Inflammatory Bowel Disease: Part 1 – The Characteristics, Causes and Symptoms of Crohn’s Disease and Ulcerative Colitis

Inflammatory bowel disease, also known as IBD, is an umbrella term for several diseases, primarily referring to Crohn’s disease and ulcerative colitis.

Crohn’s and ulcerative colitis are complex diseases whose causes are not fully understood. However, specialists know a great deal about their symptoms, treatment and long-term management, including Dr. Randy Longman, Director of the Jill Roberts Center for Inflammatory Bowel Disease and Associate Professor of Medicine at Weill Cornell Medicine, and Dr. Dana Lukin, Clinical Director at the Roberts Center and Associate Professor of Clinical Medicine at Weill Cornell Medicine.

Before moving along to the two major types of IBD, it’s important to distinguish between ulcerative colitis and other, non-inflammatory types of colitis, such as infectious or ischemic colitis. The latter two don’t belong under the IBD umbrella.

Crohn’s disease and ulcerative colitis share important characteristics. They are both immune-mediated inflammatory diseases, meaning they are driven by an abnormal immune response and feature common inflammatory “pathways”—chains of inflammatory molecules and blood cells that attack the intestines. Crohn’s disease and ulcerative colitis usually respond favorably to similar treatments. Without effective therapy, these chronic diseases tend to flare up and subside over time. At present, there is no definitive cure for either form of IBD.

During Crohn’s and colitis disease week this December, Drs. Longman and Lukin are taking the opportunity to share their insights into these challenging diseases. But first, let’s clear up a common source of confusion.


The distinction between IBD and IBS can be confusing. The “I” in IBD stands for inflammatory, while the “I” in IBS stands for “irritable.” While Crohn’s and ulcerative colitis are inflammatory diseases, IBS is a non-inflammatory condition. There is significant overlap in symptoms between IBD and IBS, however. For example, Dr. Lukin explains, people with both conditions may experience diarrhea, constipation, nausea, cramping or pain, and certain foods may be associated with symptoms.

But that’s where the similarities between them end. “We refer to IBS as a functional condition,” he says. “Its symptoms aren’t caused by inflammation in the bowel but by a mechanism affecting how the intestines function. By contrast, when a patient reports bleeding, weight loss and other systemic complications in addition to the symptoms associated with IBS, we suspect that IBD is the culprit.

“To arrive at a conclusive diagnosis, we take a thorough patient and family history, administer a variety of tests and perform an endoscopic exam and a biopsy, if necessary.

“It’s important to distinguish between IBD from IBS for another crucial reason, he adds: “The medical therapies used to treat the two conditions are completely different.

The causes of IBD: Genes and lifestyle factors

Although the ultimate causes of Crohn’s and colitis are unknown, experts trace these diseases to a combination of genetic and lifestyle factors.

IBD often travels in families, says Dr. Longman, and “some of the genes involved in Crohn’s and ulcerative colitis are well known. Sometimes, physicians can help identify genetic mutations that indicate more aggressive disease with complications such as an abscess or fistula—a channel that can develop between the intestine and another organ or body part. These complications make IBD more difficult to treat. Genetic information associated with more severe disease can help us start therapy quickly to prevent these complications.”

Another complication, he says, is dysplasia—precancerous changes in the colon: “We screen our patients regularly to monitor these changes with the goal of preventing colorectal cancer at all costs.”

As for lifestyle factors, cigarette smoking can increase a person’s risk for Crohn’s disease but, interestingly, not ulcerative colitis. Aspects of the Western diet—certain food additives, preservatives and emulsifiers—are believed to increase IBD risk as well.

Stress and IBD

Stress does not cause the inflammation seen in IBD, Dr. Lukin says, but there is a proven link between stress and disease flares. Stress may make patients more aware of already present but sub-clinically evident inflammation. “A flare can occur during an unusually busy time at work, during exams or when faced with a major life transition—welcome or unwelcome: a wedding, a breakup, the loss of a job or a move to a new home.

“We strongly advise our patients to try to find ways to deal with the stressors in their lives,” he continues. The counseling services offered at the Roberts Center are designed to help patients develop strategies for minimizing the effects of stress on their lives and their gut. A “nervous stomach” is one thing, but an inflamed bowel is quite another, he says, emphasizing that managing stress can help shorten the duration of “flare” symptoms, but that it’s also important to simultaneously identify and treat concomitant inflammation.

A team approach to a multi-system disease

As Dr. Lukin reminds us, Crohn’s and ulcerative colitis are notoriously complex diseases, and they don’t only affect the intestine. The most common extra-intestinal manifestation of IBD is within the joints, but it also frequently affects the eyes, skin and other body systems. “That’s why we have close relationships with our colleagues both inside and outside the Roberts Center,” he says, including colorectal surgeons, radiologists, rheumatologists, dermatologists, ophthalmologists, pathologists, nutritionists and social workers.

Part 2 of this article will focus on treatments and ongoing care for Crohn’s disease and ulcerative colitis. Stay tuned!

To learn more about the Jill Roberts Center for Inflammatory Bowel Disease or to make an appointment, please visit here.