Radioiodine labelled fibrinogen uptake

The uptake of radioiodine (I,125) labelled fibrinogen may be used to detect thrombus throughout the calf and in the lower three quarters of the thigh.

It is a highly sensitive technique. Only 50% of DVT's detected on labelled fibrinogen scanning are identified clinically and studies using this technique reveal post operative DVT in up to 30% of patients over 40 years old.

Despite these results, however, the technique is falling out of favour, as:

• it cannot detect thrombus which has formed before the labelled fibrinogen is given
• it is unreliable in the pelvic and hip region, since the bladder is in close proximity and may contain excreted radioiodine
• it is of little use following knee or hip surgery since labelled fibrinogen accumulates at the site of the operation
• it is contraindicated during pregnancy
• lower limb incisions may give false positive results
• there is a risk of hepatitis