Cross-sectional Anatomy: Abdomen and Pelvis

Abdominal Landmarks & Hepatosplenic Views - Core Scan Essentials

• External Landmarks (Internal Correlation):
  • Xiphoid: Superior liver
  • Umbilicus: L3-L4 level
  • Iliac Crests: L4 body
• Internal Axial References:
  • Celiac trunk: T12/L1
  • SMA: L1
  • Renal arteries: L1/L2
  • Aortic bifurcation: L4
• Hepatosplenic Planes:
  • Axial: Standard; liver segments, spleen.
  • Coronal: Diaphragm, liver dome, spleen.
  • Sagittal: Midline structures, vessels.
• Liver: Couinaud segments (I-VIII); portal & hepatic veins as guides.
• Spleen: LUQ; normal length <12-13 cm.

⭐ Cantlie's line (IVC fossa to gallbladder fossa) divides liver into right/left functional lobes.

Pancreas, GIT & Major Vessels - Digestive Ducts & Pipes

• Pancreas: Retroperitoneal (tail intraperitoneal). Head nestled in duodenal C-loop; uncinate process hooks posterior to SMV/SMA.
  • Pancreatic Duct (Wirsung): Joins CBD at ampulla. Normal diameter <3mm.
  • Accessory Duct (Santorini): Drains superior/anterior head.
• Key Vessels (Abdominal):
  • Aorta: Celiac trunk (Common Hepatic, Splenic, L. Gastric A.), SMA, IMA.
  • IVC: Receives renal & hepatic veins.
  • Portal Vein: Formed by Splenic Vein + SMV, posterior to pancreatic neck.
• Digestive Ducts:
  • Common Bile Duct (CBD): Passes posterior/through pancreatic head. Normal <6mm (add 1mm per decade >60 yrs; up to 10mm post-cholecystectomy).
• Adjacent GIT: Duodenum (C-loop), jejunum (LUQ, feathery folds), ileum (RLQ, smoother).

⭐ The relationship of the uncinate process of the pancreas posterior to the Superior Mesenteric Vein (SMV) and Superior Mesenteric Artery (SMA) is a critical anatomical landmark in cross-sectional imaging, often assessed for tumor involvement (e.g., pancreatic adenocarcinoma).

Renal System & Retroperitoneum - Bean Scene & Backstage

• Kidneys: Retroperitoneal (T12-L3). Size: 9-13 cm length, 4-6 cm width. Hilum (ant → post): Vein, Artery, Ureter (📌 VAU).
• Adrenal Glands: Superior to kidneys. Right: pyramidal/triangular. Left: semilunar/crescentic. Limb thickness: <5-7 mm.
• Ureters: Course retroperitoneally. 3 physiological constrictions: Pelviureteric junction (PUJ), crossing iliac vessels (pelvic brim), Vesicoureteric junction (VUJ).
• Perirenal Space: Contains kidneys, adrenals, perirenal fat, proximal ureters. Enclosed by Gerota's fascia.
• Anterior Pararenal Space: Pancreas, D2-D4 duodenum, ascending/descending colon.
• Posterior Pararenal Space: Fat, no major organs.

⭐ The left adrenal vein drains into the left renal vein, while the right adrenal vein drains directly into the Inferior Vena Cava (IVC). This asymmetry is a common exam point.

Pelvic Structures & Spaces - Basin Blueprint Breakdown

• Pelvic Cavity: True pelvis (inferior to pelvic brim), False pelvis (superior).
• Urinary Bladder: Anterior; key parts: trigone, detrusor.
• Rectum: Posterior; relations vary by sex.
• Male Pelvis:
  • Prostate: Surrounds urethra. Zones: PZ (📌Predominant cancer site), CZ, TZ. Size ~20-30g.
  • Seminal vesicles: Posterosuperior to prostate.
• Female Pelvis:
  • Uterus: Pear-shaped; often anteverted/anteflexed. Size ~8x5x3 cm (nulliparous).
  • Ovaries: Lateral to uterus; follicles seen.
  • Adnexa: Fallopian tubes.
• Pelvic Spaces/Pouches:
  • Pouch of Douglas (Rectouterine): Female, most dependent. Fluid <15 ml normal.
  • Vesicouterine Pouch: Female, anterior.
  • Rectovesical Pouch: Male.
  • Retropubic Space (Retzius): Prevesical, post-pubic.

⭐ Pouch of Douglas (Rectouterine): Most common site for female intraperitoneal fluid due to dependent position.

High‑Yield Points - ⚡ Biggest Takeaways

• Aorta & IVC are key; know major branches like celiac, SMA, renals.
• Master liver segments (Couinaud) & pancreatic parts (head, body, tail).
• Morrison's pouch & Pouch of Douglas are critical for free fluid.
• Understand CT contrast phases: arterial, portal venous, delayed for diagnosis.
• Locate adrenal glands above kidneys; note their characteristic shapes.
• Identify pelvic organs: uterus/ovaries (female), prostate/seminal vesicles (male).