12 - Kidney Stones Flashcards
What are the demographic of who kidney stones?
- Men > women (2:1)
- White more commonly affected
- Peak incidence in middle age
- Substantial regional variations.
Recurrence rates exceed 50% in 5 yrs
Where can kidney stones form? What are they called in these locations?
Nephrolithiasis/urolithiasis: stone forming diseases related to drugs.
Nephrocalcinosis: medullary sponge kidney, interstitial crystallization/randall’s plaque. Depisition within the kidney. Crystal nephropathy.
Bladder stones: retention of stone material within the bladder, associated with bladder dysfunction
What are the different compositions of kidney stones? What is the most common types?
Calcium oxalate and calcium phosphate are the most common types.
Can also be: urate, struvate, or cysteine.
What are key factors involved in the pathogenesis of kidney stones?
- Urinary supersaturation: concentration of substances high and volume of urine is low so you form crystals.
- Crystal retention at the renal papilla
- Associated risk factors
Know that supersaturation alone is insufficient to cause stone disease.
How frequent are calcium stones? What precipitates them?
80% of stones are calcium.
Calcium oxalate: not dependent on urine pH but low urine pH favors uric acid crytal formation which serves as a nidus
Calcium phosphate: increase pH precipitates them
What are conditions that cause calcium stones?
Hypercalciuria (increased PTH, excessive VitD, idiopathic)
Hypercalcemia (cancer, increased PTH, vitD excess)
Hyperoxaluria (vitC excess, ethylene glycol)
Taking too much vitamin C is a risk factor because vitamin C crystallizes as oxalate.
How common are struvite sontes? What precipitates them?
15% of stones.
Increase pH precipitates them.
What can be seen with struvite stones?
Urease positive organisms
Staghorn caliculi (refer to branched stones that fill all or part of the renal pelvis)
UTI
Envelope crystals
How common are uric acid stones? What can precipitate them?
5% of stones, but increasing from an increase in cancer therapy and an increase in metabolic syndrome.
Precipitated by low pH
What are characteristics of uric acid stones?
- Radiolucent
- Associted with metabolic syndrome
- Hyperuricemia
- Increased cell turnover
How common are cystine stones? What precipitates them?
1% of stones are cystine; caused by hereditary disease.
Low pH precipitates them.
What are characteristics of cystine stones?
Cystinuria
Hexagonal crystals
What are risk factors for kidney stones?
Previous renal disease
Short gut/IBD, hyperparathyroidism, hypercalcemia, gout, HIV
Family Hx
Social Hx (dehydration)
Diet risk factors: low fluid, high salt, high protein, low calcium, high oxalate (spinach, beets, rhubarbm nuts, beans, chocolate, soy products)
What drug causes stones?
Ethylene glycol
What are drugs that can form stones?
Indinavir
Acyclovir
Triamterene
Sulfamethoxazole
Guaifenesin/Guaoiacol
What are genetic diseases that cause stones?
Cystinuria - L-cystine
Primary hyperoxalosis - calcium oxalate
Dent disease - calcium oxalate or phosphate stones
Familial hypomagnesium with hypercalcemia and nephrocalcinosis (FHHNC) - calcium crystals
Adenosine phosphoribosyltransferase (APRT) deficiency
Distal renal tubular acidosis - calcium phosphate
What is primary hyperoxalosis/hyperoxaluria?
Rare genetic disorder of liver enzymes leading to excessive endogenous oxalate synthesis.
Caused by 3 known gene defects (all recessive inheritance): PH1, (80%), PH2 (10%), and PH3 (10%).
The highest oxalate excretion levels are seen in what?
Hereditary hyperoxaluria.
Then in enteric or diet related oxaluria.
What is the presentation of kidney stones?
- Renal colic (radiation to abd, groin)
- Hematuria
- Fever, chills
- Nausea, vomiting
- Urinary frequency, dysuria
- Mild-moderate CVA tenderness
- Elevated serum creatinine
- Elevated WBCs
How would you diagnose a kidney stone?
CT scan
Ultrasound
KUB: kidney and bladder Xray for surveillance
What would you do for a laboratory analysis of kidney stones?
Serum studies
24 hr urine studies
How do you treat acute (active) kidney stones?
- Pain control and fluids.
- Medical expulsive therapy (alpha-bllockers, steroids, Ca-blockers)
- Dissolution therapy (uric acid)
- Extra-corporeal shock wave lithotripsy
- Ureteroscopy if too big to pass: stone basketing/lithotripsy (laser)
How would you treat chronic uric acid kidney stones?
- Dilution
- Low protein/high fruit diet to prevent urine acidity and keep urine alkaline
- Alkalinize urine
- Xanthine oxidase inhibitors: allopurinol, febuxostate
How would you treat chronic struvite kidney stones?
- Dilution
- Sterilize urine: eliminate urea splitting bacteria
- Remove residual stone material
- Adjuvant therapies
