Stones are basically hard masses that can be present in the urinary tract and may cause pain, bleeding or an infection or block of the flow of urine.
- Small stones may cause no symptoms, but larger stones will cause severe pain in the area between the ribs and hips in the back.
- Simply, an imaging test and an analysis of urine are done to diagnose stones.
- At times, the stone formation can be prevented by changing the diet or increasing fluid intake.
- Stones which cannot pass on their own are removed with lithotripsy or an endoscopic technique.
Urinary tract stones start to develop in a kidney and may enlarge in a ureter or the bladder. Depending on where a stone is located, it may be called a kidney stone, ureteral stone, or bladder stone. The process of stone formation is called urolithiasis, renal lithiasis, or nephrolithiasis.
A urinary tract infection may result when bacteria is trapped in urine that pools above a blockage. When stones block the urinary tract for a long time, urine backs up in the tubes inside the kidney, causing excessive pressure that can cause the kidney to swell (hydronephrosis) and eventually damage it.
Types of Stones
Stones are formed of minerals in the urine that form crystals. At times, the crystals grow into stones. About 80% of the stones are composed of calcium, and the remainder is composed of various substances, including uric acid, cystine, or struvite.
Stones may develop because the urine becomes too saturated with salts that can form stones or because the urine lacks the normal inhibitors of stone formation. Citrate is that type of an inhibitor because it normally binds with calcium that is often involved in forming stones.
Stones are more common among people with certain disorders (for example, hyperparathyroidism, dehydration, and renal tubular acidosis) and among people whose diet is very high in animal-source protein or vitamin C or which do not consume enough water or calcium.
People who have a family history of stone formation are more likely to have calcium stones and to have them more often. People who have undergone surgery for weight loss (bariatric surgery) may also be at increased risk of stone formation.
Rarely, drugs and substances in the diet (such as melamine) cause stones.
Stones, especially tiny ones, may not cause any symptoms. Stones in the bladder may cause pain in the lower abdomen. Stones that obstruct the ureter or renal pelvis or any of the kidney’s drainage tubes may cause back pain or renal colic.
Renal colic is characterized by a severe intermittent pain which is usually in the area between the ribs and hip that spreads across the abdomen and often extends to the genital area.
The pain tends to come in waves, gradually increasing to peak intensity, then fading, over about 20 to 60 minutes. The pain can radiate down the abdomen towards the groin or testis or vulva.
Other symptoms include nausea and vomiting, restlessness, sweating, and blood or a stone or a piece of a stone in the urine. One may have an urge to urinate somehow, particularly as a stone passes down the ureter. Chills, fever, burning or pain during urination, cloudy, foul-smelling urine, and abdominal swelling sometimes occur.
Doctors usually suspect stones in people with renal colic. At times, doctors found stones in people with tenderness over the back and groin or pain in the genital area without an obvious cause.
Finding blood in the urine supports the diagnosis, but not all stones cause blood in the urine. Generally, the symptoms and physical examination findings are so distinctive that no additional tests are needed, particularly in people who have had urinary tract stones before.
However, most people are in so much pain and have symptoms and findings that make other causes for the pain seem likely enough that testing is necessary to exclude these other causes. Doctors need to differentiate stones from other possible causes of severe abdominal pain, including
Helical computed tomography (CT) which is done without the use of radiopaque contrast material is usually the best diagnostic procedure. CT can locate a stone and also indicate the degree to which the stone is blocking the urinary tract.
CT has the ability to detect many other disorders that can cause pain similar to the pain caused by stones. The main disadvantage of CT is that it exposes people to radiation.
Ultrasonography is an alternative to computed tomography and does not expose people to radiation. However, when ultrasonography is compared with computed tomography, more often misses small stones (especially when located in the ureter), the exact location of urinary tract blockage, and other, serious disorders that could be causing the symptoms.
X-rays of the abdomen expose people to much less radiation than computed tomography, but x-rays are much less accurate in diagnosing stones and can only show calcium stones.
Urinalysis is usually done. It can show blood or pus in the urine whether or not symptoms are present.