The colon or large intestine begins at the appendix in the right lower abdomen, climbs up to the right upper abdomen, crosses over to the left upper abdomen, and then descends to the left lower abdomen to empty in the rectum.  It has three main layers: a) the internal membrane or mucosa, b) two muscle layers, and c) an outer membrane or serosa.  When the inner mucosal layer herniates through the muscle layers and bulges into the serosal layer, causing a bleb on the outside of the colon, the bleb is called a diverticulum and the condition that allows many blebs to form is known as diverticulosis.  You can view the figure at the Mayo Clinic Foundation web site and it shows the details of this condition: www.mayoclinic.com/health/diverticulitis/DS00070

         Diverticulitis means that one or more blebs have ruptured, spilled the colon contents into the abdominal cavity outside the colon, and started an abdominal infection.  Because the diverticula tend to be more concentrated in the left lower colon, the condition tends to present with left lower abdominal pain in most cases.  Fever may come if the condition is allowed to advance; diarrhea is not a common symptom; and pain with feeling ill are the main complaints.

         Although the disease is genetically programmed, diverticulosis spares the young and increases with advancing age as the colon makes more diverticula, leading to more episodes of diverticulitis.  Untreated episodes can be catastrophic, causing abdominal abscesses, which might require surgical resection of the diseased segment and connecting the remaining colon to a bag on the outside of the abdomen via a colostomy.

         Early treatment with appropriate antibiotics such as Cipro or Tetracycline is crucial and usually aborts the disease without sequelae.  Since diverticulitis tends to be recurrent, there are two strategies that have proven helpful.  One, is to empower the patient to recognize and treat the recurring episodes without having to wait to see the doctor.  Thus, giving the patient access to antibiotics and teaching him or her to begin treatment at the onset of left lower abdominal pain can be life saving.  Two, is to give a daily dose of the antibiotic as a preventive measure to those who have very frequent recurrences and have them increase to the full therapeutic dose to treat the occasional recurrences that escape this preventive measure.  Although this preventive strategy is not backed by published scientific evidence, implementing it has proven most helpful in my own patient population.

         Many diets are advised for keeping the condition under control but none of them is scientifically proven.  Many preventive strategies are also advised such as avoiding corn, tomatoes, and other seed-bearing vegetables, but they also lack scientific validity.  The best preventive measure is to eat a high fiber diet and take fiber supplements such as psyllium (Metamucil) or methylcellulose (Citrucel).  Fiber discourages the formation of diverticula and decreases the incidence of diverticulitis.

         Elective surgery is advisable when the recurrences accelerate in spite of appropriate preventive and abortive treatments.  In such cases, with the hope of avoiding a catastrophic colon rupture, the diseased colon segment is preemptively resected and the remaining colon is reconnected to the rectum, thus avoiding a colostomy with an external abdominal bag.  One of the disadvantages of having a catastrophic colon rupture is that surgery will have to be done in two stages.  The fist, or emergency stage, is to resect the diseased segment and connect the remaining colon to an external abdominal bag.  The second, or elective stage—which takes place several months later—is to reverse the colostomy, reconnect the colon to the rectum, and get rid of the external abdominal bag.  

         Diverticulosis and diverticulitis are commoner in advanced societies whose diets do not contain enough fiber.