No specific laboratory or imaging tests can diagnose<unk> . Diagnosis should be based on symptoms, the exclusion of worrisome features, and the performance of specific investigations to rule out organic diseases that may present similar symptoms. The recommendations for physicians are to minimize the use of medical investigations. Rome criteria are usually used. They allow the diagnosis to be based only on symptoms, but no criteria based solely on symptoms is sufficiently accurate to diagnose<unk> . Worrisome features include onset at greater than 50 years of age, weight loss, blood in the stool, iron-deficiency anemia, or a family history of colon cancer, celiac disease, or inflammatory bowel disease. The criteria for selecting tests and investigations also depends on the level of available medical resources. Rome criteria The Rome IV criteria include recurrent abdominal pain, on average, at least 1 day/week in the last 3 months, associated with two or more of the following further criteria: * Related to defecation * Associated with a change in frequency of stool * Associated with a change in form (appearance) of stool Physicians may choose to use one of these guidelines or may simply choose to rely on their own anecdotal experience with past patients. The algorithm may include additional tests to guard against misdiagnosis of other diseases as<unk> . Such "red flag" symptoms may include weight loss, gastrointestinal bleeding, anemia, or nocturnal symptoms. However, red flag conditions may not always contribute to accuracy in diagnosis; for instance, as many as 31% of people with<unk>  have blood in their stool, many possibly from hemorrhoidal bleeding. The diagnostic algorithm identifies a name that can be applied to the person's condition based on the combination of symptoms of diarrhea, abdominal pain, and constipation. For example, the statement "50% of returning travelers had developed functional diarrhea while 25% had developed<unk> " would mean half the travelers had diarrhea while a quarter had diarrhea with abdominal pain. While some researchers believe this categorization system will help physicians understand<unk> , others have questioned the value of the system and suggested all people with<unk>  have the same underlying disease but with different symptoms. Differential diagnosis Colon cancer, inflammatory bowel disease, thyroid disorders (hyperthyroidism or hypothyroidism), and giardiasis can all feature abnormal defecation and abdominal pain. Less common causes of this symptom profile are carcinoid<unk> , microscopic colitis, bacterial overgrowth, and eosinophilic gastroenteritis;<unk>  is, however, a common presentation, and testing for these conditions would yield low numbers of positive results, so it is considered difficult to justify the expense. Conditions that may present similarly include celiac disease, bile acid malabsorption, colon cancer, and dyssynergic defecation. Ruling out parasitic infections, lactose intolerance, small intestinal bacterial overgrowth, and coeliac disease is recommended before a diagnosis of<unk>  is made. An upper endoscopy with small bowel biopsies is necessary to identify the presence of celiac disease. An ileocolonoscopy with biopsies is useful to exclude Crohn's disease and ulcerative colitis (Inflammatory bowel disease). Some people, managed for years for<unk> , may have non-celiac gluten sensitivity (NCGS). Gastrointestinal symptoms of<unk>  are clinically indistinguishable from those of NCGS, but the presence of any of the following non-intestinal manifestations suggest a possible NCGS: headache or migraine, "foggy mind", chronic fatigue, fibromyalgia, joint and muscle pain, leg or arm numbness, tingling of the extremities, dermatitis (eczema or skin rash), atopic disorders, allergy to one or more inhalants, foods or metals (such as mites, graminaceae, parietaria, cat or dog hair, shellfish, or nickel), depression, anxiety, anemia, iron-deficiency anemia, folate deficiency, asthma, rhinitis, eating disorders, neuropsychiatric disorders (such as schizophrenia, autism, peripheral neuropathy, ataxia, attention deficit hyperactivity disorder) or autoimmune diseases. An improvement with a gluten-free diet of immune-mediated symptoms, including autoimmune diseases, once having reasonably ruled out coeliac disease and wheat allergy, is another way to realize a differential diagnosis. Investigations Investigations are performed to exclude other conditions: * Stool microscopy and culture (to exclude infectious conditions) * Blood tests: Full blood examination, liver function tests, erythrocyte sedimentation rate, and serological testing for coeliac disease * Abdominal ultrasound (to exclude gallstones and other biliary tract diseases) * Endoscopy and biopsies (to exclude peptic ulcer disease, coeliac disease, inflammatory bowel disease, and malignancies) * Hydrogen breath testing (to exclude fructose and lactose malabsorption) Misdiagnosis People with<unk>  are at increased risk of being given inappropriate surgeries such as appendectomy, cholecystectomy, and hysterectomy due to being misdiagnosed as other medical conditions. Some common examples of misdiagnosis include infectious diseases, coeliac disease, Helicobacter pylori, parasites (non-protozoal). The American College of Gastroenterology recommends all people with symptoms of<unk>  be tested for coeliac disease. Bile acid malabsorption is also sometimes missed in people with diarrhea-predominant<unk> . SeHCAT tests suggest around 30% of people with D-IBS have this condition, and most respond to bile acid sequestrants. Comorbidities Several medical conditions, or comorbidities, appear with greater frequency in people with<unk> . * Neurological/psychiatric: A study of 97,593 individuals with<unk>  identified comorbidities such as headache, fibromyalgia, and depression.<unk>  occurs in 51% of people with chronic fatigue<unk>  and 49% of people with fibromyalgia, and psychiatric disorders occur in 94% of people with<unk> . * Channelopathy and muscular dystrophy:<unk>  and functional GI diseases are comorbidities of genetic channelopathies that cause cardiac conduction defects and neuromuscular dysfunction, and result also in alterations in GI motility, secretion, and sensation. Similarly,<unk>  and FBD are highly prevalent in myotonic muscle dystrophies. Digestive symptoms may be the first sign of dystrophic disease and may precede the musculo-skeletal features by up to 10 years. * Inflammatory bowel disease:<unk>  may be marginally associated with inflammatory bowel disease. Researchers have found some correlation between<unk>  and IBD, noting that people with IBD experience<unk> -like symptoms when their IBD is in remission. A three-year study found that patients diagnosed with<unk>  were 16.3 times more likely to be diagnosed with IBD during the study period, although this is likely due to an initial misdiagnosis. * Abdominal surgery: People with<unk>  were at increased risk of having unnecessary gall bladder removal surgery not due to an increased risk of gallstones, but rather to abdominal pain, awareness of having gallstones, and inappropriate surgical indications. These people also are 87% more likely to undergo abdominal and pelvic surgery and three times more likely to undergo gallbladder surgery. Also, people with<unk>  were twice as likely to undergo hysterectomy. * Endometriosis: One study reported a statistically significant link between migraine headaches,<unk> , and endometriosis. * Other chronic disorders: Interstitial cystitis may be associated with other chronic pain<unk> s, such as<unk>  and fibromyalgia. The connection between these<unk> s is unknown.
Irritable bowel syndrome
Bile acid malabsorption
Crohn's disease
Colorectal cancer
Ulcerative colitis
Non-celiac gluten sensitivity
IBS
Inflammatory bowel disease