Stony Stone Stones

Question 1

Answer 1

Struvite crystals

Photomicrograph of a canine urine sample

Sample shows clear, euhedral, rectangular prism crystals (struvite crystals with their characteristic coffin-lid appearance (cf. illustration); examples indicated by green overlay) composed of magnesium, ammonium, and phosphate. In humans, struvite crystals are only seen in upper urinary tract infections caused by urease-producing organisms (e.g., Proteus or Klebsiella species).

Question 2

Answer 2

Calcium phosphate crystals

Photomicrograph showing crystals with the appearance of wedge-shaped prisms (can also be described as blunt-ended needles), some bound together forming a rosette.

Question 3

Answer 3

Calcium oxalate crystals in urine

Photomicrograph of a urine sample (urine sediment wet mount, intermediate magnification)

Multiple envelope-shaped crystals can be seen (cf. illustration; examples indicated by yellow overlay) throughout the sample. These are composed of calcium oxalate dihydrate and have an octahedral structure.

Question 4

Answer 4

Cystine crystals

Photomicrograph of cystine crystals from a canine urine sample (1000x magnification)

A clump of multiple, clear, hexagon-shaped crystals is visible.

This is the characteristic appearance of cystine crystals.

Question 5

Answer 5

Uric acid crystals

Photomicrograph of a urine sample with a pH of 5 (phase contrast microscopy; high magnification)

Multiple crystals of varying sizes and shapes can be seen (blue overlay).

Their diamond-shaped (rhomboid) form is one of the characteristic appearances of uric acid crystals, which only form in urine samples with a pH < 5.5 and are typically seen in patients with gout or in healthy individuals on a high-purine diet. Uric acid crystals may also appear barrel-shaped and needle-shaped (not seen in this image).