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Gastric scintigraphy

Discuss gastric scintigraphy?

Gastric emptying scintigraphy of a radiolabeled solid meal is the gold standard for the diagnosis of gastroparesis.   Measurement of emptying of solids is more sensitive by scintigraphy. This is due to the fact that liquid emptying may remain normal despite advanced disease.

Consensus recommendations for a standardized gastric emptying procedure have recommended a universally acceptable 99-m technetium sulphur-colloid labelled low fat, egg-white meal. Retention of over 10% of the solid meal after 4 h is abnormal. A grading of severity based on 4 h values might be used: grade 1 (mild), 11%-20% retention at 4 h; grade 2 (moderate), 21%-35% retention at 4 h; grade 3 (severe), 36%-50% retention at 4 h.

What is gastroparesis and how is it diagnosed?

Gastroparesis is diagnosed when symptoms such as nausea, vomiting, early satiety, postprandial fullness, abdominal discomfort, and pain are associated with objective evidence of delayed GE in the absence of obstruction, and typically with impairment in maintenance of normal nutrition using standard food (see reference).

Rapid gastric transit (dumping syndrome) can also be diagnosed.

What are the potential problems with interpretation of gastric emptying scintigraphy?

As Gastric emptying scintigraphy is the gold standard, and there is difficulty in comparing it with any other investigation, the difficulty is establishing normal values in normal patients. There is obviously an ethical concern in doing the study in normal patients to establish normal values, owing to the radiation dose.

The recent consensus statement recommends imaging at 0, 1, 2 and 4 hours, although an older measure of gastric emptying was the T50, or time for the gastric activity to reach half of its original value. By standardizing the protocol (for timings of imaging and the nature of the meal) wherever it is used, it is hoped that normal values can be established and interpreted. Variations in the imaging protocol result in variations in the values obtained, caused by test rather than patient factors and decreases the reliability of the test.

Reference

Consensus Recommendations for Gastric Emptying Scintigraphy: A Joint Report of the American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine

Edited by Dr Iain Au-Yong


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