What is the management and workup for a patient with a high suspicion of nephrolithiasis (kidney stones)?

Management and Workup for High Suspicion of Nephrolithiasis

For patients with high suspicion of nephrolithiasis, the initial diagnostic workup should include ultrasound as the primary imaging tool, followed by non-contrast CT if needed, along with basic laboratory tests including urinalysis, creatinine, and electrolytes, while treatment should focus on pain management with NSAIDs as first-line therapy and appropriate hydration. 1, 2

Diagnostic Evaluation

Initial Assessment

• Detailed medical history focusing on:
  • Pain characteristics (location, radiation, severity)
  • Previous stone episodes
  • Family history of stones
  • Associated symptoms (nausea, vomiting, fever)
  • Medication use
• Physical examination with attention to:
  • Vital signs (especially for fever indicating possible infection)
  • Flank tenderness
  • Abdominal examination

Imaging Studies

1. Ultrasound (US): First-line imaging modality

   • Sensitivity: 45%, Specificity: 94% for ureteral stones and 88% for renal stones 1
   • Advantages: No radiation, readily available
   • Limitations: Lower sensitivity compared to CT

2. Non-contrast CT scan: Standard for acute flank pain after US

   • Strong recommendation for use after ultrasound 1
   • Provides information on stone location, burden, density, and anatomy
   • Low-dose CT maintains high diagnostic accuracy (93.1% sensitivity, 96.6% specificity) while reducing radiation exposure 1

3. KUB (Kidney-Ureter-Bladder) X-ray:

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

Laboratory Tests

• Urinalysis: Essential for all patients

  • Check for hematuria, pyuria, pH, crystals
  • Urine culture if infection suspected

• Blood tests: 1, 2

  • Creatinine (renal function)
  • Uric acid
  • Ionized calcium
  • Sodium, potassium
  • Complete blood count
  • C-reactive protein (if intervention planned or infection suspected)

Management Approach

Pain Management

1. First-line: NSAIDs (diclofenac, ibuprofen, metamizole) 1

   • More effective than opioids in reducing need for additional analgesia
   • Use lowest effective dose to minimize cardiovascular and gastrointestinal risks
   • Caution in patients with reduced renal function

2. Second-line: Opioids 1

   • Avoid pethidine due to high vomiting rates
   • Preferred alternatives: hydromorphone, pentazocine, or tramadol

Hydration

• Increase fluid intake to achieve at least 2.5 L/day of urine output 2, 3
• Balance fluid intake between day and night to avoid nighttime urinary supersaturation 3
• Water is the preferred fluid 3

Treatment Based on Stone Size and Location

Treatment decisions should follow this algorithm based on stone size and location: 2

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

• ESWL: Extracorporeal shock wave lithotripsy
• URS: Ureteroscopy
• PCNL: Percutaneous nephrolithotomy

Urgent Intervention

• Immediate decompression (percutaneous nephrostomy or ureteral stenting) is strongly recommended for: 1
  • Sepsis with obstructed kidney
  • Anuria with obstructed kidney
  • Solitary kidney with obstruction

Prevention of Recurrence

Medical Management

For patients with recurrent stones, consider: 2, 4

• Potassium citrate:

  • For calcium stones with low urinary citrate
  • For uric acid stones (to raise urinary pH to 6.0)
  • Dosage: 30-80 mEq daily in 3-4 divided doses

• Thiazide diuretics:

  • For recurrent calcium stones with hypercalciuria
  • Options: hydrochlorothiazide, chlorthalidone, or indapamide

• Allopurinol:

  • For calcium oxalate stones with hyperuricosuria and normal urinary calcium
  • Not first-line for uric acid stones (urinary alkalinization is more effective)

Dietary Recommendations

• Increase fluid intake to achieve >2.5 L/day urine output 2, 3
• Maintain normal dietary calcium (1,000-1,200 mg daily from food sources) 2
• Limit sodium intake to <2,300 mg daily 2
• Limit animal protein to 5-7 servings per week 2
• Avoid sugar-sweetened beverages and those with phosphoric acid 2
• Increase consumption of fruits and vegetables 2

Follow-up and Monitoring

• Collect 24-hour urine specimen within 6 months of starting treatment 2
• Annual 24-hour urine collection to assess adherence and metabolic response 2
• Stone analysis when material is retrieved 2
• Periodic blood testing to assess for adverse effects of pharmacologic therapy 2

Pitfalls to Avoid

• Delaying imaging in patients with fever or solitary kidney 1
• Using sodium citrate instead of potassium citrate (can increase urine calcium excretion) 2
• Using allopurinol as first-line therapy for uric acid stones 2
• Inadequate follow-up monitoring 2
• Restricting dietary calcium (may worsen oxaluria and lead to negative calcium balance) 5