Tc-99m-Sulfur Colloid⁹⁹ᵐTc-sulfur colloid
A reticuloendothelial colloid with roles across liver, marrow, lymphatics, and GI
Quick Answer
Tc-99m-sulfur colloid is phagocytosed by the reticuloendothelial system (RES) — Kupffer cells (liver), spleen, and bone marrow — and, when filtered to small particles, drains via lymphatics. This gives it a wide range of uses: liver–spleen and bone-marrow imaging, sentinel-node lymphoscintigraphy, labeling the gastric-emptying meal, LeVeen/peritoneovenous shunt patency, and rapid GI-bleeding detection. Particle size determines destination.
Mechanism
Colloidal particles are cleared by phagocytosis; biodistribution depends on particle size — larger particles favor liver/spleen, smaller (filtered) particles reach marrow and drain through lymphatics to the first-draining node. This one principle explains the agent's many roles.
Biodistribution
Liver (~85%), spleen, and marrow. Colloid shift (increased spleen/marrow relative to liver) indicates hepatocellular dysfunction or portal hypertension. Large aggregates (poor preparation) can cause lung uptake.
Clinical Indications
- Liver–spleen imaging: FNH (Kupffer cells → normal/increased uptake), colloid shift, accessory spleen/splenosis (with heat-damaged RBCs).
- Bone-marrow imaging: paired with labeled-WBC studies to separate marrow from infection (see infection page).
- Sentinel-node mapping (melanoma, breast) — filtered colloid (or tilmanocept alternative).
- Gastric-emptying meal label; LeVeen (peritoneovenous) shunt patency; GI bleed (rapid; less common than RBC).
Protocol Notes
- Sentinel node: filter the colloid to small particles for lymphatic migration; intradermal/peritumoral injection; SPECT/CT for aberrant basins.
- Liver–spleen: standard colloid; heat-damaged RBCs are splenic-specific for accessory spleen/splenosis.
- Marrow: compare distribution against labeled-WBC in periprosthetic infection.
Interpretation Highlights
- FNH: contains Kupffer cells → normal/increased colloid uptake (helps separate from adenoma/malignancy, which are photopenic).
- Colloid shift: hepatocellular dysfunction/portal hypertension.
- Marrow vs infection: incongruent WBC (positive) / marrow (negative) = infection (see infection & inflammation page).
Reporting Checklist
- Describe liver/spleen/marrow distribution and any colloid shift.
- For FNH, note Kupffer-cell uptake distinguishing it from adenoma/malignancy.
- For sentinel node, report drainage basins and node number (SPECT/CT).
- Note poor-preparation lung uptake if present.
Common Pitfalls
- Poor preparation / large aggregates causing lung uptake artifacts.
- Confusing physiologic marrow uptake with pathology on whole-body colloid studies.
- Using unfiltered colloid for sentinel-node work (poor lymphatic migration).
Board Pearls
Sulfur colloid is phagocytosed by the RES, and particle size decides where it goes: larger particles favor liver/spleen (liver–spleen imaging), smaller (filtered) particles reach marrow and drain through lymphatics (marrow imaging and sentinel-node mapping). One agent, many applications, all from that principle.
Colloid shift (spleen/marrow > liver) flags hepatocellular dysfunction/portal hypertension; FNH shows Kupffer-cell colloid uptake (distinguishing it from adenoma/malignancy); heat-damaged RBCs are splenic-specific for accessory spleen/splenosis.
In periprosthetic infection, sulfur-colloid marrow imaging paired with labeled WBC is the crux: congruent = marrow (no infection), incongruent (WBC-positive/marrow-negative) = infection. Sulfur colloid also labels the standardized gastric-emptying meal and assesses LeVeen-shunt patency — while large aggregates from poor preparation cause artifactual lung uptake.
Related Pages
- Related: Liver–spleen & hemangioma imaging, lymphoscintigraphy & sentinel node, infection & inflammation (marrow imaging), gastric emptying.
- Pitfalls: Pearls, pitfalls & normal variants.
Figure / Diagram Suggestions
- A particle-size → destination schematic (liver/spleen vs marrow/lymphatics).
- A colloid-shift teaching pair (normal vs cirrhosis/portal hypertension).
- A WBC + marrow congruence plate (infection vs marrow).
Self-Check (Board-Style)
Q1. Why can the same agent image the liver/spleen, the marrow, and sentinel nodes?
Answer: Particle size — larger particles are phagocytosed by liver/spleen RES; smaller (filtered) particles reach marrow and drain via lymphatics to the first node.
Q2. A liver lesion shows normal/increased sulfur-colloid uptake. What does this favor?
Answer: Focal nodular hyperplasia (FNH) — it contains Kupffer cells; adenoma and malignancy are typically photopenic (cold).
Q3. Increased spleen/marrow uptake relative to the liver — what is this called and what does it suggest?
Answer: Colloid shift — hepatocellular dysfunction or portal hypertension.
Q4. In a suspected periprosthetic infection, how does pairing sulfur-colloid marrow imaging with labeled WBC decide infection?
Answer: Congruent WBC + marrow uptake = marrow (no infection); incongruent (WBC-positive/marrow-negative) = infection.
Evidence & sources
https://nuc.med/tc99m-sulfur-colloid/ Report an issue