| Type | Finding |
| 0 | collecting system hardly visible, normal |
| I | just renal pelvis visible, calyces not seen. pelvic diameter <7 mm, considered normal |
| II | axial renal pelvis diameter <10 mm, some calyces visible but with normal forniceal and papillar shape / configuration |
| III | marked dilatation of calyces and pelvis, pelvic axial width >10 mm with flattened papilla and rounded fornices, but without parenchymal narrowing |
| IV | gross dilatation of entire collecting system and narrowing of renal parenchyma |
| V | extreme type IV with only thin, membrane-like residual renal parenchymal rim |