Nephrolithiasis Flashcards
What is the 3rd most common urinary tract disorder?
Nephrolithiasis
Is nephrolithiasis more common in men or women?
Men
What causes neprholithiasis?
Ambient concentrations of stone material exceed solubility in urine - allows crystals to grow
Basically “supersaturation” of urine
What could a patient with neprholithiasis be lacking that helps to fight off the production of stones?
Inhibitors that retard crystal formation and growth
What could cause supersaturation?
Increased excretion of poorly soluble substances
Genetic disorder causing stone formation involving genes SLC2A1 and SLC7A9
Cystinuria
What factors can lead to stone formation?
Supersaturation PLUS heredity or environment (diet, obesity)
Most common type of urinary stone?
Calcium oxalate
What are the different types of urinary stones?
Calcium oxalate Calcium phosphate Struvite Uric acid Cystine
Frequently have smooth-edge ground-glass appearance
Cystine stones
Can be radiolucent
Uric acid stones
If a uric acid stone is radiopaque, it must be combined with??
Calcium
What are some things that can cause calcium stones?
Idioipathic hyeprcalciuria Primary hyperparathyroidism Hypocitraturia Hyperuricosuria Renal tubular acidosis Hyperoxaluria (Dietary, enteric, primary) Colon resection, ileostomy Habit, environment
Produced by UTI with urease-producing bacteria; Usually greater than 2cm (large)
Struvite stone
What bacteria could cause a struvite stone?
Proteus, Klebsiella, pseudamonas, enterobacter
What is the treatment for Struvite stones?
Prevent UTIs
What causes uric acid stones?
Low 24h urine pH (less than 5.6)
What are some common comorbidities in patients with uric acid stones?
Obese or diabetic - both decrease urine pH via insulin resistance
What is the treatment for uric acid stones?
Increase urine pH to greater than 6 with potassium citrate
What are some other things a patient can do to prevent uric acid stones?
Allopurinol
Low purine diet (decrease fish, shellfish, meats)
Cystine stones are caused by an ____ ____ inherited abnormality
Autosomal recessive
How do you treat cystine stones?
Increase urine volume to 3L daily and increase urine pH to greater than 7 with potassium citrate
What agents may be used to prevent cystine stones?
Chelating agents
Geographic risk factors for nephrolithiasis include?
High humidity
High temperature
What type of diet can increase risk factors for nephrolithiasis?
High animal protein diet
High salt intake
A family history risk factor for nephrolithiasis is having a ___ ____ relative with a history of calcium stones
1st degree
Will decreasing calcium in the diet help decrease the risk for nephrolithiasis?
No! In fact it could increase the risk because your body will absorb more oxalate from diet
What are the most common signs and symptoms of nephrolithiasis?
Unilateral flank pain
Sudden onset
Renal colic
Hematuria
If your patient has persistent urinary frequency without evident infection, where could a stone be located?
Ureterovesical junction
Gold standard for the diagnosis of kidney stones?
Non-contrast CT
What types of radiography could you get to diagnose nephrolithiasis?
Non-contrast CT*
KUB x-rays
Intravenous pyelography
Renal ultrasonography
What is the benefit of doing a CT scan on a patient with suspected nephrolithiasis?
Stone type can be suggested by radiographic density
Low radiographic density
Uric acid or cystine
High radiographic density
Calcium
Have a laminar rugged appearance, often full casts of the renal pelvis and calyces. “Stag horn” conformation
Struvite stones
What is the procedure of choice for diagnosing nephrolithiasis in a patient who needs to avoid radiation (pregnancy, etc.)
Ultrasound
Limitations of X-ray when diagnosing nephrolithiasis
Will show large radiopaque stones like calcium, struvite, and cystine but will MISS radiolucent uric acid stones and could also miss small stones
will NOT detect obstruction
Why is IVP no longer the diagnostic procedure of choice?
Potential contrast reactions, lower sensitivity, and higher radiation exposure than non-contrast CT
What would you want to order to workup nephrolithiasis?
Urinalysis for blood and cystine crystals
Stone analysis
BMP (check calcium and creatinine); Thyroid
24 hour urine analysis for recurrent stone formers
What is the most common abnormality found in patients who produce recurrent calcium stones?
Idopathic hypercalcuria
Elevated excretion of calcium with normal blood calcium
What is the best way to acutely manage a patient with nephrolithiasis?
Pain management (opiods, NSAID)
Hydration
Strain urine
When should you consider hospitalization of a patient with nephrolithiasis?
Cannot tolerate oral intake
Uncontrolled pain or fever
How long before shock wave lithotripsy does a patient need to stop taking their NSAIDs?
3 days
Possible advantage of decreasing ureteral smooth muscle tone thereby directly treating mechanism (ureteral spasm)
NSAIDs
When does a patient with nephrolithiasis need extracorporeal shock wave lithotripsy or rigid and flexible ureteroscopy?
Stone greater than 10mm
Urosepsis requiring emergent decompression
What is emergent decompression?
When a patient needs a stent or nephrostomy tube to pass a kidney stone
Most stones less than or equal to __mm will pass spontaneously
5mm
Stones that are greater than or equal to ___mm will not pass on their own
10mm
What is the most important indicator of stone passage?
Size
Stones located in the ____ ____ are less likely to pass spontaneously compared to stones in the ureterovesicular junction
Proximal ureter
Stone passage is significantly more likely and occurs faster with ____ vs conservative treatment alone
Flomax
Alpha blocker
Tamsulosin (Flomax)
Calcium channel blocker that may increase passage rate of ureteral stones
Nifedipine
When should you have your patient consult urology?
Urosepsis Renal failure Obstruction Solitary kidney Concomitant pyelonephritis Stone greater than 10mm Have not passed stone in 4-6 weeks
What are the 3 minimally invasive surgical techniques available for removal of a kidney stone?
Shock wave lithotripsy
Percutaneous nephrolithotomy
Rigid and flexible ureteroscopy with or without stent placement
Treatment of choice for most small (Proximal) renal calculi
SWL (Shock wave lithotripsy)
Treatment of choice for stone removal of larger (greater than 2cm) renal stones including stag horn calculi
Percutaneous nephrolithotomy (PNL)
Treatment of choice for the majority of middle and distal ureteral stones and ureteral calculi that have failed shock wave lithotripsy
Ureteroscopy
___ patients will experience stone recurrence within 5 years
1/3
___ patients will experience stone recurrence within 10 years
1/2
What is key for preventing nephrolithiasis?
Increase fluid intake! Maintain urine volume of greater than 2L
What diet changes can be made to decrease Ca+ Oxalate stone formation?
Decrease oxalate intake (rhubarb, spinach, nuts, seeds)
Decrease animal protein intake
Decrease sodium intake
Increase fluid intake
