There kidney stones, also called nephrolithiasis, is a disease characterized by the presence of small "pebbles" along the course of the urinary tract. These pebbles, which are solid aggregates called precisely kidney stones, derive from the precipitation and aggregation of some substances normally present in the urine. The formation of kidney stones is favored by several factors, including an unbalanced diet and some inflammatory processes. In addition, great importance is given to family predisposition and low fluid intake. Once formed, with the passage of time, the stones tend to pass from the kidney to the lower urinary tract, then to the ureter, from there to the bladder and finally into the urethra to be expelled outside with the urine. Especially if small in size, kidney stones can be asymptomatic and be eliminated spontaneously without causing any disturbance to the patient. In many cases, however, kidney stones end up causing a very severe pain in the lumbar region, then in the lower back. This pain is characteristic of kidney stones and due to its peculiarities and associated symptoms it falls within the more general framework of the so-called "renal colic". In other cases, if the stone is large, it can even obstruct the ureter and injure it and even hinder the normal outflow of urine. I remind you, in fact, that the ureter is that thin tube that carries urine from the kidney to the bladder. Its obstruction can therefore favor, among other things, the development of pyelonephritis, ie inflammation of the kidney. For these reasons, in such circumstances, the stone must be removed immediately, by means of an appropriate, often surgical, intervention. Prompt intervention is important not only to relieve pain but also to avoid dangerous complications, which can even compromise the functionality of the affected kidney. In any case, fortunately, most of the time the stones measure less than 5 mm in diameter, and are therefore eliminated spontaneously without too many problems or with the support of measures that favor their expulsion.
Before examining the causes of kidney stones, a very brief anatomical and physiological recall can help us to better understand the subject kidneys they are two organs belonging to the urinary system, located in the posterior region of the abdominal cavity, approximately at the level of the 12th rib. Their shape is compared to that of a bean, precisely because of the clear resemblance to the legume that we know well. The primary function of the kidneys is to produce urine, filtering the blood from waste substances or in any case present in excess. From each kidney, as we have seen, a thin tube called ureter, responsible for the transport of urine. The two ureters, right and left, pour their contents into a hollow organ, called urinary bladder, which accumulates urine between one urination and the next. When the bladder fills beyond a certain level, the subject feels the need to urinate; thus, with the act called urination the bladder is emptied and the urine is expelled to the "external through a single tube connected to the bladder and called the urethra.
After this premise, it can be understood how kidney stones are the consequence of a loss of balance between the various substances present in the urine. Their formation, in fact, is favored by high concentrations of poorly soluble substances in the urine, such as, for example, calcium salts or uric acid, or stones can form when the urinary flow is slowed. In the latter case, these substances remain longer in the urinary tract, so they have plenty of time to precipitate and aggregate. If an insoluble compound is more concentrated than normal it can give rise, therefore, to a supersaturation urine, so it risks precipitating and joining to form crystals. These crystals, merging with each other in the kidney calyxes, end up giving life to real pebbles. To make a comparison, the formation of kidney stones is the consequence of a chemical process similar to that which causes the precipitation of sugar in an overly sweetened cup of coffee. Even the changes in urinary pH they can promote the formation of kidney stones. In physiological conditions, the formation of stones does not occur due to the presence in the urine of substances, such as "citric acid, which prevent the precipitation and crystallization of salts, binding them to itself to form soluble complexes. Unfortunately, these inhibitory mechanisms they do not always guarantee fully effective protection. As a result, kidney stones can form, which depending on the case can be as small as grains of sand or even as large as golf balls. The stones can also have smooth outlines or appear as masses with an irregular, jagged surface. It is not uncommon to find multiple stones in one kidney.
When a kidney stone begins to form, there are two possible evolutions. In the first case, the calculation continues to grow, due to the progressive accumulation of precipitated salts. The growth of the stone can then continue until it completely occupies the cavity in which it is located, almost as if it were a mold.In these cases, the affected kidney can completely lose its function. In the second case, which is the most common one, the precipitated material is instead dragged by the urinary stream and expelled. The risk, in these cases, is that the calculus, flowing with the urine, creates lesions on the walls of the urinary tract and then the situation becomes complicated. This can lead to the appearance of blood in the urine or, if the stone reaches a narrower point in the ureter, it can cause its occlusion causing a renal colic or even a blocking of urination.
As for the real causes of kidney stones, once again we must refer to the presence of specific substances in the urine. In fact, kidney stones can be made up of various urinary components, single or in combination with each other. kidney stones can have calcic, mixed, uric, infectious or cystinal origin. The most common circumstance involves the formation of kidney stones of a calcic nature; their formation therefore derives from the aggregation of calcium oxalate And calcium phosphate. Even the excessive amount of uric acid however, it can generate very annoying kidney stones. This type of stone is usually observed in the context of hyperuricemia, in patients with gout or with a malignant blood disease. Much rarer, however, are stones made up of an amino acid, la cystine. These formations are observed, in particular, in subjects who have a hereditary pathological condition called cystinuria. This disease causes a defect in the transport of some amino acids, including cystine, in the kidney and intestine. Not only the excess of urinary substances just seen can contribute to the formation of kidney stones, but also the lack of other substances which, under normal conditions, effectively counteract the crystallization process. Among these we have already mentioned the "importance of citrates. Finally, a separate chapter deserve the stones resulting from urinary tract infections. Some bacteria, in fact, produce protein substances that facilitate the precipitation of salts in the urine. For example, magnesium ammonium phosphate stones, also known as struvite stones, are mainly seen in urinary tract infections by urease-producing bacteria, such as those belonging to the genus Proteus. All this information on the composition of the kidney stone is important not only at a didactic level, so to speak, but also for setting the therapeutic protocol most suited to the individual case. As we will see better in the next video, in fact, the therapy of kidney stones aims to reduce the concentration of the urinary salts involved and to increase the substances that inhibit their precipitation.
From an epidemiological point of view, urinary stones is a very common pathology in the Western world. Men are more affected than women, at least in the age group ranging from 20 to 40 years. This male predisposition to kidney stones is mainly due to the lower concentration of citrate in the urine compared to women. Women, for their part, are more prone to the risk of struvite kidney stones, due to their greater susceptibility to urinary infections. Another important aspect to underline is that calculosis is a disease with a notable tendency to recur in the same subject. Question: but what are the factors that can promote the formation of kidney stones? For some forms, some are believed to be of importance hereditary factors: those with family cases of kidney stones are therefore more at risk. However, one of the major promoters of kidney stones is the dehydration, which can be the consequence of an insufficient intake of liquids with the diet or of an increased loss of them, as occurs in the case of chronic diarrhea or profuse sweating. An important risk factor is the diet, especially if the intake of protein and sodium is excessive. The formation of kidney stones can also be favored by the presence of frequent urinary infections you hate conditions that slow the outflow of urine, as often happens in the pathologies of the so-called enlarged prostate. Other predisposing diseases are anatomical anomalies and some metabolic disorders that increase the levels of calcium in the urine, includinghyperthyroidism and thehyperparathyroidism. In the formation of kidney stones, the use of some medications, such as acetazolamide, an antihypertensive that can cause kidney stones by increasing urinary pH and urinary calcium excretion. At least theoretically, attention should also be paid to the abuse of food supplements based on mineral salts.
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