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Crohn’s disease (CD)

How common is Crohn’s disease? Discuss epidemiology

  • The incidence of CD is around 5–10 (half that of UC) per 100 000 per year with a prevalence of 50–100 per 100 000.
  • In contrast to UC (stable incidence) however, the incidence of CD may be increasing.
  • Both UC and CD are diseases of young people with a peak incidence between the ages of 10 and 40 years. They may, however, affect people of any age and 15% of people are over the age of 60 at diagnosis.
  • There is a small increase in mortality for both UC (hazard ratio 1.44, 95% CI 1.31 to 1.58) and CD (HR 1.73, CI 1.54 to 1.96). The overall mortality of CD is greatest in the 2 years after diagnosis or in those with upper gastrointestinal disease.
  • CD tends to cause greater disability than UC with only 75% of patients fully capable of work in the year after diagnosis and 15% of patients unable to work after 5–10 years of disease.

Discuss the clinical patterns of Crohn’s disease?

  • The clinical patterns are inflammatory, stenosing or fistulizing. When patients are followed over time the majority of patients who start with only inflammation does tend to develop strictures or fistulae over the long term.
  • Looking at prevalence in a somewhat different manner shows that about 20% of patients with CD will be in remission for a long period of time and only about 25% will have continuously active disease. The remainder experience fluctuating symptoms that are often affected by medical therapies including initiation, discontinuation, and attempts at maintenance treatment.
  • At least 50% of patients require surgical treatment in the first 10 years of disease and approximately 70–80% will require surgery within their lifetime.  Cumulative Incidence of Surgical Resection over 1 Year in Crohn’s Disease Patients Starting Corticosteroids- is 30%.

What are the treatment goals in Crohn’s disease?

  • Induction of remission
  • Maintenance of remission
  • Prevention of long term complications- like strictures, fistulae etc

How do you measure remission?

  • The biggest problem is the definition of response. The Crohn’s Disease Activity Index (CDAI), while clinically useful and helpful in clinical trials, is not a specific index for CD. Patients who have irritable bowel or any other kind of abdominal symptoms will have an elevated CDAI. It is not specific and it is not a measure of inflammation. It has been suggested, the CRP may be a useful adjunct to CDAI, as it can be used to confirm that the symptoms are in fact related to inflammation and not, for example, to ileal resection, bile salt diarrhea, or irritable bowel symptoms.
  • Most studies to date have defined symptomatic improvement as CDAI difference of 70 points. A CDAI of less than 150 is typically considered to be indicative of remission. This cut-off was defined as remission by the developers of the CDAI because it was midway between the 100- and 200-point levels. There was actually no science supporting a CDAI of 150 as a true indicator of remission in CD.
  • Patients are not considered to be in remission until they are totally off steroid therapy, hence the concept of steroid-sparing.
  • The natural course of a remission that has been medically induced is different from the natural course of surgically-induced remission. To this point, surgery has been the best means of prolonging the symptom-free interval. The most prolonged period of quiescent disease was induced by surgery.
  • Likewise, relapse can be defined in several ways. The endoscopic appearance of the anastomotic site can predict the likelihood of a clinical relapse. Clinically, patient symptoms or, in a clinical trial, an index such as the CDAI  is used to define relapse.

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