Kidney Stones


Types of Stones

Calcium (80%)
  • pH (calcium Oxalate)
  • pH (calcium phosphate)
  • Radiopaque
  • Oxalate crystals can result from ethylene glycol (antifreeze) or vitamin C abuse.
  • Most common kidney stone presentation: calcium oxalate stone in a patient with hypercalciuria and normocalcemia.
  • Treatments for recurrent stones include thiazides and citrate.
    • HCTZ 25-50mg PO qd
    • Chlorthalidone 25-50mg PO qd
    • Indapamide 1.25-2.5mg PO qd
    • Sodium Phosphate/Potassium Phosphate (Neutra-Phos) 250 mg PO tid
 
Struvite (15%)
  • Associated with chronic infections (Urease-positive bugs = Proteus mirabilis, Staphylococcus,  Klebsiella)
  • Radiopaque
  • Urine with pH > 7
  • Staghorn formation

Treatment:

  • Urine should be acidified for prevention of calcium phosphate and struvite stones.
    • Lithostat 250 mg PO tid - QID
  • Cranberry juice or betaine can lower urine pH
 
Uric Acid (10%)
  • Associated with gout or congenital disorders
  • RadiolUcent
  • Urine with pH < 6
  • Visible on CT and ultrasound but not x-ray.
  • Strong association with hyperuricemia (e.g., gout).
  • Often seen in diseases with cell turnover, such as leukemia.
  • Tx: Alkalinization of urine (Potassium Citrate 30-60 mEq/day PO in 4 divided doses).
 
Cysteine (1%)
  • Associated with in-born errors of metabolism, staghorn formation, renal failure.
  • Radiopaque.
  • Tx:  Alkalinization of urine (Potassium Citrate 30-60 mEq/day PO in 4 divided doses)
 

 

Site Of Obstruction

  • Ureterovesical Junction (UVJ) most common
  • Renal calyx
  • Ureteropelvic Junction (UPJ)
  • Pelvic Brim
Stones < 4mm pass 90% of the time
  • 4-6 mm 50%
  • > 6 mm 10%
  • > 1 cm < 1%


Diagnosis

  • Noncontrasted CT most sensitive and specific and evaluates for stone mimics.
    • HCG in female before CT
      • HCG (+) = US
  • Hematuria
    • May in absent in 10-20%
    • May also be positive with ruptured AAA
  • Crystals in urine
  • KUB not sensitive or specific
  • Ultrasound with hydronephrosis and decreased bladder jets if obstructing stone; not sensitive

 

Common Mimmics

  • Abdominal aortic aneurysm
  • Testicular torsion
  • Ectopic pregnancy
  • Appendicitis
  • Incarcerated hernia
  • Biliary colic 

Treatment

  • NSAIDs
    • Avoid with congenital stones, history of renal failure, or bilateral stones
  • Medical expulsion therapy (Flomax 0.4 mg 1 PO qd)
  • Hydration (1L NS IV Bolus)
  • Analgesic:
    • Opioids (Dilaudid 2 mg IV q2h prn)
    • Hydrocodone/acetaminophen (Vicodin), 1-2 tab q4-6h PO prn pain OR
    • Oxycodone/acetaminophen (Percocet) 1 tab q6h prn pain OR
    • Acetaminophen with codeine (Tylenol 3) 1-2 tabs PO q3-4h prn pain.
    • Ketorolac (Toradol) 10 mg PO q4-6h prn pain, or 30-60 mg IV/IM then 15-30 mg IV/IM q6h (max 5 days).
  • Lithotripsy (Urology consult if > 5mm)
  • Percutaneous or retrograde lithotomy
  • Open surgery

 

When to consult Urology?
Obstruction
Infection
Renal Injury (staghorn calculi)
Solitary Kidney



Management by Stone Size/Location
Size/Location Management
< 4 mm Usually pass on their own in 1-2 weeks
Hydration, Analgesia, +/- alpha blocker
Urology consult if do not pass in 2 weeks
< 5 mm or distal Hydration, Alpha-blocker and/or nifedipine
5-10 mm Decide on other parameters (Location, Composition, occupation, large stone)
Location:
  RENAL stones can be followed.
  DISTAL URETERAL stone will pass.

Composition:
 
Staghorn renal calculi = Urology (associated with infections & kidney injury)

Occupation:
 Pilots cannot fly even with asymptomatic stone
> 10 mm Urology Consult
RENAL Calculi 5 mm - 2 cm Lithotripsy
LOWER POLE stone 5 mm- 1 cm Lithotripsy
URETERAL stone 5 mm - 1 cm Lithotripsy
> 2 cm or when ECL is contraindicated Percutaneous nephrolithotomy

 

 

Indication for Admission

Absolute Indications for Admission Relative Indications for Admission
Intractable pain or vomiting Fever
Urosepsis Solitary kidney or transplanted kidney without obstruction
Single or transplanted kidney with obstruction Obstructing stone with signs of urinary infection
Severe medical comorbidities Urinary extravasation
Acute renal failure Significant medical comorbidities
Hypercalcemic crisis Stone unlikely to pass — large stone (> 5mm)  in proximal ureter

 


Admit Orders: Nephrolithiasis

1. Admit to:

2. Diagnosis: Nephrolithiasis

3. Condition:

4. Vital Signs: q8h. Call physician if urine output <30 cc/hr; BP >160/90, <90/60; T >38.5°C.

5. Activity: Up ad lib.

6. Nursing: Strain urine, measure inputs and outputs. Place Foley if no urine for 4 hours.

7. Diet: Regular, push oral fluids.

8. IV Fluids: IV D5 ½ NS at 100-125 cc/hr.

9. Special Medications:

  -Cefazolin (Ancef) 1-2 gm IV q8h
  -Morphine sulfate 10 mg IV/IM q2-4h prn pain OR
  -Hydrocodone/acetaminophen (Vicodin), 1-2 tab q4-6h PO prn pain OR
 
-Oxycodone/acetaminophen (Percocet) 1 tab q6h prn pain OR
 
-Acetaminophen with codeine (Tylenol 3) 1-2 tabs PO q3-4h prn pain.
 
-Ketorolac (Toradol) 10 mg PO q4-6h prn pain, or 30-60 mg IV/IM then 15-30 mg IV/IM q6h (max 5 days).
 
-Zolpidem (Ambien) 10 mg PO qhs prn insomnia.


11. Extras:
 Intravenous pyelogram, KUB, CXR, ECG.
 

12. Labs: CBC, CMP, calcium, HCG, uric acid, phosphorous, UA with micro, urine C&S, urine pH, INR/PTT. Urine cystine, send stones for X-ray crystallography. 24 hour urine collection for uric acid, calcium, creatinine.


 

 

174. A 37-year-old male returns for follow-up after an episode of nephrolithiasis. He passed a 3-mm calcium oxalate stone and requests information about preventing further stones.
You would advise that he

A) drink up to 2 L of water/day
B) increase his consumption of meats and grains
C) increase the level of fructose in his diet
D) restrict foods high in oxalate, such as spinach and rhubarb

ANSWER: A
  • General recommendations regarding prevention of recurrent nephrolithiasis include increasing fluid intake up to 2 L of water daily (SOR B); greater volumes may lead to electrolyte disturbances and are not recommended. More specific dietary recommendations depend on the stone type. If the stone is not recovered, the type may be inferred from a 24-hour urine collection for calcium, phosphorus, magnesium, uric acid, and oxalate.
  • Approximately 60% of all stones in adults are calcium oxalate. Uric acid stones account for up to 17% of stones and, like cystine stones, form in acidic urine. Alkalinization of the urine to a pH of 6.5–7.0 may reduce stone formation in patients with these types of stones. This includes a diet with plenty of fruits and
    vegetables, and limiting acid-producing foods such as meat, grains, dairy products, and legumes. Drinking mineral water, which is relatively alkaline with a pH of 7.0–7.5, is also recommended. Restriction of dietary oxalates has not been shown to be effective in reducing stone formation in most patients.
  • Acidification of the urine to a pH 7.0 is recommended for patients with the less common calcium phosphate and struvite stones. This can be accomplished by consumption of at least 16 oz of cranberry juice per day, or by taking betaine, 650 mg three times daily.

    Ref: Frassetto L, Kohlstadt I: Treatment and prevention of kidney stones: An update. Am Fam Physician 2011;84(11):1234-1242.