Upper abdominal cross-sections

Upper abdominal cross-sections

Upper abdominal cross-sections

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Axial Slice @ T12/L1 - The Celiac Trunk Show

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  • 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

Transpyloric Plane and Upper Abdominal Organs

  • 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

Nutcracker Syndrome: CT and diagrams

  • 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.

SMA Syndrome: Axial and Sagittal CT with Diagrams

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.
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Practice Questions: Upper abdominal cross-sections

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A 40-year-old man presents with severe fatigue, dyspnea on exertion, and weight loss. He reports a weight loss of 15 kg (33.0 lb) over the past 3 months and feels full almost immediately after starting to eat, often feeling nauseous and occasionally vomiting. Past medical history is not significant. However, the patient reports a 10-pack-year smoking history. His temperature is 37.0°C (98.6°F), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 122/98 mm Hg. Physical examination reveals paleness and conjunctival pallor. Abdominal examination reveals an ill-defined nontender mass in the epigastric region along with significant hepatomegaly. Routine laboratory studies show a hemoglobin level of 7.2 g/dL. A contrast CT scan of the abdomen is presented below. Which of the following structures is most helpful in the anatomical classification of gastrointestinal bleeding in this patient?

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Flashcards: Upper abdominal cross-sections

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Which sympathetics innervate the regions of the hindgut? _____

TAP TO REVEAL ANSWER

Which sympathetics innervate the regions of the hindgut? _____

Lumbar splanchnics (L1 - L2)

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