Differences Between Ulcerative Colitis and Crohn's Disease

Ulcerative colitis and Crohn's disease share many symptoms in common. Despite this, they're different conditions. Let's find out what signs distinguish them.
Differences Between Ulcerative Colitis and Crohn's Disease

Last update: 15 March, 2023

The differences between ulcerative colitis and Crohn’s disease are frequently debated. The controversy is quite widespread, as, even among experts, doubts arise about when to diagnose one or the other of these conditions. In fact, there are conditions that are halfway between both, so that specialists have no choice but to diagnose indeterminate colitis.

However, in most cases, it’s possible to find pointers that can tip the balance towards a specific disorder. In the following article, we’re going to look at these pointers, showing you which symptoms are taken into account and which are ignored.

Main differences between ulcerative colitis and Crohn’s disease

The first thing you should know, as Harvard Health Publishing tells us, is that both ulcerative colitis and Crohn’s disease are part of what we know as inflammatory bowel disease (IBD).

These are the two possible manifestations of this condition, and so it’s not surprising that they have some characteristics in common. However, their evolution and treatment are very different.

With this in mind, let’s see what the differences are between ulcerative colitis and Crohn’s disease (UC and CD respectively).


The differences between ulcerative colitis and Crohn's disease include symptoms
Some of the more obvious clinical manifestations, such as diarrhea, are usually shared by both conditions.

Both conditions share signs such as diarrhea, abdominal pain, weight loss, and general malaise. However, according to researchers, they also develop unique symptoms. The main one is bleeding and mucus in bowel movements. This is a classic sign of UC (ulcerative colitis), but not of CD (Crohn’s Disease).

Very few patients with CD have bloody or mucous stools, and, when they do, they’re intermittent. Those who have been diagnosed with UC have to deal with this symptom permanently, even chronic bleeding can occur that requires surgical intervention.

Physiological characteristics

Perhaps where it’s possible to find most differences between ulcerative colitis and Crohn’s disease is in their physiological development. Below we’ll summarize them:

  • UC is limited to the colon only. It can affect it totally (pancolitis), partially (proctosigmoiditis), or only in the rectum (proctitis).
  • CD affects the entire digestive tract, with a higher prevalence in the large and small intestine.
  • UC is characterized by a general inflammation of the colon. As we already mentioned, it can affect specific areas but it’s usually general.
  • In CD, however, healthy areas coexist with affected areas. Thus, heterogeneous patches or buds develop throughout the digestive tract.
  • UC only affects the inner lining of the colon. This is something that is checked during the biopsy.
  • CD, on the other hand, affects any of the layers of the intestinal tract. Its concentration is more general.

These are the characteristic manifestations of both autoimmune disorders, so you can see their differences. They may not seem so big to you, but they play a leading role when doing the diagnostic test. These small details are used by researchers to hypothesize that it’s one or another disease.


Although prevalence rates vary for each country, if we consider the United States and Europe (the two regions with the highest number of cases), we find that ulcerative colitis is more common than Crohn’s disease.

According to studies, its prevalence can be up to 237 cases per 100,000 inhabitants. In contrast, researchers have stipulated that this is 150 for CD.

At least from a percentage point of view, people are more likely to develop ulcerative colitis. Case reports are increasing for both conditions in remote areas of the north, although these are still the preferred ones even for their manifestation.


The differences between ulcerative colitis and Crohn's disease include their complications
Complications in the gastrointestinal tract are possible in both conditions. For example, a small proportion of patients can develop colon cancer.

Despite the above data, CD tends to generate more complications than UC. Evidence indicates that Crohn’s disease is prone to the following:

  • Greater probability of suffering fractures (around 30-40%).
  • Pulmonary embolism and deep vein thrombosis (three times higher than in healthy patients).
  • Colonorectal cancer and small intestine (between 1.4 and 27.1 greater in contrast to the healthy population).
  • Development of lymphomas.
  • Its mortality rate is 1.4%.

In addition to this, CD tends to develop extra-intestinal manifestations such as asthma, uveitis, bronchitis, psoriasis, multiple sclerosis, rheumatoid arthritis, erythema nodosum, and many more. It doesn’t mean that UC patients aren’t exposed to these risks, but rather that they are relatively minor.

Risk factors

Both diseases have common risk factors, such as the presence of other autoimmune disorders and genetic predisposition. However, one of the most intriguing differences between ulcerative colitis and Crohn’s disease is that of smoking.

Evidence indicates that smoking can protect against the development of UC. However, the effect is the opposite for CD. The reason for this is unknown and has, of course, caused debate among critics and supporters of the theory.

What we do know is that those who smoke tend to have greater complications if they have Crohn’s disease, but not so much if they have been diagnosed with ulcerative colitis. In fact, the latter is informally known as the nonsmoker’s disease.

These are the most notable differences between the two disorders, although, as we pointed out at the beginning, it’s sometimes not so easy to determine them.

According to the Center for Inflammatory Bowel Diseases at the University of California, Los Angeles (UCLA), 10% of cases are diagnosed as indeterminate colitis. That is, they present a combination of the two disorders.

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