Study Authors 

Jeremy Adler, Shiming Dong, Sally J. Eder, Kevin J. Dombkowski

Study Background 

Crohn’s disease causes inflammation or swelling of any portion of the bowel. The inflammation can involve the entire thickness of the bowel wall from the inner lining to the outer surface. Crohn’s disease can also create ulcers (like craters) in the inflamed bowel wall. Sometimes those ulcers can be very deep and create openings connecting to whatever part of the body is next to that part of the bowel. This is called a fistula.

The most common place for fistulas to develop is around the rectum, creating openings to the skin around the anus, called perianal fistulas. Perianal fistulas can range from tiny and hardly noticed to huge and invasive. One major potential problem are abscesses. These are pockets of pus and these can also invade other structures in the pelvis such as the muscles, vagina, and bladder, leading to other complications. Unfortunately, fistulas can be very difficult to treat and often require change in medications for Crohn’s disease, antibiotics, and/or surgery.

Despite their seriousness, little research has been done to understand these fistulas, figure out how to prevent them, or how to better treat them. Most studies that have been done have been small. In addition, each study reported different information on how many people with Crohn’s disease develop perianal fistulas (most estimates are about 15-20%). Our experience is that perianal fistulas are more common than that.

There are also a handful of studies that have focused on the treatment of perianal fistulas once they develop, but no study has addressed the important question of whether or not fistulas can be prevented in the first place.

Study Overview 

We used the ImproveCareNow Network registry to try to get a more accurate answer as to how many pediatric patients with Crohn’s disease develop perianal fistulas. This is the first step of a larger study to determine if and how perianal fistulas can be prevented.

We used the ImproveCareNow registry to identify all patients with Crohn’s disease enrolled up to October 2014. Since the registry doesn’t actually record whether or not someone has a perianal fistula, we used the information in the registry to identify “perianal disease.”

With careful analysis, we found that perianal disease is more common than previously reported.

  • In the ImproveCareNow Network, about 30% of patients developed perianal disease by 6 years after diagnosis.
  • We also found that perianal disease was more common among boys (21.9%) than girls (19.6%; P=0.013), and among black (25.8%) and Asian (24.1%) patients compared to white patients (20.3%; P=0.017).
  • Perianal disease was more common if Crohn’s disease was diagnosed during teenage years, compared to those diagnosed at an early age.
  • Interestingly, the opposite was true for black patients for whom the diagnosis of Crohn’s disease at an earlier age was linked to a higher risk of perianal disease.

Study Limitations

There are some limitations to this study. The way it is currently designed, the ImproveCareNow registry may not always include everyone who has a fistula. This means that there actually may be even more people out there with perianal disease than what we found in this study. It is also possible that some doctors include people as having perianal disease if they have other findings on their bottom other than fistula. This may mean that the number is less than we found. There are likely also patients with fistulas seen on colonoscopy or on MRI, but they don’t have an opening to the skin. This may mean that the number is more than we found. In total, we did the best estimate that we could with the data.

Study Results - What does it all mean? 

We found that perianal complications of Crohn’s disease are very common, occurring in about 1 in three kids with Crohn’s disease. We can’t yet predict exactly who will develop them, but we do now have some hints that some kids may be at higher risk of developing perianal complications than others.

These results help us to understand more about perianal disease in kids with Crohn’s disease. Now that we know how common this is, we need to focus our efforts on finding ways to prevent these complications, and on improving treatment once they do develop.

We are currently working on other studies aimed at identifying predictors of fistulas. The hope is that if we can identify kids at risk for fistula development, then we can develop treatment strategies aimed at preventing fistulas.

Prepared by: Jeremy Adler
Reviewed by: Parent Working Group Research Subcommittee
About ICN Research Explained: We believe that in order to truly outsmart IBD, the questions we ask and the answers we find must be generated by and be useful to the people whose lives they will impact – patients and their families. ImproveCareNow (ICN) research is prioritized based on what matters most to patients and parents, and we are committed to sharing our results so everyone can understand and take advantage of what’s been learned. The ICN Research Committee has teamed up with the Parent Working Group Research Subcommittee to bring you this series of parent-approved research summaries called “ICN Research Explained".


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