Nephrolithiasis Notes

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

Table of Contents

Click Here for the Related IntroNotes Article: Kidney Stones 101

Stone Types and Urinary Chemical Causes

Gray's Anatomy (20e) Plate 1122
Spatial relationship between kidneys and their neighbouring viscera
  • 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 

 

Risk Factors

Prevention

Calcium Oxalate

↑ Calcium

↑ Oxalate

↑ Citrate

↓ Urine pH

Urinary alkalinisation

Sufficient Dietary Calcium*

↓ Oxalate Rich Food

↓ Dietary salt ↓ Animal proteins    Thiazide diuretics (for isolated  cases of ↑ urinary calcium

↑ Water

> 2½ L/d

 

Calcium Phosphate

↑ PTH

Type 1 RTA

Urinary acidisation

 

Uric Acid

↓ Urine pH

↑ Urate

Urinary alkalinisation

Allopurinol

 

Struvite

Urease + UTI

Urinary acidisation

UTI prevention and treatment

 

Cystine

Cystinuria

Urinary alkalinisation

  

* low calcium intake increases oxalate reabsorption 

Gray's Anatomy (20e) Plate 1128
A nephron schematic, because who doesn't love a good nephron schematic?

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

 

 

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