What does amorphous urinalysis mean

The detection of crystals is strongly dependent on the pH value and the temperature of the urine and is rarely of diagnostic importance.

Most important to the clinician are cystine crystals.

 

A selection of crystals can be found in the album.

Crystals come in a wide variety of forms, depending on their composition, concentration and pH: rhombuses, envelopes, coffin lids, etc. Uric acid and phosphates in particular can also appear as amorphous, fine, aggregated granules (amorphous means "unformed" in this context).

Amorphous urates, uric acid and calcium oxalates are found in acidic urine, while phosphates are found in alkaline urine.

The following crystals can be distinguished:

  • Cystine: hexagonal, colorless tablets that are quickly destroyed in alkaline urine. They give an indication of the very rare occurrence of cystinuria, which is a congenital, tubular re-absorption disorder of cystine.
  • uric acid
  • Calcium oxalate
  • Triple phosphate:
  • Sulfonamides
  • cholesterol
  • Tyrosine
  • Leucine
  • Hemosiderin

Sulphonamides and their metabolites are poorly soluble in acidic urine. They therefore tend to fall out as crystals, although depending on the drug and metabolite they can take on the most varied of shapes (needles, sheaves, tufts of ears). In contrast to other crystals, they can be easily dissolved by acetone.

Calcium oxalates, uric acid crystals, amorphous urates and phosphates and triple phosphates are most frequently found in everyday laboratory work. In addition, there are drugs that are excreted in crystal form, although rarely, but in a large variety of forms.

 

The results of the different methods 

Microscopic examination of the urine  
Only microscopic examination of the urine is suitable for detection and identification.

Flow cytometry 
Crystals are displayed in the Fsc / Fl scatter plot. Since they cannot be colored, they fluoresce even less strongly than erythrocytes, but because of their different sizes they show a large variation in the scattered light.
An exception are uric acid crystals, which can overlap with the area of ​​the erythrocytes due to the autofluorescence.

Amorphous crystals (phosphates and urates) are chemically bound.

Cystine and leucine crystals, which indicate severe liver damage, are important. It is possible that conclusions can be drawn about the composition of existing concrements from the type of crystal that dominates the urine, e.g. the high content of calcium oxalate crystals in the urine in kidney stones containing calcium oxalate. A massive occurrence of uric acid should suggest hyperuricemia or gout.