Inflammatory bowel disease (IBD) is an umbrella term for a group of chronic conditions in which the immune system mistakenly attacks the tissue of the digestive tract, causing ongoing inflammation. The two main forms are Crohn's disease and ulcerative colitis — related conditions that share many features but differ in important ways that shape how each is diagnosed, treated, and monitored over time.
IBD is a lifelong condition, and while it cannot currently be cured, treatment has advanced considerably in recent years. Newer biologic medications and small-molecule therapies now allow many patients to achieve sustained remission and lead full, active lives — a markedly different picture from a generation ago. In Singapore, IBD has been observed to be more prevalent among people of Indian and South Asian descent compared with other ethnic groups, and, in line with trends seen across Asia, rates of IBD have been rising as diets and lifestyles become more Westernised.
How IBD Develops?
IBD is understood to result from an interaction between several factors, rather than a single cause:
- Immune dysregulation: In IBD, the immune system mounts an abnormal, persistent inflammatory response against the gut lining, rather than the brief, self-limiting response that normally follows an infection or irritation.
- Genetic susceptibility: Certain gene variations, including those affecting how immune cells recognise gut bacteria, are more common in people with IBD, and having a close relative with IBD meaningfully raises individual risk.
- The gut microbiome: The trillions of bacteria that normally live in the digestive tract appear to interact differently with the immune system in people with IBD, potentially both contributing to and being altered by the ongoing inflammation.
- Environmental triggers: Factors such as smoking, certain medications (including NSAIDs and some antibiotics), diet, and stress do not cause IBD on their own but can trigger flares or influence disease course in someone already predisposed.
Crohn's Disease vs. Ulcerative Colitis
Location: Crohn’s disease can affect any part of the digestive tract, from the mouth to the anus, although it most commonly affects the small intestine and the beginning of the large intestine. Ulcerative colitis, on the other hand, is confined to the large intestine (colon) and rectum.
Pattern: Crohn’s disease typically causes patchy “skip lesions”, with areas of unaffected tissue in between. Inflammation can also extend through the full thickness of the bowel wall. Ulcerative colitis causes continuous inflammation that starts at the rectum and extends upwards through part or all of the colon, affecting only the innermost lining.
Typical symptoms: Crohn’s disease commonly causes abdominal pain, often in the lower right abdomen, along with diarrhoea and weight loss. It also has a higher likelihood of complications such as strictures and fistulas. Ulcerative colitis is particularly charact
IBD vs. IBS: Why the Distinction Matters
Inflammatory bowel disease and irritable bowel syndrome (IBS) are frequently confused, partly because their names sound alike and partly because both can cause abdominal pain and altered bowel habits. They are, however, fundamentally different conditions. IBS is a functional disorder — the bowel is not structurally damaged or inflamed, but its function (motility and sensitivity) is disrupted. IBD, by contrast, involves genuine, visible inflammation and tissue damage that can be seen on colonoscopy and confirmed on biopsy, and which carries risks — including malnutrition, strictures, and long-term cancer risk — that IBS does not.
This distinction has real practical value. A simple, non-invasive blood or stool marker called faecal calprotectin, which detects inflammation in the gut, is increasingly used to help distinguish the two: a normal result makes IBD unlikely and points toward a functional cause such as IBS, while an elevated result warrants further investigation, typically colonoscopy, to look for IBD directly. This means many patients can avoid an unnecessary colonoscopy, while those who do need one can be identified more confidently — sparing both delay and unnecessary invasive testing.
Beyond the Gut: How IBD Affects the Rest of the Body
IBD is increasingly understood as a systemic inflammatory condition rather than one confined to the digestive tract. Extraintestinal manifestations — problems arising outside the gut — are common, affecting a meaningful proportion of people with IBD, and can sometimes appear before digestive symptoms are even recognised.
- Joints: Inflammatory arthritis affecting large or small joints is one of the most common extraintestinal manifestations, and can flare independently of gut symptoms
- Skin: Conditions such as erythema nodosum (tender red nodules, usually on the shins) and pyoderma gangrenosum (painful skin ulcers) are recognised associations
- Eyes: Inflammation of the eye, including uveitis and episcleritis, can cause pain, redness, and visual disturbance and requires prompt ophthalmology input when it occurs
- Liver and bile ducts: Primary sclerosing cholangitis, a chronic condition affecting the bile ducts, occurs more often in people with ulcerative colitis and carries its own long-term monitoring needs
Because these manifestations can significantly affect quality of life and, in some cases, influence which IBD medication is chosen, they should always be mentioned to your care team rather than treated as unrelated issues.
Long-Term Complications and Colorectal Cancer Risk
Persistent, poorly controlled inflammation can lead to structural complications over time, and the specific risks differ somewhat between the two main forms of IBD.
- Strictures: Chronic inflammation and scarring can narrow sections of bowel, particularly in Crohn's disease, sometimes causing obstruction
- Fistulas and abscesses: Transmural inflammation in Crohn's disease can create abnormal channels between the bowel and other organs or the skin, or localised collections of infection, both of which may require surgical treatment
- Toxic megacolon: A rare but serious complication, more associated with severe ulcerative colitis, in which the colon rapidly dilates and loses normal function; a genuine medical emergency
- Colorectal cancer: Longstanding IBD colitis raises the risk of colorectal cancer to roughly a third higher than the general population, with risk increasing according to how long the disease has been present, how much of the colon is involved, and how well inflammation has been controlled over time
Because of this cancer risk, patients with longstanding colonic IBD are recommended regular surveillance colonoscopy, typically starting eight to ten years after diagnosis and repeated at intervals guided by individual risk factors, to detect any precancerous changes at the earliest, most treatable stage.
Symptoms of IBD
IBD symptoms typically follow a relapsing-remitting course — periods of active inflammation (flares) alternating with periods of reduced or absent symptoms (remission), though the timing and duration of each can be unpredictable.
- Lower abdominal pain or cramping
- Chronic diarrhoea, often with urgency
- Blood or mucus in the stool
- Fatigue
- Unexplained weight loss
- Reduced appetite
- Fever during active flares
- In children and adolescents, delayed growth or puberty can be an early sign
Risk Factors for IBD
- Family history: One of the most significant risk factors; studies show 5–20% of people with IBD have a close relative with the condition
- Age: Most people are diagnosed before age 30, though a second, smaller peak in new diagnoses occurs in the 50s and 60s
- Ethnicity: In Singapore, IBD has been observed to be more prevalent among those of Indian and South Asian descent compared with other ethnic groups
- Smoking: Associated with an increased risk and more aggressive course of Crohn's disease specifically; the relationship with ulcerative colitis is more complex and does not make smoking a recommended protective strategy
- Diet and environment: Diets higher in processed food and lower in fibre, along with other features of a more Westernised lifestyle, are associated with rising IBD rates across Asia
- Certain medications: Frequent NSAID use and some antibiotics have been linked to triggering flares in susceptible individuals
How IBD is diagnosed?
- Fecal Calprotectin: A non-invasive stool test that detects inflammation in the gut. A normal result makes IBD unlikely, while an elevated result supports the need for further investigation — an increasingly important first step in distinguishing IBD from IBS.
- Blood Tests: Checks for anaemia, signs of inflammation (such as raised CRP), and nutritional deficiencies, and helps monitor disease activity and treatment response over time.
- Colonoscopy with Biopsy: The key diagnostic test, allowing direct visualisation of the colon and, where relevant, the lower small intestine, with tissue samples taken to confirm inflammation, distinguish Crohn's disease from ulcerative colitis, and assess severity.
- MR or CT Enterography: Detailed imaging of the small intestine, which is not fully visible on standard colonoscopy, particularly important in Crohn's disease to assess disease extent and detect strictures, fistulas, or abscesses.
- Intestinal Ultrasound: An increasingly used, non-invasive imaging option for both initial assessment and ongoing monitoring of bowel wall inflammation, without radiation exposure.
- Capsule Endoscopy: A swallowed capsule containing a small camera images the small intestine as it passes through, used selectively when small bowel Crohn's disease is suspected but not confirmed on other imaging.
Living with IBD: Day-to-Day Management
- Identify and track your personal trigger foods with the help of a dietitian, while ensuring your diet still meets your nutritional needs
- Track your symptoms and their pattern, since this helps both you and your care team anticipate flares and adjust treatment
- Consider carrying a small emergency kit — spare underwear, wipes, and tissue — for reassurance during unpredictable flares
- Manage stress through sustainable strategies, since stress is a recognised trigger for flares, even though it does not cause IBD itself
- Quit smoking, particularly if you have Crohn's disease, since it is linked to more frequent flares and a more aggressive disease course
- Take maintenance medication consistently, even during remission — stopping treatment once you feel well is a common and avoidable cause of relapse
- Attend recommended surveillance colonoscopies if you have longstanding colonic disease, since this is what allows early detection of precancerous changes
