ase History 1: A 10-year-old sexually intact male mixed breed dog was examined because of a 5-year history of intermittent melena, hematochezia, and a chronic microcytic anemia. In the 5 months before examination, the hemorrhagic episodes had increased in frequency and intensity, requiring 3 whole blood transfusions for stabilization. On physical exam, a grade III/ VI left apical systolic murmur was ausculted. Physical examination also revealed tachycardia, tachypnea, and pale mucous membranes. Rectal examination revealed evidence of melena and hematochezia. CBC results revealed a severe microcytic (MCV 59 fl; reference range 60-75 fl), normochromic (MCHC 33 g/ dL; reference range 32-36 g/dL) anemia (HCT, 12.5%; reference range 37-55%) with poor evidence of regeneration (reticulocyte count 54,000; reference range 460,000) and a total protein of 4.5 g/dL (reference range; 6.0-8.0 g/dL). Red blood cell (RBC) morphology was characterized by a 1 1 anisocytosis, polychromasia, and Howell Jolly bodies. The remainder of the clinicopathologic results was unremarkable as were results of diagnostic imaging.A crossmatch was performed and a packed-RBC transfusion (12 mL/kg [5.6 mL/lb]) was administered. PCV and total solids improved after the transfusion to 22% and 8.0 g/dL, respectively. The tachypnea, tachycardia, and murmur resolved after administration of the transfusion.Endoscopic evaluation revealed a small gastric ulcer and a friable, hyperemic duodenal mucosa. Colonoscopy revealed multiple bundles of tortuous, dilated vessels, which were found diffusely throughout the length of the colon.A diagnosis of colonic vascular ectasia was made from the characteristic gross morphologic abnormalities visualized during endoscopy. The diffuse distribution and number of vascular lesions made laser coagulation or electrocautery an inappropriate method of treatment. Subtotal colectomy was considered as an option for treatment, but hormone therapy alone was eventually chosen because of the owner's desire to avoid the potential morbidity associated with surgery. The prednisone and azathioprine therapy was tapered and discontinued and hormone therapy was initiated.Diethylstilbestrol (DES) was instituted at 0.33 mg/kg (0.15 mg/lb), PO q24h, then tapered to twice weekly after a 5-day loading period. The bleeding episodes decreased in severity over the next 3 weeks, but did not resolve, and the dog was administered an additional transfusion of packed-RBCs (12 mL/kg [5.6 mL/lb]). Altrenogest a (a synthetic progestin) was added to the twice weekly estrogen therapy at 0.04 mg/kg (0.02 mg/lb), PO q24h, for 7 days, and then increased to 0.08 mg/kg (0.04 mg/lb), PO q24h. Once the combination estrogen-progesterone therapy had been initiated, the dog improved clinically. Any significant hemorrhage subsided in approximately 1 week and the PCV stabilized between 35 and 40%. Over the next several weeks the microcytosis resolved. One episode of melena and hematochezia occurred 7 months later, after Dog 1 was treated with prednisone and carprofen by...

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