It Is Time for a New IBS Paradigm

Abstract

In the 1980s, H. Pylori was discovered as the root cause of peptic ulcer disease and revolutionized treatment. Previously, this illness was treated as a somatoform illness, associated with Type A personalities. Similarly, there is now overwhelming evidence that the root cause of IBS (Irritable Bowel Syndrome) originates from the development of bacterial dysbiosis, yet diagnosis and treatment are not routinely offered to patients. Instead, patients are offered palliative measures. A paradigm shift for IBS management is urgently needed.

During my early college years, I developed stabbing abdominal pain during fasting, often relieved by eating. Acidic foods like tomato sauce or lemon juice incited the pain. Initially, I managed with just tea or milk and developed a grazing habit to keep the symptoms at bay, but the pain progressed. One day, I passed black, tarry stools. I wouldn’t learn the term “melena” for another 4 years, but I knew there was something seriously wrong, and sought medical care. My father, a cardiovascular surgeon, pulled some strings to get me seen by a GI colleague expeditiously.

The gastroenterologist agreed to see me after hours and performed an unsedated endoscopy during that first visit. That was fun. I obeyed his firm “Swallow, swallow” commands while everything inside me screamed “Eject! Eject!”—a most unnatural experience. At the end of the visit, he announced his diagnosis with gravitas and certainty: “You have gastritis and a bleeding peptic ulcer. Since you’re not an alcoholic, the cause is stress—and your Type A personality.” He prescribed a four-week course of a proton pump inhibitor (PPI) and suggested, half-jokingly, that I get a personality transplant. I was stunned. How was I supposed to not stress? It was finals week.

Fortunately for me—or not—my father often read surgical journals over dinner, planting open-viscera photos unceremoniously beside my spaghetti Bolognese and beef. I remembered seeing something in those pages about a bacterial cause of ulcers. I started reading his journals.

Helicobacter pylori was discovered in 1982 by Australian doctors Barry Marshall and Robin Warren, who’s landmark 1984 Lancet study identified the bacterium as a cause of ulcers. ¹ They would subsequently receive a Nobel Prize for their discovery in 2005. ² But in the early 1990s, when I developed my ulcer, their findings were still met with skepticism. One decade after their discovery, this knowledge had not yet percolated into mainstream awareness or changed the clinical paradigm. Indeed, Munnangi and Sonnenberg noted that by 1995, 75% of ulcers were still treated only with anti-secretory medications, and just 5% received antibiotics. ³ It would take nearly 2 decades for antibiotic therapy to become standard care for H. pylori–related ulcers.

Predictably, the PPI course abated my symptoms, but the pain returned. At the follow-up visit, I asked—humbly—whether H. pylori could be the cause. After all, I had lived in regions of South America where it’s endemic. The gastroenterologist scoffed but grudgingly ordered an H. pylori antigen—not without first expressing his irritation. It came back positive. After a course of pantoprazole, clarithromycin, amoxicillin, and pink bismuth, I was finally cured. I didn’t need a personality transplant after all.

A similar paradigm shift is overdue for the diagnosis and management of irritable bowel syndrome (IBS). IBS is common, affecting an estimated 10-20% of the population ⁴ and accounting for up to 30% of outpatient gastroenterology visits. ⁵ Like ulcers once were, IBS is still framed as a psychosomatic disorder—stress or anxiety manifesting as GI symptoms. Lacking visible signs on colonoscopy, it’s often dismissed by practitioners. Diagnosis still relies on 2021 ROME IV criteria, which are clinical rather than biologic. ⁶

Yet substantial evidence now links IBS to bacterial etiology, or more specifically, bacterial dysbiosis.^7-9 Dysbiosis may arise from:

1. Overgrowth of gas-producing bacteria in the small intestine

2. Colonic pathobionts

Small intestinal gas producers—such as E. coli, Klebsiella, Proteus, and Methanobrevibacter species—are associated with other gastrointestinal pathologies, including diverticulitis, diarrheal illnesses, constipation, and even resistant urinary tract infections. ¹⁰ Colonic pathobionts such as Desulfovibrio and Fusobacterium species, or protozoa like Giardia and Entamoeba, are also associated with diarrheal and inflammatory bowel illnesses.^15,16

Diagnostic tools exist but are not yet standard of care. Breath testing can identify small intestinal bacterial overgrowth (SIBO), intestinal methanogen overgrowth (IMO), and hydrogen sulfide overgrowth (HSO) in many cases. Breath tests have been derided for showing only 50-65% sensitivity for SIBO, but their specificity is over 80%, as such, they can be helpful in determining a cause when positive. Newer tests detect hydrogen sulfide, increasing test sensitivity. In contrast, colonic aspiration with a single-lumen catheter—the gold standard—suffers 20% contamination in the best of cases, and is inaccessible for diagnosis. Since IBS has more than one cause, breath testing will only capture IBS due to overgrowth patterns in the small intestine, not other etiologies. The 2020 ACG guidelines gave conditional recommendations for breath testing, yet its use remains infrequent in practice. ¹¹ Stool testing with microbiome analysis can detect a second type of dysbiosis, caused by toxin-producing pathobionts in the colon, increasing diagnostic accuracy. Lastly, anti-vinculin antibody testing can identify post-infectious IBS, a subtype linked to autoimmune dysmotility. ¹²

Treatment options also exist. Rifaximin monotherapy and dual therapy with anaerobic coverage (with either metronidazole or neomycin) treat traditional SIBO and methanogen overgrowth (IMO), respectively. Yet insurance coverage for both diagnostics and treatments remains poor, and rifaximin requires prior authorization—adding onerous burdens for patients and providers alike. As such, herbal treatments have shown non-inferiority to rifaximin ¹³ and may offer an accessible alternative, meriting additional study.

Rome IV guidelines define IBS as a complex functional disorder involving food sensitivities, visceral hypersensitivity, motility issues, somatization, and dysbiosis. ⁶ Mainstream IBS treatment focuses on symptom relief—motility agents, antidepressants, elimination diets, and stress reduction, but largely downplays the role of dysbiosis. While the above measures are effective at temporarily reducing symptoms, they are palliative, not curative. Patients are reassured that IBS is a chronic psychosomatic illness that must be managed with lifelong stress reduction, prokinetics, and restrictive diets, resulting in patients organizing their lives around the management of their symptoms. This is no better than treating H. pylori with lifelong PPI therapy and recommending a personality transplant. While mind-body interventions improve IBS symptoms^20,21 due to the vast collection of neurons hardwiring the enteric nervous system to the brain, this connection remains--notably--bidirectional. ¹⁴ There is increasing evidence for the role gut dysbiosis plays in neuroinflammation and neurodegeneration.^18,19 And if both IBS symptoms and neurologic symptoms resolve when the dysbiosis is corrected--as it often does in my practice--can it really be that complex?^16,17 Or are we overcomplicating a curable condition by clinging to an outdated paradigm? Rather than focusing on complexity and labeling patients with a lifelong functional disorder, isn’t it rather more elegant to start identifying—and treating—the underlying dysbiosis, especially if it reveals itself to be the main driver of illness, and particularly when it is entirely reversible?

We need more treatment options for IBS. For instance, intestinal methanogen overgrowth remains difficult to treat because methane-producing archaea resist conventional antibiotics, making this subtype of IBS more refractory to treatment. Development of more therapeutic options is necessary. Insurance coverage for breath and stool testing is essential to make diagnosis accessible. Anti-vinculin antibody testing could be made available by conventional laboratories. Gastroenterologists need training in dysbiosis-centered diagnosis and treatment—a skillset that could improve care for up to a third of their clinical encounters.

Clinical guidelines, testing, treatment, and GI training must all evolve. But we cannot push for these advances if we remain wedded to a flawed paradigm that frames IBS as a complex psychosomatic disorder with no cure. Forty-plus years after H. pylori was first reported—and one Nobel Prize later—we must finally learn the lesson: diseases long written off as “in your head” may in fact be of bacterial origin. Treating IBS as a psychosomatic illness must fall out of fashion. Evidence demands it.

IBS doesn’t have to be a chronic illness. It is often curable. We can do better.