Histopathological changes in anatomical distribution of inflammatory bowel disease in children: a retrospective cohort study

Background Anatomical progression of pediatric inflammatory bowel disease is under-reported. The aim of this work was to examine possible changes in the anatomical distribution of IBD in pediatric patients at diagnosis and at follow up. Methods In a retrospective cohort study, the medical records of children with inflammatory bowel disease were examined. Patients who had at least 2 endoscopic/colonoscopic examinations were included. Primary outcome was histopathological progression based on histopathological examination of biopsies taken during endoscopic and colonoscopic bowel examination. Factors predictive of disease progression were also examined. Results A total of 98 patients fulfilled inclusion criteria (49 female, 54 with ulcerative colitis, range 2 – 17 years, mean age at diagnosis was 10.6 years, SD ± 3.67), the mean duration of follow up was 32.9 months (range 0.1 – 60 months, SD ± 8.54). In the ulcerative colitis group, 41% had disease progression and none of the examined variables (age, gender, laboratory markers, growth and disease activity at diagnosis) appeared to effect disease progression. In the Crohn’s disease group, 75% had disease progression. Girls (OR = 0.13, 95% CI 0.02 – 0.79) and patients with high erythrocytic sedimentation rate (OR=0.942, 95% CI 0.894 – 0.99) were predictive for disease progression. Conclusions Despite maximum therapy, the majority of children with Crohn’s disease appeared to have histopathological disease progression. Female sex and high erythrocytic sedimentation rate seemed to be predictive for disease progression. None of the factors analyzed seemed predictive of disease progression in ulcerative colitis.


Background
Inflammatory bowel diseases (IBD), mainly ulcerative colitis and Crohn's disease are chronic, lifelong illnesses with young age of onset and a great potential for morbidity. The incidence of inflammatory bowel disease in the pediatric population is increasing [1,2]. About 20% of patients with IBD present before the age of 18 years old [1][2][3][4][5][6][7]. The natural history of these diseases is influenced by multiple factors of environmental and genetic origin. IBD showing colonic involvement has been reported to be more frequent in younger children when compared to older children [5]. Childhood-onset Crohn's disease (CD) might reflect a more severe form of disease. Older patients with ulcerative colitis (UC) have demonstrated more cases of proctitis than younger patients with UC [5]. The current data have suggested that IBD may be phenotypically homogenous throughout childhood [8]. However, it is not clear if the histopathological distribution of IBD varies with time or not.
The aim of this study was to examine possible change in the histopathological distribution of IBD in pediatric patients at diagnosis and at follow up. While examining the anatomical distribution, the study also aimed to determine the possible variables that may be associated with or can predict change or progression in disease distribution.

Methods
In a retrospective cohort study, the database of children with IBD at the Stollery Children's Hospital, Edmonton, Canada and medical records of children with IBD who were 17 years of age or younger at diagnosis were examined. Patients with established clinical, endoscopic and radiological diagnosis of IBD, following recommendations of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition [1], were included consecutively. All patients were diagnosed between January 2006 and December 2008.
The following variables were recorded:

Definition of disease progression
Disease progression was defined as a change in histopathological distribution of inflammatory bowel disease from diagnosis to follow up based on pathology of biopsies taken in each endoscopy and colonoscopy. Routine biopsies during upper gastrointestinal endoscopy and colonoscopy were taken from lower esophagus, gastric antrum, upper duodenum, terminal ileum (TI), cecum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum. Two biopsies were taken from each site. Successful intubation of TI was established in more than 90% of patients.

Data collection
Patients eligible for the study were identified using the pediatric IBD database and data were collected using medical records. Inclusion criteria were children with established diagnosis of IBD who had endoscopy/colonoscopy both at diagnosis and at follow up. Patients who had one endoscopy/colonoscopy at diagnosis without further endoscopic follow-up were excluded. Those with incomplete charts/data were also excluded.

Outcomes
The primary outcome was disease progression at the follow-up endoscopy/colonoscopy based on histopathology. Patients were then divided into two groups: those with disease progression and those with no disease progression. Secondary outcome was risk factors associated with disease progression.

Statistics
Data were analyzed using Stata 9.1 (TM) (Data Analysis and Statistical Software, Texas, USA). Summary statistics were obtained and analyzed. Summaries (means, medians, ranges and standard deviations (SDs)) were obtained for continuous variables, while frequency distributions were provided for categorical variables. Crosstabulations were done including all relevant variables against the outcome variable. Factors that may be associated with histopathological progression were explored using logistic regression analysis. These factors included age at diagnosis, gender, presenting symptoms, laboratory markers, growth parameters at diagnosis, and disease activity at diagnosis.
Results were considered statistically significant when P < 0.05.

Ethics
The study protocol was approved by local health research ethics board,

Patients with ulcerative colitis
Of the 54 children in the ulcerative colitis group, 22 (40.7%) showed change in disease distribution from diagnosis till the end of the follow-up period. The distribution of disease for patients with ulcerative colitis at diagnosis and at follow up is illustrated in Figure 1.
Demographic, laboratory and clinical characteristics of children with ulcerative colitis are summarized in Table 1 Age at diagnosis, gender, presenting symptoms, laboratory markers, growth parameters at diagnosis, and disease activity at diagnosis were not significantly different between the two groups (disease progression vs. no disease progression). None of these variables was predictive of disease progression in the logistic regression model.

Patients with Crohn's disease
Of the 44 children in the Crohn's disease group, 33 (75%) patients showed disease progression from diagnosis till the end of the follow-up period. The distribution of disease at diagnosis and at follow up is illustrated in Figure 2.
In patients with no disease progression, the most common distributions were terminal ileal disease and upper GI disease, followed by colonic disease then ileocecal disease.
Demographic, laboratory and clinical characteristics of children with Crohn's disease are summarized in Table 2.
Using logistic regression analysis, ages at diagnosis, presenting symptoms and disease severity at diagnosis were not significantly different between the two groups. None of these variables was predictive of disease progression. However, it appears that there was a relationship between gender (OR = 0.13, 95% CI = 0.02 -0.79) and disease progression. Disease progression was less likely in girls compared to boys. Moreover, ESR at diagnosis was significantly higher in those who had evidence  of disease progression compared to those without disease progression and was predictive of disease progression (OR=0.94, 95% CI 0.90 -0.99).

Discussion
Our study examined histopathological changes in the distribution of IBD from diagnosis through follow-up in children and attempted to determine factors that would influence the progression of inflammatory bowel disease in this population. The initial disease histopathological distribution in those ulcerative colitis patients with disease progression in our study was similar to those in previous studies, citing pancolitis, left sided colitis and proctitis as the most common distributions [1,3,4,7,8,11]. For the ulcerative colitis population, 40.7% of our patients showed disease progression. It appears that there is no relationship to age, duration of symptoms pre-diagnosis, weight, height, serum albumin levels, ESR and disease activity index at diagnosis. Interestingly, some patients with pancolitis in our series, who did not have any evidence of upper gastrointestinal involvement on initial endoscopy, had evidence of histopathological abnormalities on follow-up endoscopy. Upper gastrointestinal involvement in children with UC has been previously reported [12].
The most common initial disease histopathological involvements of Crohn's disease in our study were terminal ileum, ileocecal and upper GI involvement. This finding agreed with previous studies which found that 50 -70% of their pediatric CD patients had TI involvement at presentation [7,13,14]. About 75% of the CD patients in our study showed disease progression. It appears that there is a significant relationship between sex (OR = 0.13, 95% CI = 0.02 -0.79) and disease progression. Based on our analysis, it appears that disease progression is less likely with those patients who are female when compared to those that are male. However, a previous study by Freeman demonstrated that CD tended to be more prominent in females when compared to their male counterparts [14]. Interestingly, in a previous study, it was determined that the switch to a female predominance began at around the age of adolescence [15]. It also appears that there is a significant relationship between ESR at diagnosis and disease progression in Crohn's disease patients. Disease progression is more likely in those Crohn's disease patients that have a higher ESR at diagnosis than those with a lower ESR at diagnosis. There are no previous studies to which we can compare these results.
Although we attempted to optimize the results obtained from our retrospective chart review, our study was limited in a few areas. Firstly, our study defined disease progression strictly as histopathological changes in disease distribution from diagnosis to follow up. Although this definition served the purpose of our study, perhaps future research could also look into disease  progression in the sense of clinical presentation and symptoms, and whether or not factors affecting the clinical presentation and symptoms can predict IBD progression. Of note is that, large areas of small bowel could not normally be biopsied to explore histopathological involvement of Crohn's disease. Secondly, our study excluded those patients that did not have colonoscopy/endoscopy at follow up. Although that was necessary for the purpose of our study, perhaps future studies could look at disease status at follow up in another sense (to increase the number of IBD subjects available for the study). One can argue that patients with less controlled disease will be more likely to be scoped and hence selection bias is more likely to take place. Thirdly, for the purpose of our study, our subjects were divided into 2 main categories: disease progression and no disease progression. Future studies may benefit by further dividing the disease presentation and progression categories into mild, moderate and severe disease. In this sense, there may be a better understanding of which factors may affect certain stages of IBD in children.

Conclusions
Despite maximum therapy, the majority of children with Crohn's disease appeared to have disease progression. Female sex and high erythrocytic sedimentation rate seemed to be predictive for disease progression. None of the factors analyzed seemed predictive of disease progression in ulcerative colitis.