Updated on February 8, 2023
Despite the best efforts of clinicians, certain diseases are difficult to diagnose. Many conditions share common symptoms like inflammation, diarrhea, nausea, headache, constipation, and more, leaving physicians to make educated guesses based on the probability of a given disease. Under this framework, physicians are more inclined to diagnose common, yet relatively less harmful diseases first, than correct their diagnosis to a more serious disease later if necessary.
Although physicians are generally skilled at separating symptom clusters that occur in different diseases, irritable bowel syndrome (IBS) is a particularly common misdiagnosis due to the breadth of its symptoms and its prevalence as a disease. When added to the fact that IBS is nonfatal and its therapies are typically easy to tolerate, doctors are at high risk of making an incorrect IBS diagnosis; an IBS diagnosis is unlikely to stigmatize the patient, and the diagnosis is unlikely to traumatize the patient when compared to other possible diagnoses. Unfortunately, an incorrect diagnosis of IBS can result in protracted therapy cycling that fails to address the underlying non-IBS pathology, leaving patients to struggle with distressing and potentially dangerous symptoms.
Being an informed patient with an IBS diagnosis or other gastrointestinal pathology means staying abreast of the various conditions that might be mistaken for irritable bowel syndrome. Likewise, being a skilled practitioner means understanding the ways in which other diseases might present similarly to IBS in the clinic. Furthermore, both patient and physician should reassess the IBS diagnostic process such that the right disease is addressed.
IBS can be challenging to diagnose properly because it is not a well-understood or easily identified disease. There are no blood tests for IBS, nor does visual examination or equipment-assisted imaging provide answers. Furthermore, IBS symptoms have no single identifiable trigger, which means they can appear to be transient and without cause or incorrectly associated with a benign stimulus like certain foods. This also leads to confident yet incorrect diagnoses, because corrective action, like refraining from consuming suspected trigger foods, might coincide with a long period without an IBS flare up.
Without objective diagnostic methods, physicians often diagnose IBS using their own judgment, which they are trained to supplement with several clinical diagnostic rubrics. Like elsewhere in medicine, diagnostic rubrics for IBS are pioneered by clinicians, substantiated by research studies, and then refined and eventually replaced by subsequent cooperation between physicians and researchers. The original diagnostic rubric for IBS states there are several core symptoms that always occur:
Since the publication of this rubric, a number of others have emerged, each of which has its own advantages and disadvantages, with some being better at proving IBS specifically and others more effective at ruling out other diseases. Physicians typically use the rubric they were trained with, barring hospital policy to use a specific rubric. Rubrics also place different weights on different symptoms; where mucus and the feeling of incomplete bowel evacuation could be core symptoms to one rubric, they might only be attendant symptoms to another. This inconsistency allows for a wide degree in variation of diagnostic practices.
The tests called for by these diagnostic guidelines are not consistently applied either. According to one study on IBS diagnosis, none of 149 patients were diagnosed using all of the tests required by the most recent guidelines. Even the most common tests—including a basic blood test, a chemistry panel, blood sedimentation rate testing, and a serum thyroxine assay—were inconsistently performed. The researchers found that only 42 percent had a basic blood test, and 41 percent underwent colon imaging. Because IBS is typically diagnosed via exclusion of other similar diseases, insufficient testing leaves a larger area for misdiagnoses to occur. Certain diseases might only show up on a blood test, whereas others might only show up via an imaging study. Other conditions, like mental health disorders or illnesses, that cause a minority of gastrointestinal symptoms might only be correctly diagnosed instead of IBS if a specific questionnaire regarding that condition was administered to the patient, a highly unlikely possibility when the patient is complaining predominantly of gastrointestinal symptoms. Building a basic understanding of these alternative health conditions is necessary for clinicians who want to minimize their misdiagnosis rate and patients who want to ensure their diagnosis is correct.
Because diagnosing IBS correctly is difficult, that difficulty can spill over into making correct diagnoses of other diseases affecting the gastrointestinal tract. In the absence of biopsies or lab results confirming another condition, IBS is an easy go-to diagnosis for a clinician to make because of its transient symptoms, which tend to be of moderate severity. Owing to the inherent ambiguity of the language patients use to describe their issues to their physicians, complaints about gastrointestinal symptoms that aren’t severe enough to be viral and aren’t mild enough to be associated with a non-gastrointestinal disease are at high risk of misdiagnosis as IBS.
Inflammatory bowel diseases (IBDs), like Crohn’s disease and ulcerative colitis, are often initially misdiagnosed as IBS. IBDs are characterized by inflammation, bloating, gas, pain, and often rectal bleeding, all symptoms shared with IBS to some degree. These symptoms are accompanied by disturbances to the microbiome, a propensity for inflammatory episodes, and diminished quality of life. The reasons for misdiagnosis are simple: IBS symptoms often overlap with IBD symptoms, IBS can be comorbid with IBDs, and IBS is a much less serious diagnosis. In the event of a patient with both IBS and an IBD, it might be impossible for a physician to separate the symptoms of IBS from the symptoms of the IBD, especially if the IBD’s onset is relatively recent. Without a history of severe gastrointestinal issues, the diagnosis of IBS is more expedient.
Unfortunately, the differences between IBS and IBDs are often difficult for clinicians to determine even when both are confirmed. However, unlike IBS, IBDs are clinically diagnosable with a variety of blood tests, biopsies, and imaging tests thanks to their telltale inflammation and physical damage to the gastrointestinal tract. Notably, IBDs get better with pharmaceutical therapies targeted at the gut, whereas IBS might not. It’s easy to imagine that a patient could be diagnosed with IBS during the early development of their IBD and fruitlessly spend months or longer trying to address it.
Due to the large degree of overlap between celiac disease and IBS symptoms, physicians diagnosing a patient with both conditions could fail to recognize the presence of celiac, focusing solely on the IBS diagnosis. This problem is widespread and is often complicated by coincidence of other pathologies that more strongly suggest IBS than a diagnosis of celiac disease. One study found that of 200 patients who had IBS, 54 patients of them also had celiac disease that was diagnosable via a blood test. Notably, if these patients were initially diagnosed with IBS using a clinical rubric alone, they might never have received the blood test necessary to detect celiac disease, leaving them to suffer with celiac symptoms without understanding why. Although the diagnostic history of these 54 patients is unknown, it’s likely that at least several of them faced an initial IBS diagnosis before their celiac disease was subsequently diagnosed after their symptoms persisted.
Additionally, patients with celiac disease might not have IBS whatsoever, but could receive a fundamentally incorrect diagnosis as the result of misattributed symptomatology and an absence of testing.
Gluten sensitivity is an increasingly common disorder in which patients experience indigestion, pain, bloating, and gas after consuming gluten-rich foods, such as bread and most starchy vegetables. Although gluten sensitivity is traditionally thought to primarily be a consequence of celiac disease, a new scientific understanding of gluten sensitivity has shown that it can occur independently of other disorders. Today, gluten sensitivity is increasingly associated with IBS, although inconsistently so within the dietary history of a single person. Therefore, a person with gluten sensitivity might or might not have IBS, but a person with IBS is more likely than a healthy control to have some degree of gluten sensitivity. This complicates diagnosis substantially. Because of its seemingly unpredictable gastrointestinal symptoms and transient flare-ups, gluten sensitivity is at high risk of being misdiagnosed as IBS in patients who do not have IBS and missed in patients who have comorbid IBS and gluten sensitivity.
As noted in a study connecting IBS to gluten sensitivity and IBDs, gluten sensitivity is prone to induce symptoms similar to IBS. This is the case whether the gluten sensitivity is associated with another pathology like celiac disease or whether it is in isolation. The consequences of gluten sensitivity misdiagnosed as IBS are clear: an incorrectly diagnosed patient will continue to consume gluten and continue to have flare-ups despite ongoing therapy for IBS. Therapy for IBS will do little to address the gastrointestinal intolerance of gluten, and the patient will suffer.
Physicians have long thought that IBS has a psychiatric component. Indeed, most accounts of IBS consider anxious, depressive, and obsessive symptoms to be features of the condition. However, whether these components cause IBS or are themselves caused by IBS is unclear, which places them at high risk of misdiagnosis. As found in one 2007 study, 46 of 95 patients diagnosed with depression and IBS experienced no IBS symptoms when their depression was in remission, suggesting that IBS symptom presence and severity are closely tied to psychiatric phenomena.
Stress, mood changes, and mild anxiety are very likely to be comorbid with IBS, even though their symptoms are not commonly understood to be as viscerally uncomfortable. Patients with mild anxiety could also have gastrointestinal systems that might either indicate IBS or be subclinical and not severe enough to truly meet the diagnostic criteria for IBS. However, given that patients are more likely to go to their physician and complain about viscerally discomforting pathologies than psychological distress, IBS is an easy diagnosis to make when it’s masking emotional illnesses that are the root cause of symptoms. The growing medical consensus on IBS is thus that it is a predominantly psychosomatic disorder that could be inseparable from these other common psychiatric conditions. The takeaway is that patients diagnosed with IBS who also have low mood, excessive worry, or other symptoms consistent with mild anxiety should seriously consider getting a second opinion.
Of the diagnoses that an IBS diagnosis can mask, perhaps the most serious is that of stomach cancer. Stomach cancer is characterized by heartburn, nausea, blood in stools, indigestion, pain, diarrhea, loss of appetite, and constipation. This condition is difficult to diagnose under ideal conditions and often does not present itself symptomatically until it is in an advanced stage, at which point survival rates are extremely low; less than 10 percent of patients survive more than five years after late-stage diagnosis. Nonetheless, if the cancer is caught early and action is taken quickly, stomach cancer is survivable and even curable with the help of surgery. Under these conditions, however, an incorrect IBS diagnosis could easily be fatal.
Notably, the symptoms that differentiate true IBS from stomach cancer are likely the associated emotional disorders because stomach cancer pre-diagnosis is not associated with emotional disturbances, like mild anxiety, whereas IBS is. If an IBS diagnosis is made without a brief mental health inventory, blood test, or biopsy, then there is a chance it could be hiding a much more pernicious disease.
Colon cancer is yet another serious disease that could be hiding beneath an incorrect IBS diagnosis. Much like with stomach cancer, colon cancer’s symptoms include bloody stools, pain, fatigue, indigestion, and discomfort. Bloody stools are typically the symptom that a physician would use to easily differentiate IBS from a more serious illness like colorectal cancer, which means that a patient going to their physician before experiencing that symptom might be misdiagnosed. Patients with inflammatory bowel diseases are at a much higher risk for colon cancer, which means an initial missed diagnosis or misdiagnosis could cause the physician to miss critical signs of subsequent cancer.
Colon cancer is more treatable than stomach cancer, however. Patients who are misdiagnosed with IBS might have a greater chance of survival thanks to a plethora of surgical and chemotherapy options that are effective enough to rescue a patient with a somewhat late diagnosis. Furthermore, unlike stomach cancer, failure to make a colorectal cancer diagnosis is likely to be addressed in a subsequent screen as part of general adult health maintenance for patients at risk.
Most of the diseases commonly misdiagnosed as IBS are chronic and unlikely to respond to IBS therapies. Likewise, IBS itself is chronic and might not always respond to therapies specifically targeted at it after a correct diagnosis. Patients and their physicians are thus left in a difficult position where they are forced to act on incomplete and potentially incorrect information under the best of circumstances. If an incorrect IBS diagnosis—or missed diagnosis in the presence of comorbid conditions—prevents treatment of another disease that can carry permanent damage, then the chance of long-term consequences is very high. In the case of Crohn’s disease, for example, scarring to the gastrointestinal tract might be impossible to repair even after the diagnosis is rectified, resulting in chronic difficulty with bowel movements, nutrient absorption, and comfortable digestion.
Not all hope is lost, however. Diligence and awareness of IBS’s common position as a first and incorrect diagnosis can address the danger of prolonged misdiagnosis. This means that a patient needs to ensure their physicians has ruled out the most common misdiagnoses after receiving an IBS diagnosis. Patients also need to remain vigilant even after they leave the clinic; if patients receive an IBS diagnosis and their symptoms do not reside quickly, then they must follow up with their physician promptly. Doing so will limit the damage caused by a misdiagnosis and get therapy on the right track. Rather than hoping for a correct initial diagnosis, patients need to take an active role in their care.
For their part, physicians need to use differential diagnostic techniques that take into account the possibility of comorbidities or non-IBS root causes. Following up with the patient regularly will also help to confirm or refute the initial diagnosis. Likewise, physicians must endeavor to be consistent and comprehensive in their diagnostic practices of IBS lest they damage the therapeutic relationship with their patients and tarnish their reputations. With a strong therapeutic alliance and careful application of diagnostic guidelines for a panorama of diseases, moving beyond systemic IBS scapegoating is possible.
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