What is urinary tract stones?
It is the presence of solid mineral formations, also known as calculi or stones, which can be formed in the kidney, the ureters or bladder.
How do urinary stones form?
They are formed due to the union of certain substances in the urine (calcium, uric acid, oxalate), which cannot be diluted or eliminated by the kidney and, consequently, small crystals are generated, that by adhering to each other, increase in size to form the stone.
How common is this disease?
Nephrolithiasis is estimated to affect 4% of the global population, being more frequent in males, estimating that 13% of men and 7% of women have had at least one urinary stone in their life.
At what age is it manifested?
Although there is no age, country or ethnic group particularly prone to the disease, it has been determined that the highest incidence is recorded in the population between 30 and 60 years.
Are there different types of stones?
Yes, and each has different causes of formation. Among the most common we can mention:
Calcium stones. They are the most frequent. They occur by urinary calcium loss (hypercalciuria) from bones or increased intestinal absorption of that mineral. These patients may have a higher risk of osteoporosis and fractures.
Uric acid stones. Are formed by the increase in the excretion of uric acid in the urine, accompanied by acidic urine (acid pH). They are common in obese and diabetic patients.
Struvite (of infectious origin). They are more common in women. Bacteria such as Proteus and Klebsiella increase urinary acidity and give rise to these stones, which tend to be large and occupy much of the kidney, taking the form of a coral or a deer antler, as they are also known.
Symptoms vary depending on the size and location of the stone. Generally most stones less than 7 mm in diameter can be managed with medical treatment or spontaneously. When symptoms occur, these are the most common:
Renal colic. It occurs when the stone obstructs the passage of urine because it is “stuck” in the ureter (the tube that carries urine from the kidney to the bladder) and prevents the free flow of urine, which dilates the urinary tract and causes very intense pain localized according to the site of obstruction and which may extend into the lower abdomen and even the genitals.
Hematuria. Is the presence of blood in the urine, which can be detected by eye or by studying the urine. This bleeding is caused by the friction of the stone passing through the urinary tract.
Other symptoms. Nausea, vomiting, persistent urge to urinate, painful or difficult urination. In some cases, the urine that cannot pass by the obstruction of the stone gets infected and causes chills and fever. These urinary tract infections can complicate and affect the kidneys (pyelonephritis).
How is it diagnosed?
Today, computed tomography with three-dimensional reconstruction is the most accurate, fast and less invasive method to determine the presence and location of the stone. You can also use abdominal radiography and renal ultrasonography, but these provide less accurate information.
To find the root cause of the stones special studies must be made of the urine and blood for the determination of calcium, phosphorus, uric acid, oxalate, citrate, determination of urinary pH and a urine culture to determine the presence of a urinary infection. Once the patient expels a urinary calculus or one is removed by surgery, this should be sent for testing to know its exact chemical composition and to make a specific treatment plan. The determination of the parathyroid hormone that regulates the concentration of calcium in the body is equally important.
What is the treatment?
It varies with the number of stones, their size and location. In general, the following are key indications that are an essential part of the treatment.
Water consumption should be abundant, between 2 to 2.5 liters daily. This stimulates the production of urine, which can help reduce stone formation and also to push those already formed to facilitate their removal. Moreover, this fluid intake dilutes the substances that make up the stones thereby facilitating their elimination through the urine. In hot climates it is necessary to ingest more water to compensate for the fluid loss through sweating. This helps keep the urine less concentrated and reduces the risk of stone formation.
According to the chemical characteristics of the stone, the doctor may make some dietary modifications. Although traditionally it has been recommended to reduce calcium intake to combat stones consisting of that mineral, recent studies show that patients with a low calcium diet may have a higher recurrence of urolithiasis. The reason is that calcium oxalate excretion increases when the diet is low in calcium. In addition, low calcium diet for long periods can cause osteoporosis. So, the diet should be normal and can be complemented with a low intake of salt and animal protein (meat).
They are drugs that increase the excretion of urine. Some of them are used to decrease urinary calcium excretion and reduce the occurrence of urinary stones.
Is a drug that reduces the uric acid concentration in the blood, which also decreases its presence in the urine and is effective in the treatment of stones from uric acid.
Increases the pH of the urine to correct acidic urine and prevent the formation of calcium crystals.
It is the technique known as extracorporeal lithotripsy. It uses electromagnetic waves that are directed from outside the body to the place where the stones are located and pulverizes them into small fragments that can be expelled with the urine. The method requires no incisions and is less painful than surgery, although it may require several treatment sessions.
Is the use of minimally invasive surgical techniques, which use modern instruments equipped with optical and working devices that allow access to the urinary tract through natural openings or small incisions created to locate and remove the stone without major surgical wounds. It is the most common and probably the most effective treatment for urinary lithiasis.
Laparoscopic and robotic surgery
These minimally invasive techniques are employed in academic and scientific centers of excellence where the above treatments are not sufficient to remove stones in the urinary tract.
Due to the wide range of minimally invasive treatments, which report high success rates, this type of surgery is falling into disuse in most of the world.
Can the stones recur?
This disease has a hereditary component and tends to recur, especially if the cause has not been identified or when treatment has not been received to prevent stone formation. Recent research shows that approximately 70% of patients who have had a stone will have another in less than 10 years, 50% within 5 years and 15% within the first year.