This anatomical diagram illustrates a longitudinal cross-section of the human rectum and anal canal, emphasizing spatial dimensions and clinical landmarks relevant for transrectal procedures. The illustration identifies the rectum ampulla as the proximal, dilated portion, transitioning distally toward the anal canal. Key muscular structures labeled include the internal sphincter and external sphincter. A horizontal scale at the top provides anatomical distance markers: 0 cm at the anal opening, 2.5-3 cm at the anal canal, 5-6 cm at the sphincter level, 11-13 cm at the mid-rectum, and 15-17 cm at the proximal rectal boundary. Vertical arrows also indicate the anal canal depth (2.5-3 cm). The diagram highlights the mucosal surface texture and the relative narrowness of the anal canal compared to the wider rectal ampulla, providing critical orientation for the insertion of diagnostic tools such as transrectal ultrasound (TRUS) probes used in prostate biopsies.

This medical illustration depicts a coronal cross-section of the rectum and anal canal, demonstrating the anatomical landmarks and surgical technique for a Transanal Hemorrhoidal Dearterialization (THD) 'Anolift' procedure. The diagram highlights the internal and external anal sphincters, the rectal mucosa, and key vascular structures including the Superior Rectal Artery (S.R.A.) and Middle Rectal Artery (M.R.A.). On the right side of the illustration, a hemorrhoidal prolapse is shown being addressed with a surgical suture. The suture is anchored superiorly with a locking button and continues as a running plication through the mucosa and submucosa, stopping proximal to the dentate line. This visualizes the mechanism of mucopexy, where the prolapsed tissue is lifted and repositioned proximally by tightening the suture to create a concertina effect on the rectal wall. A scale marker of 1 cm is provided near the anal transition zone for spatial orientation. This diagram is intended for surgical education regarding the management of Grade III and IV internal hemorrhoids.

This composite educational image features a Comparison Chart and Diagnostic Image set correlating perianal anatomy with radiological findings. On the left, a coronal anatomical diagram of the rectum and anal canal illustrates two fistulous tracts originating from a shared internal orifice in the rectal wall. One tract demonstrates an extrasphincteric path, while the other shows the placement of a surgical seton. The diagram highlights key landmarks including the internal and external anal sphincters, the levator ani muscle, and the dentate line. Horizontal reference lines extend from different anatomical levels of the schematic to a series of six axial CT scans (labeled as MRI in context) on the right. These cross-sectional diagnostic images display the pelvic floor, rectal lumen, and surrounding soft tissues at sequential heights, facilitating a 3D understanding of the fistula's complex trajectory relative to the pelvic musculature. This material is designed for advanced medical education in colorectal surgery and radiology, focusing on the diagnosis and management of complex anal fistulas.

This composite educational image illustrates a surgical technique for rectal cancer resection, specifically focusing on the eversion and stapling of the rectal stump. Panel A provides a schematic diagram showing the eversion of the rectum through the anal canal, with a tumor located on the mucosal surface. Panel B presents a sagittal cross-section anatomical illustration of the male pelvis, depicting the distal rectum pulled through the perineum. A linear stapler is shown positioned to provide a safe distal clearance margin from the tumor, while preserving pelvic structures like the bladder and prostate. Panel C is an intraoperative clinical photograph demonstrating the real-world application of the technique. It shows a dark red, fleshy, and irregular tissue mass—the everted rectal stump containing the tumor—protruding from the perianal region. The image series demonstrates key steps in a modified pull-through procedure aimed at achieving an oncologically safe margin before performing a low colorectal or coloanal anastomosis. This material is designed for surgical education in colorectal oncology and gastrointestinal surgery.

Anatomical diagram in a cross-sectional view illustrating the Transanal Hemorrhoidal Dearterialization (THD) with mucopexy procedure. The schematic is divided into two parts showing the progression of the surgical technique within the rectum and anal canal. The left side depicts a longitudinal continuous suture line being applied to the rectal mucosa and submucosa, targeting a prolapsed hemorrhoidal pile. The suture starts approximately 4-5 cm above the anal verge. The right side illustrates the effect of tying the suture, showing the clinical result where the redundant rectal tissue is plicated and lifted proximally (mucopexy), reducing the prolapse and repositioning the tissue within the distal rectum. Key anatomical features visible include the internal and external anal sphincters, the dentate line, and the rectal wall layers. This diagram serves as a surgical guide for colorectal residents and surgeons to visualize the lifting of pathologic piles during hemorrhoidal dearterialization.

**Imaging Modality:** Medical illustration/Anatomical diagram. **Anatomical Region:** Coronal cross-section of the anorectal region, including the anal canal, rectum, internal and external anal sphincters, and surrounding perianal soft tissues. **Observed Pathology:** The illustration classifies various types of anorectal fistulas and abscesses based on their anatomical trajectory and location. **Characteristic Visual Features:** * **Fistula Tracts:** Three distinct epithelial-lined tracks are labeled. A **superficial fistula** is shown confined to the perianal skin and distal anal canal. A **transsphincteric fistula** is depicted crossing both the internal and external sphincter muscles into the ischioanal fossa. A **suprasphincteric fistula** is illustrated looping above the puborectalis muscle before descending to the skin surface. * **Abscess Formations:** Two localized collections of fluid/pus are identified. An **intersphincteric abscess** is positioned within the space between the internal and external sphincter muscles. A **perineal (perianal) abscess** is shown as a larger pocket located in the subcutaneous tissue adjacent to the anal verge. **Key Diagnostic Features:** The diagram emphasizes the relationship between inflammatory tracts and the sphincter complex, following the Parks classification system for fistula-in-ano. Suitable for clinical education on perianal sepsis and surgical planning.

This diagnostic image is an axial T2-weighted magnetic resonance imaging (MRI) scan of the human pelvic region, specifically focusing on the pelvic floor anatomy. The image demonstrates a significant soft tissue mass representing a tumor, likely rhabdomyosarcoma, which has extensively infiltrated the pelvic musculature. Key findings include the replacement of the normal hypointense signal of the puborectalis muscle with a heterogeneous, hyperintense tumor signal. Furthermore, there is clear bilateral involvement of the levator ani muscles (indicated by the white arrow), leading to a marked loss of normal muscle morphology and anatomical symmetry. The mass is positioned centrally within the posterior pelvic floor, compressing adjacent structures. This image is clinically significant for staging pelvic soft tissue sarcomas and evaluating the invasion of the anal sphincter complex and levator ani, which are critical for determining surgical resectability and treatment planning in oncology.

This diagnostic imaging set consists of two T2-weighted turbo spin-echo (TSE) MRI scans of the pelvic floor, demonstrating normal rectal and perianal anatomy. Image 7a is a coronal view illustrating the spatial relationship between the levator ani muscle (EAM), visible as a low-signal intensity band extending laterally and superiorly, and the puborectalis muscle (PRM) forming a muscular sling around the anal canal. The ischio-rectal fossa (IRF) is identified as a hyperintense region of fat lateral to the sphincter complex. The anal canal (ANUS) is shown in the midline. Image 7b is a sagittal view providing a longitudinal perspective of the levator ani muscle (EAM), appearing as a hypointense linear structure supporting the pelvic viscera. These images serve as an educational reference for identifying normal pelvic floor musculature, including the internal and external anal sphincters, and are critical for the staging and preoperative planning of rectal carcinomas and pelvic floor disorders.

This composite educational image illustrates the pelvic floor and anal canal anatomy and its clinical relevance in rectal cancer staging. Panel (a) is an anatomical diagram depicting the coronal view of the anal canal, highlighting the levator ani, puborectalis muscle, external sphincter, and internal sphincter, with a dashed line marking the intersphincteric plane. Panel (b) is a coronal T2-weighted MRI showing a cT3a rectal tumor in a male patient. An arrow indicates irregular wall thickening with minimal (±1 mm) perirectal extension invading the right internal anal sphincter. Panel (c) is a coronal T2-weighted MRI of a female patient with a cT4b rectal tumor. The tumor (outlined by a dashed line) shows extensive infiltration, invading both internal sphincters and extending into the external sphincter, levator ani, and puborectalis muscles on the left side. Muscles and sphincters appear characteristically hypointense on T2 imaging, while the tumor presents as an intermediate-signal mass disrupting normal anatomical boundaries, essential for determining surgical management such as abdominoperineal resection.