SM 216a - Kidney Stones Flashcards
List the kidney stones in order of prevalence
Ca2+ containing stones >>>>>>>
Struvite stones > Uric acid stones > cysteine stones
Does this condition promote or inhibit kidney stone formation?
High citrate
Inhibits stone formation
What are the main risk factor for calcium stones?
What contributes to these risk factor?
- Hypercalciuria
- Secondary to hyeprcalcemia
- Idiopathic
- Hyperoxaluria
- Dietary intake of high-oxalate foods
- Vitamin C intake (metabolized to oxalate)
- General malabsorption in the GI tract
- > increased oxalate reabsorption
- Low Ca2+ intake -> increased oxalate absorption
- Primary hyperoxalosis
A 45-year-old Caucasian male with a history of chronic myeloid leukemia for which he is receiving chemotherapy presents to the emergency room with oliguria and colicky left flank pain. His serum creatinine is 3.0 mg/dL and is urine pH is 5.0. You diagnose nephrolithiasis. His kidney stones, however, are not visible on abdominal x-ray. His stone is most likely composed of which of the following?
- Calcium oxalate
- Struvite
- Uric acid
- Cysteine
c. Uric acid
What are the general risk factors for kidney stone formation?
- Low urine volume
- High sodium diet
- Leads to increased urinary Ca2+
- Reabsorption of Na+ and Ca2+ are coupled
- High sodium diet
- Leads to increased urinary Ca2+
- *->** **decreased Na+ reabsorption
- > decreased Ca2+ reabsorption**
- High protein diet
- Protein metabolism
- -> Increased acid load
- -> Bone resorption to buffer acid = Ca2+ release
- -> Increased urinary Ca2+
What kind of kidney stones are hexagonal?
Cysteine stones
Uric acid stones are more likely to form in [acidic/basic] urine
Uric acid stones are more likely to form in acidic urine
A 30-year-old male with history of two prior episodes of nephrolithiasis presents to establish care in your clinic. He would like to discuss strategies to prevent future kidney stones. He has not had analysis done of his prior kidney stones. You order a 24-hour urine collection for Ca, Na, phosphorus, uric acid, and citrate. Before even obtaining results, which of the following would be an appropriate recommendation?
- Increase dietary sodium intake
- Increase dietary protein intake
- Lower dietary calcium intake
- Increase fluid intake
d. Increase fluid intake
What kind of kidney stones are likely to be the largest?
Struvite stones
Can form staghorn calculi (kidney stones so large that they block more than one renal calyx)
What are the risk factors for cysteine kidney stones?
Inherited disorder of metabolism that impairs cysteine reabsorption in the proximal tubule
What are staghorn calculi?
What kind of kidney stones can form them?
Staghorn calculi = very large kidney stone that blocks more than one renal calyx
Struvite stones are most likely to form staghorn calculi
What are the major risk factors for uric acid stone formation?
- Hyperuricosuria
- Increased dietary intake of purines and animal protein
- High-cell turnover states: uric acid is released from cells when they die
- Hematologic malignancies
- Tumor-lysis syndrome
- Low urinary pH
- Uric acid is less soluble in acidic conditions
What kind of kidney stone is this?
Struvite
Rectagular, “coffin lid”
About ____% of people will have an episode of nephrolithiasis in their lifetime (United States)
About 10% of people will have an episode of nephrolithiasis in their lifetime (United States)
What kind of kidney stone is this?
Calcium stone
Square shaped, looks like an envelope
Why might urease-producing bacteria lead to kidney stones?
What kind of stones?
Infection by urease-producing bacteria (ex: P**roteus)
- -> Increased urease production
- -> Alkalization of the urine
- -> Increased urinarey pH = phosphate is less soluble
- -> Phosphate complexes with surrounding ions to form struvite stones
Which populations are at an increased risk for kidney stones?
Asians
Caucasians
Men
What kind of kidney stone is this?
Cysteine
Hexagonal shape
Which stones are radiolucent on x-ray?
What does this mean?
Uric acid stones
They do not show up brightly on x-ray like other stones, so they can be easy to miss on x-ray
Does this condition promote or inhibit kidney stone formation?
Low volume
Promotes stone formation
What complications of kidney stones require urgent intervention?
- Concurrent urinary/kidney infection
- Stone + infection
= increased risk of pyelonephritis -> sepsis
- Stone + infection
- Acute kidney injury
- Stone is blocking flow to such an extent that it causes AKI
Describe the long-term management of patients with kidney stones
Aggressive prevention!
- 24h urine collection
- Look for Ca2+, oxalate, Na+, uric acid, citrate, posphate, Cr, total volume, pH
- Helps to figure out what is causing stones
- LithoLink is the major company that does this
- Use results to modify risk factors
- Thizaide diuretics to reduce calciuria
- K+ citrate supplementation to increase urinary pH and citrate
- Diet
- Increase fluid intake
- Decrease Na+ intake
- Limit animal protein
- Normal Ca2+ intake
- Lifestyle
- Aim for normal BMI
- Limit stress
- Adequate physical activity
- Balance excessive fluid loss
Which substances become less soluble as urinary pH increases?
Ammonium urate
Phosphate
What interventions are used to remove kidney stones?
- Extracorporeal shock-wave lithotripsy (ESWL)
- Forceful ultrasound waves are directed at the stone
- Breaks the stone in to tiny pieces that can be urinated out
- Most common intervetion
- Percutaneous nephrolithotomy
- Go into ureters/urinary tract and remove the stone
- Much less common now
What is the major factor that determines whether a kidney stone will pass?
Size
- Most stones <5mm will pass
- Stones 5-10mm are case by case
- Stones >1cm will not pass on its own
What kind of kidney stones are most common?
Calcium-containing stones
Calcium oxalate > Calcium phosphate
What are the determinants of solubility?
Conceentration of the compunt
pH of the solution
Temperature
Describe the clinical presentation of kidney stones
- Flank pain, RLQ, or LLQ abdominal pain radiating to the groin
- Cannot find comfortable position
- Very painful!!
Hematuria (gross or macroscopic) is common
What are the two types of Ca2+ kidney stones?
Calcium-oxalate
Calcium-phosphate
What kind of kidney stone is this?
Uric acid
Diamond/rhomboid shape
How are kidney stones diagnosed?
Non-contrast CT of the abdomen
Some stones (uric acid) do not show up on x-ray
Are kidney stones more prevalent in men or women?
Men
What are struvite stones usually composed of?
Struvite stones = infection stones
Magnesium ammonium phosphate
or
Calcium carbonate apatite
Does this condition promote or inhibit kidney stone formation?
Low pH
Promotes
(Higher pH generally inhibits stone formation, except for struvite and cysteine stones)
Which substrated become more soluble as urinary pH inceases?
Uric acid
Cystine
Risk of kidney stones is significantly decreased when urine volume increases to ______L/day
Risk of kidney stones is significantly decreased when urine volume increases to 2-2.5 L/day
This means drinking ~3L of water/day
What is the major risk factor for struvite kidney stones?
Infection by urease-producing bacteria (ex: proteus species)
- -> Alkalization of urine
- -> Insolubility of urinary phosphate
- -> Compelxes with surrounding ions to form kidney stones
