How should I evaluate and manage a patient with nephrolithiasis, including appropriate imaging, pain control, medical expulsive therapy, criteria for urologic intervention, and preventive measures?

Evaluation and Management of Nephrolithiasis

Initial Imaging

For adults with suspected renal colic, ultrasound with color Doppler of the kidneys and bladder is an appropriate first-line imaging modality that can identify moderate-to-severe hydronephrosis (which is 94.4% specific for symptomatic renal stone) and guide immediate management decisions without radiation exposure. 1

Imaging Algorithm by Clinical Presentation

Symptomatic patients with suspected stone:

• Point-of-care ultrasound (POCUS) should be performed first to assess for hydronephrosis and visible stones 1
• Moderate or greater hydronephrosis on ultrasound is highly specific (94.4%) for obstructing stone and may obviate need for CT 1
• CT without contrast is reserved for: patients with moderate-to-severe hydronephrosis on ultrasound (higher risk of stone passage failure), when ultrasound is nondiagnostic, or when alternative diagnosis is suspected 1
• Ultrasound identifies 75% of all urinary tract stones but only 38% of ureteral stones 1

Key imaging pitfall: Severe hydronephrosis is rare in simple stone disease and should prompt consideration of alternative causes of obstruction 1

Ultrasound Technical Details

• Evaluate for hydronephrosis grade, stone visualization, and increased renal echogenicity 1
• Assess ureteral jets bilaterally, bladder distension, and post-void residual 1
• Measure resistive indices (unilateral elevation suggests obstruction, though nonspecific) 1

Pain Control

NSAIDs such as diclofenac or ibuprofen must be used as first-line analgesics, with opioids reserved only as second-line options if NSAIDs fail. 2

This approach directly addresses the opioid epidemic while providing effective analgesia for renal colic. 3

Medical Expulsive Therapy (MET)

Alpha-blockers are strongly recommended for all distal ureteral stones, with particular benefit for stones >5 mm, though smaller stones also benefit from this therapy. 2

MET Implementation

• Alpha-blockers are used off-label for this indication 2
• Inform patients of potential side effects including orthostatic hypotension and retrograde ejaculation 2
• Stones <10 mm in the distal ureter have high likelihood of spontaneous passage 2
• Stones <5 mm have particularly favorable outcomes with conservative management 2

Conservative Management Protocol

The maximum duration for conservative management is 4-6 weeks from initial presentation. 2

Monitoring Requirements During Observation

• Mandatory follow-up imaging to monitor stone position and assess for worsening hydronephrosis 2
• Ensure well-controlled pain throughout observation period 2
• Monitor for clinical signs of sepsis 2
• Assess renal function serially 2

Urgent Intervention Criteria

Immediate urologic intervention with ureteral stenting or percutaneous nephrostomy is mandatory if any of the following develop: 2

• Signs of infection or sepsis with obstructing stone
• Worsening hydronephrosis on follow-up imaging
• Intractable pain despite adequate analgesia
• Deteriorating renal function

Critical pitfall: All three cases with severe hydronephrosis in one study required urologic intervention, emphasizing the need for urgent evaluation when severe obstruction is present. 1

Surgical Management

When conservative management fails after 4-6 weeks, ureteroscopy (URS) is the recommended first-line surgical treatment for distal ureteral stones, offering higher stone-free rates than shock wave lithotripsy. 2

URS Complication Rates

• Ureteral injury: 3% 2
• Stricture formation: 1% 2
• Urinary tract infection: 4% 2

Post-Procedure Management

• Routine stent placement after uncomplicated URS is not necessary 2
• If stent is placed, alpha-blockers may reduce stent-related discomfort 2

Preventive Measures

Dietary Modifications (All Patients)

Low fluid intake and excessive protein, salt, and oxalate intake are the most important modifiable risk factors. 4

• Increase fluid intake to produce adequate urine volume 4
• Reduce dietary sodium (target 100 mEq/day) 5
• Limit oxalate-rich foods (nuts, dark leafy greens, chocolate, tea) 5
• Moderate protein intake 4
• Do not restrict calcium - calcium restriction is not useful and may potentiate osteoporosis 4

Metabolic Evaluation for Recurrent Stone Formers

24-hour urine collection with measurement of calcium, oxalate, citrate, and uric acid is reserved for patients with recurrent stone formation. 4

Medical Prophylaxis Based on Stone Composition

Calcium oxalate stones with hypercalciuria:

• Thiazide diuretics to lower urinary calcium 4

Hypocitraturic calcium stones:

• Potassium citrate 30-80 mEq/day in 3-4 divided doses increases urinary citrate to normal range (400-700 mg/day) and raises urinary pH to approximately 6.5 5
• Stone formation rate reduced by 80% overall in treated patients 5
• Treatment sustained urinary citrate from subnormal to normal values 5

Hyperuricosuric calcium stones or uric acid stones:

• Citrate supplementation to increase urinary pH 4
• Allopurinol therapy to lower uric acid excretion when indicated 4
• Potassium citrate raised urinary pH from 5.3 to 6.2-6.5 in uric acid stone formers 5

Renal tubular acidosis with stones:

• Potassium citrate 60-80 mEq daily in 3-4 divided doses 5
• Stone-passage remission rate of 67% achieved 5

Underlying Metabolic Conditions to Screen For

Consider hyperparathyroidism, sarcoidosis, and renal tubular acidosis in the differential diagnosis. 4

Follow-Up Strategy

• Periodic imaging is essential to confirm stone passage 2
• Long-term follow-up recommended as stone disease is recurrent 2
• Metabolic evaluation after successful stone passage to prevent recurrence 2
• Data support cost-effectiveness of evaluation and treatment in recurrent stone formers 4