Diverticular disease

Diverticular disease is when problems occur due to diverticulosis, a benign condition defined by the formation of pouches (diverticula) from weak spots in the wall of the large intestine. This disease spectrum includes diverticulitis, symptomatic uncomplicated diverticular disease (SUDD), and segmental colitis associated with diverticulosis (SCAD). The most common symptoms across the disease spectrum are abdominal pain and bowel habit changes such as diarrhea or constipation. Otherwise, diverticulitis presents with systemic symptoms such as fever and elevated white blood cell count whereas SUDD and SCAD do not. Treatment ranges from conservative bowel rest to medications such as antibiotics, antispasmodics, acetaminophen, mesalamine, rifaximin, and corticosteroids depending on the specific conditions.

The signs and symptoms of diverticular disease stem from inflammation and irritation of the colonic tissues, which can manifest as:

Acute diverticulitis is thought to arise from either trauma or lack of blood flow to the existing diverticulum in the colon.

Complicated acute diverticulitis is distinguished from uncomplicated diverticulitis by the presence of abscess or colonic perforation.  

Chronic smoldering diverticulitis is caused by recurrent acute diverticulitis that does not respond to medical treatment but does not progress to complications such as abscess, peritonitis, enteric fistula, or bowel obstruction.

Similar to the diverticulitis ischemia theory above, SUDD is thought to be caused by sustained colonic contraction leading to mucosal ischemia within the diverticulum. However, SUDD occurs when only abdominal pain with bowel habit change is present, without any other systemic symptoms of diverticulitis like fever, elevated white blood cell count, elevated C-reactive protein.

Low grade inflammation of the colonic mucosa within the diverticulum and visceral hypersensitivity are also thought to cause SUDD.

SCAD, also known as diverticular colitis, is when there is mucosal inflammation in a colonic segment with diverticulosis that may or may not have evidence of diverticulitis, or inflammation within or around a diverticulum itself. The involved colonic segment is mostly confined to the sigmoid. The cause is currently unknown. It is thought to be multi-factorial, including colonic ischemia secondary to old age and other cardiovascular risk factors, diverticulosis causing mucosal prolapse, fecal stasis and subsequent microbiome disturbance, eventually leading to inflammation of the colon segment.