Kidney Stones

Kidney stones…where to start. They’ve been described as “more painful than childbirth” (I can’t confirm as I’ve been fortunate enough to not had a kidney stone…or given birth) and are responsible for >1 million ED visits per year. In this wonderful blog post we will cover what you, as an ED physician, need to know for diagnosis, management, and disposition. Gear up, this will be a rocky ride (pun intended).

Basics

• Common demographic is Caucasian, men, middle age (peak incidence age 40-60)
• certain predisposing diseases (i.e. diabetes, obesity, Crohn’s/ulcerative colitis, metabolic disease, etc)
• Up to 80% of calculi are composed of calcium oxalate or calcium phosphate
  • Less commonly:
    •  struvite (aka staghorn calculi…think of the urea splitting bacteria we all definitely remember from our Step 1 days)
    • Uric acid (not uncommon in our gout patients)
    • Cystine (hereditary)
• Common sites of stone obstruction are areas of anatomical narrowing
  • Uretopelvic junction
  • Uretovesicular junction

Diagnosis

• Get that history and physical…have they had stones before, what medications are they on that would predispose to stones, have they had systemic symptoms such as fever or chills, etc
• Abdominal exam often non focal
• Get urine pregnancy test in all females of childbearing age (as always)
• Look at their urine. Gross hematuria is present in 30% and microscopic hematuria in 85-90%
  • Think of these calculi as an avalanche of gravel stampeding down the delicate straw of a ureter

• Consider lab work
  • Leukocytosis in the setting of systemic symptoms such as fever/chills is concerning for infected stone…which warrants emergent urology consultation
  • Measure kidney function
    • Creatinine often normal, as unaffected kidney can increase function up to 185% in otherwise healthy patients             
• Imaging
  • KUB vs US vs CT vs MRI…WHAT DO I DO???
    • Noncontrast helical CT is gold standard for diagnosing uretolithiasis
      • Both sensitive and specific
      • Can evaluate for hydronephrosis, calculi location in urinary tract, and stone size
      • Can evaluate for other pathology if diagnosis is uncertain
    • US
      • Useful if concern for radiation exposure (pregnancy, children, etc)
      • May miss smaller stones (<5mm)
      • Sensitivity up to 78% for detecting hydronephrosis
    • KUB
      • Not sensitive or specific enough to rule in or out stones
      • Many stones are radiopaque and can possibly be seen on plain films
      • Comes in handy if stone after stone is detected by CT to follow progression of the stone
    • MRI
      • Mostly used for evaluation of kidney stone in first trimester of pregnancy if US is equivocal
        • ACOG recommends use of CT in 2^nd and 3^rd trimester
• Don’t anchor your diagnosis…even if it sounds like a kidney stone at least consider alternative diagnoses

Treatment

• PAIN CONTROL PAIN CONTROL PAIN CONTROL
  • NSAIDs are commonplace for renal colic
    • Decrease smooth muscle tone…which dilates the ureter so it’s not clamping down so hard on the piece of gravel that cascading down your urinary tract
    • Toradol 15mg IV or Ibuprofen 600mg q6h
  • Opioids often needed for severe pain
• Hydration
  • PO vs IV
  • Dehydration common precipitant of urolithiasis
• Antiemetic
  • Zofran
  • Reglan
• Expulsion therapy
  • Tamsulosin 0.4mg PO QHS
    • Nighttime dosing to reduce risk of orthostatic hypotension…use with caution in elderly patients
  • Likely more effective for stones >5mm

Disposition

• Many patients safe for discharge home with urology follow up within 7 days
  • Small stone size, pain/nausea well controlled, able to arrange follow up
  • Send these patients home with urine strainer and instruct to bring stone to follow up
    • Allows for identification of stone composition and appropriate risk stratification and preventative measures
  • Patients with UTI and non-obstructed or minimally obstructed stone can be considered for discharge home with antibiotics and close follow up
• Consider Admission
  • Signs of systemic illness
    • SIRS/sepsis criteria
  • Intractable pain/nausea/vomiting
  • Solitary or transplanted kidney
  • Significant co-morbidities
  • Acute renal failure
  • Obstructed stone with presence of UTI
    • These patients are at risk for decompensation
• Urology consultation
  • Large stone size (>6mm)
  • Signs of systemic illness
    • i.e. SIRS/Sepsis criteria
  • Presence of UTI
• Average time for expulsion
  • Based on stone size
    • <2mm = average 8.2 days
    • 2-4mm = average 12.2 days
    • 4-6mm = average 22.2 days

Sources

Manthey DE, Nicks BA. Urologic Stone Disease. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8eNew York, NY: McGraw-Hill; 2016. http://accessmedicine.mhmedical.com.ezproxy.rush.edu/content.aspx?bookid=1658&sectionid=109433849. Accessed December 07, 2019.