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Objective:
The purpose of this retrospective review is to better understand the frequency with which patients with anorectal malignancy undergo imaging in the STAT or emergency setting, as well as to classify and characterize the relevant imaging findings.

Materials and Methods:
The picture archiving and communication system (PACS) of a large tertiary medical system was queried over a 7-year period for patients who had undergone locoregional staging of anorectal cancer with MRI. Subsequently, such patients who had also undergone STAT or emergent imaging at any time since diagnosis were included in this review. Emergency room (ER) visits without imaging performed were excluded. This resulted in a total of 179 patients with a total number of 391 imaging studies. These were further subdivided into i) imaging at presentation and ii) imaging in patients with known and/or treated malignancy. Finally, the imaging diagnosis was then characterized for each subset as i) being secondary to the primary neoplasm itself, ii) complications related to metastatic disease/malignancy in general, or iii) effects attributable to treatment (radiation, chemotherapy, surgical complications, etc.).

Results:
A total of 179 patients with anorectal malignancy (age range 34-94 years, Male:Female ratio of 1.2:1) underwent a total of 391 emergent imaging/ED visits. Of these, 89 visits (23%) were ultimately positive for findings related to an underlying anorectal malignancy. There were 12 patients who presented emergently without known disease (7%). The most common indication for imaging at the time of a new diagnosis was related to local symptoms secondary to the primary neoplasm itself (e.g., rectal bleeding, local perforation). Only a single instance of presentation due to pain related to metastatic disease (vertebral body compression fracture) was found. Of the imaging performed in patients with a known history of malignancy, a large majority (53/77, 69%) of the positive cases had findings related to treatment complication (typically postoperative obstruction or abscess). These were followed by studies showing worsening local tumor burden (26%). Emergency presentation of complications related to metastatic disease itself was relatively uncommon.

Conclusion:
Patients presenting with undiagnosed or diagnosed anorectal cancer as well as those having undergone treatment may undergo emergent imaging for complications related to the primary tumor, metastatic disease, or relevant surgical/chemoradiation regimens. Interestingly, a relatively small percentage of this cohort presented emergently with undiagnosed malignancy, potentially reflecting success of routine screening methods. Treatment-related complications were among the most common reasons for emergent imaging in these patients. These findings suggest that radiologists who specialize in emergency imaging must be familiar with the classic presentations of anorectal malignancy as well as the most common complications related to management.