What are the recommended tests and treatments for nephrolithiasis (kidney stones)?

Diagnostic Testing and Treatment for Nephrolithiasis

Ultrasound should be used as the primary diagnostic tool for nephrolithiasis, followed by non-contrast CT when additional information is needed, with treatment tailored to stone size, location, and composition. 1

Diagnostic Evaluation

Initial Imaging

• Ultrasound: First-line imaging modality

  • Sensitivity: 45%
  • Specificity: 94% for ureteral stones, 88% for renal stones 1
  • Advantages: No radiation exposure, readily available
  • Should not delay emergency care in acute presentations

• KUB (Kidney-Ureter-Bladder) X-ray:

  • Sensitivity: 44-77% 1
  • Helps differentiate radioopaque from radiolucent stones
  • Useful for follow-up monitoring

• Non-contrast CT scan:

  • Standard modality for acute flank pain after ultrasound 1
  • Provides detailed information on:
    • Stone location
    • Stone burden
    • Stone density
    • Anatomy
  • Low-dose CT maintains high diagnostic accuracy (93.1% sensitivity, 96.6% specificity) while reducing radiation exposure 1

Laboratory Testing

Every patient with nephrolithiasis requires:

• Urine tests:

  • Urinalysis (dipstick)
  • Urine culture if infection is suspected

• Blood tests:

  • Creatinine
  • Uric acid
  • Ionized calcium
  • Sodium, potassium
  • Complete blood count
  • C-reactive protein (CRP) 1

• Stone analysis:

  • Should be performed for all first-time stone formers 1
  • Helps guide prevention strategies

Special Populations

• Pregnant women:

  1. Ultrasound (first-line)
  2. MRI (second-line)
  3. Low-dose CT (last resort) 1

• Children:

  1. Ultrasound (first-line)
  2. KUB or low-dose CT if ultrasound is insufficient 1

Treatment Approaches

Pain Management

• First-line: NSAIDs (diclofenac, ibuprofen, metamizole)

  • More effective than opioids
  • Use lowest effective dose to minimize cardiovascular and gastrointestinal risks
  • Caution in patients with reduced renal function 1

• Second-line: Opioids (except pethidine)

  • Preferred alternatives: hydromorphone, pentazocine, or tramadol 1

Medical Expulsive Therapy

• α-blockers are effective for ureteral stones, especially those >5 mm in the distal ureter 1

Treatment Based on Stone Type

1. Uric Acid Stones:

   • Oral chemolysis with alkalinization (citrate or sodium bicarbonate)
   • Target pH: 7.0-7.2
   • Success rate: 80.5% 1
   • Potassium citrate: 30-80 mEq daily in 3-4 divided doses 2

2. Calcium Stones with Hypocitraturia:

   • Potassium citrate therapy
   • For severe hypocitraturia (<150 mg/day): 60 mEq/day
   • For mild to moderate hypocitraturia (>150 mg/day): 30 mEq/day 2
   • Monitor urinary citrate and pH every four months

Surgical Management Based on Stone Size and Location

Stone Size	Location	Recommended Treatment
<10 mm	Renal pelvis or upper/middle calyx	ESWL or flexible URS
10-20 mm	Renal pelvis or upper/middle calyx	ESWL or flexible URS
<10 mm	Lower pole	Flexible URS or ESWL
10-20 mm	Lower pole	Flexible URS or PCNL
>20 mm	Any location	PCNL
[3]

Management of Complications

• Sepsis/anuria with obstructed kidney:
  • Urgent decompression via percutaneous nephrostomy or ureteral stenting
  • Collect urine for culture before and after decompression
  • Immediate antibiotics, adjusted based on culture results
  • Delay definitive stone treatment until sepsis resolves 1

Prevention Strategies

Dietary Recommendations

• Increase fluid intake to produce at least 2 liters of urine per day 3
• Maintain adequate calcium intake (1,000-1,200 mg daily) from food sources 3
• Limit sodium intake to <2.4 g/day 3
• Reduce animal protein intake to 5-7 servings per week 3
• Avoid foods high in oxalates (wheat bran, rice bran, chocolate, tea, strawberries) 3
• Consume calcium with meals to reduce oxalate absorption 3

Follow-up Monitoring

• 24-hour urine collection to evaluate effectiveness of interventions 3
• Target parameters:
  • Urinary citrate: 400-700 mg/day
  • Urinary pH: 6.2-6.5 for calcium and uric acid stones; 7.0 for cystine stones 3
• Periodic imaging to assess for stone growth or new stone formation

Common Pitfalls to Avoid

1. Inadequate imaging leading to missed stones or inaccurate size estimation 3
2. Failure to perform 24-hour urine collections in high-risk patients 3
3. Missing underlying conditions like primary hyperparathyroidism, renal tubular acidosis, or cystinuria 3
4. Not monitoring for adverse effects of medications 3
5. Delaying treatment in cases of infection with obstruction, which can rapidly progress to sepsis 4

By following this structured approach to diagnosis and treatment, the morbidity and mortality associated with nephrolithiasis can be significantly reduced while improving patients' quality of life.