Histopathology in giardiasis: a correlation with diarrhoea.

There is controversy both in regard to the severity of small bowel mucosal damage attributable to giardiasis and to the causal relationship of these changes to the associated diarrhoea. In this series of 17 consecutive patients with giardiasis, small bowel histology and diarrhoea were independently assessed and compared. Disaccharidase assays were performed in 16 of these patients and a repeat biopsy obtained in seven cases. On histological examination the villous architecture varied from normal to sub-total villous atrophy. When these changes were compared with the severity of diarrhoea, a direct correlation was obtained, the more severe symptoms being associated with the more severe villous changes. Repeat biopsy after treatment demonstrated improvement in the histology which correlated with improvement in diarrhoea. Lactase activity was low in all patients with moderate or severe diarrhoea as well as in some patients with mild diarrhoea, two of whom had normal histology. This series demonstrates the occurrence of a spectrum of mucosal changes in giardiasis and supports the concept that these changes mediate the diarrhoea associated with this gut parasite.