Does a pregnant woman with a kidney stone require hospital admission or can she be managed as an outpatient?

Management of Kidney Stones in Pregnant Women: Outpatient vs. Inpatient Care

Pregnant women with kidney stones can be managed as outpatients if they have well-controlled symptoms, no signs of infection, and no severe obstruction, with observation as the first-line therapy. 1, 2

Initial Assessment and Indications for Hospitalization

Kidney stones represent the most common non-obstetric cause of abdominal pain requiring hospitalization during pregnancy 2, 1. When evaluating a pregnant woman with suspected kidney stones, consider:

Outpatient Management Criteria:

• Well-controlled pain with appropriate analgesics
• No signs of infection (normal vital signs, no fever)
• Ability to maintain hydration
• Normal renal function
• Stone size and location favorable for spontaneous passage
• Reliable patient for follow-up

Hospitalization Indications:

• Failed outpatient pain management
• Signs of infection or sepsis
• Solitary kidney with significant obstruction
• Severe hydronephrosis (renal pelvis AP diameter >16.5mm in first two trimesters)
• Abnormal resistive index (RI >0.70 or difference >0.04 between kidneys)
• Bilateral obstruction
• Acute kidney injury
• Intractable nausea/vomiting preventing oral hydration

Diagnostic Approach

For pregnant women with suspected kidney stones:

1. First-line imaging: Renal ultrasonography with color Doppler 1

   • Evaluate for hydronephrosis, resistive index, direct visualization of stones, and ureteral jets
   • Avoids radiation exposure to the fetus

2. Second-line imaging (if ultrasound is inconclusive):

   • MRI/MRU in second and third trimesters 1
   • Low-dose CT only if absolutely necessary and other imaging is inconclusive 1

Management Algorithm

Step 1: Conservative Management (First-line for most patients)

• Adequate hydration (aim for urine output >2L/day)
• Appropriate pain control (avoid NSAIDs as they are contraindicated in pregnancy) 2, 1
• Regular ultrasound monitoring every 2-4 weeks 1
• Most stones <10mm will pass spontaneously

Step 2: If Conservative Management Fails

• Coordinate with obstetrician for any interventional management 2, 1
• Options include:
  1. Ureteroscopy: Preferred definitive intervention during pregnancy 2, 3
  2. Temporary drainage:
     • Ureteral stent placement (requires frequent exchanges due to rapid encrustation) 2
     • Percutaneous nephrostomy (if retrograde stenting fails or in cases of severe infection) 1

Important Considerations

• Contraindications during pregnancy: Shockwave lithotripsy and percutaneous nephrolithotomy 4
• Medication cautions: NSAIDs are contraindicated; use appropriate analgesics in consultation with obstetrician 1
• Complications risk: Stone events during pregnancy carry increased risk of maternal and fetal morbidity, including potential for preterm labor 2, 1
• Follow-up: Regular ultrasound monitoring for patients managed conservatively

Key Pitfalls to Avoid

1. Delaying diagnosis: Symptoms may be attributed to normal pregnancy discomforts
2. Unnecessary radiation exposure: Always start with ultrasound
3. Inadequate pain control: Untreated pain can lead to complications
4. Failing to recognize infection: Infected obstructing stones require immediate intervention
5. Multiple stent changes: Rapid encrustation of stents in pregnancy requires frequent exchanges; ureteroscopy may be preferable for definitive management 2, 3

By following this approach, most pregnant women with kidney stones can be safely managed as outpatients, reserving hospitalization for those with complications or failed outpatient management.