Crohn’s Disease

Radiology

Fluoroscopy is the study of choice for evaluation of luminal contour and mucosal integrity of the small bowel. Fluoroscopic findings in Crohn’s disease can be divided into two stages, early and late. Early findings represent active inflammation, while late findings represent chronic inflammation and/or fibrosis.

Early fluoroscopic findings include:

Mucosal ulcers (punctate collections of barium surrounded by radiolucent mounds of edema) are best demonstrated on double contrast studies

Luminal narrowing from edema, spasm

Fold thickening or “thumbprinting”

Late/chronic fluoroscopic findings include:

Deeper, larger, linear ulcers (most frequently in terminal ileum)

Strictures, manifest by the “string sign”

Fistulas

CT augments fluoroscopy by assessing for bowel wall and extraintestinal involvement, as well as allowing for therapeutic percutaneous drainage of abscesses. CT will demonstrate transmural spread of inflammation, with findings such as bowel wall thickening, mesenteric stranding, adenopathy, and abscesses. CT also helps evaluate for malignancy.

Plain films are most often acquired in the acute setting to evaluate for obstruction or free air. They may identify extraintestinal abnormalities, such as nephrolithiasis or sacroileitis.

Ultrasound is an alternative to CT for patients that cannot tolerate contrast material. Sonographically , the normal intestinal wall is comprised of 5 concentric layers, alternating between echogenic and hypoechoic (“gut signature”). Sonographic findings in Crohn’s disease entail the distortion or destruction of these layers.  Similar to CT, ultrasound can also detect extraintestinal manifestations, such as abscesses. Real-time imaging allows for the evaluation of gut peristalsis, and Doppler imaging often demonstrates increased blood flow associated with active inflammation.

Nuclear medicine is also used on occasion to evaluate Crohn’s disease. Tagged WBC scans (technetium-99m-HMPAO, indium-111) can assess for active inflammation.