Tagged RBC Scan

General

  • For active bleeding of mid to lower GI system

  • Tc-99m-RBC

  • Dose

    • Adult = 15-30 mCi

    • Children = 0.3 mCi/kg (minimum 2, max 20)

  • Detection of 0.1 ml/min

  • Images typically obtained for 60-90 min

  • Image rate not to exceed 1 min (too slow)

  • Bilateral photopenic areas with central hazy area of increased uptake = ascites with centrally located bowel

Bleeds

  • Angiodysplasia

    • Typically in cecum/right colon

    • Typically should see cluster of small vessels at the bleeding site on angio

  • Diverticular bleed

    • Typically in sigmoid/left colon

Management

  • If patient is stable —> endoscopy/colonoscopy

  • If patient is unstable or management cannot be done with endoscopy —> Angio

  • In Angio typically will use coils

    • Want coils to be placed as far distally as possible because

      • Prevent collateral vessels from also supplying the bleed

      • If you go to proximal the area of ischemic bowel will be large and you’ll kill all the bowel

  • Particulate embolization is typically contraindicated in lower GI bleeds due to risk of bowel ischemia

Diverticular Bleed

  • Notice extravasated blood in left colon

Technical Points

  • Look at the first pictures and follow normal course, do not just skip to the end. If you skip to the end and there is a bleed you will definitely see blood but you will think the bleed is in the distal colon because that is what the last pictures are taken of. However you can have a bleed in the more proximal bowel which will be seen on the earlier studies and because of normal bowel peristalsis it will carry blood to the distal bowel and you will be fooled into thinking the bleed is more distal than it actually is.

  • Need to be able to identify the vascular distribution and what portion of bowel the bleed is from

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