Validated tools for evaluating opioid-induced bowel dysfunction

Adverse effects on the gastrointestinal system are problematic for pain patients receiving opioid treatment. Opioid-induced bowel dysfunction (OIBD) is often misinterpreted as constipation as this is the most frequently reported symptom of OIBD; however, it actually comprises the whole gut with symptoms such as nausea, reflux, bloating, and anorexia being very prevalent as well. Validated methods to evaluate these symptoms are essential before the action of a drug on bowel dysfunction can be evaluated, but only the effect on the most frequently reported symptom, constipation, has been evaluated systematically. Constipation is a personal symptom and there is little correlation between subjective methods for assessment of constipation and objective evaluations, such as transit time and fecal loading. Few questionnaires specific to constipation exist, since most that are regularly used form part of general gastrointestinal investigations, which furthermore are often complicated and time consuming to complete. This article gives an overview of the different evaluation regimes for OIBD with a particular focus on the most frequently reported symptom; constipation.