spleen: Lies posterolaterally on the left.
  • Stomach: Anterior to the spleen and pancreas.
  • Pancreas: Body and neck are located anterior to the aorta.
  • Kidneys: Superior poles are visible.

⭐ The celiac trunk is the artery of the foregut, supplying structures from the distal esophagus to the second part of the duodenum.

Axial Slice @ L1/L2 - The Transpyloric Tour

• The Transpyloric Plane (of Addison): A key horizontal plane at the L1 vertebral level, halfway between the jugular notch and pubic symphysis.
• Key Structures Visualized:
  • Stomach: Pylorus
  • Gallbladder: Fundus
  • Pancreas: Neck, overlying the great vessels.
  • Kidneys: Hila, containing renal arteries and veins.
  • Vessels: Superior Mesenteric Artery (SMA) origin; Portal Vein formation.
  • Spleen: Tip
• 📌 Mnemonic (L1 GHOST): Gallbladder, Hila of kidneys, Origin of SMA, Spleen, Termination of spinal cord.

⭐ The portal vein is formed posterior to the pancreatic neck by the union of the splenic and superior mesenteric veins (SMV), a critical surgical landmark.

Axial Slice @ L2/L3 - The Nutcracker Crunch

• Key Structures: Kidneys, renal vessels, aorta, IVC, superior mesenteric artery (SMA), and duodenum.
• Vascular Relationship: The left renal vein (LRV) courses between the SMA anteriorly and the abdominal aorta posteriorly.
• Clinical Correlation: Compression of the LRV in this "nutcracker" can lead to renal venous hypertension, causing hematuria and flank pain.

⭐ Exam Favourite: Nutcracker syndrome is a key cause of unexplained left-sided varicocele, as the left gonadal vein drains into the high-pressure LRV.

Axial Slice @ L3 - The Duodenal Squeeze

• Key Vessels: Abdominal Aorta, IVC. The Inferior Mesenteric Artery (IMA) typically originates here-the last major unpaired branch.
• The "Squeeze": The 3rd (horizontal) part of the duodenum is compressed between the Superior Mesenteric Artery (SMA) anteriorly and the Aorta posteriorly.
• Musculature: Psoas major, Quadratus lumborum, Erector spinae.
• Viscera: Lower poles of kidneys, ureters, loops of small bowel.

⭐ SMA syndrome classically presents with postprandial epigastric pain and bilious vomiting, relieved by leaning forward or lying prone, which widens the aortomesenteric angle.

High‑Yield Points - ⚡ Biggest Takeaways

• At the T12/L1 level, identify the celiac trunk branching from the aorta, just below the diaphragm's crura.
• The L1 plane is key for the pancreas, lying transversely with its head nestled in the C-loop of the duodenum.
• The left renal vein's path between the aorta (posteriorly) and SMA (anteriorly) is a classic anatomical relationship (Nutcracker syndrome).
• The portal vein is formed posterior to the pancreatic neck by the union of the splenic and superior mesenteric veins.
• The right renal artery is longer and passes posterior to the IVC.