Struvite

Struvite
Crystals of struvite from dog urine
General
Category	Phosphate mineral
Chemical formula	(NH4)MgPO4·6H2O
Identification
Color	Colourless, white (dehydrated), yellow or brownish, light gray
Crystal habit	Euhedral to platey
Crystal system	Orthorhombic - Pyramidal
Twinning	On {001}
Cleavage	{100} perfect
Fracture	Uneven
Mohs scale hardness	1.5 - 2
Luster	Vitreous to dull
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	1.7
Optical properties	Biaxial (+) 2V Measured: 37°
Refractive index	nα = 1.495 nβ = 1.496 nγ = 1.504
Birefringence	δ = 0.009
Solubility	Slightly soluble, dehydrates in dry, warm air
Other characteristics	Pyroelectric and piezoelectric
References	[1][2][3]

Struvite (ammonium magnesium phosphate) is a phosphate mineral with formula: ((NH₄)MgPO₄·6H₂O). Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platey mica-like forms. It is a soft mineral with Mohs hardness of 1.5 to 2 and has a low specific gravity of 1.7. It is sparingly soluble in neutral and alkaline conditions, but readily soluble in acid.

Name

Struvite was first described from medieval sewer systems in Hamburg Germany in 1845 and named for geographer and geologist Heinrich Christian Gottfried von Struve (1772-1851).^[2]

Occurrence

Upper urinary tract stones that involve the renal pelvis and extend into at least 2 calyces are classified as staghorn calculi.Although all types of urinary stones can potentially form staghorn calculi, approximately 75% are composed of a struvite-carbonate-apatite matrix.

Struvite is occasionally found in canned seafood, where its appearance is that of small glass slivers, objectionable to consumers for aesthetic reasons but of no health consequence. It is also a problem in sewage and waste water treatment, particularly after anaerobic digesters release ammonium and phosphate from waste material, as it forms a scale on lines and clogs system pipes. Recovery of phosphorus from wastestreams as struvite and recycling those nutrients into agriculture as fertilizer appears promising, particularly in agricultural manure and municipal waste water treatment plants.^[4]North America's first struvite recovery system, built and constructed by the Ostara corporation, is at the Durham Treatment Facility, Tigard, Oregon, USA. Use of struvite as an agricultural fertilizer was in fact first described in 1857.

Struvite kidney stones

Dog struvite bladder stones

Struvite precipitates in alkaline urine, forming stones. Struvite is the most common mineral found in urinary tract stones in dogs,^[5] and is found also in urinary tract stones of cats and humans. Struvite stones are caused by a bacterial infection that hydrolyzes urea to ammonium and raises urine pH to neutral or alkaline values. Urea-splitting organisms include Proteus, Pseudomonas, Klebsiella, Staphylococcus, and Mycoplasma. Accumulation of struvite crystals in the urinary bladder is a problem frequently seen in housecats, with symptoms including difficulty urinating (which may be mistaken for constipation) or blood in the urine (hematuria. In the past surgery was required to remove struvite uroliths; today, special diets and antibiotics are more commonly used to dissolve sterile struvite stones.

Struvite enteroliths

Struvite is a common mineral found in enteroliths (intestinal concretions) in horses.^[6]

Mangagement of Staghorn Calculi

Extensive literature review has been used to create guidelines for the management of staghorn cacluli. The most extensive review was done under the auspices of the American Urological Association www.auanet.org. The initial guidlines were issued in 1994. ^[7]

References

External links

• Website of the Technische Universität Darmstadt and the CEEP about Phosphorus Recovery