Urochromes

The term "urochromes" is used to describe the natural nitrogen-containing yellow urine dyes that are responsible for the typical coloration of urine. The yellow dyes (haemoglobin breakdown products) urochrome A and urochrome B together are responsible for about 95 percent of the urine colour value. Uroerythrin complements the urine colouring to about 4%.

Urochromes also include coloured metabolic products that are formed during the metabolism of consumed food and medicines. The urine colour can vary considerably as a result.

In addition to the coloration by metabolic products, the urine color is mainly based on the fluid balance. The urochrome content is contrary to the urine volume and proportional to the specific gravity. After thirst, during diarrhoea, after sweating, e.g. during sporting activity, the urine becomes dark yellow, amber-coloured. The specific weight increases.

After water load, urine becomes watery light or pale yellow with low specific gravity and low osmolarity. Exception: Diabetes mellitus: in case of strong diuresis, a pale urine color and a relatively high specific gravity due to glucosuria is found.

Pathological staining of the urine indicates the presence of haematuria, haemoglobulinuria, myoglobulinuria, pyuria, porphyria or metastatic melanoma.