Drug related crystalluria - Iatrogenic crystalluria


The presence of iatrogenic crystals is a rare event. Except for the Indinavir crystal, a light crystalluria due to a medication or from a contrast agent for X-ray imagery has no clinical significance. On the other hand, an abundant crystalluria associated with a hematuria, a marked cellularity, and oliguria could indicate an obstructive renal disease. The presence of casts with crystalline inclusions clearly indicates that the crystallization is intratubular.
The majority of these drugs crystallize in an acid media often around a pH of 5,0. Drugs of the sulfamides group (sulfamethoxazole, acetylsulfadiazine, sulfadiazine) are the most frequently observed.

A few drugs seen in the urinary sediment
Name Characteristics General aspect Comments
Acetylsulfadiazine, sulfadiazine Yellow brown crystals of variable shape Asymetric rosette
Birefringent
sulfa Not to be confused with urates and uric acid.
Rarely used today.
Sulfamethoxazole
(Septra, Bactrim)
Brown spheres
thin plates and rosette
sulfa2 Seen in overdosage
Ampicilline Fine needles, uncolored ampi Rare, seen only at very high dose
Contrast agent
Renografin
Hypaque
Uncolored plates
Strongly birefringent
Mimics cholesterol
contrast Seen in pale specimen with a density >1,040

Indinavir

Indinavir, a protease inhibitor (antiviral agent) widely used, to treat patients with HIV infection, has been associated with nephrolithiasis. Indinavir is insoluble at physiological pH so that, 20% of the person receiving Indinavir have characteristic crystal in their urine. The crystal are seen as plate-like rectangles exibiting rosette formation
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The crystal are birefringent under polarized light with a color dispersion as seen with uric acid. Indinavir crystal, unlike uric acid, are seen at a neutral (6,5 7,5) while uric acid crystals are seen at a more acidic pH (5,0 - 5,5)
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