Diarrhea

Diarrhea is characterized by the elimination of feces that present excessive volume and frequency, and are abnormally liquid – more than 3 stools for day. The subjective evaluation of the feces by the patient is influenced by his bowel habits. The diarrhea can be acute (up to 3 to 4 week with infectious cause) or chronic (more than 4 weeks).

The diarrhea can be classified as osmotic, secretory or oily.

The osmotic diarrhea is caused by the poor nutrients absorption or by the poor absorption of electrolytes that retain the water in the lumen. The secretory diarrhea occurs when the secretory cells maintain a high rate of liquid transportation of the GI tract to the lumen. The oily diarrhea (by poor absorption) occurs when the ability to digest or absorb a certain nutrient is deficient.

Ethiology

The flow in the GI tract involves the massive discharge of liquid in the lumen and its absorption, causing the a dynamic balanced state. Changes in these characteristics (excessive osmotic charge, increased discharge or decreased liquid absorption) can origin diarrhea.

Causes:

Osmotic diarrhea –low absorbable solutes ingest (fructose, magnesium salts, phosphate and citrate anion); poor absorption of carbohydrates (flatulence by the sugar digestion made by bacteria).

 Secretory diarrhea – the substances that stimulate the electrolyte discharge by the bowel mucosa by the increased AMPc or GMPc (enterotoxins or production of VIP by the pancreas tumours).

Inflamatory diarrhea – organic injury of the bowel (colon) where occurs a decrease of water absorption and a production of exudate rich in proteins and sometimes pus (diarrhea with mucus, blood and pus of bacterial cause or non-infectious).  

Motor (mobility) – increased peristalsis by prokinetic agents, decreasing the available time for the absorption of any nutrient or liquid.

Pathology and Pathogenesis

The infectious agents are the most important cause of diarrhea because they cause severe diseases that sometimes are fatal. Diarrhea  caused by infectious agents symptoms are caused by toxins that changes the bowel discharge and the absorption.   

Clinical Manifestations

Depending of its cause, intensity and chronicity, the most common signs consists of dehydration (severe diahrrea mostly in children), height loss and specific vitamin deficiency syndrome (glossitis, stomatitis). It may also be hypokalemia and metabolic acidosis (bicarbonate loss).