Clinical Manifestations and Complications

• Abnormalities in the mucosa
• Gross abnormalities and pathology
• Extraintestinal manifestations

Abnormalities in the mucosa

Crohn's disease (CD) evolves from an excessive and persistent inflammatory immune response (likely a response to microflora in the lumen), in which bacteria infiltrate the intestinal epithelium causing inflammation of the full thickness of the bowel.¹

Gross abnormalities and pathology

An overall effect of inflammation of the mucosa is fibrosis that can affect the full thickness of GI tissue and result in loss of functional anatomy of the GI tissue.² Fibrosis is the formation of fibrous tissue as a reparative or reactive inflammatory process, with fibrous tissue being composed of bundles of collagenous white fibers between connective tissue.³ Upon the formation of this fibrous tissue, the barrier between intestinal tissue layers is no longer distinct. This thickening of the mucosa leads to failure of the muscle coat and failure of the nerve plexuses to allow for peristalsis.²

Extraintestinal manifestations

The presence of inflammatory bowel disease (IBD) may stimulate the emergence of other disorders. Extraintestinal complications develop in approximately one-quarter to one-third of patients with IBD and can be divided into 3 categories⁴:

1. Those intimately related to the activity or extent of disease, such as arthritis or iritis.
2. Those independent of the severity of disease, such as sclerosing cholangitis or ankylosing spondylitis.
3. Those that result from inadequate or disordered intestinal function, such as cholelithiasis or nephrolithiasis.

Systemic inflammatory conditions that can appear concurrently with CD are inflammation of the joints, liver, skin, eyes, and hematologic organs (which cause anemia).⁴

References:

1. Shanahan F. Crohn's disease. Lancet. 2002;359:62-69.
2. Cortina G, Lewin K. Pathology of inflammatory bowel diseases: a critical appraisal in diagnosis and management. In: Targar SR, Shanahan F, Karp LC, eds. Inflammatory Bowel Disease: From Bench to Bedside. 2nd ed. New York, NY: Springer; 2005:337-356.
3. Stedman's Medical Dictionary. 27th ed. Philadelphia, PA: Lippincott, Williams, and Wilkins; 2000.
4. Fitzgerald E. Radiologic (radiographic) and imaging features of ulcerative colitis and Crohn's disease. In: Targar SR, Shanahan F, Karp LC, eds. Inflammatory Bowel Disease: From Bench to Bedside. 2nd ed. New York, NY: Springer; 2005:371-408.
5. Sartor RB, Lichman SN. Mechanisms of systemic inflammation associated with intestinal injury. In: Targar SR, Shanahan F, Karp LC, eds. Inflammatory Bowel Disease: From Bench to Bedside. 2nd ed. New York, NY: Springer; 2005:305-335.