Who should a patient with hydronephrosis (swelling of the kidney due to urine flow obstruction) be referred to for further evaluation and treatment?

Referral of Hydronephrosis

Refer patients with hydronephrosis to urology for evaluation and management, with nephrology consultation considered for bilateral cases, renal functional impairment, or when chronic kidney disease management is needed. 1, 2, 3

Primary Referral: Urology

Urology is the primary specialty for hydronephrosis evaluation and surgical management. 1, 2 Urologists provide definitive diagnosis of the underlying cause and perform necessary interventions including:

• Immediate urologic referral is required for: 1, 2

  • Suspected posterior urethral valves (PUV) in male infants—the most common cause of neonatal bladder outlet obstruction 1
  • Moderate to severe hydronephrosis (UTD P2-P3 classification) 1
  • Bilateral hydronephrosis with painless hematuria (concern for malignancy) 4
  • Hydronephrosis with infection/sepsis requiring urgent decompression 2, 3
  • Acute symptomatic obstruction 5

• Urologic evaluation determines need for: 1, 2

  • Voiding cystourethrography (VCUG) to identify vesicoureteral reflux (VUR) or bladder outlet obstruction 1
  • Surgical interventions (pyeloplasty, valve ablation, stent placement, nephrostomy) 2, 3
  • Cystoscopy when hematuria is present 4

Nephrology Consultation

Nephrology consultation is appropriate when hydronephrosis affects renal function or requires chronic kidney disease management: 1

• Refer to nephrology for: 1

  • eGFR <30 mL/min/1.73 m² (CKD stages G4-G5) 1
  • Bilateral hydronephrosis causing acute kidney injury 3, 4
  • Persistent proteinuria >1 g/day (ACR ≥60 mg/mmol or PCR ≥100 mg/mmol) 1
  • Sustained fall in GFR >20% 1
  • Refractory hypertension or persistent electrolyte abnormalities 1

• Nephrology provides: 1, 4

  • Management of CKD complications (anemia, bone disease, acidosis) 1
  • Medication adjustments (avoiding ACE inhibitors/ARBs in bilateral obstruction) 4
  • Long-term renal function monitoring 2, 4

Pediatric Considerations

For infants and children with antenatal or postnatal hydronephrosis, early referral to pediatric urology and/or pediatric nephrology is recommended for UTD P2-3 cases to allow shared decision-making: 1

• Immediate pediatric urology referral for: 1

  • Male infants with suspected PUV (bladder wall thickening, dilated posterior urethra) requiring bladder catheterization at birth 1
  • Severe postnatal hydronephrosis (UTD P3) 1
  • Ureteral dilation ≥7 mm (increased UTI risk) 1

• Virtual/telemedicine consultation is appropriate for initial evaluation 1

Timing and Urgency

The urgency of referral depends on clinical presentation: 2, 3, 5

• Emergent (same-day): Hydronephrosis with infection/sepsis, acute kidney injury, or severe pain requiring immediate decompression via percutaneous nephrostomy or retrograde stenting 2, 3

• Urgent (within days): Bilateral hydronephrosis, suspected malignancy, or progressive renal dysfunction 3, 4

• Routine (weeks to months): Asymptomatic unilateral hydronephrosis with stable renal function can be observed with serial imaging, but urology consultation ensures appropriate diagnostic workup 1, 5

Common Pitfalls

Avoid these errors in hydronephrosis management: 2, 4

• Delaying intervention when infection is present leads to irreversible renal damage and sepsis 2
• Relying solely on ultrasound without advanced imaging (CT urography, MR urography, or MAG3 renal scan) fails to identify the underlying cause 1, 2
• Missing bilateral disease by imaging only one kidney alters management significantly 2
• Continuing ACE inhibitors or ARBs in bilateral obstruction precipitates acute kidney injury 4

1, 2, 3, 4, 5