Nephrolithiasis Notes

Basic Med Student Summary of Nephrolithiasis: Causes, Epidemiology, Clinical Presentation, Diagnosis, Management, Prognosis, Complications.

Click Here for the Related IntroNotes Article: Kidney Stones 101

Stone Types and Urinary Chemical Causes

• Calcium Oxalate (75%) ↑ Calcium ↑ Oxalate ↑ Urate ↑ Citrate
  • Oxalate: meat, dietary sodium, nuts, beans, cruciferous vegetables, fatty acid malabs (Crohn’s), high vit C, low B6
• Uric Acid (10%) ↑ Urate
  • Aciduria
  • Uric Acid: Alcohol, seafood, fatty and organ meats
• Struvite (5%) ↑ Urease Positive UTIs
  • Proteus mirabilis, Klebsiella, Pseudomonas UTIs
  • Form largest stones, including STAGHORN calculi (which fill the renal pelvis and calyces)
• Calcium Phosphate ↑ Calcium ↑ Phosphate
• Cystine ↑ Cysteine (familial cysteinuria)

 Epidemiology

General Risk Factors

• ♂ > ♀
• 30-60 years old
• Dehydration
• +ve FHx or PHx

Stone-Specific Risk Factors 

* low calcium intake increases oxalate reabsorption 

Note that the three locations that stones are most likely to get ‘stuck’ are:

• the pelvi-ureteric junction (PUJ)
• the ureter enters the pelvis (crossesing the common iliac artery bifurcation)
• the vesicoureteric junction (VUJ)

Clinical Presentation and Diagnosis

• Symptoms
  • Paroxysmal progressive unilateral flank colic
  • Radiation: to lower abdomen, groin, labia, testicles, perineum
  • Haematuria
  • Nausea/Vomiting
  • Dysuria, Frequency, Urgency
• Signs
  • Observed haematuria
  • Reduced bowel sounds
• Investigations
  • WBC (?UTI)
  • BUN, Creatinine (?AKI)
  • Dipstick (?UTI, pH >7 ?Urease +)
  • Urine Microscopy + Straining (?Crystals)
    • Dumbbell/Octahedron (?Oxalate)
    • Rhomboid/Needles (?Urate)
    • Coffin-Prism (?Struvite)
  • Urine Culture (?UTI)
  • Bloods (UEC, PTH, Urate, HCO3, ALP)
  • Nonenhanced CT Abdo-Pelvis (Gold-Standard)
    • Calculus size, site, densite, obstruction, hydronephrosis)
  • Ultrasound (pregnant, children, gynae/abdo DDx)
  • KUB X-Ray
    • Radiopaque = Calcium-containing
    • Weakly + = Struvite or Cysteine
    • Radiolucent = Urate
  • Intravenous pyelogram
• Differentials
  • Testicular torsion
  • Acute abdomen
  • Hydronephrosis
  • UTI

Management

• ?Complicated Urolithiasis
  • High-grade hydronephrosis
  • Pyelonephritis
  • Urosepsis
  • AKI
  • Vomiting or Intractable Pain
  • < 4w of Stone Hx
  • Failed medical therapy
• Stable Pt, Uncomplicated Stone, <10mm
  • Support and Surveil
  • Hydrate
  • NSAIDs, IV Morph
  • Tamsulosin (a-blocker) or Nifedipine (CCB)
• Uterorenoscopy + Extracorporal Shockwave Lithotripsy  for < 20mm
• Percutaneous Nephrolithotomy for >20mm
• Complicated Cases
  • Ureteral stenting or percutaneous nephrostomy (pyelo/hydro-decompression)
  • Shock Wave Lithotripsy
  • Last resort = laproscopic or open surgical removal (e.g. staghorn stones)

• If known stone cause = Urine pH Modification

Prognosis and Complications

• <5mm often to pass spontaneously,
• >10mm typically won’t, especially if ureteric sphincter or proximal.
• 50% 10 year relapse rate
• Complications
  • Recurrent UTI → pyelonephritis, urosepsis, and perinephric abscess
  • Obstruction → hydronephrosis → glomerular damage
  • Acute kidney injury

Banner image edited from glomerulus micrograph by Ed Uthman