Uric acid crystalluria

Uric acid crystals are often yellow or yellowish brown and may appear in a great amount of forms. The most typical ones are diamond shaped or rhombic plates which may contain concentric rings (Fig. 57-61). They may appear as rosettes which are constituting themselves to agglomerates of uric acid crystals. From time to time uric acid crystals are developing rhombic plates with one or more pairs of laterally spikes (Fig. 62-63). Seldom they appear as hexagonal crystals similar to cystine. However, the hexagonal crystals appear together with typical diamond- or rhombic form. Uric acid crystals are dissolving in sodium hydroxide but not in alcohol, hydrochloric- and acetic-acid.

Interpretation Although often occurring in humans the natural uric acid crystalluria is quite rare in dogs and cats. If detected the crystals have the same significance as described for ammonium- and amorphous urates. Uric acid crystals are forming themselves quite rapid after addition of 10%ual acetic acid in urine sediment emanated from dogs and cats which contains amorphous urates or ammonium urate crystals. Sodium urate crystals may appear. Many times it’s necessary to expose the uric acid crystals to acetic acid for about 20-30 minutes before they are getting visible. They may grow to an astonishing size when they are being stored in a covered Petri dish which is has been moistened by a water-soaked sponge.

Fig. 57)

Microphotographic picture from natural occurring uric acid crystals in the urine sediment from a four-years-old castrated male racoon.

Fig. 58)

Microphotographic picture from uric acid crystals in the urine sediment from the dog from Fig.44. These crystals have built themselves up after addition of 10%ual acetic acid to the sediment that contained ammonium urate crystals.

Fig. 59)

Microphotographic picture from a layered uric acid crystal in the urine sediment from the dog from Fig. 49. This appearance demonstrates the active crystal growth.

Fig. 60)

Microphotographic picture from uric acid crystals in acidified urine sediment from the dog from Fig. 43.

Fig. 61)

Scanning electron microscope picture from a diamond shaped uric acid crystal in acidified urine sediment from the dog from Fig. 43.

Fig. 62)

Microphotographic picture from uric acid crystals in acidified urine sediment from a three-years-old male Dalmatian.

Fig.63)

Scanning electron microscope picture from different uric acid crystal forms in acidified urine sediment from the dog from Fig. 49.