Hydronephrosis; Kidney/abnormalities; Polycystic Kidney Diseases; Ureter/abnormalities; Ureteral Obstruction; Ureterocele; Urethra/abnormalities; Urethral Stricture; Vesico-Ureteral Reflux; Age Factors; Animals; Anti-Bacterial Agents/administration & dosage; Anti-Bacterial Agents/therapeutic use; Child; Diagnosis, Differential; Disease Models, Animal; Drainage; Follow-Up Studies; Humans; Hydronephrosis/diagnosis; Hydronephrosis/diagnostic imaging; Hydronephrosis/embryology; Hydronephrosis/physiopathology; Hydronephrosis/surgery; Infant; Infant, Newborn; Kidney/embryology; Nephrectomy; Nephrostomy, Percutaneous; Polycystic Kidney Diseases/diagnosis; Radiography; Radionuclide Imaging; Time Factors; Ultrasonography; Ureter/embryology; Ureteral Obstruction/diagnosis; Ureteral Obstruction/diagnostic imaging; Ureteral Obstruction/embryology; Ureteral Obstruction/physiopathology; Ureteral Obstruction/surgery; Ureterocele/diagnosis; Ureterocele/diagnostic imaging; Ureterocele/surgery; Urethra/diagnostic imaging; Urethral Stricture/diagnosis; Urinary Calculi/diagnosis; Urinary Calculi/surgery; Urinary Tract Infections/prevention & control; Vesico-Ureteral Reflux/diagnosis