When a doctor orders a urinalysis to test for certain conditions, one of the analyses performed is called “amorphous sediment.” It is used to determine the state of a person’s health. These sediments found in the urine can be classified as either amorphous phosphates or amorphous urates, and their makeup is an indicator of overall health.
Urates are crystals found in overly acidic urine. By contrast, phosphates are crystals found in overly alkalinic (basic) urine. Uric acid crystals will form if a person’s pH level falls below 5.5. The presence of uric acid stones or other kidney stones can be determined by an amorphous sediment test. The pH level determines the overall level of a person’s acidity or alkalinity in the body (eating excess sugar, for example, will cause a body to become overly acidic, which can leach calcium from the bones). An amorphous sediment test will help determine a person’s pH level.
Amorphous sediment can be mistaken for an accumulation of bacteria in the urine. A simple test - dissolving the sediment in an acidic or alkaline solution - will determine whether the sediment is crystalline in nature, or if it is bacteria. Sediment will dissolve in the opposite pH solution; bacteria will not. Heating the solution to 37 degrees C is another way to test whether amorphous sediment is crystalline or bacterial.
It’s normal to find amorphous sediment in healthy urine, so its presence is not necessarily an indicator of any underlying problems. Calcium oxalate, amorphous phosphates and triple phosphate crystals are found in healthy urine. Under the microscope, oxalate crystals resemble tetrahedrons, or small envelopes. "Triple phosphate" crystals resemble coffin lids, or small rectangles. These crystals are generally made up of magnesium ammonium phosphate and struvite and again, they are often found in the urine of healthy individuals, particularly those whose urine tends to be neutral or slightly alkaline.
Urinary tract infections raise the pH level of the urine and increase free ammonia. These infections with urease producing bacteria (Proteus vulgaris) can cause struvite crystalluria (and urolithiasis). Rare urinary crystals can include cystine crystals (shaped like stop signs) in the urine of neonates with severe liver disease or congenital cystinuria; tyrosine crystals with liver impairment or congenital tyrosinosis; or leucine crystals in patients with maple syrup urine disease or severe liver disease.