Nephrolithiasis: Difference between revisions
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== Background == |
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* Also known as kidney stones or renal stones |
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* 10% lifetime prevalence in men, 5% in women |
* 10% lifetime prevalence in men, 5% in women |
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=== Stone Types === |
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{| class="wikitable" |
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!Stone |
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!% |
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!Composition |
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!Risk Factors |
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|- |
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|Calcium oxalate |
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|75% |
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|calcium oxalate monohydrate, or calcium oxalate dihydrate |
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|usually in acidic urine; [[hyperparathyroidism]], [[hypercalciuria]], [[hyperoxaluria]], [[hypomagnesemia]], and [[hypocitraturia]] |
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|- |
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|Calcium phosphate |
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|10% |
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|calcium phosphate, including apatite and brushite |
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|usually in alkaline urine; [[hyperparathyroidism]], [[renal tubular acidosis]] |
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|- |
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|Uric acid |
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|10% |
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|uric acid |
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|only in acidic urine, pH <5.5; associated with purine-rich food intake (fish, legumes, meat), gout, and cancer |
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|- |
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|Struvite |
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|<10% |
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|calcium, ammonium, and magnesium phosphate |
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|usually in alkaline urine; caused by gram-negative urease-producing bacteria, including [[Pseudomonas]], [[Proteus]], and [[Klebsiella]] (but not [[Escherichia coli]]) |
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|- |
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|Cystine |
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|<5% |
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|cystine |
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|from intrinsic metabolic defect that lead to decreased reabsorption of cystine, lysine, ornithine, and arginine in the renal tubules |
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|} |
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=== Pathophysiology === |
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* Varies by stone type |
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* Low urine output/poor oral intake |
* Low urine output/poor oral intake |
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* Increased uric acid, which precipitates in low pH |
* Increased uric acid, which precipitates in low pH |
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* Decreased citrate (i.e. 3 bicarbs), e.g. from RTA |
* Decreased citrate (i.e. 3 bicarbs), e.g. from RTA |
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* Increased phosphate, e.g. from carbonated beverages, which precipitates in high pH |
* Increased phosphate, e.g. from carbonated beverages, which precipitates in high pH |
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* |
* [[Urinary tract infection]] caused by [[urease-positive]] bacteria, leading to [[struvite stones]] |
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* Urinary stasis, e.g. in polycystic kidney disease, medullary sponge kidney |
* Urinary stasis, e.g. in polycystic kidney disease, medullary sponge kidney |
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* Medications, |
* Medications, including [[atazanavir]] and other HIV medications, [[guiafenesin]], [[indinavir]], [[sulfonamides]], and [[triamterene]] |
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== Clinical Manifestations == |
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* Common cause of hematuria and abdominal, flank, or groin pain |
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== Investigations == |
== Investigations == |
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Latest revision as of 19:43, 19 August 2024
Background
- Also known as kidney stones or renal stones
- 10% lifetime prevalence in men, 5% in women
Stone Types
| Stone | % | Composition | Risk Factors |
|---|---|---|---|
| Calcium oxalate | 75% | calcium oxalate monohydrate, or calcium oxalate dihydrate | usually in acidic urine; hyperparathyroidism, hypercalciuria, hyperoxaluria, hypomagnesemia, and hypocitraturia |
| Calcium phosphate | 10% | calcium phosphate, including apatite and brushite | usually in alkaline urine; hyperparathyroidism, renal tubular acidosis |
| Uric acid | 10% | uric acid | only in acidic urine, pH <5.5; associated with purine-rich food intake (fish, legumes, meat), gout, and cancer |
| Struvite | <10% | calcium, ammonium, and magnesium phosphate | usually in alkaline urine; caused by gram-negative urease-producing bacteria, including Pseudomonas, Proteus, and Klebsiella (but not Escherichia coli) |
| Cystine | <5% | cystine | from intrinsic metabolic defect that lead to decreased reabsorption of cystine, lysine, ornithine, and arginine in the renal tubules |
Pathophysiology
- Varies by stone type
- Low urine output/poor oral intake
- Increased uric acid, which precipitates in low pH
- Low pH, which precipitates animal protein
- Hypercalciuria
- Genetic (familial)
- Hypercalcemia: hyperparathyroidism, vitamin D
- Increased oxalate
- Genetic
- Diet: nuts, greens, chocolate, etc.
- IBD: fatty acids bind to calcium in gut, allowing oxalate absorbtion
- Malabsorption
- Vitamin C
- Decreased citrate (i.e. 3 bicarbs), e.g. from RTA
- Increased phosphate, e.g. from carbonated beverages, which precipitates in high pH
- Urinary tract infection caused by urease-positive bacteria, leading to struvite stones
- Urinary stasis, e.g. in polycystic kidney disease, medullary sponge kidney
- Medications, including atazanavir and other HIV medications, guiafenesin, indinavir, sulfonamides, and triamterene
Clinical Manifestations
- Common cause of hematuria and abdominal, flank, or groin pain
Investigations
- Dietary assessment
- Electrolytes (especially for K and HCO3), calcium profile, PTH, urinalysis, urine microscopy
- 24h urine collection, sent for
- volume
- creatinine, CrCl
- Na, K, urea
- calcium
- oxalate
- uric acid
- phosphate
- spot test for cystine
- citrate and magnesium in a separate collection
Management
- Imaging
- Stone diet
- Maintain urine output 2L/d
- Low salt
- Normal calcium
- Increased fruit and vegetables
- Moderate meat and alcohol
- Potassium citrate 20mEq BID, to increased citrate and pH of the urine
- Hydrochlorothiazide, to decrease urine calcium
- Allopurinol, to decrease urine urate
