Constipation and diarrhea

The emptying of the stomach takes place in a period of three to four hours, the digested food reaches the ileocecal valve within two to three hours and in about nine hours the passage of substances through the digestive tract is completed. Water absorption is done in the cecum and ascending colon. Massive peristaltic waves (gastrocolic reflex) arise after food ingestion and propel the bolus from the hepatic angle forward. Defecation occurs when joint peristaltic waves of relaxation of the rectosigmoid junction propel the contents of the left hemicolon and sigmoid to the rectum. The main portion of ingested material requires several days for evacuation. Serial intestinal motility involves the pneumogastric, splanchnic and pelvic nerves in an important role. Motility is intensified by parasympathetic stimulation and inhibited by sympathetic stimulation. Finally, the receptive relaxation of the internal anal sphincter depends on a lower medullary reflex, while that of the external sphincter is under voluntary control. Pharmacological influences on gastrointestinal transit include increased activity by cholinergics, serotonin, vasopressin and other substances. Motility decreases with potassium, morphine, codeine and atropine deficiency. Normal stools contain 60 to 70% water.


It is the abnormal retention of stool or excessive delay in its expulsion, compared to the usual habits of defecation. Psychogenic causes include inadequate "training", resulting in functional megacolon. Dietary factors include not eating high-fiber foods and laxative abuse. (For drugs, refer to the intestinal transit section). Constipation also causes decreased muscle power of the abdomen wall, diaphragm and pelvic muscles. Neurogenic causes include tabes dorsal, multiple sclerosis, spinal tumors, trauma, and Hirschsprung's disease.

Intrinsic causes are tumors, fecal impaction, volvulus, intussusception and anal spasm (by cracks, proctitis, hemorrhoids). Extrinsic causes include large intra-abdominal masses and obstructive adhesions.


It is the excessive and rapid expulsion of liquid stool. By definition, diarrheal feces contain at least 90% water. The average daily weight of feces is 200 grams.

  • Causes. Among the many possible are: functional diseases, organic blood diseases (colitis, neoplasms), disorders of the small intestine (inflammatory bowel disease, poor absorption, fistulas, short intestine), gastric factors (Zollinger-Ellison syndrome, rapid emptying syndrome, postvagotomy state), diseases of the pancreas and bile ducts, intestinal infections (by bacteria or parasites), metabolic disorders (thyroid diseases, uremia and disorders of parathyroid) and drugs.
  • Physiopathology. The primary abnormality lies in the transport of water and electrolytes through the intestines. Distension in these cases stimulates propulsive contractions. The main mechanisms include: a) excessive intestinal secretion or secretory diarrhea. It comprises active ion secretion, in which cholera is a classical model. The aggressor agent stimulates the enteric or colonic mucosa to secrete rather than absorb. b) Osmotic diarrhea comes from inadequate intraluminal absorption or osmotically active solutes. They are a consequence of incomplete digestion, insufficient absorption or ingestion. An important example is lactose deficiency. c) Exudative diarrhea results from the luminal release of protein, blood or mucus. It may be due to inflammation, ulcers, or infiltration. Causes include IBD, infections, lymphoma, Whipple's disease. d) Alterations of the contact between the chyme and the absorption surface. They may be due to traffic disorders, IBD, or drugs.
  • Aftermath. Severe and long-lasting diarrhea can lead to dehydration, acidosis, and loss of electrolytes (hypokalemia).
  • Clinical assessment. Anamnesis. It includes duration, time of day, description of stool, presence of blood, mucus or fats, pain or urgency to defecate and other manifestations of gastrointestinal disease. Epidemiological factors must be analysed and the water and fat content of faeces measured.
  • Physical examination. The doctor should look for fever and arthritis (inclusion body diseases); He or she will also examine your abdomen carefully for lumps and pain to the touch. Digital rectal examination and proctoscopy are helpful, as well as a total colonoscopy with biopsy.
  • Stool analysis. In the feces you have to look for blood (carcinoma, inclusion body disease), mucus and excess fat (pancreatic insufficiency). Radiographic studies. X-rays of the abdomen, barium enema and gastroduodenal series are essential studies. Other diagnostic studies may include laparotomy and biopsy of the small intestine.