1. The Structure of the Normal and Hydronephrotic Upper Urinary Tract -- Structure of the Normal Upper Urinary Tract -- Innervation of the Upper Urinary Tract -- Functional Considerations -- Structure of the Upper Urinary Tract in Idiopathic Hydronephrosis -- Aetiological Considerations in Idiopathic Hydronephrosis -- 2. Urodynamics of the Multicalyceal Upper Urinary Tract -- Functional Activity of the Normal Upper Urinary Tract -- Physiology of the Unobstructed Upper Urinary Tract -- The Experimentally Obstructed Upper Urinary Tract -- Functional Activity of the Upper Urinary Tract in Idiopathic Hydronephrosis -- Summary of the Physiology of the Hydronephrotic Upper Urinary Tract -- 3. The Intravenous Urogram in Idiopathic Hydronephrosis -- Acute and Chronic Obstruction -- Normal and Abnormal Standard IVUs -- Clinical Judgement and the Standard IVU -- IVU Modifications -- Conclusions -- 4. Nuclear Medicine -- Parenchymal Transit Time Studies -- Diuresis Renography -- Comparison of Parenchymal Mean Transit Time with Diuresis Renography -- 5. Pressure Flow Studies I -- Clinical Application -- Technique -- Complications -- Interpretation of Results -- Indications in Equivocal Hydronephrosis -- Results of Pressure flow Measurement -- Summary -- 6. Pressure Flow Studies II -- Technique -- Interpretation -- Contraindications -- Conclusions -- 7. Experimental Validation of Diagnostic Methods -- Materials and Methods -- Results -- Discussion -- 8. Idiopathic Hydronephrosis in Children -- Morphological Anomalies -- The Renal Parenchyma -- The Opposite Kidney: Other Congenital Anomalies -- Secondary Pelviureteric Obstruction -- Complications -- Clinical Features -- Treatment -- Results -- 9. The Role of Percutaneous Nephrostomy -- Technique -- Materials -- Renal Drainage -- Retroperitoneal Drainage -- Dilatation of Operative PUJ Strictures -- Stone Dissolution -- Stone Extraction -- Complications -- Summary -- 10. Clinical Management -- Clinical Material -- Discussion