[Renal cystic involvement in equidae].

Four types of abnormalities has been recorded on a study about cystic diseases of donkey's kidneys, collected at the Madrid Slaughter-house. These four categories are as follows: a) simple isolated renal cysts; b) multiple renal cysts; c) adult polycystic kidneys; and d) focal renal cystic dysplasia and hypoplasia. From a total of 26 cases macroscopically and histopathologically studied, 7 exhibed unilateral and 19 bilateral lesions. Different combinations of the four types above mentioned were found when both kidneys were affected. The evidence of some of the cysts being communicated with normal tubulus or with other cysts, suggests that some of them could represent simple dilatations involving segments of nephrone or collecting system. These findings do not fit with the previous explanation of the no occurrence of communication between the metanephric blastema and the ureteral bud or with the obstructive theory, and suggest the occurrence of various etiopathologic factors as responsible for the three first types of cystic abnormalities above mentioned.