Pros and Cons of the SeHCAT Test in Bile Acid Diarrhea: A More Appropriate Use of an Old Nuclear Medicine Technique

Bile acid malabsorption (BAM) causing chronic diarrhea may be due to organic as well as functional disorders, and some of them were included under the general label of diarrheic-type irritable bowel syndrome (IBS-D). The 75-selenium homocholic acid taurine (SeHCAT) test is a nuclear medicine investigation considered to be the gold standard for the diagnosis of bile acid malabsorption (BAM). Many studies demonstrate that it could be effective in the clinical workout of chronic diarrhea due to different conditions. The SeHCAT test provides a quantitative assessment to estimate the severity of BAM and the possible response to therapy with bile acid sequestrants (BASs). However, there is no general agreement regarding its cutoff value and the test is not widely available. The aim of this review is to discuss the advantages and disadvantages of the SeHCAT test in clinical practice.

General Medical Issues

People with DLB and PDD tend to be middle-aged and older. In this age group, selected general health issues deserve discussion. Comprehensive medical care is beyond the scope of this book, but several general medical topics should be addressed here. People with Lewy disorders commonly experience walking difficulties. The risk of falling may surface early or later in the condition. Fracture risk is also a concern, and preemptive action is wise. Falls can be tolerated if bones are strong; witness athletes who fall on a football field. Over the course of a lifetime, bones tend to lose their strength and become more prone to fractures. When the loss of bone integrity is substantial we categorize this as osteoporosis. There are specific criteria that doctors use to define osteoporosis. While bone integrity is measured in several ways, the most common and accepted measurement is by imaging with a nuclear medicine technique. A quick scan after injection of a radioisotope that is taken up by bones generates a picture and numeric data; these can be compared to those of normal subjects. This analysis is termed a nuclear medicine bone density study and sometimes is called a DEXA scan. Using the numeric measures from a bone density scan, reductions of bone integrity fall into two classes. We have already mentioned that substantial loss of bone strength is termed osteoporosis. A less severe reduction of bone integrity has been defined and termed osteopenia. Restated, mild bone weakening is osteopenia, and marked loss of bone integrity is osteoporosis. Conventionally, osteoporosis is treated with prescription medications, whereas the lesser problem of osteopenia is not. However, if there is a substantial fall risk, some clinicians would advise treating osteopenia with a prescription drug (see below). Who is at risk for osteoporosis? In the general population, advancing age is the major risk factor. Women over age 60 and men over age 70 fall into these risk categories, as well as those with very sedentary lives. In the context of DLB or PDD, osteoporosis is especially important to consider.

Positron Emission Tomography: A Technology Assessment

Positron emission tomography (PET) is a new nuclear medicine technique that has recently entered the clinical realm of medicine. Although it is a technique that can be utilized for assessment of biochemical and physiological parameters of any organ in the body, it has particular utility in the investigation of the brain. PET poses unique advantages over previous imaging devices. For the first time, it is feasible to investigate directly various biological parameters of the brain in a noninvasive way. PET allows for investigating the functional, biochemical, physiological, and pharmacological characteristics of various areas within the brains of normal and psychiatric or neurological patients. Although it has already started to give promising results, it is too new a technique to obtain an accurate appraisal of its true potentials. This is a problem that seems always to surface when one tries to evaluate the utility of a new technique in a new area of research. The problem is accentuated in the case of PET where there is no other technique available with which to compare results. This paper will discuss the basic principles of PET, its relationship to other existing imaging devices, and the issues to be considered when making a technological assessment of positron emission tomography.