The ultimate guide to inflammatory bowel disease

The ultimate guide to inflammatory bowel disease
Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the gastrointestinal tract. Here is what you need to know.
Written by Orchid Team

What is inflammatory bowel disease?

Inflammatory bowel disease (IBD) is the medical term for two conditions, Crohn’s disease (CD) and ulcerative colitis (UC). Each is characterized by chronic inflammation of the gastrointestinal tract, though in different locations–UC is limited to the colon whereas CD can occur anywhere between the mouth and anus. IBD appears to be caused by systemic immune dysfunction, where the body’s immune system attacks the gastrointestinal tract rather than foreign viruses or bacteria. 

Symptoms differ between the two conditions. A recent study compared the presenting symptoms in CD and UC and found fatigue and abdominal pain were the most common in CD, while bloody or watery stools were the most common in UC. Long-term complications of IBD include malnutrition from problems absorbing nutrients, intestinal problems like strictures, inflammation in other parts of the body, and a higher risk of colon cancer.

At what age is inflammatory bowel disease usually diagnosed?

Crohn’s disease tends to be diagnosed in people aged 20-30, while ulcerative colitis is diagnosed between 30 and 40 years of age. Both are also diagnosed in children, with pediatric diagnoses accounting for 7 to 20% of cases. 

What are the risk factors for inflammatory bowel disease?

  • Family history
  • Genetics
  • Lifestyle choices 

How does my family history impact my risk for inflammatory bowel disease?

There is a substantial familial component to IBD: having a first degree relative with the disease is the highest risk factor, and those with two affected parents have a 30% risk of developing the disease, compared to a population prevalence of 1.3%.

How do my genetics impact my risk for inflammatory bowel disease?

The heritability of IBD is approximately 70% based on a literature review of several twin studies drawn from a number of European twin registries, including those of Denmark, Sweden, and Britain. Genetic variants identified from large-scale GWAS have been linked to autophagy, immune system function, and more.

How do lifestyle factors impact my risk for inflammatory bowel disease?

IBD has increased about 9-fold in incidence over the past 100 years. While IBD incidence is much lower in developing countries, children of immigrants to Western countries appear to converge to Western rates by the 2nd generation. 

For these reasons, environmental factors are likely very important in increasing the risk of IBD. These environmental risk factors are not well understood but the most important is tobacco smoking, which increases the risk of Crohn’s but may be protective against ulcerative colitis. A general “hygiene” theory of IBD proposes that decreased exposure to infectious diseases in IBD may increase risk, but this is still controversial, with some data indicating the opposite

Is there anything I can do to reduce my child’s risk of developing inflammatory bowel disease?

As explained in the inflammatory bowel disease whitepaper, genetics plays an important role in determining the risk of IBD. Using Orchid’s embryo screening, you can prioritize the embryo with the lowest genetic risk for IBD and lower their risk of IBD.  

Is there anything I can do to reduce my risk of developing inflammatory bowel disease?

There are no proven interventions to reduce the risk of developing IBD overall, but smoking cessation is recommended for patients with Crohn’s disease, since it appears to reduce flare ups

How is inflammatory bowel disease managed?

What medications are used to manage inflammatory bowel disease?

Treatment of IBD depends on severity and other factors. 

For ulcerative colitis (UC) patients, treatment usually starts with the class of drugs, 5-aminosalicylates (5-ASA). Acute flare-ups are treated with corticosteroids. If these are insufficient for remission, more powerful immunosuppressant drugs are used. 

For Crohn’s disease patients, treatment is similar to UC treatment, involving escalation of treatment from 5-ASA drugs and steroids to immunosuppressants. 

What surgeries are used to manage inflammatory bowel disease?

Some ulcerative colitis (UC) patients can have part of the intestines removed if they do not respond to medical therapy, have severe complications, or have long-standing UC that raise their risk for cancer. Some complications of Crohn’s disease are also treated surgically.

How can the increased colon cancer risk be managed?

The key to managing colon cancer risk is frequent surveillance through colonoscopy and chemoendoscopy, typically every 1-3 years. How often and which methods of surveillance are used is dependent on other factors that include family history of colon cancer as well as specific symptoms such as primary sclerosing cholangitis (PSC), prior history of dysplasia or colonic strictures, extent of inflammatory polyps, etc.  

How is inflammatory bowel disease diagnosed? 

There is no single standardized imaging technique to diagnose IBD. Diagnosis relies on a combination of biochemical results (eg, inflammatory markers), symptoms, imaging, and biopsy results. 


  1. Crohn’s disease and ulcerative colitis are chronic conditions that have flares and remissions
  2. There are no lifestyle changes that are proven to reduce risk, but smoking cessation is recommended.
  3. Treatment is complicated, depends on disease severity, and should be managed by an experienced gastroenterologist. 

Where can I learn more?

  1. A patient guide on IBD from Cedars Sinai
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