What is the initial treatment and workup for a patient with nephrolithiasis (kidney stones)?

Nephrolithiasis: Initial Workup and Treatment

The initial management of nephrolithiasis should include pain control with NSAIDs as first-line therapy, increased fluid intake to achieve at least 2L of urine output daily, and appropriate diagnostic imaging with ultrasound as the first-line modality. 1, 2, 3

Initial Diagnostic Workup

Imaging

• Ultrasound is recommended as the primary diagnostic tool for suspected kidney stones (45% sensitivity, 94% specificity for ureteral stones) 3
• If ultrasound is inconclusive, non-contrast CT scan should be performed as the second-line imaging (93.1% sensitivity, 96.6% specificity) 3
• Plain kidney-ureter-bladder (KUB) radiography helps differentiate between radioopaque and radiolucent stones and is useful for follow-up 3

Laboratory Evaluation

• Urinalysis with dipstick and microscopic evaluation to assess urine pH, presence of blood, signs of infection, and crystal identification 2, 3
• Serum chemistries including electrolytes, calcium, creatinine, and uric acid to identify underlying medical conditions 2, 3
• Urine culture if urinalysis suggests infection or if patient has history of recurrent UTIs 2, 3
• Stone analysis should be performed for all first-time stone formers when stone material is available 2, 3

Acute Management

Pain Control

• NSAIDs are first-line treatment for renal colic due to superior efficacy and fewer side effects compared to opioids 1, 2
• Opioids should be reserved as second-choice analgesics when NSAIDs are contraindicated or ineffective 1, 2
• If opioids are required, agents other than pethidine (such as hydromorphine, pentazocine, or tramadol) are recommended 1

Conservative Management vs. Intervention

• Conservative management is appropriate for uncomplicated ureteral stones up to 10 mm according to AUA guidelines and up to 6 mm according to EAU guidelines 2
• Medical expulsive therapy (MET) with alpha-blockers is efficacious, particularly for stones >5 mm in the distal ureter 1, 2
• Maximum duration of conservative treatment should be 4-6 weeks from initial presentation 2

Urgent Intervention Criteria

• Patients with fever, signs of infection, intractable pain, solitary kidney, bilateral obstruction, or acute kidney injury require immediate referral 3
• In cases of sepsis and/or anuria in an obstructed kidney, urgent decompression via percutaneous nephrostomy or ureteral stenting is strongly recommended 1
• Definitive treatment of the stone should be delayed until sepsis is resolved 1

Prevention of Recurrence

Fluid Intake

• Increased fluid intake spread throughout the day to achieve at least 2 L of urine per day is recommended to prevent recurrent nephrolithiasis 1, 4
• For severe forms of nephrolithiasis, fluid intake should be increased to produce 3.5-4 L of urine daily 4
• Fluid intake should be balanced between day and night to avoid urinary supersaturation during the night 4

Dietary Modifications

• Maintain normal calcium intake (1,000-1,200 mg/day) from dietary sources rather than supplements 2, 5
• Limit sodium intake to 2,300 mg daily 5
• For calcium oxalate stones, limit intake of oxalate-rich foods while maintaining normal calcium consumption 5
• Avoid calcium supplements, which may increase stone risk unlike dietary calcium 5, 6

Pharmacologic Therapy

• For recurrent nephrolithiasis where increased fluid intake fails to reduce stone formation, pharmacologic monotherapy with a thiazide diuretic, citrate, or allopurinol is recommended 1
• For calcium stones with hypocitraturia or elevated urine pH, potassium citrate is recommended 2
• For uric acid stones, oral chemolysis with alkalinization using citrate or sodium bicarbonate (pH 7.0-7.2) is strongly recommended 1, 2
• For cystine stones, first-line therapy includes increased fluid intake, restriction of sodium and protein intake, and urinary alkalinization 2

Follow-up and Monitoring

• A 24-hour urine specimen should be obtained within six months of initiating treatment to assess response to dietary and/or medical therapy 2
• After initial follow-up, a 24-hour urine specimen should be obtained annually or with greater frequency, depending on stone activity 2
• Periodic blood testing should be performed to assess for adverse effects in patients on pharmacological therapy 2
• Repeat stone analysis should be obtained when available, especially in patients not responding to treatment 2, 3

Common Pitfalls to Avoid

• Neglecting to address underlying metabolic abnormalities that contribute to stone formation 2
• Not considering the type of stone when determining appropriate medical therapy 2
• Prescribing allopurinol as first-line therapy for uric acid stones instead of urinary alkalinization with potassium citrate 2
• Restricting dietary calcium, which may actually increase stone risk by increasing intestinal oxalate absorption 5, 6