Kidney Dystrophy: Causes, Pathogenesis and Clinic
The term "dystrophy" is a derivative of two terms and in translation means a metabolic disorder. It affects a large number of organs. Especially it concerns those of them, which play an important role in the metabolism. Not for nothing renal dystrophy can serve as a marker of many such diseases.
Short anatomical and physiological characteristics of the kidneys
Kidneys are paired organs. Outwardly they resemble the shape of the legume fruit. Located on both sides of the spine, in the region of 11-12 thoracic and 1-2 lumbar vertebrae. The average organ size does not exceed 12 cm in length and 3-5 cm in thickness. Their concave surfaces face the vertebral column, respectively, convex - from it.
Each kidney consists of several layers of dense tissue.
- Connective tissue capsule. It covers almost the whole organ. In the area of the sinus( located almost in the center of the side facing the spine), it passes into the ureter's membrane. There are two large vessels in the kidney. This is the renal vein and artery.
- The cortex is located directly under the capsule. Immediately below it lies the brain substance. It contains nephrons. From the brain substance, in the direction of the sinus, shoots leave. Here are the blood and lymph vessels. On a cut the color of cortical, cerebral substances and processes is the same. Therefore, they are considered a single anatomical structure.
- Almost in the center of the organ, between the processes are the so-called renal pyramids. Named for their trapezoid shape. The base is directed to the cortical substance, and the tip is toward the sine.
- Kidney calyx. Cavities in which the pyramids pass. They open into the pelvis, from which, in turn, the ureter emerges.
The basic functioning of the kidneys can be represented as follows. The renal artery after the "entrance" into the organ begins to branch into several branches. They pass into the tissue of the appendages and penetrate into the brain substance. Here they are further divided into smaller vessels to the size of the arterioles that go into the nephron. There, due to an even finer branching, they form a vascular tangle. Due to its dense environment, special cells( podocytes), there is a primary filtration of blood. Further in the venules are only blood cells, part of the plasma and some proteins.
All the rest, but slags, electrolytes, carbohydrates, lipids and some proteins are retained by the filters of the podocytes and, together with a part of the plasma, enter the tubules of the nephron. This is called primary urine. It accumulates in a bowl of Bowman-Shumlyansky, which is surrounded by a semicircle of the vascular glomerulus. Its base is the beginning of the renal tubule. On it, the primary urine enters the tubule, which is quite long, which comes from the brain substance into the pyramids. Here he makes a loop and "rises" into the brain substance.
On all the way it is densely enveloped by venous vessels coming from the vascular vessel. This is necessary for the reabsorption( re-absorption) of proteins, lipids, carbohydrates, certain electrolytes and water. As a result, only the slags, electrolytes and part of the water fall from the tubules into the renal calyx. This is called secondary urine. She goes to the pelvis, from which she is excreted on the ureter.
This is important! In humans, up to 180 liters of primary urine per day is formed. About 90-95% of this quantity is reabsorbed. Thus, the daily volume of secondary urine does not exceed 2 liters. One can only imagine how many organic molecules pass through the kidneys. This circumstance gives a clear explanation why the metabolic disorder often affects the kidneys.
Mechanisms and causes of dystrophy
Common to all types of dystrophies is the initial stage of development. It consists in the following:
- Violation of the exchange of a group of molecules.
- Excessive accumulation of these molecules in the cells of the organ.
The further mechanism differs depending on the specific type of dystrophy. But this will be discussed below. As for the causes of dystrophy, they are divided into two large groups.
- Congenital dystrophy. Due to genetic and / or congenital defects at any stage of the metabolism of the substance: from synthesis, to decay. For kidneys, congenital dystrophies, the most characteristic is the violation of protein and fat metabolism.
- Acquired dystrophy occurs as a result of the violation of any stage of the metabolism of a substance under the influence of external causes. The most likely causes are viral infections, chronic bacterial infections, radiation, chronic intoxications, as well as certain diseases. These include diabetes, some neoplasms, injuries.
Types of dystrophy
This is important! All kidney dystrophies can be divided depending on the causes of the occurrence and the specific substance. In the first case, these diseases are divided into congenital and acquired dystrophies. But more correct from the point of view of practical medicine is the division of dystrophies by types of substances.
According to the above-described situation, dystrophy is divided into three categories:
- Dysproteinosis. This is a dystrophy caused by a disorder in the metabolism of proteins. They can be both congenital and acquired. The following types of kidneys are characteristic:
- Grainy dystrophy. It develops as a result of intracellular edema and the release of protein into the cytoplasm. But since the protein is an insoluble substance, in the cytoplasm it forms peculiar "grains."Therefore, granular kidney dystrophy and got its name.
- Hyaline-drip dystrophy. It is the result of the further development of the first species. Here, protein molecules, as a result of significant accumulation, begin to unite into distinctive "drops" of cartilaginous consistency and color. By their structure, these protein formations resemble hyaline - the main protein "building material" of cartilage. This circumstance explains why the hyalin droplet dystrophy of the kidneys has received such a name.
- Horny dystrophy. It develops with excess accumulation of keratin. This white is normal only for epithelial cells. But in the case of a permanent effect on the non-epithelial cell of the damaging factor from cytoplasm fibrils, the "assembly" of keratin molecules begins.
- Hydropic dystrophy. A special kind of albuminous dystrophies. It occurs when an excessive increase in the water vacuoles of the cell. Most often in the cell there is one giant vacuole containing a transparent liquid. In this case, the remaining organelles are practically nonexistent. In particular, there is no nucleus, which is destroyed by this vacuole. The main cause of dystrophy is a viral infection. For kidney structures, this species is most characteristic of tubules. However, the hydropic degeneration of the epithelium of the tubule of the kidney is caused not so much by viral infections, but by chronic inflammation in general.
- Fatty degeneration or lipidosis. There are fewer occurrences. Moreover, they often have acquired character than protein ones. For which both are equally characteristic. And one of the main factors of fatty degeneration is ischemia - lack of oxygen. This is well demonstrated by the fact that fatty kidney dystrophy is often observed in chronic infections and intoxication with some inorganic substances: arsenic, bismuth, mercury, and chronic alcoholism.
- Carbohydrate dystrophy is less common in the kidneys. This is largely due to the fact that the kidneys play a small role in the metabolism of carbohydrates. However, in some diseases carbohydrate dystrophy of the kidneys can occur quite often. It is based on the deposition of molecules of carbohydrates with their excess. The most striking example of this type of dystrophy is diabetes mellitus.