Nephrolithiasis Flashcards
What is the pain with a stone in the upper tract?
- flank pain
- upper anterior abdominal pain
What is the pain with a stone in the lower tract?
- groin pain
- ipsilateral testicular/labial pain
What is an atypical presentation of a stone?
- painless hematuria
- persistent UTI
What is the most common type of stone? What are the two next common?
70-80%=calcium oxalate or calcium phosphate
10-15%=uric acid
10-15%=magnesium ammonium phosphate a.k.a struvite
What are the steps for stone formation?
- supersaturation
- increased urinary ion excretion
- decreased urine volume - nucleation
- crystal growth and aggregation
What are the promoters of crystallization?
- hydrogen ions (low pH)
- sodium
- magnesium
- uric acid
- sites of prior injury
- gravity dependent locations (lower pole calyx)
What are inhibitors of crystallization?
- high urine flow rates
2. citrates and other substances
What are the states that lead to calcium stones?
- HYPERCALCIURIA*
- +/-hypercalcemia
- chronic metabolic acidosis
- low urine volume
- hyperuricosuria
- hyperoxaluria
- hypocitraturia
- high protein, low carb diet
- mark acid load, decreased calcium balance
What are causes of calcium stones?
- idiopathic
- hyperparathyroidism*
- vitamin D excess
- sarcoidosis (D production in granules)
- glucocorticoid excess
- RTAs (basic urine)
- Hyperthyroidism
- Malignant neoplasms
- loop diuretics
How do calcium and oxalate interact in the lumen of the GI tract, how does this affect how they interact in the kidney?
Lumen:
dietary calcium binds oxalate and impedes oxalate absorption
Kidney:
absorbed oxalate binds urinary calcium and can lead to stone formation
What are factors that favor calcium stone formation?
- high dietary oxalate
- increased fractional oxalate absorption
- low dietary calcium
- IBD (via fat malabsorption)-dietary calcium binds to FFAs in small bowel - Increased endogenous oxalate production-genetic causes
What causes uric acid stones?
ACIDIC URINE
- chronic metabolic acidosis
- low urinary pH
What causes struvite stones?
Chronic upper respiratory tract infection with urease producing bacteria:
- proteus species
- haemophilus species
- klebsiella species
- ureaplasma urealyticum
- results in ammonia and persistently alkaline urine–> promotes struvite formation
- more common in women, chronic urinary obstruction (neurogenic bladder)
What causes cystine stones?
Cystinuria: autosomal recessive condition
GI and renal transport disorder of four amino acids:
- cystine
- ornithine
- arginine
- lysine
-cystine insoluble in normally- acidic urine, so cystinuria in genetic disorders leads to stones
What is the preferred method of detecting stones?
CT without contrast
Do you need to retrieve the stone?
yes it is crucial
How do you prevent future calcium stones?
- low sodium, low animal protein diet
- normal dietary calcium
- medication: thiazide diuretics–>decrease calcium excretion in urine
How do you prevent future uric acid stones?
low purine, low animal protein diet
Medications: 1st line: -sodium bicarbonate, potassium citrate -alkalinize urine, maintain ph>6.5 2nd line: allopurinol -decrease uric acid levels -useful with hyperuricemia, marked hyperuricosuria -also useful in patients that cannot maintain urine ph>6.5
HOw do you prevent struvite stones?
eradicat infection with antibiotic therapy
- complete removal of all stones-including residual fragments, often requires intervention
- prevent future UTIs
How do you prevent future cystine stones?
alkalinize urine
-sodium bicarbonate, potassium citrate
-D-penicillin, tiopronin (increase solubility)
What does vitamin C do to oxalate?
facilitates urine oxalate excression
WHat are foods high in purines?
meats
-offal, seafood, shellfish
alcohol
What are foods high in oxalate?
black tea chocolate soymilk nuts berries beans, spinach, okra beets rhubarb carrots celery swiss chard sweet potatoes
If you have hyperuricosuria what should you do?
low purine, low animal protein diet
allopurinol therapy
If you have hypocitraturia what should you do?
low animal protein diet
increase fruits/veggies (high in citrate)
citrate supplements (potassium citrate)
