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Allocation patholologically of plentiful watery fecal masses is called diarrhea. Normal about 9 l of liquid daily come to intestines. As a rule, with food no more than 2 l arrive, other liquid is represented by secrets of sialadens, a stomach, system of a zhelchevydeleniye, a pancreas and small intestine. About 8 l of this liquid are soaked up in a small intestine, and the rest (from 0,5 to 1,5 l) via the ileocecal gate gets into a large intestine where it is also soaked up, except for 100 g which are removed with a stake. At increase in consumption of liquid or secretion intestines adapt to the raised loading absorption strengthening. When reception or secretion of liquid exceed normal ability of intestines to absorption, and also at disturbance of absorption there is diarrhea.
Increase in consumption or secretion of liquid
Diarrhea owing to overconsumption of liquid meets seldom though cases of its emergence at the persons who drank at once a large amount of water are described or at unlimited consumption of beer. Cases of the diarrhea connected with supersecretion of sialadens of a pancreas or system of a zhelchevydeleniye are not described, it is obvious because the small intestine can easily cope with excess of liquid of a secretory origin. Ellison's syndrome — Zollingera is followed patholologically by high secretion of a gastric juice and diarrhea, however the diarrhea at such patients can be explained rather with an effect of acid on digestion and transport of contents in a small intestine, than excess gastric secretion. Thus, the small or large intestine happens a source of the supersecretion capable to cause diarrhea, almost always. In a small intestine excessive secretion can be observed at the tumors emitting polypeptide hormones, similar to vasoactive intestinal polypeptide as a result of infection with pathogenic microorganisms like colibacillus, staphylococcus, a cholera vibrio and, perhaps, some other; and also in connection with reception of laxatives of an irritant action. Supersecretion in a large intestine most often is explained by disturbance of absorption in a small intestine or long-chain fatty acids, or" bile acids. Bacteria of a large intestine do these substances sekretogenny.
Liquid absorption lowering
The most part of liquid and electrolytes is soaked up in intestines only in the course of a resorption of soluble substances, for example sugar and amino acids. Therefore, any process breaking absorption of soluble substances in a small intestine interferes also with absorption of liquid and electrolytes. Chronic insufficiency of a pancreas and defects of absorption (for example, a Gee's disease or to a spr) and, perhaps, the disturbances of motility of intestines causing too fast passing of contents on a small intestine belong to such diseases; because of insufficient contact of food with an epithelium absorption is broken. At any of these diseases not absorbed soluble substances due to the osmotic action detain liquid in an intestines gleam. Very seldom the defects of absorption of liquid and electrolytes which are not connected with disturbance of absorption of soluble substances meet; can be an example inborn hloridoreya at which, apparently, there is pathology chloride - a bicarbonate exchange in distal department of an ileal gut.
Absorption of liquid in a large intestine
Ability of a colon to soak up the substances arriving from an ileal gut considerably exceeds normal requirement. So, the large intestine can soak up 4 — 7 l of the plasma substitute entered into a caecum with a constant speed a day. The large intestine is able to process also the remains of feedstuffs including 40 — 60 g of carbohydrates; however higher dose of carbohydrates causes emergence them in a chair and diarrhea. Anaerobic bacteria turn carbohydrates into volatile fatty acids, mainly acetic, propionic and oil. These substances are easily soaked up by an epithelium of a large intestine and as a result of lowering of osmolarity of contents, water absorption increases. Ease to which there is a dissolution of carbohydrates, explains why many patients with insufficiency of lactase can drink milk without development of diarrhea and also why patients with an active form of a Gee's disease not always complain of a diarrhea.
The scheme of distribution of liquid in a large intestine is normal, at excess intake of liquid in a large intestine and at absorption disturbance.
It is logical to assume that diarrhea develops only when the large intestine cannot cope with amount of the liquid arriving from an ileal gut. Such pathology is observed in two cases:
1) when the quantity or structure of contents of an ileal gut exceeds normal absorbing capacity of a large intestine;
2) at dysfunction or a disease of a large intestine absorption of the contents (fig.) coming to it is broken.
Among factors; the substances breaking normal absorption in a large intestine arriving from an ileal gut it is necessary to mention:
1) a disease or damage of an epithelium of a large intestine, for example at ulcer colitis;
2) the disturbance of motility of a large intestine causing too fast passing of contents therefore time necessary for fermentation and absorption is reduced;
3) pathological secretion in a large intestine;
4) the lack of bacteria causing the slowed-down enzymatic transformation of carbohydrates into volatile fatty acids and causing secondary disturbance of absorption of liquid. Diarrhea after intake of antibiotics of a broad spectrum of activity is explained by reduction of intestinal microflora. Disturbance of absorption of fats and bile acids in a small intestine can also oppress absorption of liquid in a large intestine as the bacteria inhabiting a large intestine turn fats and bile acids into the products possessing laxative action and strengthening secretion and motility of a large intestine.