- Hydronephrosis on imaging is not synonymous with obstruction — functional studies (MAG-3 with diuretic) confirm true obstruction.
- UPJO is the most common cause of antenatal hydronephrosis; intrinsic narrowing or aberrant lower-pole vessel are typical causes.
- Pyeloplasty (Anderson-Hynes dismembered) is the gold standard for UPJO; success rates >90%.
- Endopyelotomy is an option for UPJO but has lower success rates than pyeloplasty, particularly with crossing vessels.
- Ureteral strictures are most commonly iatrogenic (ureteroscopy, prior surgery).
- Retroperitoneal fibrosis is associated with methysergide, ergot derivatives, beta-blockers, and phenacetin.
- Idiopathic RPF is treated with corticosteroids; surgical ureterolysis is reserved for failure of medical therapy.
- In bilateral ureterolysis, ureters must be protected by intraperitonealization or omental wrapping.
- Post-obstructive diuresis requires careful electrolyte and volume management; replace 50–75% of urine output with hypotonic fluid.
- Obstruction with infection is a urological emergency requiring urgent decompression (stent or nephrostomy) before definitive treatment.