Toxopathology of gout induced in laying pullets by sodium bicarbonate toxicity

A total of 60, 3-week-old, laying pullets were used in the present experiment. The exposed birds received excess sodium bicarbonate (SB) in their drinking water for 35 days at the levels of: 2 g/l (0.2%), 7.5 g/l (0.75%), 20 g/l (2%) and 40 g/l (4%). All birds were subjected to pathological and toxicological examination. Birds of the 0.75% and 2%-groups developed gross picture of visceral gout, while birds of 4%-group showed acute kidney damage without manifesting visceral urate deposition. Erythrocytic count, packed cell volume (PCV), and hemoglobin (Hb) levels were all increased in the exposed birds. There were dose-related increments in the serum level of sodium (Na(+)). Serum levels of chloride (Cl(-)), and potassium (K(+)) were relatively decreased in some cases. Serum levels of uric acid were increased in a dose-related pattern. Blood pH of the treated birds was shifted toward the alkaline side. Microscopic examination revealed significant renal changes in birds manifesting visceral gout and these changes included urate deposits associated with tubular necrotic changes. Some birds in the third group (2%) developed urate granulomas (tophi) in their renal interstitium. It was concluded that development of gout in birds may be related to a state of metabolic alkalosis which is associated with significant changes of the electrolyte balance.