Triple Phosphate Crystals are found in alkaline or neutral urine. They are soluble in dilute acetic acid.
These crystals are usually not clinically significant but may indicate struvite calculi.
Coffin Lid
Triple phosphate crystals are typically rectangular prisms with a “coffin lid” appearance.
Check out more images in the gallery below.
Fern
Rarely, partially dissolved triple phosphate crystals may have a fern or feather-like appearance.
Check out more images in the gallery below.
Lookalikes
Sometimes, dihydrate calcium oxalate can look similar to coffin lids. The pH of the urine can help distinguish the type of crystal, as calcium oxalate is not found in alkaline urine, but this may not help if the urine is more on the neutral side. Looking around for a more classic shape of the crystal typically helps.
Coffin Lid Gallery
Fern Gallery
Other Crystals
Hippuric Acid
Tyrosine
