Radiographic Anatomy of Abdomen

Radiographic Anatomy of Abdomen

Radiographic Anatomy of Abdomen

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Abdominal X-rays - The Inside Story

  • Key Projections & Purpose:
    • Supine (AP): Standard initial view; gas pattern, calcifications, soft tissues.
    • Erect AP: Detects free intraperitoneal air (under diaphragms), air-fluid levels.
    • Left Lateral Decubitus: Alternative to erect for free air (over liver).
  • Common Clinical Indications:
    • Suspected bowel obstruction or perforation.
    • Renal/ureteric colic (KUB for calculi).
    • Ingested foreign bodies.
  • Normal Intestinal Gas:
    • Stomach: Air bubble in fundus.
    • Small Bowel: Minimal, central; diameter <2.5 cm.
    • Large Bowel: Peripheral, feces/gas; haustra. Erect abdominal X-ray

⭐ Plain abdominal X-ray is often the first imaging modality for suspected bowel obstruction or perforation.

Organ Spotting - Shadows & Shapes

  • Liver: RUQ, largest solid organ shadow; inferior angle often visible.
  • Spleen: LUQ, ovoid shadow; posterior to stomach, often obscured by gas.
  • Kidneys: Retroperitoneal, bean-shaped; typically T12-L3. Right often slightly lower. Outlines visible due to perinephric fat.
  • Psoas Margins: Triangular, extend inferomedially from transverse processes of lumbar vertebrae. Clearly defined by fat.

    ⭐ Loss of the psoas muscle outline can indicate retroperitoneal pathology like abscess, hematoma, or tumor.

  • Properitoneal Fat Stripe: Thin radiolucent line lateral to ascending/descending colon.
  • Gas Patterns (Normal):
    • Stomach: LUQ, variable air-fluid level.
    • Small Bowel: Central, few loops, feathery (valvulae conniventes).
    • Large Bowel: Peripheral, sacculated (haustra), contains gas/faeces. Abdominal X-ray with organ and fat stripe labels

Trouble Bubbles - Air Apparent

  • Pneumoperitoneum: Free air (perforation).
  • Key Signs:
    • Rigler's sign 📌 (bowel wall visible)
    • Cupola sign (subphrenic air)
    • Football sign (massive)
  • Best View: Erect CXR, L. Lat. Decubitus.

Erect chest X-ray: Free air under diaphragm

FeatureSBOLBOIleus
LocationCentralPeripheralGeneralized
Size (Dilated)SB >3cmLB >6cm, Cecum >9cmBoth SB & LB
MarkingsValvulae (complete)Haustra (incomplete)Both
A-F LevelsStep-ladderFewerLong, same height
Rectal GasAbsent/↓Absent/↓ distallyPresent
SignsString of pearlsCoffee bean 📌 (sigmoid), Kidney bean 📌 (cecal)Uniform distension

Stone Cold Evidence - Calcifications & Co.

  • Renal Calcifications:
    • Nephrocalcinosis (medullary/cortical).
    • Renal calculi:
      • Radio-opaque: Calcium oxalate/phosphate (most common).
      • Radiolucent: Uric acid, xanthine.

    Staghorn calculi are typically composed of struvite (magnesium ammonium phosphate) and are associated with recurrent UTIs by urease-producing bacteria.

  • Biliary System:
    • Gallstones: ~10-20% radio-opaque on X-ray.
    • Porcelain gallbladder: Calcified wall, ↑ malignancy risk.
  • Pancreatic Calcifications:
    • Pathognomonic for chronic pancreatitis; scattered throughout gland.
  • Vascular Calcifications:
    • Atherosclerosis: Linear/tram-track (e.g., aorta, iliacs).
    • Phleboliths: Common pelvic calcifications, often with lucent centers.
  • Miscellaneous:
    • Appendicolith, adrenal (TB, old bleed), LN (TB, histo), fibroid (popcorn). KUB X-ray: Renal calculi and phleboliths

High‑Yield Points - ⚡ Biggest Takeaways

  • Diaphragm domes separate chest and abdomen; clear costophrenic angles are crucial.
  • Liver occupies the RUQ; its inferior edge is a vital plain film landmark.
  • Spleen resides in the LUQ, often obscured by gastric or colonic gas.
  • Kidneys are retroperitoneal; perinephric fat aids their visualization; right kidney is typically lower.
  • Clear Psoas muscle outlines are important indicators of retroperitoneal integrity.
  • Bowel gas patterns (stomach, small/large bowel) are key to identifying obstruction or ileus.
  • Note properitoneal fat lines and their displacement in abdominal pathology.
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Practice Questions: Radiographic Anatomy of Abdomen

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CT scan of abdomen showing a structure branching within the liver. Identify the structure.

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Flashcards: Radiographic Anatomy of Abdomen

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_____ bladder is one whos normal round or ovoid shape has been extrinsically compressed to resemble a pear.

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_____ bladder is one whos normal round or ovoid shape has been extrinsically compressed to resemble a pear.

Pear-shaped (or tear-drop-shaped)

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