They tend to precipitate onto other formed elements in the urine.

Bilirubin crystalsīilirubin crystals form from conjugated bilirubin (water soluble) and are needle-like to granular crystals that are yellow in color. They are rarely, if ever, seen in urine from normal cats or dogs of other breeds and have not been reported in large animals. They can be seen in urine from normal Dalmatians and Bulldogs, both of which. These crystals are fairly common in dogs and cats with congenital or acquired portal vascular anomalies, with or without concomitant ammonium urate uroliths. They are frequently seen with amorphous urates. Though possible in urine of any pH, their formation is favored in neutral to alkaline urine. Due to their potential pathologic relevance, crystal identification should be verified by examination at high magnification. These crystals can be observed under low magnification, particularly when seen in large number, however low numbers may only be seen at higher magnification. In some urine samples, they do not have irregular protrusions but have smooth borders and can resemble calcium carbonate (although these do not occur in the urine from dogs and cats). Ammonium biurateĪmmonium urate (or biurate) crystals generally appear as brown or yellow-brown spherical bodies with irregular protrusions (“thorn-apples”). Degenerating crystals or cells can also resemble “amorphous” crystals. Small amorphous crystals can be confused with bacterial cocci in some cases, but can be distinguished by gram-staining. Generally, no specific clinical interpretation can be made based on the finding of amorphous crystals. These crystals occur in Dalmations on allopurinol therapy for urate urolithiasis. Xanthine crystals are usually in the form of “amorphous” crystals. Amorphous phosphates are similar in general appearance, but tend to form in alkaline urine and lack color and are Coffin-lid shape. they mimic bacteria.Īmorphous urates (Na, K, Mg, or Ca salts) tend to form in acidic urine and may have a yellow or yellow-brown color, rhomboid. They can be comprised of urates, phosphates or xanthine. They are usually small crystals that are usually only observed at high magnification (unless there are large amounts of them), i.e. “Amorphous” crystals appear as aggregates of finely granular material without any defining shape at the light microscopic level.

The last crystal drawing