4 Kidney stones Flashcards
What are the common demographics for kidney stones?
- lifetime prevalence in US= 5-15%
- men > women (2:1)
- white race more affected
- peak incidence in middle age
- substantial regional variations (genetic component)
What causes nephrolithiasis?
- “stone forming diseases”, conditions in which individuals form calculi (stones) within the renal pelvis and tubular lumens
- drug related disorders
What is nephrocalcinosis? What can cause it?
- Deposition of calcium salts in the renal parenchyma
- Caused by:
- “interstitial crystallization“/Randall’s Plaques
- Medullary Sponge Kidney
- Crystal (urate) nephropathy
What are bladder stones?
- retention of stone material within the bladder
- associated with bladder dysfunction
What are the most common type of kidney stones?
Calcium stones (oxalate and phosphate) make up 80% of kidney stone cases
Although the exact pathogenesis is unknown, what are 3 key factors behind kidney stones?
- urinary supersaturation (dehydration)
- crystal retention at the renal papilla
- associated risk factors (male, family history, diet, etc)
What types of kidney stones are favored at low urine pH?
- uric acid crystals
- serve as nidus for CaOx crystals
- cystine crystals (rare)
What types of kidney stones are favored at high urine pH?
- CaPhos
- Struvite/infectious
What can cause calcium stones?
- hypercalciuria
- high PTH
- excessive vitamin D
- idiopathic
- hypercalcemia
- high PTH
- excessive vitamin D
- cancer
- hyperoxaluria
- excessive vitamin C
- ethylene glycol (metabolized to oxalate)
- gastric bypass (Ca binds FAs because of decreased bile, leaving free oxalate to be absorbed)
What are the 4 types of stones we discussed and their prevalence?
- Calcium= 80%
- Struvite= 15%
- Uric acid= 5% (but increasing)
- Cystine= 1%
How would you describe struvite stones? What disorders are they part of?
- Phosphate stones described as “Envelope crystals”
- Disorders:
- Staghorn calculi (branched stones that fill all or part of the renal pelvis and branch into several or all of the calyces)
- Urease positive organisms
- UTI
**struvite stones like high pH urine!
How would you describe uric acid stones? What disorders are they part of?
- Radiolucent crystals (like low pH)
- Disorders:
- metabolic syndrome
- hyperuricemia/gout
- increased cell turn over
How would you describe cystine stones? What disorder are they part of?
- hexagonal crystals
- associated with cystinuria
What are some major risk factors for kidney stones?
- previous renal disease
- other medical history
- IBD/short gut
- hyperparathyroidism
- hypercalcemia
- gout
- HIV (from medications)
- family history
- social history
- dehydration
- diet
What diet risk factors are associated with kidney stones?
- low fluid intake
- high salt intake
- high protein intake (especially meat)
- low calcium intake
- high oxalate intake (spinach, beets, rhubarb, nuts, beans, chocolate, soy, tea)
What drugs are associated with causing kidney stones?
- topiramide (for seizures/migraine)
- ethylene glycol
- vitamin C
- indinavir (for HIV)
- acyclovir (antiviral for herpes)
- triamterene (K sparing diuretic)
- sulfamethoxazole (antibiotic)
- guaifenesin (cough suppressant)
What is the cause of cystinuria?
- genetic disorder
- caused by 2 possible defective genes
- SLC3A1
- SLC7A9
- causes cystine stones (rare)
What are some genetic diseases that can cause kidney stones?
- cystinuria (cystine stones)
- primary hyperoxalosis (CaOx stones)
- Dent disease (causes CaOx/Phos stones)
- familial hypomagnesemia with hypercalcemia and nephrocalcinosis (FHHNC)
- adenosine phosphosribosyltransferase (APRT) deficiency
- distal renal tubular acidosis
How can urinary oxalate levels predict the cause of stones?
Slightly high oxalate= enteric or dietary cause
Very high oxalate= genetic/hereditary cause
What are some symptoms of kidney stones?
- renal colic (pain, radiation to abdomen/groin)
- hematuria
- nausea/vomiting
- urinary frequency, dysuria
- fever/chills (elevated WBCs)
- elevated serum creatinine
What imaging can help diagnose kidney stones?
- CT scan (multiple thin slices, no contrast)
- ultrasound
- IVP (Intravenous pyelogram)
- KUB (kidney, urethra, bladder xray)
What would you look for in a 24 hr urine study of a patient with possible kidney stones?
- creatinine
- crystal constituents (Ca, Ox, Phos, uric acid)
- supersaturation issues (volume, pH, Na)
- inhibitors (citrate, Mg, K)
How do you treat acute kidney stones?
- removal of stones (only if large and won’t pass)
- symptom (pain) control
-
“Medical expulsive therapy”
- fluids
- alpha/Ca blockers and steroids to relax ureter
- let stones pass on their own
What is the chronic treatment for a patient with recurrent uric acid kidney stones?
- dilution (increase fluid intake)
- low protein/high fruit diet
- protein=acidic, fruit/veg= alkaline
- alkalinize urine
- xanthine oxidase inhibitors (prevent hyperuricemia)
- allopurinol, febuxostat
What is the chronic treatment for a patient with recurrent struvite kidney stones?
- dilution (increase fluid intake)
- sterilize urine (eliminate urea splitting bacteria)
- proteus, haemophilus, pseudomonas, klebsiella, staph epidermidis (NOT E coli)
- remove residual stone material (surgical)
- adjunctive therapies (urease inh, chemolysis)
What is the chronic treatment for a patient with recurrent calcium kidney stones?
- dilution (increase fluid intake)
- maintain normal calcium intake
- reduce urine calcium excretion
- limit Na (salt) and protein in diet
- thiazide diuretics
- reduce urin oxalate
- increase urine citrate (low protein, high fruit diet)
