Imaging is used in suspected cases of anorectal abscess and/or fistula to confirm the diagnosis, assist in surgical planning, predict surgical outcome, assess for recurrent or residual disease, and monitor medical therapy in patients with CD [10]. CT Pelvis The appropriate CT protocol for imaging a patient with an anorectal complaint depends upon the presentation and differential diagnosis. Intravenous (IV) contrast is preferred to a noncontrast examination to help visualize and characterize fluid collections, abscesses, and fistulous tracts. Water-soluble rectal contrast is generally not necessary to diagnose a rectal abscess and may be challenging to administer depending on symptom severity. However, rectal contrast may help delineate perforation or leak in a patient with a history of trauma or recent surgery. Water-soluble rectal contrast is preferred over barium to avoid the possibility of barium spilling into the peritoneal cavity or spaces of the extraperitoneal pelvis. Water-soluble rectal contrast is also preferred in a patient who could potentially be undergoing surgery. CT is commonly used in the acute setting to evaluate for anorectal abscess. The inherent lack of contrast resolution of CT limits the differentiation of subtle attenuation changes to differentiate small abscesses and fistulae from the anal sphincter complex and the soft tissue of the pelvic floor. To our knowledge, there is no recent literature evaluating the accuracy of modern CT technology for the detection of anorectal abscesses and there are no studies comparing IV contrast-enhanced scans to scans obtained without IV contrast. CT with and without IV contrast would only be useful when there is benefit from dual-phase imaging (eg, gastrointestinal bleeding). However, IV contrast is important to delineate rim-enhancement of fluid collections to aid in the diagnosis of abscess. The reported sensitivity of CT for anorectal abscess is 77% [11].
Anorectal Disease. Imaging is used in suspected cases of anorectal abscess and/or fistula to confirm the diagnosis, assist in surgical planning, predict surgical outcome, assess for recurrent or residual disease, and monitor medical therapy in patients with CD [10]. CT Pelvis The appropriate CT protocol for imaging a patient with an anorectal complaint depends upon the presentation and differential diagnosis. Intravenous (IV) contrast is preferred to a noncontrast examination to help visualize and characterize fluid collections, abscesses, and fistulous tracts. Water-soluble rectal contrast is generally not necessary to diagnose a rectal abscess and may be challenging to administer depending on symptom severity. However, rectal contrast may help delineate perforation or leak in a patient with a history of trauma or recent surgery. Water-soluble rectal contrast is preferred over barium to avoid the possibility of barium spilling into the peritoneal cavity or spaces of the extraperitoneal pelvis. Water-soluble rectal contrast is also preferred in a patient who could potentially be undergoing surgery. CT is commonly used in the acute setting to evaluate for anorectal abscess. The inherent lack of contrast resolution of CT limits the differentiation of subtle attenuation changes to differentiate small abscesses and fistulae from the anal sphincter complex and the soft tissue of the pelvic floor. To our knowledge, there is no recent literature evaluating the accuracy of modern CT technology for the detection of anorectal abscesses and there are no studies comparing IV contrast-enhanced scans to scans obtained without IV contrast. CT with and without IV contrast would only be useful when there is benefit from dual-phase imaging (eg, gastrointestinal bleeding). However, IV contrast is important to delineate rim-enhancement of fluid collections to aid in the diagnosis of abscess. The reported sensitivity of CT for anorectal abscess is 77% [11].