NEPHROLITHIASIS (quick review)

10 Feb

submitted by Christina Brown, M.D. 

Kidney stones:anatomy_kidneystones

  • Most common cause of renal colic
  • Stone composition:
    • 80%: Calcium stones (calcium oxalate > calcium phosphate)
    • 5% uric acid
    • Others: Magnesium ammonium phosphate (struvite), cystine
  • Associated with infections caused by urea-splitting organisms (eg, Pseudomonas, Proteus, Klebsiella) along with an alkalotic urine
  • 90% of urinary calculi are radiopaque.

 

Epidemiology and Etiology

  • 1% of the population
  • Twice as common in men as women
  • Theories on stone formation:
    • Urinary supersaturation of solute followed by crystal precipitation
    • Decrease in the normal urinary proteins inhibiting crystal growth
    • Urinary stasis from a physical anomaly, catheter placement, neurogenic bladder, or the presence of a foreign body

 

Pediatric Considerations

  • Rare in children
  • When present, indication of an overt metabolic or genetic disorder
  • Painless hematuria common presentation (up to 30%)

 

Causes of stone formation:

  • Metabolic abnormalities (50%)
  • Urologic abnormalities (20%)
  • Infection (15%)

 

History

  • Sudden onset of severe pain in the costovertebral angle, flank, and/or lateral abdomen
  • Colicky or constant pain: Patient cannot find a comfortable position
  • Hematuria: Gross hematuria in 1/3 of patients
  • Nausea/vomiting

 

ESSENTIAL WORKUP

  • Urinalysis
  • Microscopic hematuria present in >80%
  • Gross hematuria
  • Absent urinary blood in 10–30%
  • No correlation between the amount of hematuria and the degree of urinary obstruction
  • WBC/bacteria suggests infection

 

Imaging – CT:

  • Helical CT has replaced IV pyelogram (IVP) as test of choice.
  • Detects calculi as small as 1 mm in diameter
  • Advantages over IVP:
    • Performed rapidly
    • Does not require IV contrast media
    • Detects other non-urologic causes of symptoms, such as abdominal aortic aneurysms (AAAs)
  • Indications:
    • 1st-time diagnosis
    • Persistent pain
    • Clinical confusion with pyelonephritis

 

Renal Ultrasound:

  • unilateral hydronephrosis suggests possible obstructive stone
  • no radiation involved, but does not eval for non-urologic causes of symptoms

 

ED TREATMENT/PROCEDURES

  • Hydration:
    • Initiate IV crystalloid infusion with 1 L of normal saline infused over 30–60 min followed by 200–500 mL/hr.
    • Bolus volume compromised patients with 500-mL increments until urine output adequate
  • Analgesics (morphine, ketorolac):
    • Combination of IV NSAIDS and opioids decrease ED stay.
  • Antiemetics (prochlorperazine, ondansetron, droperidol, hydroxyzine)
  • α-Blockers (tamsulosin) or calcium-channel blockers (nifedipine) have been shown to decrease time to spontaneous stone passage:
    • Most efficacious for stones <5 mm in diameter
    • Tamsulosin and nifedipine equally effective
    • prescribe on discharge.

 

DISPOSITION

Admission Criteria

  • Obstruction in the presence of infection mandates immediate urologic intervention.
  • Intractable pain with refractory nausea and vomiting
  • Severe volume depletion
  • Urinary extravasation
  • Hypercalcemic crisis
  • Solitary kidney and complete obstruction
  • Relative admission indications (discuss with urologist):
    • High-grade obstruction
    • Renal insufficiency
    • Intrinsic renal disease
    • Stones of size <5 mm usually pass spontaneously; those >8 mm rarely do.

Discharge Criteria

  • Normal vital signs
  • No evidence of concomitant urinary tract infection
  • Adequate analgesia
  • Able to tolerate PO fluids to maintain hydration status

 

PEARLS AND PITFALLS

  • Do not miss a vascular catastrophe mimicking as renal colic.
  • Aggressive pain management and hydration promote passage of stones
  • The absence of hematuria does not exclude the diagnosis of acute renal colic.

 

References:
1. Bartosh S M.: Medical management of pediatric stone disease. Urol Clin North Am. 2004; 31:575–587. [PMID: 15313066]
2. Hollingsworth J M, Rogers M A, and Kaufman S R et al.: Medical therapy to facilitate stone passage: A meta-analysis. Lancet. 2006; 368:1171–1179.
3. Marx J A, Hockberger R S, and Walls R M: eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed.St. Louis, MO:Mosby;2009.

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