Crystalluria

Question 1

Risk factors for drug crystallization:

Answer 1

supersaturation of drug level in urine
volume depletion (low urine flow)
urine pH
reduced levels of inhibitors of crystallization

Question 2

Crystalluria

Answer 2

Most drug-crystalluria-induced acute kidney injury (AKI) resolves with drug withdrawal and supportive therapy

Question 3

Sulfadiazine (used to treat toxoplasmosis):

Answer 3

Risks: high dose > 4 to 6 g/d, urine pH < 5.5, volume depletion

Question 4

Sulfadiazine (used to treat toxoplasmosis):

Answer 4

Crystals are strongly birefringent as “shocks of wheat” or “bow-tie” with an amber color and radial striation.

Question 5

Sulfadiazine (used to treat toxoplasmosis):

Answer 5

Treatment: volume repletion, urine alkalinization with sodium bicarbonate to pH > 7.15

Question 6

Ciprofloxacin:

Answer 6

Risks: alkaline urine (pH > 7.0), elderly patients, volume depletion

Question 7

Ciprofloxacin:

Answer 7

Typically crystallizes in high urine pH > 7.3, but may occur in acidic pH

Question 8

Ciprofloxacin:

Answer 8

Crystals may take forms as needles, stars, fan shaped; all with lamellar structures and are strongly birefringent under polarized light.

Question 9

Ciprofloxacin:

Answer 9

Preventive measures: volume repletion, avoid concurrent use of alkalinizing agents, use with caution in patients > 65 to 70.

Question 10

Acyclovir:

Answer 10

Risks: rapid intravenous bolus (500 mg/m2) for herpes simplex virus–associated encephalitis, volume depletion.

Question 11

Acyclovir:

Answer 11

Crystals are birefringent and needle shaped

Question 12

Acyclovir:

Answer 12

Preventive measures: use low dose, or slow infusion with normal saline support. Acyclovir is dialyzable.

Question 13

Indinavir (HIV protease inhibitor):

Answer 13

Crystallizes at physiologic pH 5.5 to 7.0; soluble at pH of ≤3.5.

Question 14

Indinavir (HIV protease inhibitor):

Answer 14

Crystals are pleomorphic and may range from plate-like rectangles, fan shaped, to start burst shaped.

Question 15

Indinavir (HIV protease inhibitor):

Answer 15

Associated with tubular obstruction, chronic tubulointerstitial nephritis (CTIN)

Question 16

Indinavir (HIV protease inhibitor):

Answer 16

Treatment: volume intake of at least 2 to 3 L/d is suggested while on indinavir; dose adjustment in liver disease; avoid concurrent use of trimethoprim–sulfamethoxazole as it can increase indinavir blood levels. Urine acidification difficult to achieve and not recommended.

Question 17

Methotrexate:

Answer 17

Risks: low urine pH, low volume

Question 18

Methotrexate:

Answer 18

May cause both tubular obstruction and direct tubular toxicity

Question 19

Methotrexate:

Answer 19

Treatment: urine alkalinization to pH > 6.0, volume repletion, leucovorin rescue.

Question 20

Triamterene:

Answer 20

Risks: urine pH < 5.5

Question 21

Triamterene:

Answer 21

Crystals are spherical shaped, brown in color, appear as maltese crosses under polarized light.

Question 22

Triamterene:

Answer 22

Preventive: use low dose, adequate volume intake, avoid concurrent nonsteroidal anti-inflammatory drugs (NSAIDS) use.

Question 23

Triamterene:

Answer 23

Treatment: volume repletion, urinary alkalinization

Question 24

Orlistat (inhibitor of gastric and pancreatic lipase, induces fat malabsorption):

Answer 24

Associated with calcium oxalate deposition within renal tubules and interstitium. Mechanism for calcium oxalate stone formation is thought to be similar to that seen in patients with inflammatory bowel disease.

Question 25

Orlistat (inhibitor of gastric and pancreatic lipase, induces fat malabsorption):

Answer 25

Risks: underlying kidney disease, volume depletion

Question 26

Orlistat (inhibitor of gastric and pancreatic lipase, induces fat malabsorption):

Answer 26

Preventive: avoid use in patients with underlying kidney disease, volume repletion

Question 27

Ampicillin:

Answer 27

Needle Shaped

Question 28

Oral sodium phosphate solution used as bowel preparation for colonoscopy:

Answer 28

Calcium phosphate precipitations in renal tubular cells as well as tubular lumen

Question 29

Oral sodium phosphate solution used as bowel preparation for colonoscopy:

Answer 29

Risks: underlying kidney disease, females, and possibly hypertension (HTN) with concurrent use of angiotensin-converting enzyme inhibitor (ACEI) or angiotensin-receptor blocker (ARB)

Question 30

Oral sodium phosphate solution used as bowel preparation for colonoscopy:

Answer 30

Preventive measures: volume repletion, appropriate dosing, avoid concurrent use with ACEI, ARB, diuretics, and/or NSAIDS; Exercise caution with use in older patients.

Question 31

Vitamin C

Answer 31

(converts to oxalate, calcium oxalate stones)

Question 32

Other drug crystalluria:

Answer 32

foscarnet, pseudoephedrine

Question 33

Natural sources:

Answer 33

star fruit (oxalate), rhubarb leaves (oxalate), cranberry juice (oxalate), ma huang (ephedra), djenkol beans (needle like)