What is the management for a 20-week pregnant woman with a solitary kidney and hydronephrosis diagnosed on ultrasound?

Management of Hydronephrosis in a 20-Week Pregnant Woman with Solitary Kidney

Retrograde ureteral stenting is the preferred first-line intervention for a pregnant woman at 20 weeks with hydronephrosis in a solitary kidney when conservative management fails. 1

Initial Assessment and Management

Diagnostic Evaluation

• Perform color Doppler renal ultrasound to:
  • Measure anteroposterior diameter of renal pelvis (critical parameter)
  • Assess resistive index (RI) of the kidney
  • Look for direct visualization of any ureteral stones
  • Evaluate ureteral jets

Risk Stratification

• Hydronephrosis severity indicators requiring intervention:
  • Renal pelvis anteroposterior diameter >16.5 mm in first two trimesters 1
  • RI >0.70 (suggestive of underlying kidney dysfunction) 1
  • Difference in RI >0.04 between affected and normal kidneys 1

Conservative Management (First Line)

• Implement conservative measures initially:
  • Adequate hydration (aim for urine output >2.5L/day) 2
  • Appropriate pain control (avoid NSAIDs)
  • Position patient in lateral decubitus position (opposite to the affected side)
  • Monitor for signs of infection or worsening obstruction

Indications for Intervention

Intervention is necessary if any of the following occur:

• Persistent pain despite conservative management
• Progressive hydronephrosis (>2 cm dilatation of renal pelvis) 3
• Signs of infection/sepsis
• Impaired renal function
• Uterine contractions 3
• Solitary kidney with significant obstruction (critical to preserve function)

Interventional Management

First-Line Intervention

• Retrograde ureteral stenting under ultrasound guidance 1
  • Advantages:
    • Minimal radiation exposure
    • Lower risk of urine leak
    • Technically less challenging than PCN
  • Technique:
    • Use ultrasound guidance to minimize radiation
    • Improved imaging resolution and smaller caliber scopes have made this procedure safe and feasible 1

Alternative Intervention

• Percutaneous nephrostomy (PCN) if retrograde stenting fails 1, 4
  • Indications:
    • When retrograde stenting is technically not possible
    • In cases of severe infection/pyonephrosis requiring immediate drainage
  • Technique:
    • Can be performed using ultrasound guidance alone to avoid radiation 1
    • Usually left in place until after delivery 1

Special Considerations for Solitary Kidney

• More aggressive monitoring of renal function is required
• Lower threshold for intervention compared to patients with two kidneys
• More frequent follow-up ultrasounds to monitor hydronephrosis progression
• Consider earlier intervention to preserve renal function

Follow-up Management

• Regular ultrasound monitoring every 2-4 weeks
• Stent exchange every 4-6 weeks to prevent encrustation 2
• Monitor for signs of urinary tract infection
• Coordinate care with obstetrician for any interventional management 2
• Definitive treatment of any underlying cause (e.g., stones) should be performed postpartum 1

Complications to Monitor

• Ureteral injury, perforation, or sepsis that could lead to preterm labor 1
• Stent encrustation (occurs more rapidly during pregnancy) 2
• Urinary tract infections
• Deterioration of renal function
• Risk of premature labor with persistent obstruction 2

The management approach must be particularly aggressive in this case due to the solitary kidney, as preserving renal function is critical for both maternal and fetal outcomes.