A high percentage of the long-term inhabitants of public institutions, but also patients at home, live with indwelling catheters, such as transurethral, suprapubic or Pigtail catheters.

Pathogenic germs, that also can cause urinary tract infections, are responsible for the increasing of the pH value of the urine and subsequently the crystallization. These crystals attach themselves to the catheters (encrustation) and are responsible for a progressive outflow obstruction. Also other deposits, such as cell fragments, enhance this outflow obstruction. These biofilms on the surface of the catheters can be sharp-edged and thereby cause additional problems.

Urethral damages can be caused by the changes of encrusted catheters. A high risk for complications is the closure of the catheter provoking an emergency change. 

A high percentage of patients suffer from urinary tract infections requiring treatments with antibiotics. Catheters change the urine milieu and provoke the formation of bladder stones. Ultimately, all these complications include also a certain increased risk of mortality.