This composite educational image illustrates a case of an intersphincteric anorectal abscess through multi-modal diagnostic views. The panel includes original MRI scans and corresponding color-coded 3D reconstructions across axial (a, b), sagittal (c, d), and coronal (e, f) planes. The MRI images demonstrate the complex anatomy of the perianal region with the abscess appearing as a localized, high-signal intensity lesion on T2-weighted imaging. In the 3D models, the red structure represents the abscess, highlighting its spatial relationship to the anal canal, internal and external sphincters (represented by concentric green and yellow layers), and the levator ani muscle. Panel (g) provides a clinical photograph of the preoperative perianal region, and panel (h) displays a detailed 3D modeling view. This visual aid is designed to teach colorectal surgeons and radiologists the volumetric assessment and anatomical mapping of perianal fistulas and abscesses, emphasizing the value of 3D reconstruction in clarifying tissue demarcations that may be obscured in standard 2D grayscale radiology.

This composite diagnostic image demonstrates computerized tomography (CT) segmentation techniques for identifying a perianal abscess. Image (a) is an axial (transverse) CT slice of the pelvic and upper thigh region, showing high-density (white) femoral and pelvic bone structures, lower-density soft tissues, and the anal canal area where a perianal lesion is located. Images (b) and (c) present the results of automated lesion extraction using different machine learning models. Subfigure (b) shows the segmentation output of a standard Convolutional Neural Network (CNN), which identifies the abscess as scattered, less-defined white pixels against a masked dark background. Subfigure (c) demonstrates the result of a Deep Learning Fusion Convolutional Neural Network (DLFCNN) algorithm, showing a more precise and localized segmentation of the abscess tissue with reduced noise and clearer borders compared to the standard CNN. This comparison illustrates the clinical application of deep learning in radiology for the accurate classification and boundary delineation of soft tissue infections in the perianal region.

This diagnostic image is an axial MRI of the male pelvic region, showing the anatomy at the level of the anal canal and ischioanal fossa. The scan reveals a post-procedural state following the drainage of a complex perianal abscess. A red arrow points to a hypointense, linear tubular structure representing a percutaneous drain coursing through the right ischioanal fossa toward the central perianal area. The surrounding tissue shows a reduction in high-signal inflammatory fluid compared to a pre-drainage state, indicating abscess involution. Key visible structures include the central anal canal, the prostate gland located anteriorly, the external genitalia, and the bilateral gluteus maximus muscles and ischioanal fat. The image demonstrates the clinical application of interventional radiology in managing pelvic infections and the use of MRI for monitoring treatment response in complex fistulating disease.

This diagnostic image displays two panels of transrectal endoscopic ultrasonography (TRUS) alongside corresponding endoscopic views. The TRUS images provide a cross-sectional view of the perianal and rectal anatomy. Key features include the internal anal sphincter (IAS), which is visualized as a continuous circular band with a measured thickness of approximately 2.2 mm. In the right posterior-lateral quadrant, a well-defined pathological lesion measuring approximately 30 mm x 15 mm is evident. This structure is predominantly hypoechoic, indicating fluid or soft tissue, and contains internal hyperechoic foci suggestive of gas bubbles—features characteristic of a perianal abscess with gas-forming components. The adjacent rectal mucosa appears normal in the integrated endoscopic inset. This imaging is clinically significant for evaluating the depth, extent, and specific echogenic characteristics of perianal inflammatory conditions or abscesses relative to the sphincteric complex.