The gut microbiota is an essential part of the human organism, which plays a crucial role in maintaining its homeostasis. Peaceful coexistence with trillions of microorganisms mainly depends on the normal functioning of cellular and extracellular components of the intestinal mucosa, often called the "intestinal barrier". This barrier protects the organism against pathogenic infections while and at the same time satisfying its requirements for digestion and absorption of nutrients. It is not surprising that structural and functional intestinal barrier abnormalities are involved in the pathogenesis of many diseases including various nephropathies. The pathogenetic interconnection between the intestine and the kidneys is bidirectional. On the one hand, uremia affects the microbiota composition and the integrity of the intestinal epithelium. On the other hand, uremic toxins trans-location, formed as a result of abnormal microbial metabolism, from the intestine into circulation through the ultra-permeable barrier contributes to the progression of renal dysfunction. Furthermore, according to a number of researchers, dysbiosis and the leaky gut syndrome are considered as one of the possible causes of anemia, nutritional disorders, cardiovascular and many other complications, often diagnosed in patients with chronic renal disease. The first part of the review reflects modern data about normal intestinal barrier structure and physiology, as well as methods for studying the intestinal wall integrity and permeability. The significant role of microbiota in the regulation of the barrier properties of the intestinal mucous and epithelial layer is emphasizing. The main differences between the intestinal microflora of patients with nephropathies from healthy people are presented, possible causes of their occurrence are discussed.