Spleen and Lymphatic System

Spleen: Anatomy & Imaging - Spleen Scene Setter

• Location & Size: LUQ, intraperitoneal. Avg. 12x7x4 cm. Wt: ~150g.
  • 📌 Mnemonic "1,3,5,7,9,11": 1x3x5 inches, 7 oz, deep to ribs 9-11.
• Vasculature: Splenic artery (from celiac trunk); Splenic vein (joins SMV → portal vein).
• Imaging:
  • USG: Homogeneous, echogenic cf. liver.
  • CECT: Gold standard. Homogeneous enhancement. NECT: 40-60 HU.
  • MRI: T1 hypointense, T2 hyperintense.

⭐ Accessory spleen (splenunculus): Most common congenital anomaly, often at hilum; found in up to 30% of cases at autopsy/CT.

Splenomegaly & Diffuse Disease - The Swollen Spleen

• Definition: Spleen length > 12-13 cm or weight > 200g.
• Common Causes:
  • Congestive: Portal hypertension (cirrhosis), heart failure.
  • Infective: Malaria, Kala-azar, EBV, TB.
  • Hematological: Leukemias, lymphomas, hemolytic anemias, myeloproliferative disorders.
  • Storage: Gaucher's, Niemann-Pick.
  • Inflammatory: Sarcoidosis, SLE.
• Imaging:
  • USG: Measures size, assesses echotexture. Doppler for portal flow.
  • CT/MRI: Confirms size, evaluates density/signal, aids in identifying cause.

⭐ In portal hypertension, USG may show dilated portal vein (>13mm), splenic vein (>10mm), collaterals, and ascites.

Focal Splenic Lesions - Spleen Spotting

• Common Benign: Simple cyst, Hemangioma, Hamartoma.
• Common Malignant: Lymphoma, Metastases (melanoma, lung, breast, ovary).
• Infectious/Inflammatory: Abscess, Granulomas (TB, sarcoidosis).

⭐ Splenic lymphoma is the most common malignant tumor of the spleen, often presenting as diffuse infiltration or multiple nodules rather than a single discrete mass.

Splenic Trauma - Spleen Under Siege

• Most common: blunt trauma. CT is gold standard. Non-operative management (NOM) for stable patients.
• AAST Splenic Injury Grading: | Grade | Description | |-------|-----------------------------------------------------------------------------| | I | Subcapsular hematoma <10%; Capsular tear <1cm | | II | Hematoma 10-50% or intraparenchymal <5cm; Laceration 1-3cm | | III | Hematoma >50% or ruptured; Intraparenchymal >5cm; Laceration >3cm | | IV | Laceration involving segmental/hilar vessels (>25% devascularization) | | V | Shattered spleen; Hilar vascular injury devascularizing spleen |

⭐ Kehr's sign: referred left shoulder pain, may indicate splenic rupture due to diaphragmatic irritation.

Lymph Nodes & Lymphoma - Node Network News

• Normal Nodes: Oval, fatty hilum. Short axis: Abdomen/Pelvis <10mm; Mesentery <5mm.
• Benign vs. Malignant Node Features:

  Feature	Benign	Malignant
  Shape	Oval, reniform	Round
  Hilum	Fatty, preserved	Lost, effaced
  Calcification	Granulomatous (TB)	Treated lymphoma, some mets
  Necrosis	TB, suppurative	Common, esp. high-grade

• Lymphoma:
  • Bulky, homogeneous adenopathy; splenomegaly common.
  • NHL: Commoner, often extranodal. HL: Contiguous spread.
  • Ann Arbor Staging (Simplified):

    Stage	Involvement
    I	Single LN region or single extralymphatic (IE)
    II	≥2 LN regions, same side diaphragm
    III	Both sides diaphragm; +/- Spleen (S)
    IV	Diffuse extralymphatic disease

  • B-symptoms: Fever, night sweats, wt loss >10%. E: Extranodal.

  ⭐ "Floating aorta sign" or "Sandwich sign": Mesenteric/retroperitoneal nodes encasing vessels, characteristic of lymphoma.

High‑Yield Points - ⚡ Biggest Takeaways

• Splenomegaly (>12 cm length): common, due to portal hypertension, hematological disorders.
• Splenic trauma: most common in blunt injury; note Kehr's sign, use AAST grading.
• Splenic infarcts: wedge-shaped peripheral defects; causes include embolic, hematologic.
• Accessory spleen (splenunculus): common congenital variant, usually near splenic hilum.
• Lymphadenopathy (>1 cm short axis): suggests malignancy/infection; PET-CT for lymphoma staging.
• Splenic calcifications: often from old granulomatous disease (TB) or healed infarcts.