Diarrhea

Dr.Adnan Hamawandi

Professor of pediatrics

Definition and significance

An increase in stool frequency and fluidity that is considered abnormal by the mother.

It is the leading cause of illness and death among children in developing countries.

It is an important cause of malnutrition. Each episode of diarrhea contribute to malnutrition, when episodes are prolonged, their impact on growth is increased.

Types of diarrhea

Acute watery diarrhea: begins acutely, lasts less than 14 days and

involves passage of frequent watery stools without visible blood. Acute diarrhea causes dehydration and when food intake is reduced it contributes to malnutrition.

Dysentery: is diarrhea with visible blood in the feces.

Types-cont.

Important effects of dysentery include anorexia, weight loss, and damage to the intestinal mucosa by the invasive organism.

Persistent diarrhea: is diarrhea that begins acutely but is of

unusually long duration(14 days and more). The episode may begin as watery diarrhea or as dysentery. Marked weight loss is frequent.

Epidemiology

Transmission of agents that cause diarrhea is usually by the fecal-oral route. A number of specific behavior promote the transmission of enteric pathogens and increase the risk of diarrhea:

1. Failure of breast feeding exclusively for the first 6 months of life.

2. Using infant feeding bottles.

Epidemiology-cont.

3. Storing cooked food at room temperature. 4. Using drinking water contaminated with fecal bacteria.

5. Failure to wash hands after defecation. 6. Failure to dispose feces hygienically.Host factors that increase susceptibility

to diarrhea: 1. Early weaning from breast feeding.

Epidemiology-cont.

2. Malnutrition. 3. Measles. 4. Immunodeficiency or immunosupression.Age: most episodes of diarrhea occur during

the first two years of life. Incidence is highest in the age group 6-11 months.

Seasonality: Bacterial diarrhea peaks during warm seasons.

Pathophysiology

Normally absorption and secretion of water and electrolytes occur through out the intestine. About 90% in small intestine and 10% in the large intestine, leaving 5-10gm/kg being excreted in formed stools.

Water and electrolytes are simultaneously absorbed by the villi and secreted by the crypts. “two-directional flow”

Pathophysiology-Cont.

Any change in the two-directional flow of water and electrolytes in the small intestine results in either reduced net absorption or actual net secretion and causes increased volume of fluid to enter the large intestine. When this volume exceeds the limited absorptive capacity of the large bowel, diarrhea occurs.

Pathophysiology-Cont.

Absorption of water from the small intestine is caused by the osmotic gradients that are created when solutes are actively absorbed from bowel lumen by the villous epithelial cells.

There are several mechanisms whereby sodium us absorbed from the bowel lumen. 1. Direct absorption as sodium ion.

2. Chloride linked co-transport.

Pathophysiology-Cont.

3. Hydrogen ion exchanger. 4. Glucose and a. a. co-transport. After being absorbed Na is transported out of

the epithelial cells by the Na K ATPase pump this transfers sodium into the ECF elevating its osmolality and causing passive flow of water and other electrolytes from the small bowel lumen through intercellular channels into the ECF

Pathophysiology-Cont.

Secretion of water and electrolytes normally occurs in the crypts of the small bowel epithelium where NaCl is transported from the ECF into the epithelial cells across the basolateral membrane. The Sodium is then pumped back into the ECF by the Na K ATPase, while the Chloride ion pass through the luminal membrane of the crypt cells into the bowel lumen, followed by water passively

Mechanism of diarrhea

There are two principal mechanisms:- 1. Secretory and 2. Osmotic. Secretory diarrhea: is caused by abnormal

secretion of water and electrolytes into the small bowel lumen. This occurs when the absorption of Sodium by the villi is impaired while the secretion of Chloride in the crypt cells continues or is increased. The net result is fluid secretion which leads to loss of water

Mechanism of diarrhea-Cont.

In infectious diarrhea secretory effect on the bowel mucosa can result from bacterial toxins like E.coli, and Vibrio cholerae OR viruses such as rotavirus.

Osmotic diarrhea: The small bowel mucosa is a porous epithelium across which water and electrolytes move rapidly to maintain osmotic balance between the bowel contents and the ECF. Diarrhea can occur when a

Mechanism of diarrhea-Cont.

Poorly absorbed osmotically active substance is ingested, if the substance is isotonic solution the water and solute will simply pass through the gut unabsorbed causing diarrhea like MgSO4(used as purgative), Lactose or glucose. When the substance taken as hypertonic solution water will move from ECF into gut lumen until osmolality of intestinal contents and ECF is equalized.