Lymphoscintigraphy is a nuclear medicine scan used to assess the lymphatic system, which helps drain fluid and fight infection. This scan helps detect blockages in lymphatic drainage, evaluate lymphoedema (limb swelling), or locate the sentinel lymph node (first lymph node to which cancer may spread).

It involves a small injection of a safe radiotracer (usually 99mTc-labeled Sulphur Colloid or Nanocolloid) just under the skin. A special gamma camera then takes images showing how the tracer moves through the lymphatic vessels.