The natural history of diverticulitis: fact and theory.

Epidemiological and anatomic evidence indicates that approximately 60% of humans of westernized societies living into the sixth decade will develop diverticulosis of the colon. The cause remains unknown, but epidemiological studies indicate it is a combination of decreased dietary fiber intake and increased intracolonic pressure. The intraluminal pressure exerted on the wall causes a diverticular outpocketing at any one of the three areas in which vessels enter the wall. In this paper, we advance a hypothesis that fiber deficiency not only leads to diverticula formation but also causes a change in the microecology that results in decreased colon immune response and permits a low-grade chronic inflammatory process that precedes a full-blown acute diverticulitis. Pathophysiologic studies reveal that complications do not occur until there is microperforation through the wall of the diverticulum into the pericolic tissue. The perforation might be small and cause a microabscess, or extend to a phlegmon, or extend to a large abscess formation. Free perforation occurs rarely, but fistulization does occur and most commonly to the bladder. The clinical findings vary. Most often, the clinical picture is one of fever, abdominal pain, a change in bowel habit, and localizing findings associated with leukocytosis. Computerized tomography scanning has become the procedure of choice to evaluate the symptoms since it is of less risk than a barium enema and obtains more information. The differential diagnosis may be difficult but usually can be made with accuracy. Medical treatment is preferred with appropriate antibiotic therapy and variations in fiber intake. When abscess occurs, percutaneous drainage may be tried, but when it is unsuccessful, surgical intervention is necessary. Sudden hemorrhage from a vessel in diverticula may also occur. It is estimated that approximately 20% of all patients that develop diverticula will have either inflammatory or bleeding episodes. In conclusion, fiber deficiency results in diverticular formation and a chronic inflammation that may progress to acute or chronic diverticulitis that can be treated medically but may require surgical intervention.