GIT and HB Contrast Agents

Tissues in the body attenuate x-ray beams at different degrees therefore to see tissues with similar densities can be difficult e.g. vessels within organs. Overcome this by artificially altering density or atomic no with a contrast agent.

1. decrease density of a hollow organ by filling it with gas/air.
2. increase atomic no of a hollow structure by filling it with a liquid of a higher atomic no then blood e.g. iodine.

Negative contrast = gas or air, appears black on film, less x-ray absorption.

Positive contrast = iodine/barium based compounds, appear white on film, increased x-ray absorption.

1. orally - calcium or magnesium citrate tabs (co2 foaming tabs), sucking air through holed straw.
2. rectally - part of barium enema or CT colonography, via inflating bag.

1. orally - swallow contrast solution
2. rectally
3.IV

1. orally
2. IV
3. via catheter e.g. t-tube (inserted into bile duct to allow drainage of bile outside body)

1. Barium sulfate suspension
2. Gastrograffin - needs to be diluted, water soluble, iodinated contrast media, 15mls/500mls h2o

Visulaisation of upper GIT e.g. oesophagus, stomach, small intestine

- Used for GIT imaging
- better coating properties then iodine, forms thin layer over lining of gut.

Any chance there is perforation along GIT as barium is toxic e.g. recent surgery , resection. Use GG instead.

Any risk of aspiration or if pt is sensitive to iodine high osmolar contrast as GG can induce pulmonary oedema or cause pneumonitis e.g. stroke pt, pt with decreased swallowing reflex, kids. Use low osmolar contrast (ultravist) instead.

1. Air - inflate colon
2. Ba - outline large intestine when looking for polyps, Ca, diverticula
3. GG - used instead of Ba in case of ? bowel perforation

Iodine based due to form soluble compounds and relatively low toxicity.

Either 1. Low Osmolar contrast medium (LOCM) or
2. High Osmolar Contrast Medium (HOCM).