Ureteral growth in animal models with increased renal excretion of urine

The influence of increased functional load on the macroscopical and histolo gical appearance of the ureter was investigated. Sixty rats were divided in to five groups: (1) sucrose-fed rats with non-osmotic polyuria; (2) diabeti c rats with osmotic polyuria; (3) uninephrectomized rats; (4) sham-operated control rats; and (5) control rats. The 24-hour urinary volume was measure d on days 7, 14 and 21. Growth of the kidney, ureter and bladder was invest igated and the histological appearance of the ureter was further evaluated. Diabetic and sucrose-fed rats had comparable polyuria with a seven-fold in crease in urinary output. The urinary volume for the remaining kidney was d oubled in uninephrectomized rats. After 3 weeks, diabetic rats had increase d weight of the kidney, ureter and bladder, sucrose-fed rats had increased weight of the bladder, whereas uninephrectomized rats had increased weight of the kidney and ureter. The cross-sectional area (CSA) of the ureter wall from control rats increased from the proximal to the distal portion. The s ize of the whole ureter from diabetic rats was dramatically increased, the CSA of the wall of the distal ureter portion being four times that of the c ontrols. The CSA of the ureter wall from sucrose-fed rats was increased onl y in the distal portion, whereas the ureter from uninephrectomized rats was increased only in the proximal portion. The results demonstrate the import ance of differentiating between different portions of the rat ureter when e xamining histological sections of this organ. Moreover, polyuria perse is s hown to induce growth of the bladder and of the adjacent distal part of the ureter, whereas uninephrectomy and diabetes caused growth of the kidney an d the upper parts of the ureter, in addition to the growth induced by polyu ria.