Giardiosis and colitis in a dog

An 18-month-old Cavalier King Charles Spaniel with recurrent diarrhoea for 2 months had signs suggesting dysfunction of small and large bowel. No helminth ova, protozoa or fat were found on faecal examination. Proctoscopy, barium enema examination and colonic biopsy revealed mucosal colitis. Biopsied small intestine was histologically normal but Giardia trophozoites were numerous in fluid aspirated from the duodenum. Absorption of d-xylose was normal. Giardiosis and idiopathic colitis were diagnosed. Clinical signs abated after 2 courses of metronidazole administration.