MANAGEMENT OF KIDNEY STONES

Introduction

• A kidney stone is a solid piece of material that forms in a kidney when substances that are normally found in the urine become highly concentrated

• Kidney stones are one of the most common disorders of the urinary tract

• One in every 20 people develop kidney stones at some point in their life

Symptoms

• Intermittent colicky flank pain – radiation to lower abdomen or groin

• Nausea and vomiting• Dysuria• Urinary urgency• Restlessness• Hematuria

Risk factors

• Family history• Hypercalciuria• Cystic kidney disease• Hyperparathyroidism• Renal tubular acidosis• Dehydration from low fluid intake• High dietary intake of animal protein• Crohn’s disease

Diagnosis• Detailed medical and dietary history

– Medical conditions– Nutritional factors in diet– Medications (probenecid, some protease inhibitors, lipase inhibitors, triamterene,

chemotherapy, vitamin C, vitamin D)• Serum chemistries

– electrolytes (sodium, potassium, chloride, bicarbonate), calcium, creatinine and uric acid• Urinanalysis

– Dipstick and microscopic evaluation• Review of imaging studies

– Plain radiography– Ultrasonogrphy– CT

• 24 hour urine profile• Stone analysis

Management

• Pain relief – IV NSAIDs, opioids• Diet therapy• Pharmacologic therapy

Diet therapy• Fluid intake that will achieve a urine volume of at least 2.5 liters

daily• Calcium stones and relatively high urinary calcium – limit sodium

intake and consume 1,000-1,200 mg per day of dietary calcium• Calcium oxalate stones and relatively high urinary oxalate - limit

intake of oxalate-rich foods and maintain normal calcium consumption

• Calcium stones and relatively low urinary citrate - increase intake of fruits and vegetables and limit non-dairy animal protein

• Uric acid stones / calcium stones and relatively high urinary uric acid - limit intake of non-dairy animal protein

• Cystine stones - limit sodium and protein intake

Pharmacologic therapy• Thiazide diuretics - high or relatively high urine calcium and recurrent calcium stones• Potassium citrate - recurrent calcium stones and low or relatively low urinary citrate• Allopurinol - recurrent calcium oxalate stones who have hyperuricosuria and normal

urinary calcium• Thiazide diuretics and/or potassium citrate - recurrent calcium stones in whom other

metabolic abnormalities are absent or have been appropriately addressed and stone formation persists

• Potassium citrate - uric acid and cystine stones to raise urinary pH to an optimal level• Cystine-binding thiol drugs (tiopronin) - cystine stones who are unresponsive to

dietary modifications and urinary alkalinization, or have large recurrent stone burdens• Acetohydroxamic acid (AHA) - residual or recurrent struvite stones only after surgical

options have been exhausted• Should not routinely offer allopurinol as first-line therapy to patients with uric

acid stones

Other procedures

• Lithotripsy• Percutaneous nephrolithotomy• Ureteroscopic surgery

Follow up• Should obtain a single 24-hour urine specimen for stone risk

factors within six months of the initiation of treatment to assess response to dietary and/or medical therapy

• After the initial follow-up, should obtain a single 24-hour urine specimen annually or with greater frequency, depending on stone activity, to assess patient adherence and metabolic response

• Obtain periodic blood testing to assess for adverse effects in patients on pharmacological therapy

• Obtain a repeat stone analysis, when available, especially in patients not responding to treatment

• Monitor patients with struvite stones for reinfection with urease-producing organisms and utilize strategies to prevent such occurrences

• Periodically obtain follow-up imaging studies to assess for stone growth or new stone formation based on stone activity

Reference

• http://www.guideline.gov/content.aspx?id=48229&search=kidney+stone

• http://www.niddk.nih.gov/health-information/health-topics/urologic-disease/kidney-stones-in-adults/Pages/facts.aspx