After x-ray verification of its position, suction was applied to collect part of the intestinal wall inside the capsule. Often-utilised capsule systems were the Watson capsule and the Crosby–Kugler capsule. This method has now been largely replaced by fibre-optic endoscopy, which carries a higher sensitivity and a lower frequency of errors.Capsule endoscopy (CE) allows identification of typical mucosal changes observed in coeliac disease but has a lower sensitivity compared to regular endoscopy and histology. CE is therefore not the primary diagnostic tool for coeliac disease. However, CE can be used for diagnosing T-cell lymphoma, ulcerative jejunoileitis, and adenocarcinoma in refractory or complicated coeliac disease. Pathology
The classic pathology changes of coeliac disease in the small bowel are categorised by the "Marsh classification":
Marsh stage 0: normal mucosa
Marsh stage 1: increased number of intra-epithelial lymphocytes (IELs), usually exceeding 20 per 100 enterocytes
Marsh stage 2: a proliferation of the crypts of Lieberkühn
Marsh stage 3: partial or complete villous atrophy and crypt hypertrophy
Marsh stage 4: hypoplasia of the small intestine architectureMarshs classification, introduced in 1992, was subsequently modified in 1999 to six stages, where the previous stage 3 was split in three substages. Further studies demonstrated that this system was not always reliable and that the changes observed in coeliac disease could be described in one of three stages:
A representing lymphocytic infiltration with normal villous appearance;
B1 describing partial villous atrophy; and
B2 describing complete villous atrophy.The changes classically improve or reverse after gluten is removed from the diet.
Less commonly, some individuals inherit the DQA1*05 allele from one parent and the DQB1*02 from the other parent (DQ2.5trans) (called a trans-haplotype association), and these individuals are at similar risk for coeliac disease as those with a single DQ2.5-bearing chromosome 6, but in this instance, the disease tends not to be familial. Among the 6% of European coeliacs that do not have DQ2.5 (cis or trans) or DQ8 (encoded by the haplotype DQA1*03:DQB1*0302), 4% have the DQ2.2 isoform, and the remaining 2% lack DQ2 or DQ8.The frequency of these genes varies geographically. DQ2.5 has high frequency in peoples of North and Western Europe (Basque Country and Ireland with highest frequencies) and portions of Africa and is associated with disease in India, but it is not found along portions of the West Pacific rim. DQ8 has a wider global distribution than DQ2.5 and is particularly common in South and Central America; up to 90% of individuals in certain Amerindian populations carry DQ8 and thus may display the coeliac phenotype.Other genetic factors have been repeatedly reported in coeliac disease; however, involvement in disease has variable geographic recognition. Only the HLA-DQ loci show a consistent involvement over the global population. Many of the loci detected have been found in association with other autoimmune diseases. One locus, the LPP or lipoma-preferred partner gene, is involved in the adhesion of extracellular matrix to the cell surface, and a minor variant (SNP = rs1464510) increases the risk of disease by approximately 30%.