Cannabis Users May Get False Positive Results on Nuclear Imaging Tests

A new study has found that cannabis users may get false positive results on nuclear imaging tests that are used to diagnose gastrointestinal disorders. The study, published in the Journal of Nuclear Medicine Technology, suggests that cannabis users should avoid consuming the drug for at least six hours before undergoing a gastric emptying scan, which measures how fast food moves through the stomach.

Gastric emptying scans are commonly used to evaluate patients with symptoms such as abdominal pain, nausea, bloating, or loss of appetite. The scans involve eating a meal that contains a radioactive tracer, and then taking images of the stomach at different time intervals to see how much of the tracer remains in the stomach. A normal result is when about half of the tracer leaves the stomach within two hours. A delayed result is when more than half of the tracer stays in the stomach after two hours, which indicates a condition called gastroparesis, or slow stomach emptying.

However, the study found that cannabis users may get delayed results even if they do not have gastroparesis, because cannabis can lower the gut motility, or the movement of food through the digestive tract. Cannabis can affect the gut motility by interacting with the cannabinoid receptors in the gastrointestinal system, which regulate the digestion and appetite. Cannabis can also affect the gut motility by altering the gut microbiome, or the balance of bacteria in the intestines.

The study reviewed the literature on the effects of cannabis on the gut motility and the gastric emptying scans, and found that cannabis can cause significant delays in gastric emptying in infrequent users, but not in chronic users. The study also found that the type, dose, and timing of cannabis intake can influence the results of the scans. The study recommended that patients should avoid cannabis intake for at least six hours before the scans, to avoid the risk of false positive results.

Why False Positive Results Matter

False positive results on gastric emptying scans can have serious consequences for patients and doctors, as they can lead to misdiagnosis, unnecessary treatments, or missed treatments. For example, patients who get false positive results may be diagnosed with gastroparesis, and may be prescribed medications or dietary changes that are not suitable for them. Alternatively, patients who have gastroparesis but get normal results because of chronic cannabis use may not get the proper diagnosis and treatment that they need.

False positive results can also affect the research and the understanding of the gastrointestinal disorders, as they can skew the data and the statistics. For example, false positive results may inflate the prevalence and the severity of gastroparesis, and may obscure the role of other factors, such as diabetes, obesity, or infections, in causing the condition.

Therefore, the study authors urged the nuclear medicine providers to be aware of the effects of cannabis on the gut motility and the gastric emptying scans, and to ask the patients about their cannabis use history and habits. The study authors also suggested that the nuclear medicine providers should educate the patients about the benefits and risks of cannabis use, and the importance of abstaining from cannabis before the scans.

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