Nephrolithiasis (Kidney Stones)

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Nephrolithiasis Wisit Cheungpasitporn, M.D. 02/07/2014

Transcript of Nephrolithiasis (Kidney Stones)

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NephrolithiasisWisit Cheungpasitporn, M.D.

02/07/2014

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Case

• A 78-year-old gentleman with a past medical history significant for end-stage renal disease thought to be secondary to esophageal cancer treatment in the past. S/P living unrelated kidney transplant in 2010.

• He had gross hematuria and was found to have a 5- to 6-mm stone in the mid-transplant ureter.

• He underwent ureteroscopy by Urology and removed the stone.

• Stone analysis was done and showed calcium oxalate stone.

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• Repeat CT scan also revealed evidence of a stone in the upper pole of the right pelvic kidney transplant.

• Nephrology consulted for medical management for his kidney stone.

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Recommendation

• GI evaluation for his diarrhea

• Increase fluid intake

• Oral citrate

• Nutrition consult• Decrease dietary oxalate and fat

• Oral Calcium supplements

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Epidemiology

• Incidence 1:1000 per year

• Peak onset 20 - 35 years of age

• Male:Female 3 - 4 : 1

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Natural HistoryRecurrence Rates

• 40 % in 2 - 3 years

• 55% in 5 - 7 years

• 75% in 7 - 10 years

• 100% in 15 - 20 years

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Stone Formation

Urine saturation

Supersaturation

Crystal nucleation

Aggregation

Retention and growth

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Saturation

• Saturation level - specific concentration of a salt = solubility product and no more salt can be dissolved

• Crystals form in supersaturated urine

• Saturation is dependent on chemical free ion activities of the components of a stone

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Chemical free ion activities

• concentration of the relevant ions

• urine pH

• complexation with substances in the urine

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Clinical Presentation

• Renal colic begins suddenly and intensifies over 15 - 30 minutes

• Associated with nausea & vomiting

• Pain passes from the flank anteriorly to the groin

• At the ureterovesicular junction, urinary frequency and dysuria may occur

• Microscopic hematuria> 75%, gross - 18%

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Patient Evaluation: BasicSingle Stone Former

• Stone history

• Medical disease

• Meds

• Family history

• Lifestyle/occupation

• Diet/fluids: protein, coffee, tea, dairy

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Patient Evaluation: BasicSingle Stone Former

• Physical Examination

• Laboratory data• Urinalysis, urine for cystine• Urine culture

• Blood tests• electrolytes, creatinine, calcium, phosphorous, uric acid,

intact PTH if calcium elevated

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Patient Evaluation: BasicSingle Stone Former

• Radiology• KUB• IVP: anatomic abnormality, medullary

sponge kidney

• Ultrasound• Unenhanced CT

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Patient Evaluation: Complete

• Optimal values of 24-hr urine constituents:• volume > 2 - 2.5 L/day• calcium < 4 mg/kg or < 300 mg M,< 250 mg

F• uric acid < 800 mg M, < 750 mg F• citrate > 320 mg• sodium < 200 meq• phosphorous < 1100 mg• pH > 5.5 and < 7.0

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Etiology

• Calcium oxalate & calcium phosphate

• Calcium oxalate

• Calcium phosphate

• Uric Acid

• Struvite

• Cystine

• 37%

• 26%

• 7%

• 5 - 10 %

• 10 - 20%

• 2%

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COMPARATIVE INCIDENCES OF FORMS OF

URINARY LITHIASIS

Stone analysis in Percentage

Form of Lithiasis India USA Japan UK

Pure Calcium Oxalate 86.1 33 17.4 39.4

Mixed Calcium Oxalate and 4.9 34 50.8 20.2

Phosphate

Magnesium Ammonium 2.7 15 17.4 15.4

Phosphate (Struvite )

Uric Acid 1.2 8.0 4.4 8.0

Cystine 0.4 3.0 1.0 2.8

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Calcium Stones

• 70 - 75% of all stones

• Calcium oxalate - brown, gray, or tan

• Calcium oxalate monohydrate - dumbbell

• Calcium oxalate dihydrate - pyramidal

• Calcium phosphate - white or beige

• Calcium phosphate - elongated (brushite)

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Calcium oxalate monohydrate

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Calcium oxalate dihydrate

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Calcium phosphate brushite

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Calcium StonesPathophysiology

• Hypercalciuria

• Hypocitraturia

• Hyperoxaluria

• Unclassified

• 40 - 50%

• 20 - 30%

• 5%

• 25%

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Rx: Calcium StonesIdiopathic Hypercalciuria

• Maintain urine volume > 2 liters/day

• Thiazide diuretics

• Potassium citrate

• Sodium restriction (2 - 3 grams/day)

• Protein restriction ( 0.8 - 1.0 g/kg/day)

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Calcium StonesHyperparathyroidism

• 85% adenoma, 15% multigland hyperplasia

• Urine pH tends to be higher than in idiopathic hypercalciuria so the fraction of calcium phosphate stones is higher

• Rx: Parathyroidectomy

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Calcium StonesHypocitraturia

• Occurs alone (10%) or with other abnormalities (50%)

• More common in females

• May be idiopathic or secondary

• Acidosis reduces urinary citrate by tubular reabsorption

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Calcium StonesHypocitraturia

• Associated with distal RTA, metabolic acidosis of diarrhea, & consumption of a diet rich in meat

• Tend to form calcium oxalate stones (except Type I RTA)

• Rx: dietary protein, alkali (K citrate or K bicarbonate), avoid sodium bicarbonate

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Calcium StonesHyperoxaluria

• Most patients with calcium oxalate stones excrete normal urinary oxalate: <40 mg/day

• Excessive urinary oxalate • Dietary hyperoxaluria• Endogenous hyperoxaluria• Enteric hyperoxaluria

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Calcium StonesDietary Hyperoxaluria

• Normal people absorb < 5% of dietary oxalate

• Foods rich in oxalate (spinach, chocolate, beets, peanuts) can absorption 25 - 50%

• Low calcium diets urinary oxalate excretion

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Calcium StonesEndogenous hyperoxaluria

• Primary hyperoxaluria - enzymatic deficiencies that result in massive oxaluria

• Widespread calcium oxalate deposition in tissues ( bone marrow, blood vessels, heart, and renal parenchyma)

• Rx: P.O. fluids, pyridoxine and orthophosphate urinary crystallization

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Calcium

Calcium Oxalates

Calcium Soaps

Oxalic Acid

FattyAcids

NORMAL

A AB BS SO OR RP PT T I IO ON N

Calcium StonesEnteric Hyperoxaluria

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Calcium StonesEnteric Hyperoxaluria

Calcium

Calcium Oxalates

Calcium Soaps

Oxalic Acid

FattyAcids

ENTERIC HYPEROXALURIA

A A

B BS SO OR RP PT T I IO ON N

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Calcium StonesEnteric Hyperoxaluria

• Treatment• Decrease dietary oxalate and fat• Oral Calcium supplements• Cholestyramine• Increase fluid intake• Oral citrate

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Calcium StonesHyperuricosuria

• Increased frequency of hyperuricosuria (> 800 mg/day M, > 750 mg/day F) in patients who form calcium stones

• Urate crystals serve as a nidus for calcium oxalate nucleation & comprise 4 - 8% of the cores of calcium stones

• Rx: Allopurinol, Potassium citrate

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Uric Acid Stones

• Smooth, white or yellow-orange

• Radiolucent

• Crystals form various shapes: rhomboidal, needle like, rosettes, amorphous

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Uric acid

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Uric Acid Stones

• Main determinants of uric acid stone formation• Urinary pH < 5.5, urine volume

Hyperuricosuria• Genetic overproduction• Myeloproliferative disorders• High purine diet• Drugs

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Uric Acid Stones

• Rx: fluid intake, purine diet, urinary alkalinization (pH 6.5 - 7.0) with potassium citrate , allopurinol to reduce 24 hour uric acid excretion

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Struvite Stones - Magnesium Ammonium Phosphate

• More common in women than men

• Most common cause of staghorn calculi

• Grow rapidly, may lead to severe pyelonephritis or urosepsis and renal failure

• Light brown or off white

• Gnarled and laminated on X-ray

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Struvite

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Struvite StonesInfection Stones

• Caused in part by infections by organisms with urease ( Proteus, Klebsiella, Pseudomonas, and Serratia)

• Hydrolysis of urea yields ammonia & hydroxyl ions, consumes H+ & thusurine pH

• urine pH increases saturation of struvite

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Struvite StonesInfection Stones

• Rx: Remove existing stones (harbor causative bacteria) with ESWL or PUL

• Prolonged antibiotics

• Acetohydroxamic acid (urease inhibitor) - use limited because of side effects

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Cystine Stones

• Hereditary disorder caused by a tubular defect in dibasic amino acid transport, autosomal recessive

• Excrete excessive amounts of cystine, ornithine, lysine and arginine

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Cystine Stones

• Cystine is soluble in the urine to a level of only 24 - 48 mg/dl

• In affected patients, the excretion is 480 - 3500 mg/day

• Nephrolithiasis usually occurs by the 4th decade

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Cystine Stones

• Hexagonal, radiopaque, greenish-yellow

• Often present as staghorn calculi or multiple bilateral stones

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Cystine

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Cystine

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Cystine Stones

• Treatment• estimate urine volume to maintain solubility

( 240 - 480 mg/l)• urine pH > 7.5• Restrict dietary sodium (60 meq/d)• Troponin or D-penicillamine bind cystine and

reduce urine supersaturation• Urological: removal difficult (2nd hardest) -

PUL often required

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Urological Treatment of Nephrolithiasis - Ureteral

• Most ureteral stones < 5mm pass spontaneously

• Stones 7mm in size have a poor chance of passing

• Stones in the distal ureter that stop progressing should be removed via ureteroscope or EWSL

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Urological Treatment of Nephrolithiasis - Ureteral

• Stones in the proximal ureter that stop progressing should be pushed upward into the renal pelvis, then disrupted with EWSL

• If above fails, PUL

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Urological Treatment of Nephrolithiasis - Renal Pelvis

• Stones that are < 2 cm and > 5 mm - EWSL

• Stones > 2 cm or exceed 1 cm and are in the lower poles require PUL

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Questions & Discussion