Bladder stones may be formed in the bladder or deposited there via the ureters from the pelvis of the kidneys. Stones are usually formed in the bladder if urine is contaminated with bacteria responsible for the breakdown of urine, particularly in cases of urinary retention. A stone sometimes forms around a foreign body in the bladder, for example a hairpin. Other stones ‘grow’ on much smaller ones that have originated in the kidney. Bladder stones usually produce the symptoms of cystitis; also the stone can abruptly close the junction of bladder and urethra during urination, causing acute retention. Stones or foreign bodies are often visible on X-rays, and diagnosis may be confirmed by examination with an instrument inserted through the urethra (cystoscope). Bladder stones are removed surgically or dispersed using a cystoscope and rinsed out of the bladder, or by a new painless technique using ultrasound waves. Bleeding (haemorrhage) Escape of blood from the vascular system. Haemorrhage can occur in various forms and to various extents. External haemorrhage is loss of blood from the surface of the body, and usually not dangerous; it stops of its own accord or can be staunched by firmly applying a dressing. Internal haemorrhage cannot be seen from outside, is thus not usually discovered until late, by which time a great deal of blood can be lost. The danger of heavy blood loss is that shock may set in. The function of blood is to transport oxygen and nutrients to the tissues and to remove carbon dioxide and waste products. If a great deal of blood is lost this transport function is endangered; in such a case the body attempts for as long as possible to maintain the supply of blood, and therefore oxygen and nutrients, to those organs which most require them – the heart, the lungs and the brain. Other organs, for example skin, muscles and intestines, receive less blood and oxygen; the blood vessels supplying these areas are practically closed.