Nephrolithiasis

Aka: Nephrolithiasis, Urolithiasis, Kidney stone, Renal Calculi, Ureteral Calculus, Renal Colic

1. Epidemiology
   1. Prevelance: 0.2% in U.S.
   2. Life-time risk
      1. Males: 10-12%
      2. Females: 3-5%
   3. Recurrence of Nephrolithiasis
      1. One recurrence in 50% of patients
      2. More than 3 recurrences in 10% of patients
   4. Peak age 20-50 years
   5. Gender associations: Overall Male:Female ratio 4:1
      1. Males: Calcium oxalate
      2. Females: Struvite
      3. Both: Urate Stones and Cystine Stones
2. Pathophysiology
   1. Stone formation is inhibited by Citrate
   2. Women have much higher levels of citrate than men
   3. Low citrate levels are related to most stone forms
3. Risk Factors
   1. See Nephrolithiasis Risk Factors
4. Types: Stones
   1. Calcium Nephrolithiasis (75%)
      1. Calcium oxalate (70%)
      2. Calcium Phosphate (5-10%)
         1. Approaches 75% in pregnant women
         2. Also more common in children
   2. Uric Acid Nephrolithiasis (10-15%)
   3. Struvite (15-20%)
   4. Cystine (1%)
   5. Drug-Induced (1%)
      1. Indinavir
      2. Triamterene
5. Symptoms: Renal Colic
   1. Severe Abdominal Pain of sudden onset
      1. Unilateral flank pain
      2. Lower Abdominal Pain
   2. Associated symptoms
      1. Nausea and Vomiting
      2. Hematuria
      3. Fever may be present
         1. Consider Pyelonephritis associated with stone (requires emergent management)
6. Symptoms: By stone location
   1. Kidney
      1. Vague flank pain
      2. Hematuria
   2. Proximal Ureter
      1. Flank pain
      2. Upper Abdominal Pain
      3. Renal Colic
   3. Mid-Ureter
      1. Flank pain
      2. Anterior Abdominal Pain
      3. Renal Colic
   4. Distal ureter (Ureteropelvic junction)
      1. Dysuria
      2. Urinary frequency
      3. Anterior Abdominal Pain
      4. Flank pain
      5. Renal Colic
7. Differential Diagnosis
   1. Acute onset of symptoms
      1. Urinary Tract Infection
      2. Acute Prostatitis
      3. Musculoskeletal spasm
      4. Acute Constipation or other acute bowel disorder
   2. Chronic intermittent or insidious onset of symptoms
      1. Bowel disease
      2. Interstitial Cystitis
      3. Inguinal Hernia
      4. Testicular mass
      5. Urothelial or Renal Mass
      6. Benign prostatitic hyperplasia
8. Imaging
   1. See Nephrolithiasis Imaging
9. Labs
   1. Initial diagnostics
      1. Urinalysis
         1. Microscopic or Gross Hematuria in 90% of cases
      2. Urine Culture
   2. Evaluation of single stone former without risk
      1. Chemistry panel
         1. Serum electrolytes
         2. Serum Calcium
         3. Serum Phosphorus
      2. Renal Function tests
         1. Blood Urea Nitrogen
         2. Serum Creatinine
      3. Serum Uric Acid
      4. Stone Analysis (nidus and outer layer)
         1. Stone analysis is critical
         2. Microscopic Crystal Analysis
            1. Envelope shape crystal: Calcium oxalate
            2. Diamond shape crystal: Uric Acid
            3. Coffin-lid shape crystal: Struvite
            4. Hexagon shape crystal: Cystine
      5. Urinalysis
      6. Urine Culture (when indicated)
   3. Evaluation of recurrent stone formation
      1. See those labs listed above
      2. Parathyroid Hormone level
         1. Obtain if Urine Calcium >10 mg/dl
      3. 24 hour Urine Collection
         1. Urine pH
            1. Acidic urine predisposes to Uric Acid stones, Cystine Stones and Calcium Oxalate Stones
            2. Alkaline urine predisposes to Struvite Stones and Calcium Phosphate Stones
         2. Urine Sodium
         3. Urine Creatinine
         4. Urine Calcium (Hypercalciuria >300 mg/day)
         5. Urine Uric Acid (Hyperuricosuria >750 mg/day)
         6. Urine Oxalate (Hyperoxaluria >40 mg/day)
         7. Urine Citrate (Hypocitraturia <320 mg/day)
         8. Urine Magnesium (Hypomagnesuria <50 mg/day)
         9. Other urine labs to consider
            1. Urine pHosphorus
            2. Urine Calcium Oxalate (Supersaturation)
            3. Urine Calcium Phosphate
10. Management: Indications for Urology Consultation
    1. Failure to pass stone
       1. Unpassed stone after several days
       2. Large calculus >5 mm
          1. Calculi <5 mm pass spontaneously in 90% of cases
          2. Calculi 10 mm pass spontaneously <10% of cases
    2. Fever and urosepsis
       1. Emergent management required
    3. Signficant Hydronephrosis or renal dysfunction
    4. Intractable pain and Vomiting
    5. High grade ureteral obstruction
    6. Severe pain requiring Narcotics >2 days
    7. Multiple stones
    8. Recurrent stone formation
    9. Occupation (unable to return to work until clear)
       1. Police officer
       2. Firefighter
       3. Train engineer
       4. Airline pilot
11. Management: General
    1. See Prevention below
       1. Fluid and dietary measures apply to both acute management and prevention
       2. Maintain >2-2.5 liters of oral fluid daily
       3. Administer NS in emergency department (consider D5 1/2NS if calciuria)
    2. See Specific Types
       1. Calcium Nephrolithiasis
       2. Uric Acid Nephrolithiasis
    3. Adequate Analgesics
       1. NSAIDs
          1. Highly effective in Renal Colic
             1. Cordell (1994) Ann Emerg Med 23(2):262
             2. Cordell (1996) Ann Emerg Med 28:151-8
          2. NSAIDs compared with Opioids
             1. Equal to or more effective than Opioids
             2. Less Vomiting than with Opioids
             3. Holdgate (2004) BMJ 328:1401-4
       2. Opioids typically required for adequate analgesia
          1. Vicodin 1-2 every 6 hours as needed
    4. Medications to shorten course (standard of care)
       1. Nifedipine (Procardia) 30 mg orally daily for 14 days
          1. Hollingsworth (2006) Lancet 368:1171-9
       2. Tamsulosin (Flomax) 0.4 mg orally daily for 14 days
          1. Becoming standard of care (not yet FDA approved)
          2. Other alpha blockers are probably effective
          3. Increases chance of passing ureteral stone to >80%
          4. Preferred over Nifedipine
          5. Porpiglia (2004) J Urol 172:568-71
       3. Doxazosin (Cardura) 4 mg orally daily for 14 days
12. Management: Specific Stone Therapy
    1. See Urate Stones
    2. See Calcium Stones
    3. See Struvite Stones
    4. See Cystine Stones (Cystinuria)
13. Management: Interventions
    1. Anatomic directed stone therapy
       1. Stone above Illiac crest
          1. Extracorporeal Shock Wave Lithotripsy (ESWL)
          2. Pushback and Extracorporeal Shock Wave Lithotripsy
          3. Antegrade or retrograde Ureteroscopy
          4. Percutaneous nephrostomy tube
          5. Open surgery (See Below)
       2. Stone below Illiac Crest
          1. Pushback and Extracorporeal Shock Wave Lithotripsy
          2. Cystoscopy and stent placement
          3. Ureteroscopy and Stone Manipulation (Loop, basket)
          4. Open surgery (See Below)
    2. Available Interventions
       1. Ureteroscopy
          1. Ureteral stone
       2. Ureterorenoscopy
          1. Renal stones <2 cm
       3. Extracorporeal Shock Wave Lithotripsy (ESWL)
          1. Radiolucent calculi
          2. Renal stones <2 cm
          3. Ureteral stones <1 cm
       4. Percutaneous Nephrolithotomy
          1. Renal stones >2 cm
          2. Proximal ureteral stones >1 cm
       5. Open Surgery Procedures in refractory cases
          1. Anatomic nephrolithotomy
          2. Partial nephrectomy
          3. Illeal ureter
14. Prevention
    1. Maintain fluid intake >2.5 Liters per day
       1. Most important single measure
       2. Ingest 8 to 12 ounces fluid on awakening and at bedtime
       3. Recommended fluids
          1. Water
          2. Citrus juice
    2. Maintain Urine volume > 2 Liters per day
       1. Periodically measure urine output in a 2 liter bottle
       2. Urine should be clear in appearance with minimal color
    3. Dietary restrictions
       1. Limit animal protein to 8 ounces per day (or <1 gram/kg/day)
          1. Animal protein increases urinary calcium and Uric Acid excretion
          2. Animal protein decreases urinary pH and urinary citrate excretion
       2. Limit sodium intake to 2-4 grams per day
       3. Limit Oxalate Containing Foods (e.g. tea, tomatoes, cashews)
       4. Limit high sugar or fat content (Obesity predisposes to stone formation)
       5. Avoid excessive Vitamin C
    4. Lifestyle
       1. Move toward target BMI, Ideal Weight
       2. Encourage daily physical Exercise
    5. Dietary increases or no restriction
       1. Increase vegetable Dietary Fiber
       2. Maintain calcium intake at at least 1000 mg/day
          1. No Dietary Calcium restriction (unless absorptive Hypercalciuria)
          2. Calcium binds oxalate in the Intestine and decreases oxalate absorption
          3. Take calcium with meals
15. References
    1. Mobley (Feb 1999) Hospital Medicine, p. 21-38
    2. Goldfarb (1999) Am Fam Physician 60(8): 2269-76
    3. Houshiar (1996) Postgrad Med 100(4): 131-8
    4. Frassetto (2011) Am Fam Physician 84(11): 1234-42
    5. Pietrow (2006) Am fam Physician 74(1): 86-94
    6. Preminger (2007) J Urol 178(6): 2418-34
    7. Portis (2001) Am Fam Physician 63(7):1329-38
    8. Segura (1997) J Urol 158:1915-21
    9. Teichman (2004) N Engl J Med 350:684-93
    10. Trivedi (1996) Postgrad Med, 100(6): 63-78