Dilatation of the ureter and renal pelvis may be caused by these etiologic factors: mechanical obstruction, infection, and disturbance of innervation. The various types may be recognized by differences in (1) outline, as observed in the pyelo-ureterogram, (2) pathology, and (3) clinical data.
Continued mechanical obstruction in any portion of the urinary tract is necessarily followed by dilatation of the portion above it. It may be conceivable that an occasional obstruction may cause urinary retention of such short duration that no dilatation in the ureter or pelvis would be apparent; but in the presence of a more or less permanent obstruction causing urinary retention, it would be impossible not to have a visible permanent distention of the ureter and the renal pelvis.
—Dilatation in the pelvis caused by mechanical obstruction is usually characterized by (1) predominance of dilatation in the plevis rather than in the calices or