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FIGURE 5
Envelope shaped calcium oxalate dihydrate and dumbbell- shaped calcium oxalate monohydrate crystals.
are other factors that place patients on these medications at increased risk for drug induced crystal formation. These factors include intravascular volume depletion, chronic kidney disease, chronic liver disease, inappropriate drug dosing for a given urinary drug concentration and pH.2 Sulfonamides and acyclovir typically precipitate in acidic urine, while protease inhibitors precipitate in alkaline urine.
The patients who develop drug induced crystalluria are often asymptomatic. In such cases, the acute kidney injury may only be found on routine laboratory testing. Others may present week after the offending drug is started.2 Urinalysis often is diagnosis is established on kidney biopsy by the presence of dilatation of the collecting tubules on light microscopy. Electron microscopy may also show lamination of peritubular capillary basement membranes.
cessation of the offending drug are the mainstays of treatment in drug induced crystalluria. Loop diuretics may be considered, but
Sulfonamides such as sulfasalazine are highly insoluble in acidic urine. The risk of crystal precipitation increases with
doses greater than 4-6 grams per day. The solubility of the drug is increased more than 20-fold when the urine is alkalinized
to a pH greater than 7.15.3 The risk of sulfazaladine induced intake of up to 3L per day. Patients started on sulfasalazine should have serial urinalyses performed to monitor for crystalluria. Once crystalluria develops, it is recommended
that intravenous bicarbonate be started to protect against the development of acute kidney injury. It is important to monitor for the development of hypocalcemia and volume overload. Urine alkalinization also comes with the risk of promoting calcium phosphate deposition especially is hyperphosphatemia is present. The bicarbonate infusion should be stopped if alkalinization fails and the patient develops acute kidney injury or metabolic alkalosis.
CONCLUSION
Drug induced crystalluria often occurs in the setting of other risk factors. Patients started on medications associated with crystalluria should be monitored frequently with urinalyses to monitor for crystalluria. Volume depletion should be avoided in these patients and volume resuscitation up to 3L per day must be encouraged. Urine alkalinization is indicated in sulfasalazine induced crystalluria to prophylaxis against acute kidney injury to keep urine pH greater than 7.15.
ACKNOWLEDGEMENTS
Prayus Tailor, MD and Manthodi Faisal, MD
CONTRIBUTING AUTHOR
■ EFUA ASAMOAH-ODEI, MD is a Nephrology Fellow with Nephrology Associates and Christiana Care Health System in Newark, Del.
REFERENCES
1. Daudon, M; Jungers, P; Drug-induced renal calculi-epidemiology,
prevention and management. Drugs. 2004;64:245-275.
2. Perazella MA. Crystal-induced acute renal failure. Am J Med.
1999;106:459.
3. Simon DI, Brosius FC, Rothstein DM. Sulfadiazine crystalluria revisited. The treatment of toxoplasma encephalitis in patients with acquired immunodeficiency syndrome. Arch Intern Med. 1990;150:2379.
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Del Med J | August 2016 | Vol. 88 | No. 8
