11.10 : Inflammatory Bowel Disease I: Ulcerative Colitis

Introduction

Inflammatory bowel disease, or IBD, encompasses a group of disorders characterized by chronic inflammation or ulceration of the gastrointestinal tract.

Risk Factors

The exact cause of IBD remains unclear, although it is believed to be due to a mix of genetic, environmental, microbial, and immune factors. Genetic factors are significant in determining susceptibility to IBD, with family history being a critical risk factor. Individuals with a first-degree relative who has IBD are at a substantially increased risk. Environmental factors, such as diet, smoking, nonsteroidal anti-inflammatory drugs, and prior infections, also play roles. For example, diets high in fat and sugar but low in fiber are linked to a higher risk of IBD. An imbalance in gut microbiota and dysregulation of the immune system, where immune cells mistakenly attack the intestinal lining, are also implicated in the disease's development.

Types

IBD primarily presents as either ulcerative colitis, affecting only the colon, or Crohn's disease, which can impact any segment of the gastrointestinal tract from the mouth to the rectum.

Ulcerative Colitis

Ulcerative colitis is a chronic condition that causes inflammation and ulceration of the colon and rectum's mucosal and submucosal layers. It features cycles of remission and exacerbation, with symptoms like abdominal cramps and bloody or purulent diarrhea.

Pathophysiology

The disease explicitly affects the colon's superficial mucosa, leading to ulcerations, diffuse inflammation, and the shedding of the colonic epithelium, which can cause bleeding. Progression brings about structural changes in the bowel, including narrowing, shortening, and thickening due to muscular hypertrophy and fat deposition. Unlike Crohn's disease, ulcerative colitis usually does not cause abscesses, fistulas, obstruction, or fissures.

Clinical Manifestations

Symptoms of ulcerative colitis include diarrhea with mucus, pus, or blood, left lower quadrant abdominal pain, intermittent tenesmus, and signs of systemic involvement like anorexia, weight loss, fever, vomiting, dehydration, and the occurrence of six or more liquid stools daily. Complications include hypoalbuminemia, electrolyte imbalances, and anemia, along with possible extraintestinal symptoms such as skin, eye, joint, and liver abnormalities.

Complications

Ulcerative colitis can lead to complications like toxic megacolon, perforation, and bleeding. Toxic megacolon involves inflammation that impairs the colon's ability to contract, causing distention. Perforation, a result of severe inflammation and ulcer formation, can lead to peritonitis. Bleeding is a direct consequence of ulceration and inflammation.