Gastrointest Endosc. 2004 Jan;59(1):116-8. 06/28/2004 - This study, although small, indicates that there may be additional damage to the second part of the duodenum caused by celiac disease, and that this can also be used for a marker for diagnosing the disease:

Dickey W, Hughes D.
Department of Gastroenterology, Altnagelvin Hospital, Londonderry, Northern Ireland, UK.
BACKGROUND: There are various, well-documented, duodenal endoscopic markers caused by the villous atrophy of celiac disease. Another abnormality seen in association with villous atrophy, erosions in the second part of the duodenum, is described. To our
knowledge, this finding has not been heretofore described in patients with celiac disease.
METHODS: Five patients with celiac disease and erosions were encountered over a period of 2 years.
OBSERVATIONS: The erosions were multiple, superficial, and present in the second part of the duodenum but not the duodenal bulb. All 5 patients had findings typical of celiac disease (iron deficiency, osteopenia/osteoporosis), and 4 had at least one other endoscopic marker: scalloped duodenal folds (3), fold loss (2), or mosaic pattern mucosa (2). These patients represented 7% of new cases of celiac disease during the same time period. This pattern of erosion was not observed in over 1200 other patients undergoing upper endoscopy during the study period.
CONCLUSIONS: In a European population, the finding of erosions confined to the second part of the duodenum is specific for villous atrophy, although sensitivity is low. Erosions in the second part of the duodenum should be added to the list of endoscopic markers of celiac disease. welcomes your comments below (registration is NOT required).