Granulomas obstruct lymphatics in all layers of the intestine in Crohn's disease

Abstract

After an earlier study defining immunolabeled lymphoid follicles, obstructed lymphatics, and granulomas of the diseased ilea of 24 Crohn's disease patients, we chose to trace the lymphatics of these cases and 10 additional by serial sectioning. Particular attention was given to establishing physical continuity between granuloma-obstructed lymphatics and lymphatics with 'lymphocytic thrombi'. Formalin-fixed paraffin-embedded tissue blocks from resected diseased ilea and proximal colons from 34 patients were reviewed. Patients were 13 men and 21 women, aged 14-60 years. Duration of disease ranged from 1 month to 10 years. Immunohistochemistry employed D2-40 antibody to label lymphatics and anti-CD68 to label granulomas. Twenty-nine of the 34 (85%) resection tissues had lymphangectasia, in mucosa, submucosa, and subserosa. In 53% of the specimens, lymphatics of the various layers were obstructed by granulomas that filled the lumina. In 44%, 15/34, there were also distended lymphatics that were totally plugged with lymphocytes. In 10 of the 15, serial sections revealed continuity between the lymphocyte-plugged lymphatics and the endolymphatic granulomatous obstruction downstream. In 5 of the cases, D2-40 immunostaining revealed redundant lymphatic endothelium interwoven with the granuloma cells. Granulomas totally obstruct lymphatics in all layers of the intestine in Crohn's disease. Upstream of these obstructions, lymphatics are distended with lymphocytes. The degree and extent of this potentially irreversible 'lymphangitis nodosa' have undoubtedly confounded treatment regimens and clinical trials. There currently are no imaging methods to demonstrate the lymphangitis, nor treatments to resolve it.

Keywords: Crohn's disease; Inflammatory bowel disease; endoscopy; lymphangitis; regional enteritis.