Oct. 31, 2023
Celiac disease (CD) affects approximately 1% of Americans, causing changes or damage in the small bowel mucosa. Most individuals with CD show characteristic histologic changes in the distal duodenum. Historically, confirmatory biopsies were obtained from the distal duodenum only, rather than the duodenal bulb. However, researchers have observed that some patients with CD have histopathologic mucosal changes limited to the duodenal bulb only. This subtype, called isolated bulb CD, has been estimated to occur in up to 12% of individuals diagnosed with CD. Thus, to improve the sensitivity of biopsies in diagnosing CD, updated pediatric and adult guidelines now recommend obtaining both duodenal bulb and distal duodenum biopsies.
Researchers from Mayo Clinic and the University of Illinois College of Medicine at Peoria recently sought to learn more about the characteristics of isolated bulb CD in children and to determine whether bulb biopsies need to be separated from distal duodenal biopsies. To explore these questions, they conducted a retrospective chart review of records from pediatric patients diagnosed with CD. Study results were published in the Journal of Pediatric Gastroenterology and Nutrition in 2023.
"Biopsying the duodenum has been happening for a long time," explains Imad Absah, M.D., a pediatric gastroenterologist at Mayo Clinic in Rochester, Minnesota, and a lead author on the study publication. "Initially, we grabbed 2 to 3 pieces of tissue, from both the distal bowel and the duodenal bulb. However, the villi found in the bulb are naturally shorter. So if you see that as a normal variation, you might miss the diagnosis. Thus, we have always wondered whether we need to separate these specimens, and if doing so has an impact on the diagnostic yield," says Dr. Absah.
Methods
Children included in the study were required to have at least one duodenal bulb biopsy between January 2011 and January 2022 that was placed in a separate specimen container from the distal duodenum biopsies.
Researchers identified a total of 224 children who met the study's inclusion criteria and assigned them to one of two groups:
- Isolated bulb CD group: patients with characteristic histologic changes of CD in the duodenal bulb only, and normal or Marsh 1 in the distal duodenum.
- Conventional CD group: patients with diffuse characteristic histologic changes involving the distal duodenum.
A pathologist blinded to the location of the biopsies performed Marsh-Oberhuber grading on 28 randomly selected cases of isolated bulb CD and 10 randomly selected cases of conventional CD.
Results
According to Dr. Absah and co-investigators, the study yielded findings about the characteristics of isolated bulb CD in children and the impact of separating bulb and distal biopsies.
- Almost 15% of patients (33 of 224) had histologically confirmed CD that was isolated to the duodenal bulb only.
- Patients in the isolated bulb CD group had a higher median age at diagnosis than the patients in the conventional CD group.
- Patients in the isolated bulb CD group had significantly lower median anti-tissue transglutaminase immunoglobulin A (anti-TTG IgA) levels than those in the conventional CD group (2.8 times versus 16.7 times the upper limit of normal).
- Almost 88% of patients (29 of 33) in the isolated bulb CD group had an anti-TTG IgA value of less than 10 times the upper limit of normal. Time to anti-TTG IgA normalization (mean 14 months) was similar between the two groups.
- A pathologist review of diagnostic biopsies could not distinguish between the bulb and distal duodenum biopsies in approximately one-third of the reviewed samples.
"Overall, we observed that adding a separate biopsy specimen from the duodenal bulb increases sensitivity of this diagnostic test by 10%," explains Dr. Absah. "Additionally, our study suggests that there's a unique entity called isolated bulb celiac disease. These patients tend to have milder presentation and lower celiac serology levels than patients with the conventional form of celiac disease. In patients with milder symptoms, and numbers that are less than10 times more than the normal range, separating biopsy samples may be a more effective, more sensitive way of diagnosing this condition."
Next steps
According to Dr. Absah, performing prospective studies with bigger sample sizes will help researchers clarify whether the bulb celiac disease observed in this study is a unique subtype or just a very early stage of celiac disease.
For more information
Behl S, et al. The characteristics of isolated bulb celiac disease in children. Journal of Pediatric Gastroenterology and Nutrition. 2023;77:79.
Refer a patient to Mayo Clinic.