Diseases of the Urinary System

The kidney is a filtration-resorption organ and relatively simple in its mode of operation in regulating the salt and water balance and excretion of nitrogen metabolites. The kidneys are richly supplied by blood vessels. In terms of primary renal pathologic processes, there are developmental abnormalities, glomerular diseases, tubular diseases, pelvic diseases, vascular diseases, and neoplasms. Renal infarcts occur from vascular occlusions by thromboemboli showered from different sources, usually the heart. Infarcts are hemorrhagic when acute and white when chronic. Inflammation in the kidney may involve glomeruli, the tubulointerstitial apparatus, and the pelvis. Although rare in horses, pyelonephritis is indicative of ascending inflammation from obstruction of the urinary passages or from the lower urinary tract bacterial infection. Organs of the lower urinary tract are the ureters, urinary bladder, and urethra. They have in common urothelium as mucosal lining. Most diseases in this system affect the urinary bladder.