Annals of Coloproctology

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Original Article

Anorectal benign disease

New anatomical insight into the muscular structure of the anal canal: revealing Treitz muscle as a directional shift of the internal anal sphincter: Satoru Muro, Kumiko Yamaguchi, Naoko Inoshita, Yasuo Nakajima, Danyo Jennifer Edinam, Akimoto Nimura, Keiichi Akita; Ann Coloproctol. 2025;41(6):501-509. Published online December 29, 2025; DOI: https://doi.org/10.3393/ac.2024.00647.0092

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Purpose
Understanding the muscular structure of the anal canal is crucial for the diagnosis and treatment of anorectal diseases. Treitz muscle is a vital yet poorly understood component. It supports the anal venous plexus and contributes to anal cushion formation. However, its anatomical details remain unclear, and various theories suggest different origins for its muscle bundles, which affects our understanding of the pathophysiology of hemorrhoids. In this study, we sought to clarify the origin and localization of Treitz muscle to provide an anatomical foundation for understanding anal function.
Methods
In this descriptive cadaveric study of 11 cadavers, we performed macroscopic examinations and immunohistological analyses on tissues from the anterior, lateral, and posterior walls of the anal canal. The origin and localization of Treitz muscle were qualitatively evaluated.
Results
Treitz muscle is a smooth muscle formed by a directional change in the muscle bundles of the internal anal sphincter, running longitudinally along its surface. A shift in the direction of muscle bundles originating from the internal anal sphincter, giving rise to Treitz muscle, was frequently observed in the anterolateral wall of the anal canal.
Conclusion
In summary, Treitz muscle, a smooth muscle extending from the internal anal sphincter, is considered part of the muscularis propria. Its directional shift was localized to the anterolateral wall, indicating that Treitz muscle is not uniformly distributed around the anal canal. This site-specific localization may influence the risk of hemorrhoids or cancer invasion depending on its anatomical position.

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Histological architecture of the intersphincteric region of the anal canal: implications for the anatomical basis of anal fistula pathways
Satoru Muro, Yasuo Nakajima, Akimoto Nimura, Keiichi Akita
International Journal of Colorectal Disease.2026;[Epub] CrossRef

Review

Anorectal benign disease

Pharmacotherapy for fecal incontinence: potential treatment with a traditional Japanese medicine Kampo: Kotaro Maeda, Toshinobu Sasaki, Tomohisa Hattori; Ann Coloproctol. 2025;41(5):369-378. Published online October 23, 2025; DOI: https://doi.org/10.3393/ac.2025.00283.0040

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Abstract PDF: Fecal incontinence (FI) significantly impairs patient quality of life and creates substantial distress not only for affected individuals but also for nurses and caregivers. The prevalence of FI among older adults is estimated at up to 20%, although the sensitive nature of the condition often prevents active reporting by patients. This article reviews risk factors and pharmacotherapies for FI, emphasizing the therapeutic potential of Daikenchuto (DKT). The etiology of FI is multifactorial and lacks a singular definition. Currently, no prescription drugs specifically approved for FI are available, leaving treatment options limited. Nonetheless, major clinical guidelines have identified several viable pharmacological approaches. Strongly recommended treatments include the antidiarrheal agent loperamide and stool bulking or solidifying agents, such as dietary fiber and polycarbophil. Other therapeutic options include ramosetron, a 5-HT3 receptor antagonist; amitriptyline, a tricyclic antidepressant; and sodium valproate and diazepam, which are GABAergic neuromodulators. Recently, research has explored the efficacy and mechanism of action of DKT, a traditional Japanese medicine Kampo. Historically used for abdominal symptoms like bloating and known for promoting intestinal motility, emerging evidence suggests DKT may also effectively manage FI.

Original Articles

Anorectal benign disease

Validation of a novel imaging-guided and anatomy-based classification system for anorectal fistulas: a retrospective clinical evaluation study: Antonio Brillantino, Francesca Iacobellis, Luigi Marano, Adolfo Renzi, Pasquale Talento, Luigi Brusciano, Claudio Gambardella, Umberto Favetta, Michele Schiano Di Visconte, Luigi Monaco, Maurizio Grillo, Mauro Natale Maglio, Fabrizio Foroni, Alessio Palumbo, Maria Laura Sandoval Sotelo, Luciano Vicenzo, Elisa Palladino, Giovanna Frezza, Maria Paola Menna, Paolino Mauro, Stefano Picardi, Mario Massimo Mensorio, Vinicio Mosca, Vincenzo Bottino, Giovanna Ioia, Corrado Rispoli, Marco Di Serafino, Martina Caruso, Roberto Ronza, Barbara Frittoli, Daria Schettini, Luca Stoppino, Franco Iafrate, Giulio Lombardi, Carmine Antropoli, Salvatore Cappabianca, Ludovico Docimo, Roberto Grassi, Alfonso Reginelli; Ann Coloproctol. 2025;41(3):207-220. Published online June 16, 2025; DOI: https://doi.org/10.3393/ac.2024.00675.0096

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Graphical Abstract Abstract PDF

Purpose
This study was conducted to evaluate the validity of a new imaging-guided, anatomy-based classification of anorectal fistulas in defining disease severity and predicting surgical outcomes.
Methods
This multicenter, retrospective cohort study analyzed data from patients with perianal fistulas who underwent surgery between 2017 and 2023. All patients underwent preoperative 3-dimensional endoanal ultrasound, with adjunctive magnetic resonance imaging performed if ultrasound indicated a complex fistula. Imaging examinations were retrospectively evaluated to categorize fistulas according to the Garg classification and the newly proposed classification system. The new classification included 6 severity grades based on the characteristics of the primary tract: submucosal, intersphincteric, low transsphincteric, high transsphincteric, multiple, and suprasphincteric/extrasphincteric. Each grade was further subdivided into 3 subtypes (A, B, C) based on the extension of secondary tracts.
Results
When compared with the new classification, the Garg classification demonstrated a slightly lower ability to predict the feasibility of fistulotomy in simple fistulas (94.2% vs 99.1%; Fisher exact test, P=0.006). A strong positive correlation was found between the surgery failure rate and the severity grade of the new classification (Spearman rho, 0.90; P<0.001), whereas the Garg classification showed a nonsignificant positive correlation with surgical failure rate (Spearman rho, 0.90; P=0.08).
Conclusion
The new imaging-guided, anatomy-based classification of anorectal fistulas demonstrates high accuracy in defining disease severity. It represents a valuable tool for preoperative grading of anal fistulas, standardizing the reporting of diagnostic imaging, and improving the communication of findings among healthcare professionals.

Citations

Citations to this article as recorded by

Comparison of the proposed new classification of anal fistulas with the Garg classification
Pankaj Garg, Nicola Clemente, Kaushik Bhattacharya, Sattyadeep Garg
Annals of Coloproctology.2026; 42(1): 145. CrossRef
Histological architecture of the intersphincteric region of the anal canal: implications for the anatomical basis of anal fistula pathways
Satoru Muro, Yasuo Nakajima, Akimoto Nimura, Keiichi Akita
International Journal of Colorectal Disease.2026;[Epub] CrossRef

Anorectal benign disease

Ligation of the intersphincteric fistula tract (LIFT) for high transsphincteric fistulas: a double-center retrospective study with long-term follow-up: Leichang Zhang, Chuanyu Zhan, Lu Li, Wanjin Shao, Guidong Sun, Yugen Chen, Guanghua Chen, Yulei Lang, Zenghua Xiao, Xiao Xiao; Ann Coloproctol. 2025;41(1):77-83. Published online January 17, 2025; DOI: https://doi.org/10.3393/ac.2024.00024.0003

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5 Citations

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