What is a bladder stone?
A bladder stone is a crystallized mass in the urine that usually develop within the bladder. These stones may vary in size and small stones may pass out with the urine totally undetected. However, larger stones may remain in the bladder and cause a host of signs and symptoms. Overall, bladder stones are an uncommon occurrence when compared to other urinary stones like kidney stones.
Bladder stones should not be confused with kidney stones, which develop within the renal pelvis, pass down the ureter and then eventually pass out with the urine. Kidney stones that can enter and travel down the ureter are usually small enough to pass out of the bladder. Bladder stones may resemble kidney stones in chemical composition but most of these stones develop entirely within the bladder. However a kidney stone that remains in the bladder can grow further from the chemicals present in the stored urine.
Size, Number and Types of Bladder Stones
A bladder stone is also known as a vesical calculus. It may be a single stone or multiple stones within the bladder. The size of the stones can vary from minute stones that pass out of the bladder and urethra without causing any symptoms or it may be large enough to occupy almost the entire volume of the bladder.
There are different types of bladder stones but the most common are uric acid stones. Other types include calcium oxalate (most common type of kidney stone), calcium phosphate, cysteine, ammonium urate or magnesium ammonium phosphate (triple phosphate) stones. Many bladder stones are mixed in that the core may be of one type but other chemicals deposit around it. The types of bladder stone may vary based on regional and dietary variance – in some countries, calcium oxalate stones are the more common type of stone.
Causes of Bladder Stones
Bladder stones may form without any identifiable predisposing conditions. It is believed that many of these cases are associated with living in hotter climates resulting in dehydration, or the consumption of certain foods that are low in phosphorus and high in oxalate.
The formation of bladder stones is often associated with urinary stasis. When urine remains in the bladder for a prolonged period of time, the likelihood of a bladder stone forming increases. If the urine is concentrated, then precipitation of solutes in the urine is more likely to occur.
The predisposing factors for bladder stone formation in both men and women includes :
- Bladder outlet obstruction due to anatomical defects, tumors (bladder cancer) and urethral strictures.
- Neurogenic bladder is when there is damage of the bladder nerves due to spinal cord injury, neurodegenerative diseases, diabetic neuropathy or stroke.
- Bladder diverticula
- Non-infectious bladder inflammation (cystitis) caused by radiation or injury
- Infections – read more on urinary tract infections, bladder infection.
- Foreign bodies in the bladder.
- Medical devices such as urethral catheters and stents.
- Surgery to the bladder and urethra.
Bladder Stones in Men
Benign prostatic hyperplasia (enlarged prostate gland) is one of the main causes of bladder outlet obstruction in men thereby contributing to urinary stasis. Prostate cancer and prostate surgery may be other contributing factors, along with radiation therapy for prostate cancer.
Bladder Stones in Women
The causes of bladder stone formation in women may include a cystocele (prolapsed bladder), contraceptive devices, vaginal reconstruction and cloacal malformations. Infections of the urethra (urethritis) in women are more likely to progress to cause cystitis (bladder infection) due to the shorter urethra than in men. Recurrent cystitis is a risk factor for bladder stone formation.