After observing one case, the authors review the contemporary literature on ruptures of single kidney cysts in the pyelo-calicial cavity. They comment upon the pathogenesis of this entity which is produced by an increase in the intracystic pressure, an increase in the pressure inside the pyelo-calicial cavity or a decrease in the resistence of the wall separating the cyst from the intrarenal cavities. They review all the possible etiological causes (intracystic haemorrhaging, infection, traumatism, idiopathic disorder in the dynamics of the cystic fluid, obstructions in the excretory ducts, previously pathological stones, etc.). They enumerate the principles for the radiological diagnosis issued by McLaughlin and Pfister, to which the authors of this paper add, as a matter of interest, the retraction of the cortical at the level of the renal cavity.