Although IV contrast can help define and characterize postoperative fluid collections, in patients with severe renal insufficiency CT without IV contrast, but with positive oral Acute Nonlocalized Abdominal Pain contrast, it can be used as a substitute to screen for fluid collections and anastomotic leaks. Similarly, in patients with recent renal or liver transplantation in whom IV contrast cannot be administered, CT with oral contrast can be used to evaluate for intra-abdominal abscesses. CT with and without IV contrast typically is not necessary for this indication. Contraindications are not considered in the appropriateness assessment. MRI Abdomen and Pelvis There are no recent studies evaluating the use of MRI in the setting of nonlocalized abdominal pain and fever in the postoperative patient. CT is most commonly performed; however, MRI can be an accurate examination for detecting abdominal and pelvic abscesses when the image acquisition is optimized [35]. Although not specifically performed in postoperative patients, a retrospective review of 29 patients with known abscesses who underwent MRI admixed with 29 patients with simple noninfected ascites, MRI demonstrated 100% accuracy for 2 observers in the detection of abdominal abscesses in examinations performed with standard T2-weighted and postcontrast T1-weighted sequences. Interestingly, there were similar sensitivities for 2 observers when the images were reviewed with only T2-weighted and diffusion-weighted imaging (100% for observer 1, and 96.6% for observer 2), demonstrating the feasibility to detect and discriminate infected from noninfected fluid on noncontrast MRI [38]. In addition to appendicitis detection, in the retrospective study by Singh et al [37], the authors were able to detect 5 abscesses (2 tubo-ovarian abscesses) in female patients who underwent MRI presenting with acute pelvic pain.
Acute Nonlocalized Abdominal Pain. Although IV contrast can help define and characterize postoperative fluid collections, in patients with severe renal insufficiency CT without IV contrast, but with positive oral Acute Nonlocalized Abdominal Pain contrast, it can be used as a substitute to screen for fluid collections and anastomotic leaks. Similarly, in patients with recent renal or liver transplantation in whom IV contrast cannot be administered, CT with oral contrast can be used to evaluate for intra-abdominal abscesses. CT with and without IV contrast typically is not necessary for this indication. Contraindications are not considered in the appropriateness assessment. MRI Abdomen and Pelvis There are no recent studies evaluating the use of MRI in the setting of nonlocalized abdominal pain and fever in the postoperative patient. CT is most commonly performed; however, MRI can be an accurate examination for detecting abdominal and pelvic abscesses when the image acquisition is optimized [35]. Although not specifically performed in postoperative patients, a retrospective review of 29 patients with known abscesses who underwent MRI admixed with 29 patients with simple noninfected ascites, MRI demonstrated 100% accuracy for 2 observers in the detection of abdominal abscesses in examinations performed with standard T2-weighted and postcontrast T1-weighted sequences. Interestingly, there were similar sensitivities for 2 observers when the images were reviewed with only T2-weighted and diffusion-weighted imaging (100% for observer 1, and 96.6% for observer 2), demonstrating the feasibility to detect and discriminate infected from noninfected fluid on noncontrast MRI [38]. In addition to appendicitis detection, in the retrospective study by Singh et al [37], the authors were able to detect 5 abscesses (2 tubo-ovarian abscesses) in female patients who underwent MRI presenting with acute pelvic pain.