Multiple small intestinal pseudodiverticula associated with lymphoma in three horses

Summary Three mature horses presented with progressive weight loss, inappetence, ventral abdominal oedema and lethargy. Two of the animals had intermittent signs of low grade abdominal pain. At presentation, all 3 had hypoalbuminaemia; 2 had hyperfibrinogenaemia and the other had neutrophilia. An oral glucose tolerance test was performed in 2 cases, both of which demonstrated impaired glucose absorption. One pony treated with corticosteroids failed to improve and developed peritonitis and was subjected to euthanasia after 2 weeks. One pony had small intestinal biopsies obtained via a standing flank laparotomy, which revealed a mainly mononuclear cell infiltrate of the mucosa. It failed to respond to treatment with antibiotics and corticosteroids and, after 2 months, developed sternal oedema in addition to the ventral abdominal oedema and peritonitis and was subjected to euthanasia. The remaining pony deteriorated despite symptomatic therapy and was subjected to euthanasia after one week. At post mortem examination, all 3 animals had multifocal lesions of small intestinal wall thickening, mucosal ulceration, pseudodiverticula and enlarged mesenteric lymph nodes. One pony also had a multinodular mass at the root of the mesentery, a mediastinal mass and a lung mass. Histological examination confirmed the presence of lymphoma of the intestinal wall at post mortem examination in each case and immunohistochemistry (including retrospective evaluation of the intestinal biopsies obtained from the pony that underwent a flank laparotomy) indicated that the lymphomas were of T cell origin.