📋 Stepwise Approach to Urinary Obstruction
🔑 Key Principles — Nelson Ch 577
• UPJ obstruction: Most common obstructive lesion (left > right, male:female 2:1). Intrinsic stenosis or crossing vessel. Prenatal hydronephrosis (grade 3-4). Diuretic renogram (MAG-3) shows delayed drainage (t½ >20 min). Pyeloplasty success 91-98%.
• Posterior urethral valves (PUV): 1 in 8,000 males; most common cause of severe obstructive uropathy in children. Presents with bilateral hydronephrosis, distended bladder, oligohydramnios. VCUG shows dilated prostatic urethra, valve leaflets. Prognosis depends on nadir creatinine.
• Primary obstructed megaureter: Adynamic distal ureteral segment. Diuretic renogram ± Whitaker test. Resolves spontaneously in many; surgery (ureteral reimplantation + tapering) if obstruction or recurrent UTIs.
• Ureterocele: Cystic dilation of terminal ureter, often with duplex system. Ectopic ureterocele causes obstruction ± incontinence. Treatment: endoscopic incision or upper pole nephrectomy/reimplantation.