# Understanding Tauroselcholic Acid (SeHCAT) Testing: A Patient's Guide to Diagnosing Bile Acid Malabsorption SeHCAT testing is a specialized diagnostic procedure that measures how well your intestines absorb bile acids, using a tiny amount of a radioactive tracer that mimics natural bile acids. When the body retains less than 15% of this tracer after seven days, the test is considered positive for bile acid malabsorption — a frequently overlooked cause of chronic diarrhea. The test is especially valuable for people with persistent diarrhea who have conditions such as Crohn's disease, prior gallbladder removal, or certain intestinal surgeries, and it helps doctors target treatment with medications called bile acid sequestrants. # Understanding Tauroselcholic Acid (SeHCAT) Testing: A Patient's Guide to Diagnosing Bile Acid Malabsorption ## Table of Contents - Key Points - What Is SeHCAT Testing and Why It Matters - Who Should Consider This Test - How the SeHCAT Test Works - Understanding Your Results - Conditions Linked to Bile Acid Malabsorption - Clinical Implications: What the Results Mean for You - Treatment Options After Diagnosis - Limitations of the Test - Recommendations for Patients - Frequently Asked Questions - Source Information ## Key Points - SeHCAT testing is a non-invasive diagnostic procedure that uses a tiny amount of radioactive tracer to measure bile acid absorption in the intestines. - It is recommended for chronic nonbloody diarrhea when there is Crohn's disease, prior gallbladder removal, intestinal surgery, radiotherapy, or chronic pancreatitis. - Retention of less than 15% of the tracer after seven days indicates bile acid malabsorption; retention of 15% or higher is normal. - A positive result helps guide treatment with bile acid sequestrants such as cholestyramine, colestipol, or colesevelam. - Limitations include limited test availability, possible medication interference, a small radiation exposure, and inability to identify the underlying cause. ## What Is SeHCAT Testing and Why It Matters SeHCAT stands for Selenium-75 Homocholic Acid Taurine. It is a diagnostic test designed to answer one specific question: are your intestines properly absorbing bile acids? Bile acids are digestive fluids produced by your liver and stored in your gallbladder. Normally, after helping you digest fats, most of these acids are reabsorbed in the final section of your small intestine (the terminal ileum) and recycled back to your liver. When this recycling process fails, excess bile acids spill into your colon, where they draw in water and stimulate bowel movements. The result is chronic, often watery diarrhea — a condition known as bile acid malabsorption (BAM) or bile acid diarrhea (BAD). This condition is more common than many people realize, yet it is frequently missed. The SeHCAT test provides a **non-invasive way to identify this often-overlooked cause of chronic diarrhea**, allowing doctors to guide treatment decisions that can significantly improve a patient's quality of life. ## Who Should Consider This Test According to the guidelines referenced in this article, the SeHCAT test is recommended for patients with **chronic nonbloody diarrhea**, particularly those who have any of the following: - A history of **terminal ileal resection** (surgical removal of the end portion of the small intestine) - A history of **cholecystectomy** (gallbladder removal surgery) - A history of **radiotherapy** (radiation treatment) to the abdomen or pelvis - A diagnosis of **Crohn's disease**, which often affects the terminal ileum - A diagnosis of **chronic pancreatitis** (long-term inflammation of the pancreas) The test is particularly useful when other common causes of chronic diarrhea — such as celiac disease, infections, or inflammatory bowel disease — have already been ruled out. In these situations, the SeHCAT test can uncover bile acid malabsorption as the hidden culprit behind persistent symptoms. ## How the SeHCAT Test Works The SeHCAT test is a straightforward procedure that takes place over two visits, roughly one week apart. ### Step 1: Ingesting the Tracer On your first visit, you will swallow a **capsule containing a radiolabeled synthetic bile acid**. This capsule contains a very small amount of radioactivity — specifically, selenium-75, a radioactive form of the element selenium, attached to a synthetic bile acid molecule. This tracer behaves exactly like a natural bile acid in your body, which is the key to the test's accuracy. ### Step 2: Measuring Retention Immediately after ingesting the capsule, you will have a baseline measurement taken using a **whole-body counter or scanner**. This device is similar to a large scanner that detects the small amount of radiation emitted by the tracer in your body. This baseline reading tells your doctor how much of the tracer you absorbed initially. You will return approximately **7 days later** for a second measurement. The scanner measures how much of the tracer remains in your body. The difference between the two readings tells your doctor what percentage of the bile acid tracer your intestines retained — and by extension, how well your body is reabsorbing bile acids. ## Understanding Your Results The results are expressed as the **percentage of SeHCAT retention** at day 7. Here is how doctors interpret the numbers: - **Retention less than 15%:** Considered a positive test, indicating bile acid malabsorption. This threshold is the standard diagnostic cutoff used in clinical practice. - **Retention of 15% or higher:** Considered normal, suggesting that bile acid absorption is functioning properly. In other words, if your body absorbs and recycles bile acids normally, most of the tracer will be retained in your body's recycling system after a week. If you have bile acid malabsorption, your body loses the tracer through the stool, and the retention percentage drops below that critical 15% mark. Lower retention percentages indicate more severe bile acid malabsorption. Some research studies also use additional thresholds — such as 10% for moderate and 5% for severe malabsorption — to guide treatment intensity, though the 15% cutoff remains the primary diagnostic standard referenced in this article. ## Conditions Linked to Bile Acid Malabsorption The research cited in this article identifies several conditions that can cause bile acid malabsorption and therefore trigger a positive SeHCAT test: 1. **Ileal resection or disease:** Surgery to remove part of the terminal ileum, or disease affecting this region, directly impairs the site where bile acids are normally reabsorbed. 1. **Crohn's disease:** This inflammatory bowel disease frequently affects the terminal ileum, disrupting bile acid absorption. 1. **Cholecystectomy (gallbladder removal):** Without a gallbladder to store and release bile acids in a controlled manner, bile acids can enter the intestine at different rates, overwhelming the ileum's absorption capacity. 1. **Chronic pancreatitis:** Long-term pancreatic inflammation can alter digestion in ways that interfere with bile acid handling. 1. **Radiotherapy:** Radiation treatment to the abdomen or pelvis can damage the intestinal lining, including the cells responsible for bile acid absorption. When no identifiable cause is found, the condition is called **idiopathic bile acid malabsorption** — meaning the malabsorption occurs without a clear underlying disease. Research cited in this article, including a study from the *Scandinavian Journal of Gastroenterology* (1988), has examined bile acid malabsorption in chronic diarrhea with special attention to the impact of gallbladder removal. ## Clinical Implications: What the Results Mean for You A positive SeHCAT test has important implications for your care. First, it provides a clear explanation for chronic diarrhea that may have been mysterious for months or years. Many patients report that simply having a diagnosis — and knowing that their condition is real and treatable — is a relief. Second, and more practically, a positive test identifies you as someone who is likely to benefit from treatment. The implications cited in the source article include: - The test helps identify patients with bile acid malabsorption, allowing for **targeted treatment with bile acid sequestrants**. - The test can help **rule out other causes of chronic diarrhea**, reducing the risk of misdiagnosis and unnecessary treatments (including unnecessary antibiotics, dietary restrictions, or other therapies that won't help). - Patients with bile acid malabsorption may experience **significant improvements in symptoms and quality of life** with appropriate treatment. The article also notes that SeHCAT testing has been **shown to be effective in identifying patients with bile acid diarrhea**, with a significant positive impact on patients' quality of life. ## Treatment Options After Diagnosis If your SeHCAT test is positive for bile acid malabsorption, your doctor will likely recommend treatment with a class of medications called **bile acid sequestrants**. These are medications that bind to bile acids in the intestine, preventing them from reaching the colon and causing diarrhea. Common examples include: - **Cholestyramine** (brand name Questran) — a powder mixed with liquid - **Colestipol** (brand name Colestid) - **Colesevelam** (brand name Welchol) — often better tolerated Your doctor will typically start you on a low dose and adjust it gradually based on your response. The SeHCAT test is not only useful for initial diagnosis — research cited in this article notes that it can also be used to **monitor your response to treatment and adjust the dosage of bile acid sequestrants as needed**. If your symptoms improve with treatment, that confirms the diagnosis and helps your doctor find the right maintenance dose. ## Limitations of the SeHCAT Test While the SeHCAT test is a valuable diagnostic tool, it does have limitations that you should understand. **The test is not widely available everywhere.** The radioactive tracer used in the test requires specialized facilities and nuclear medicine equipment, which means it may only be available at larger hospitals or referral centers. This article notes that the test requires no special preparation, which is a convenience, but the logistical barrier of availability remains real for some patients. **Medication interference is possible.** The article emphasizes that patients should inform their doctor of any medications they are taking, as **some medications may interfere with the test results**. Certain drugs that affect bile acid handling — such as bile acid sequestrants themselves — may need to be temporarily stopped before testing. **The test involves a small amount of radiation.** While the dose from selenium-75 is very small and generally considered safe, it is still a radioactive substance. Pregnant women and nursing mothers should discuss the risks and benefits with their doctor before undergoing this test. **It does not reveal the underlying cause.** A positive SeHCAT test tells you that bile acid malabsorption is present, but it does not tell you *why*. Additional testing — such as imaging, endoscopy, or blood work — may be needed to determine the root cause, especially if you don't have a known condition like Crohn's disease or prior gallbladder surgery. **The evidence base includes older studies.** Some of the research supporting SeHCAT testing dates back to the late 1980s and 1990s, including the study from *Medizinische Klinik* (1995) and the *Postgraduate Medical Journal* (1992). More recent prospective studies, such as the multicenter diagnostic accuracy protocol published in *JMIR Research Protocols* (2016), are ongoing or have been published since, continuing to strengthen the evidence base. ## Recommendations for Patients If you are experiencing chronic diarrhea and haven't found answers, here is what the guidelines and research suggest you should know: 1. **Talk to your doctor about SeHCAT testing** if you have chronic nonbloody diarrhea, especially if you have Crohn's disease, have had your gallbladder removed, have had intestinal surgery or radiation therapy, or have been diagnosed with chronic pancreatitis. 1. **Make sure other causes have been looked for first.** The test is most useful when other causes of chronic diarrhea have been ruled out. Your doctor may recommend stool tests, blood tests, or a colonoscopy before pursuing SeHCAT testing. 1. **Ask about the test before you undergo it.** The test requires no special preparation, but you should inform your doctor about all medications and supplements you take, as some can interfere with the results. 1. **Be aware of the testing schedule.** The test involves swallowing a capsule on day one, followed by a scan, and returning about 7 days later for a second scan. Plan accordingly. 1. **If your test is positive, ask about bile acid sequestrants.** Treatment with medications like cholestyramine, colestipol, or colesevelam can significantly improve symptoms. Your doctor may need to adjust the dose over time based on your response. 1. **Remember that a positive test is treatable.** Bile acid malabsorption is not something you simply have to live with. Many patients experience marked improvement in diarrhea and overall quality of life once they start appropriate treatment. ## Frequently Asked Questions ### What is SeHCAT testing and what does it measure? SeHCAT testing measures how well your intestines absorb bile acids using a tiny amount of a radioactive tracer that mimics natural bile acids. It helps diagnose bile acid malabsorption, a commonly overlooked cause of chronic diarrhea. If less than 15% of the tracer is retained after seven days, the test is considered positive. ### Who should consider having a SeHCAT test? The test is recommended for people with chronic nonbloody diarrhea, especially those with a history of terminal ileal resection, gallbladder removal, abdominal or pelvic radiotherapy, Crohn's disease, or chronic pancreatitis. It is also useful when other causes like celiac disease, infections, or inflammatory bowel disease have been ruled out. ### How does the SeHCAT test work? The test involves two visits about a week apart. You swallow a capsule containing a radiolabeled synthetic bile acid with a small amount of radiation. A baseline scan measures how much tracer is in your body. You return about seven days later for a second scan; the difference shows how much bile acid your intestines retained. ### What do my SeHCAT results mean? Results are expressed as the percentage of tracer retained at day 7. Retention below 15% is considered positive for bile acid malabsorption. Retention of 15% or higher is normal. Lower percentages indicate more severe malabsorption; some research uses 10% for moderate and 5% for severe cases. ### What treatment is available after a positive SeHCAT test? Your doctor will likely recommend bile acid sequestrants such as cholestyramine, colestipol, or colesevelam. Treatment usually starts at a low dose and is adjusted gradually. The SeHCAT test can also be used to monitor your response and adjust the dosage as needed. ### What are the limitations and risks of SeHCAT testing? The test is not widely available because it requires specialized nuclear medicine facilities. Some medications may interfere with results, so tell your doctor about all medicines. It involves a small radiation dose, generally considered safe, but discuss with your doctor if pregnant or nursing. A positive result does not reveal the underlying cause. ### When should a patient with chronic diarrhea and suspected bile acid malabsorption seek a second opinion? Consider a second opinion if you have chronic nonbloody diarrhea with risk factors like Crohn's disease, gallbladder removal, ileal surgery, pelvic radiation, or chronic pancreatitis, and standard evaluations have not identified a cause. The SeHCAT test is the diagnostic tool for bile acid malabsorption, but it is not available everywhere and requires specialized equipment. A positive result still does not explain why malabsorption occurs, so additional testing may be needed. A second opinion can help clarify whether SeHCAT testing is appropriate, interpret borderline results, or guide further investigation and treatment with bile acid sequestrants. Diagnostic Detectives Network provides independent expert second opinions. ## Source Information This patient-friendly article is based on peer-reviewed research and guideline-directed content compiled by the Dr.Oracle Medical Advisory Board. The original article, titled **"What is Tauroselcholic Acid (SeHCAT) testing?"**, was last updated on February 24, 2025, and was reviewed by a Medical Advisory Board. Key sources cited in the original article include: - **Guideline references (1 and 2):** Guideline Directed Topic Overview, Dr.Oracle Medical Advisory Board & Editors, 2025. - **Research reference 3:** "[Results of the 75selenium homotaurocholic acid retention test (SeHCAT test) in diagnosis of diarrhea]," *Medizinische Klinik* (Munich, Germany: 1983), 1995. - **Research reference 4:** "A Multicenter Prospective Study to Investigate the Diagnostic Accuracy of the SeHCAT Test in Measuring Bile Acid Malabsorption: Research Protocol," *JMIR Research Protocols*, 2016. - **Research reference 5:** "Use of the SeHCAT test in the investigation of diarrhoea," *Postgraduate Medical Journal*, 1992. - **Research reference 6:** "Bile acid malabsorption demonstrated by SeHCAT in chronic diarrhoea, with special reference to the impact of cholecystectomy," *Scandinavian Journal of Gastroenterology*, 1988. - **Research reference 7:** "Idiopathic bile acid malabsorption: qualitative and quantitative clinical features and response to cholestyramine," *Alimentary Pharmacology & Therapeutics*, 1998. *Note: This patient-friendly article is provided for educational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider for diagnosis and treatment recommendations specific to your situation.* --- Publisher: Diagnostic Detectives Network (https://diagnosticdetectives.com) — independent multi-expert medical second opinions, worldwide, private-pay. Author byline: Anton Titov, MD, PhD. Contact: https://diagnosticdetectives.com/pages/contact Canonical page: https://diagnosticdetectives.com/products/understanding-tauroselcholic-acid-sehcat-testing-a-patients-guide-to-diagnosing-bile-acid-malabsorption