Foam in the urine

Within certain limits, the occasional presence of foam in the urine is a typical characteristic of this liquid, produced by the filtering activity of the kidney with the aim of eliminating the metabolic waste circulating in the blood. This feature can be further enhanced by detergent residues on the toilet surfaces.

If present, the foam in the urine should consist of large bubbles, which disappear quickly; smaller and more persistent bubbles, similar to those of beer, are instead a sign of various pathologies affecting, above all, the kidney. Foamy urine is in fact associated with proteinuria (protein found in the urine) which is associated - in turn - with diseases such as renal and heart failure, severe hypertension or diabetes. The renal filtration system can also be damaged by other diseases, such as systemic lupus erythematosus, chronic liver diseases or infectious diseases. Because of these damages, the proteins - normally retained - are poured out in variable quantities in the urine, resulting in the formation of foam. Among all, albumin is the protein fraction that is most lost (albuminuria).

The morbid processes responsible for proteinuria are often also accompanied by edema, ie the accumulation of fluids in the interstitial spaces, following the decrease in the oncotic pressure of the plasma.

Like proteinuria, the accumulation of bile salts (cholaluria) is typically associated with foamy urine (with yellowish foam and dark color). Diseases that can cause cholaluria are those that obstruct the biliary tract, such as gallbladder stones.

Finally, the loss of very small amounts of protein in the urine is common following the excesses of a high-protein diet, particularly heavy physical activity or during pregnancy.