Urology: Nephrolithiasis Flashcards
What % of kidney stones are radio-opaue and can be seen on KUB or clean Abd. X-ray?
90%
What % of patients with stones have a metabolic abnormality (hypercalciuria- Excreting too much Ca)?
Over 95%
What is the most common type of stone in industrialized countries?
Calcium oxalate
What is the most common cause of urolithiasis?
Dehydration (spike in summer and fall…sweating)
Is there a family inheritance with stones?
Yes… there is a 3 fold increase among family members
Who gets more stones, men or women?
Men (1.3:1)
What is the peak age for stone formation?
30-60
Where is the stone belt?
In the southern US… hotter, more dehydrated, less fluids
Does body size obesity increase the risk of stones?
Yes
What kind of diet increases stones and why?
High in aminal protein: Nucleic acids lead to uric acid stones which are not seen on KUB X-ray
What season are more stones seen in and why?
Summer…there is an increase in insensible water loss (sweating) and an increase in light exposure which results in increased calcium absorption due to increased vitamin D production
What are 10 Etiologies of Stone Formation?
- Anatomic
- Urine composition
- Urine volume
- Diet
- Metabolic
- Disease states
- Medications
- UTI (Staghorn stones
- Sedentary lifestyle
10, Supersaturation point (If decreased, need fluids)
What are the anatomic features associated with stone formation?
Stasis v. obstruction
- Poor ureter drainage (kidney stones)
- BPH: Can’t empty bladder…urine is stagnant and warm and it can crystallize
What are the urine composition features associated with stone formation?
- pH, crystal inhibitors, stone forming substances
- Ex. Uric acid stones can only form in acidic urine (pH 5.), so if you alkalize the urine to 6.5-7.0 you can dissolve the stone
What are the 2 stones you can dissolve?
Uric acid and cysteine
What are the urine volume features associated with stone formation?
Smaller urine volume, more likely to form stones (decrease suprasaturation of urine)
-2.5 L of urine per day = Stone former
What type of diet can decrease stone formation?
Vegetarian (decrease protein)
-High protein diets have lots of nucleic acid and can lead to uric acid stones
What are the metabolic features associated with stone formation?
- Hypercalciuria
- Hypocitraturia
- Hyperoxaluria
- Hyperuricouria
- Hypomagnesuira
- Hypokalemia
What disease states lead to stone formation?
- DM
- Type I RTA
- Chronic diarrhea: Dehydrated
- Medullary sponge kidney
- Hyperparathyroidism: Increase Ca excretions (remove PTH, fixes stones)
- PCKD
- IBD
- Sarcoidosis
- Obesity
- Metabolic acidosis
What medications lead to stone formation?
- Vitamin C: Metabolized to oxalate (this binds to Ca and forms stones)…only need 500mg a day of C
- Vitamin D: Increases calcium absorption (in kidney)
- Triamterene: Precipitates in the urine (crystalizes)..This is an old BP medication
- Protease Inhibitors: Used in HIV…crystallizes in urine
- Lasix: Increases Ca++ excretion
- Acetazolamide
- Agents that increase uric acid in urine (i.e. salicylates and probenicid)
What are some organic inhibitors of stone formation?
- Citrate: Directly inhibits Ca crystalization*
- Urea
- Nephrocaclcin
- Tamm-Horsfall Protein (native)
- Glycosaminoglycans
What are some inorganic inhibitors of stone formation?
- Phosphate
- Mg
- Trace elements: Zinc?
What is the recurrence after 1st stone in year 1?
10-15%
What is the recurrence after 1st stone in year 5?
50-50%
What is the recurrence after 1st stone in year 10?
70-80%
What should we do about stones?
PREVENT THEM!
What are the 5 types of stones and their incidence?
- Calcium containing stones: 70%
- Calcium Oxalate: 27%
- Calcium Phosphate: 7%
- Mixed: 36% - Infection stones (Struvite, Magnesium ammonium phosphate, matrix): 15-20%
- Uric Acid Stones: 5-10%
- Cystine Stones: 1-5%
- Protease Inhibitor Stones (Indinavir): Rare
What is the number 1 type of stone?
Calcium oxalate
What is the only stone to form in alkaline urine (pH 6.7-7)?
Calcium Phosphate
Are uric acid stones radio-opaque?
NO…they are radiolucent
What type of urine does uric acid stones form in?
Acidic urine (pH 5.0)
What type of patient might get a lot of uric acid stones?
A diabetic one…. ketoacidosis, always in an acidotic state, leads to uric acid
Describe cystine stones
The are super hard and smell like sulfuric acid when you lazer then (because it release a disulfide bond)
- They are seen in people with an aberhation in COLA AA metabolism
- These patients need to drink a ton of fluids to keep suprasaturation really low
What is the only stone not visible on a non-contrast CT scan?
Protease inhibitor stones (indinavir)…from HIV meds
What is the gold standard for imaging stones?
Non-contrast CT
Are calcium oxalate stones radioopaque?
Yes
What type of urine do calcium oxalate stones form in?
Wide range of pH
What is the most common cause of calcium oxalate stones?
Idiopathic (besides dehydration)
What are some other causes of calcium oxalate stones?
- Primary hyperparathyroidism: 5 %
- Secondary hyperparathyroidism (Renal failure most common cause)
- Bone disease- primary and metastatic leading to hypercalcuria and hypercalcemia- Steroids
- Hyperoxaluria (primary and enteric)
- Sarcoidosis
What does increase Ca in the blood and urine lead to?
Calcium oxalate stones
What are staghorn calculi due to?
Infection
What kind of urine do staghorn calculi form in?
Alkaline (pH of 7)
What are staghorn calculi usually composed of?
Magnesium-Ammonium-Phosphate (along with Ca phosphate)
What kind of bacteria form staghorn calcui?
Urea Splitting Bacteria: Proteus, Staphylococcus, Klebsiella, Pseudomonas, Ureaplasma, anaerobes
Does E. Coli produce urease?
NO…it doesn’t cause staghorn calculi
What is the treatment for staghorn caluli and why?
Complete stone removal
-These stones have little crannies in them that bacteria can hide in and antiobiotics can’t get to
What drug inhibits urease and can prevent stone formation and infection?
Lithostat
Are staghorn calculi branched?
Yes
What are staghorn calculi associated with?
Recurrent UTI
What kind of urine are uric acid stones post soluble in?
Urine pH of 7.0 or greater
What is uric acid?
The end point of purine metabolism (there fore uric acid stones are associated with protein/meat intake)
What % of stones are uric acid stones?
5-10%
What 4 conditions/states were mentioned that are associated with uric acid stones?
- Gout
- Meloproliferative diseases
- Increased water and bicarbonate loss due to diarrhea diseases
- Chemotherapy: Lysed cells release nucleic acid (increase uric acid stones)
Are uric acid stones radioopaque?
No…they are radiolucent (on plain XR… can be seen on CT)
What are cysteine stones associated with?
Interited autosomal recessive defect in transport of COLA AA at the renal tubule
What are COLA AAs?
Cystine, ornithine, lysine, and argine)
What is the only known pathology of cystinuria?
Urolithiasis (there are no other clinical manifestations)
What pH are cysteine stones more soluble in?
Urine pH greater than 7.5
Describe cysteine stones?
They are radiodense stones with a hexagon shape
- Looks like a stop sign
- These are super hard stones (like a diamond)
What is the level of urinary cystine associated with these stones?
Over 400mg/day
What can be done to the urine to help dissolve these stones?
Alkalize the urine with oral K-citrate to a pH of greater than 7.5
What is the presentation with an acute stone?
- Renal colic (waxing and waning of pain) - Unilateral flank pain on the side of the stone
- Nausea and vomiting
- Frequency with persistent urgency
- Hematuria
- Flank pain without peritoneal signs
Where are the kidney and ureter located?
RETROPERITONEAL
What are some imaging studies used for stones?
- Non-contrast CT scans
- US: Hydroneprosis and kidney swelling are + signs for a potential stone
- KUB
What is the poor mans CT?
US and a KUB
If you have increased suspicion of a stone, what will you do?
Urine, vitals, fever, imaging (go to CT)
What are 8 things done in acute management of a kidney stone?
- Is the patient sick/toxic?
- Fever? Elevated WBC? Low BP? Treat accordingly
- Send urine for UA and culture (BEFORE ANTIBIOTICS)
- Imaging
- Pain management
- IV Hydration
- Antibiotics?
- Management of Nausea
When is urgent intervention for stones requires?
Stones associated with:
- Solitary kidney
- Infection
- Renal failure
- Unrelenting pain/nausea
- Children
What can be given to help dilate the mid-distal ureter (and prostate) and help pass a kidney stone?
Alpha-blockers
If a stone is equal to or less than 4mm how often will it pass?
90% of the time
Stones 5-7mm pass what % of the time?
50%
Do stones greater than 7mm pass on their own?
Rarely
If waiting for a stone to pass, what do you need to do and how long do you wait?
- You need to control pain and increase hydraion
- Wait 4-6 weeks if not febrile
What are 2 form of acute treatment for stones?
- JJ Ureteral stent
2. Percutaneous nephrostomy tube
What can a JJ ureteral stent and percutaneous neprostomy tube do for a patient?
Alleviate pain (it is usually colicky because of the intermittent blockage of the ureter)
Describe the use of a JJ ureteral stent.
- It is placed cystopically under sedation
- You canulate a wire above the stone to unobstruct the kidney/ureter to move urine and relieve their symptoms
- Also, it can help the stone to pass with the bolus of urine
Desribe percutaneous nephrostomy tube
You place a tube in the back to the kidney to drain it (this is typically done by interventional radiology)
What are the 3 definitive surgical managements used for stones?
- Percutaneous Nephrolitholomy (PCNL)
- Extracorproeal Shock Wave Lithotripsy (ESWL)
- Ureteroscopy (URS)
What can mid-ureteral stones be treated by?
URS or ESWL
What can distal ureteral stones be treated by?
URS or ESWL
Describe percutaneous neprolithotomy (PCNL)
Treatment of choice for stone over 2cm in size
- You go through the back to the kidney for the stone
- This is typically done for staghorn stones because you need bore access
Describe ureteroscopy
You put a scope through the ureter, the stone is surrounded by a basket and pulled out
- If the stone is under 5mm you can pull it out
- If it is too big, you can laser it to crack it and break it into little pieces, then you use a basket to pull the pieces out
Is ureteroscopy better for stones in the upper pole or lower pole?
Upper pole (it is harder to get the scope into the lower pole because it has to curve around)
Describe extracorporal shockwave lithotripsy
- US shock waves crush stones: Break stones into sand-like particles
- Smaller pieces pass out of body in urine
- This is well tolerated and only requires light sedation
If a stone is over 8mm what needs to be done before ESWL?
You need to place a pre-operative stent to keep the ureter open to pass particles and facilitate passage (this prevents Steinstrasse)
Does ESWL cause damage?
Yes…it can cause tissue damage so you need to let it recover 4-6 weeks before the 2nd treatment if needed
What is Steinstrasse?
A complication of extracorporeal shock wave lithotripsy for urinary tract calculi in which stone fragments block the ureter to form a stone sheet
What is involved in chronic management of stones?
- H&P
- Stone composition analysis (NEED to analyze stones)
- UA & Urine culture (check for infection)
- Serum chemistries; PTH if serum calcium elevated (if Ca is elevated check for PTH increase)
- 24-hour urine collection
What patients require 24-hour urine collection?
All high-risk patients: Young, multiple stones or 2+ stones in a short time
- Pediatric population
- Solitary kidney
- Staghorns or multiple stones
- Bone disease
- GI disease
- Professional such as pilots, truck drivers, etc
How is 24-hour urine collection done?
The first pee of the day goes in the toilet, then you collect every other one for 24 hours and measure pH, volume, look for rist factors, ect.
What is something that is good for stones that we want to be high?
Citrate
What is the goal in medical management of stones?
Prevent new ones
What 2 stones can be dissolved under certain circumstances?
Uric acid and cystine
Is treatment for stones life-long?
Yes
What is the hub of treatment of kidney stones?
To increase the super saturation point
How can you increase the supersaturation point?
- Increase fluids (over 2.5L of urine per day)
- Change diet
- Adding stone inhibitors
What else is important in medical management?
Recognizing and reversing other medical factors
What drugs are used for management of stones?
- Thiazide diuretics
- Allopurinol
- Antibiotics
- Alkalinizing agents: K-citrate, sodium bicarbonate, sodium citrate
- Lithostat® for survite stones
- Thiola & D-penicillamine for cysteine stones
- Water
- B6
- Mg
What is example of a thiazide diuretic used for stones and what is the dose?
Hydroclorothiazide: Low dose of 12.5-25mg per day
How should thiazide diuretic be given for stones?
- 6 months on, 6 months off
- Low Na diet
What do thiazide diuretic do to help prevent stones?
- Increase reabsorption of Ca in the proximal and distal tubules
- Inhibit sodium reabsorption (in proximal and distal tubule of kidney
What does allopurinol do?
It decreases serum uric acid by inhibiting xanthine oxidase (so it’s used with increased levels of uric acid)
What are antibiotics used for?
Struvite stones (infection)
What are alkalinizing agents used for?
Uric acid stones…the increase the pH to dissolve stones
What is lithostat used for?
Struvite stones… it is a urease inhibitor
What are thiola and D-penicillamine used for?
Cysteine stones (but they aren’t well tolerated because they cause GI distress
What does thiola do?
It forms a disulfide bond with cysteine
What can you drink that is good for kidney stones?
Lemonade…because it has citric acid
