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Inflammatory bowel disease, or IBD, is an immune system-mediated inflammation of the digestive tract that can result in a portion or portions of the intestines.

The most common types of are Crohn’s disease and ulcerative colitis.

In the US there are approximately 785,000 patients with Crohn’s disease and 910,000 patients with ulcerative colitis.

Of these, 25% of patients are diagnosed before the age of 18, and the majority of patients are diagnosed before age 35.

While the symptoms of Crohn’s disease and ulcerative colitis are similar, there are key differences.

Shared symptoms include abdominal pain, diarrhea, and fatigue. Fatigue and abdominal pain are the most common symptoms in Crohn’s disease, while in ulcerative colitis, the most common symptom bloody diarrhea.

Symptoms that are unique to Crohn’s disease are abdominal pain, diarrhea, fatigue, and weight loss.

Symptoms unique to ulcerative colitis include blood in the stool and increased frequency of bowel movements.

Because both diseases are inflammatory disorders, they may also result in systemic symptoms, such as fatigue due to trouble sleeping and weight loss, and extraintestinal symptoms, such as joint pain, achiness, and overlapping skin conditions.

The inflammatory pathways that cause Crohn’s disease and ulcerative colitis are similar, but there are some key differences.

In Crohn’s disease, inflammation occurs throughout the entire length of the digestive tract, from the mouth to the anus, but most often is seen in the terminal ileum and proximal colon.

The inflammation in Crohn’s disease is transmural, which is a key reason why, unlike ulcerative colitis, Crohn’s disease is often progressive in symptomology.

In ulcerative colitis, inflammation is limited to the colon and occurs in only the mucosal layer.

More than 50% of patients with ulcerative colitis suffer from iron deficiency due to excessive bleeding related to ulcerations.

Patients with ulcerative colitis also have a more than twofold risk of developing colorectal cancer. This risk increases with disease extent, length of time with disease, and level of active disease.

Genetics can play a role in the incidence of both Crohn’s disease and ulcerative colitis, although this correlation is stronger in patients with Crohn’s disease.

For example, a first-degree relative with IBD represents a fivefold increase in relative risk of developing IBD.

While researchers have identified numerous genes and genetic loci associated with IBD, genetics account for about 25% of IBD cases.

Incidence of Crohn’s disease and ulcerative colitis are also affected by environmental factors.

Interestingly, smoking is a risk factor in the development of Crohn’s disease but is protective in the development of ulcerative colitis.

Diets rich in saturated fatty acids and processed meats may increase the risk of IBD, while a higher fiber diet is thought to reduce the risk of Crohn’s disease by 40%.

The use of certain medications, such as antibiotics, NSAIDs, statins and anti-contraceptives have also been associated with increased risk of IBD.

C-reactive protein is an acute indicator of inflammation, and elevation of C-reactive protein can differentiate IBD from other disorders.

While C-reactive protein is the most studied serology marker and is the preferred indicator in IBD, not every patient will have an elevated C-reactive protein.

A fecal calprotectin test may be used to detect inflammation markers in IBD and may have a higher specificity than serum markers as they measure the inflammation of intestinal tissue rather than systemic inflammation, but they are not specific for IBD diagnosis.

Endoscopy is useful for diagnosis of Crohn’s disease and to distinguish it from ulcerative colitis.

Different types of endoscopy used for the diagnosis and management of Crohn’s disease include ileocolonscopy, capsule endoscopy, esophagogastroduodenoscopy, and enteroscopy.

Additionally, cross-sectional imaging techniques can complement endoscopy in the diagnosis and management of Crohn’s disease.

This can include computer tomography, magnetic resonance enterography, and ultrasonography. [Veauthier2018/p663/col1/para4/ln1-4, ln7-12]

Disease scoring is necessary for diagnosis and to determine the extent of disease.

Severity of Crohn’s disease is measured by the Crohn’s disease activity index (CDAI). Disease scoring ranges from non-active disease, also known as remission, to extremely severe disease.

Endoscopic Crohn’s disease scoring was previously assessed using the Crohn’s disease endoscopic index of severity (CDEIS) but has since been replaced by the simple endoscopic score for Crohn’s disease (SES-CD), which is easier to use.

While there is currently no standard method for ulcerative colitis scoring, there are various indices that can be used to evaluate clinical disease activity. Common scoring indices are Baron Score, Rachmilewitz Endoscopic Index, Mayo Score, and Sutherland Mucosal Appearance Assessment.

The severity of ulcerative colitis is most often assessed using the Mayo Score. This scoring tool uses variables that are known to significantly correlate with disease severity.

In this video we have learned that while Crohn’s disease and ulcerative colitis may display similar symptoms, there are key differences clinicians can use to accurately diagnose the patient and assess the disease severity, which are essential to ensuring proper management of IBD.

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