Gastroenterology

Gastroenterology is the branch of medicine focused on the digestive system and its disorders — encompassing everything from the esophagus and stomach to the small intestine, colon, liver, gallbladder, and pancreas. For patients with chronic illness, digestive complications are often an overlooked but profoundly impactful dimension of daily life. Understanding your gut is a critical part of understanding your overall health.

IBS vs. IBD: Understanding the Difference

Two of the most commonly confused digestive conditions are Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD). While they share some overlapping symptoms — abdominal pain, cramping, changes in bowel habits — they are fundamentally different conditions with distinct causes, mechanisms, and treatments.

Irritable Bowel Syndrome (IBS)

IBS is a functional disorder — meaning the digestive system appears structurally normal on imaging and biopsy, but does not function correctly. There is no inflammation, no tissue damage, and no increased risk of colorectal cancer. IBS is diagnosed based on symptoms using the Rome IV criteria, which requires recurrent abdominal pain at least one day per week, associated with changes in stool frequency or form. IBS affects an estimated 10–15% of the global population and is one of the most common reasons people visit a gastroenterologist, according to the International Foundation for Gastrointestinal Disorders (IFFGD). It is classified into subtypes: IBS-C (constipation-predominant), IBS-D (diarrhea-predominant), and IBS-M (mixed).

The exact cause of IBS is not fully understood, but contributing factors include gut-brain axis dysregulation, altered gut motility, visceral hypersensitivity (the gut feeling pain more intensely than normal), post-infectious changes, and psychological stress. IBS does not cause permanent harm to the intestines, but it can severely impact quality of life.

Inflammatory Bowel Disease (IBD)

IBD is a structural, autoimmune condition characterized by chronic inflammation of the gastrointestinal tract. Unlike IBS, IBD causes real, visible damage to the intestinal lining — which can be seen on colonoscopy, imaging, and biopsy. Left untreated, IBD can lead to serious complications including bowel obstruction, fistulas, abscesses, perforation, and an increased long-term risk of colorectal cancer. IBD affects approximately 3 million Americans, according to the CDC, and its incidence is rising globally, particularly in newly industrialized countries.

Crohn's Disease & Ulcerative Colitis: The Two Forms of IBD

The two primary forms of IBD are Crohn's disease and ulcerative colitis (UC). Though both involve chronic inflammation of the digestive tract, they differ in location, depth of inflammation, and clinical presentation.

Crohn's Disease

Crohn's disease can affect any part of the GI tract from mouth to anus, though it most commonly involves the end of the small intestine (the terminal ileum) and the beginning of the colon. The inflammation in Crohn's is transmural — meaning it penetrates through all layers of the intestinal wall — which is why it more frequently leads to complications like strictures, fistulas, and abscesses. Symptoms include severe abdominal cramping, chronic diarrhea, fatigue, weight loss, and nutritional deficiencies. Crohn's can also cause extraintestinal manifestations affecting the joints, skin, and eyes. The Mayo Clinic notes that Crohn's disease follows a relapsing-remitting course — periods of active disease alternate with periods of remission.

Ulcerative Colitis

Ulcerative colitis is confined to the colon (large intestine) and rectum, and the inflammation is limited to the innermost lining (mucosa). It typically begins in the rectum and extends proximally in a continuous pattern. Key symptoms include bloody diarrhea, urgent bowel movements, rectal pain, and fatigue. UC is classified by extent: proctitis (rectum only), left-sided colitis, or pancolitis (entire colon). The risk of colorectal cancer increases significantly with long-standing, extensive UC, making regular surveillance colonoscopies essential. The Crohn's & Colitis Foundation provides comprehensive resources for patients navigating both conditions.

The Role of Stress in Crohn's, Ulcerative Colitis, and Other GI Conditions

Stress doesn't merely make gastrointestinal symptoms feel worse — it is a physiologically active trigger that can initiate, perpetuate, and worsen both IBD and IBS through measurable biological mechanisms. The gut and brain are in constant two-way communication via the gut-brain axis — a bidirectional network involving the enteric nervous system (the "second brain" embedded in the gut wall), the vagus nerve, and the hypothalamic-pituitary-adrenal (HPA) axis. When psychological or physiological stress activates the HPA axis, it elevates cortisol and pro-inflammatory cytokines, disrupts intestinal barrier function ("leaky gut"), alters gut microbiome composition, and accelerates or slows gut motility depending on the individual. In people with IBD, multiple studies have confirmed that perceived stress is independently associated with increased disease activity, shorter time to relapse, and reduced response to treatment. In IBS, stress amplifies visceral hypersensitivity — the gut's exaggerated pain response — and disrupts the normal rhythm of intestinal contractions. Treating GI conditions without addressing their psychological and stress dimensions is, in many cases, treating only half the picture.

What Does a Flare-Up Look Like?

Understanding what a flare-up looks and feels like is critical — both for patients managing their own condition and for caregivers providing support. Flares differ significantly between IBD and IBS, and between Crohn's disease and ulcerative colitis.

Best Diet During a Flare-Up

Nutrition during an active flare is one of the most important and least discussed aspects of GI disease management. For IBD flares (Crohn's and UC), the goal is to reduce the workload on an already inflamed gut while maintaining adequate nutrition. A low-residue, low-fiber diet is typically recommended during acute flares: white rice, plain pasta, white bread, peeled and cooked vegetables, lean proteins (chicken, fish, eggs), bananas, applesauce, and canned low-fiber fruits. Broths and oral rehydration solutions help replace fluids and electrolytes lost through diarrhea. Avoid raw vegetables, whole grains, seeds, nuts, high-fat foods, alcohol, and caffeine during active flares. In moderate-to-severe Crohn's flares, exclusive enteral nutrition — liquid formulas delivering pre-digested nutrients that bypass the need for normal digestion — has been shown to induce remission in up to 80% of pediatric Crohn's patients and is an effective first-line therapy. Small, frequent meals (5–6 per day) are better tolerated than large meals. For IBS flares, the evidence-based low-FODMAP diet remains the gold standard, combined with soluble-fiber foods (oats, bananas, potatoes) that soothe rather than irritate the bowel.

Managing Stress to Reduce Flares

Both IBD and IBS respond meaningfully to stress reduction interventions — not as alternatives to medical treatment, but as powerful complements. The most evidence-supported approaches include: cognitive behavioral therapy (CBT), which has demonstrated reduced IBD flare frequency and significantly improved IBS symptom scores in randomized controlled trials; gut-directed hypnotherapy, which has shown 70–80% symptom improvement in IBS in multiple studies; and mindfulness-based stress reduction (MBSR), which reduces perceived stress, anxiety, and IBD disease activity scores. Regular moderate aerobic exercise reduces systemic inflammation and cortisol levels, benefiting both IBD and IBS. Adequate, consistent sleep is critical — poor sleep is an independent predictor of IBD relapse. Biofeedback and progressive muscle relaxation have also demonstrated measurable benefit in functional GI disorders. For patients with IBD, collaborative care models that integrate gastroenterology and behavioral health — sometimes called "GI-psychiatry" — are increasingly recognized as best practice in managing the chronic stress-inflammation cycle.

Chronic Intestinal Inflammation & Latest Treatments

Chronic gastrointestinal inflammation — whether from IBD, microscopic colitis, or other conditions — represents the immune system in a state of sustained, misdirected attack against the intestinal lining. Over time, this damages the gut barrier, disrupts the microbiome, and contributes to systemic inflammation that can affect organs well beyond the digestive tract. Managing this inflammation is the cornerstone of IBD treatment.

Biologic Therapies

The most significant advancement in IBD treatment over the past two decades has been the development of biologic medications — targeted therapies that block specific inflammatory proteins or pathways. Key classes include:

• Anti-TNF agents (infliximab/Remicade, adalimumab/Humira, certolizumab): Block tumor necrosis factor, a key driver of intestinal inflammation. These were the first biologics approved for IBD and remain widely used.
• Anti-integrin agents (vedolizumab/Entyvio): Block immune cells from entering the gut wall, offering a gut-selective approach with a favorable safety profile.
• Anti-IL-12/23 agents (ustekinumab/Stelara): Target specific interleukins involved in the immune cascade, effective for both Crohn's and UC.
• Anti-IL-23 agents (risankizumab/Skyrizi, mirikizumab/Omvoh): Newer, more selective agents showing strong efficacy with promising long-term safety data in both Crohn's and UC.

Small Molecule Therapies (JAK Inhibitors)

Janus kinase (JAK) inhibitors — including tofacitinib (Xeljanz) and upadacitinib (Rinvoq) — are oral medications that block intracellular signaling pathways involved in inflammation. They offer a rapid onset of action and are particularly valuable for patients who have not responded to biologics. They do carry a more significant safety profile, requiring careful patient selection and monitoring.

Conventional Therapies

For milder disease, conventional therapies remain important. Aminosalicylates (5-ASA, mesalamine) are the first-line treatment for mild-to-moderate UC. Immunomodulators such as azathioprine and 6-mercaptopurine are used for maintenance of remission and are often combined with biologics. Corticosteroids (prednisone, budesonide) are used for short-term flare control but are not suitable for long-term use due to their significant side effect profile — including the bone and joint complications discussed in our Hip, Knees & Bones section.

Emerging Treatments

The frontier of IBD treatment is expanding rapidly. Research into the gut microbiome has highlighted the role of microbial imbalance (dysbiosis) in driving intestinal inflammation. Fecal microbiota transplantation (FMT) — transferring gut bacteria from a healthy donor — has shown particular promise for recurrent C. difficile infection and is being actively studied in UC. Stem cell therapy, selective cytokine blockers, and precision medicine approaches based on genomic profiling are all areas of active investigation, as outlined in the journal Gastroenterology.

Other Common Digestive Conditions

GERD (Gastroesophageal Reflux Disease)

GERD occurs when stomach acid repeatedly flows back into the esophagus, irritating its lining. Chronic, untreated GERD can lead to esophagitis, Barrett's esophagus (a precancerous condition), and esophageal cancer. It affects approximately 20% of adults in Western countries. Treatment includes lifestyle modifications, proton pump inhibitors (PPIs), H2 blockers, and in select cases, surgery.

Celiac Disease

Celiac disease is an autoimmune disorder in which ingestion of gluten (found in wheat, barley, and rye) triggers an immune response that damages the small intestinal villi — the finger-like projections responsible for nutrient absorption. This leads to malabsorption of critical nutrients including iron, calcium, and fat-soluble vitamins. Symptoms range from classic GI complaints (diarrhea, bloating, weight loss) to atypical presentations including anemia, osteoporosis, neurological symptoms, and infertility. The only effective treatment is a strict, lifelong gluten-free diet.

SIBO (Small Intestinal Bacterial Overgrowth)

SIBO occurs when bacteria that normally reside in the colon migrate into and overpopulate the small intestine. This causes fermentation of carbohydrates in the wrong location, producing gas, bloating, abdominal discomfort, and diarrhea — symptoms that frequently overlap with IBS. SIBO is diagnosed via breath testing and treated with targeted antibiotics (most commonly rifaximin), followed by dietary modifications and attention to the underlying motility or structural cause.

Gastroparesis

Gastroparesis is a condition in which the stomach empties too slowly — not due to a blockage, but due to damage to the vagus nerve or gastroparesis-related autonomic dysfunction. It is particularly common in patients with diabetes and in those who have undergone certain surgeries or experienced neurological injury. Symptoms include nausea, vomiting, early satiety, and bloating. Management involves dietary changes (small, frequent, low-fat, low-fiber meals), medications to promote gastric motility (metoclopramide, domperidone), and in severe cases, a gastric pacemaker or jejunal feeding.

Diverticular Disease

Diverticulosis refers to the presence of small pouches (diverticula) that form in weak spots in the colon wall — extremely common in adults over 60. When these pouches become inflamed or infected, the condition is called diverticulitis, which can cause severe abdominal pain, fever, and complications including abscess, perforation, and fistula formation. A high-fiber diet is protective against diverticulosis, and acute diverticulitis is typically treated with antibiotics and dietary rest.

Foods to Avoid with IBS

Diet is one of the most powerful tools for managing IBS symptoms. The low-FODMAP diet, developed by researchers at Monash University, is the most evidence-supported dietary approach for IBS. FODMAPs are fermentable short-chain carbohydrates that are poorly absorbed in the small intestine and rapidly fermented by gut bacteria, producing gas and triggering symptoms. Studies show that 70–75% of IBS patients experience significant improvement on a low-FODMAP diet, according to the NIH.

High-FODMAP Foods to Limit or Avoid

• Wheat and rye products: Bread, pasta, cereals, crackers — major sources of fructans, a type of FODMAP. Many IBS sufferers find significant relief by switching to gluten-free alternatives, even without celiac disease.
• Dairy products high in lactose: Milk, ice cream, soft cheeses, and yogurt. Lactose intolerance and IBS frequently coexist. Lactose-free dairy and hard cheeses (which are naturally low in lactose) are often better tolerated.
• Certain fruits: Apples, pears, mangoes, cherries, peaches, and watermelon are high in fructose or sorbitol. Lower-FODMAP alternatives include bananas, blueberries, grapes, kiwi, and oranges.
• Legumes and pulses: Beans, lentils, chickpeas, and soybeans contain galacto-oligosaccharides (GOS) that trigger fermentation and gas. Canned and rinsed legumes in small portions may be better tolerated.
• Certain vegetables: Garlic, onions, leeks, asparagus, cauliflower, and mushrooms are among the highest-FODMAP vegetables. Garlic and onion in particular are among the most common IBS triggers — garlic-infused oil (without the garlic solids) is a useful flavoring substitute.
• Artificial sweeteners: Sorbitol, mannitol, xylitol, and maltitol — found in sugar-free gum, candies, and some diet products — are poorly absorbed and potent IBS triggers.
• Fatty and fried foods: High-fat meals stimulate exaggerated colon contractions in IBS patients, often triggering urgent diarrhea. Fast food, fried foods, and heavy cream-based sauces are common culprits.
• Caffeine and alcohol: Both stimulate gut motility and can worsen diarrhea-predominant IBS. Coffee — even decaffeinated — contains compounds that directly stimulate colonic activity.
• Carbonated beverages: The gas in carbonated drinks contributes directly to bloating and distension in people with visceral hypersensitivity.

The low-FODMAP diet is ideally implemented in three phases — elimination, reintroduction, and personalization — ideally with the guidance of a registered dietitian with expertise in GI disorders. It is not intended as a permanent diet but as a structured way to identify individual triggers. The Monash University FODMAP app is considered the gold standard resource for patients following this approach.

The Gut-Brain Connection

IBS is increasingly understood as a disorder of the gut-brain axis — the bidirectional communication network between the enteric nervous system (the "second brain" embedded in the gut wall) and the central nervous system. Stress, anxiety, and depression are strongly linked to IBS flares, and psychological interventions including cognitive behavioral therapy (CBT), gut-directed hypnotherapy, and mindfulness-based stress reduction have been shown in clinical trials to meaningfully reduce IBS symptoms — independent of dietary change. This connection reinforces that treating IBS comprehensively means addressing both body and mind.

Sources & Further Reading