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Crystals in the urine (crystalluria) can increase chances of bladder stone (urolith) formation. There are various types of crystals found in pets urine, with struvite and calcium oxalates being the most clinically prevalent.
Struvite (triple phosphate) crystals
Crystals formed out of magnesium, ammonium and phosphate have a 'coffin-lid' appearance, and are most likely to appear in alkaline urine. In dogs, urease-producing bacteria, which produce alkaline urine (usually Staphs and Proteus species and sometimes Streps, Klebsiella and some other bacteria) predispose the patient to to struvite stone formation. They can be found in healthy patients but when found in vast amounts, often are an indication of a concurrent bacterial infection, and increase the risk of bladder stone (urolith) formation. (Source: http://www.ctdslab.co.uk/triplephosphate.html). Commercially prepared urinary diets like Royal Canin Urinary S/O or Hill's c/d actively dissolve these crystals and reduce the likelihood of reformation of these crystals. Unlike in dogs, over 90% of struvite uroliths in cats are sterile and are thought to be metabolic in origin.
Calcium Oxalate Crystals
Highly concentrated or acidic (less than urine pH 6.5) urine and use of antibiotics which impact the intestinal gut flora Oxalobacter formigenes (whose sole nutrient is oxalate) can influence calcium oxalate crystal formation. Other contributing factors to the formation of Calcium Oxalate include hypercalcaemia, the use of furosemide, glucocorticoids and hyperadrenocorticism. Some male dogs in some breeds are more predisposed to Calcium Oxalate crystal formation. Dogs with high numbers of this Oxalobacter formigenes flora have been found to have higher secretions of oxalate secreted into the bladder and become predisposed to oxalate crystal formation (Source: http://www.vcahospitals.com). Hills u/d, Royal Canin Urinary s/o and Hills c/d will dissolve these crystals and prevent reformation.
A detailed list of all urinary crystals can be found here: http://www.eclinpath.com/urinalysis/crystals
Diet plays a key role in the type and likelihood of crystalluria, with diets low in magnesium having a direct relationship with lower rates of struvite crystal formation and pets fed human food high in oxalates and/or calcium such as spinach, sweet potato, chocolate (toxic) and peanuts at higher risk of developing calcium oxalate crystalluria. (Source: Grauer, FG)
If crystals form and remain in the right environment, bladder stones (uroliths) may develop.
Bladder stones (uroliths) are formed when excessive crystals are allowed to form into stones within the bladder. These can be influenced by diet, concentration of urine, pH and presence of bacteria. Uroliths cause inflammation within the bladder and urogenital tract. This has the potential to cause partial or complete blockage, a life threatening situation which can lead to bladder rupture or kidney failure. Immediate veterinary attention is required! An anaesthetic is generally indicated to remove the blockage and is usually achieved by placing a urinary catheter, whereby removing the plug in the process. Male cats are especially susceptible to urethral blockage due to their anatomy. Some pets will lose the ability to contract their bladder muscles and sphincter after having a full bladder for extended periods of time and may require ongoing care and medication to rectify the issue.
Uroliths can range in size and structure and can occasionally be diagnosed by feeling (palpation) if they are large enough, or if there are vast quantities, x-rays or ultrasounds may also be indicated based on the type of suspected urolith. Some uroliths are radio-opaque (visible upon x-ray), and may require special radiographic techniques to demonstrate their presence. Ultrasound may be indicated in some cases.
Blockages can be caused by inflammation and protein plugs, without the presence of stones. Blockages of any kind are deemed life threatening, contact us immediately if you suspect your pet has a blockage. Cats are especially prone to blockages of this nature. Feline Lower Urinary Tract Disease (FLUTD) or Feline Idiopathic Cystitis (FIC) are described in further detail below.
Feline Lower Urinary Tract Disease (FLUTD) covers several syndromes (including those above). However, it is mainly used to refer to the cystitis which has no definitive cause (idiopathic) (Feline Idiopathic Cystitis - FIC). The symptoms are similar to other diseases: Inappropriate urination, blood in the urine and increased frequency are common. If you suspect changes in your cat's urinating behaviour, it is important to have your cat's urine analysed to differentiate between infection, crystalluria or bladder stones as other potential causes.