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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Abstract PDF: 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.

Review

Benign proctology

A systematic review of translation and experimental studies on internal anal sphincter for fecal incontinence: Minsung Kim, Bo-Young Oh, Ji-Seon Lee, Dogeon Yoon, Wook Chun, Il Tae Son; Ann Coloproctol. 2022;38(3):183-196. Published online June 9, 2022; DOI: https://doi.org/10.3393/ac.2022.00276.0039

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6 Citations

Abstract PDF

The complexity in the molecular mechanism of the internal anal sphincter (IAS) limits preclinical or clinical outcomes of fecal incontinence (FI) treatment. So far, there are no systematic reviews of IAS translation and experimental studies that have been reported. This systematic review aims to provide a comprehensive understanding of IAS critical role in FI. Previous studies revealed the key pathway for basal tone and relaxation of IAS in different properties as follows; calcium, Rho-associated, coiled-coil containing serine/threonine kinase, aging-associated IAS dysfunction, oxidative stress, renin-angiotensin-aldosterone, cyclooxygenase, and inhibitory neurotransmitters. Previous studies have reported improved functional outcomes of cellular treatment for regeneration of dysfunctional IAS, using various stem cells, but did not demonstrate the interrelationship between those results and basal tone or relaxation-related molecular pathway of IAS. Furthermore, these results have lower specificity for IAS-incontinence due to the included external anal sphincter or nerve injury regardless of the cell type. An acellular approach using bioengineered IAS showed a physiologic response of basal tone and relaxation response similar to human IAS. However, in both cellular and acellular approaches, the lack of human IAS data still hampers clinical application. Therefore, the IAS regeneration presents more challenges and warrants more advances.

Citations

Citations to this article as recorded by

A single-center retrospective analysis of endorectal advancement flaps used for the treatment of simple rectovaginal fistulas
Xuexiao Li, Wanjin Shao, Guidong Sun
Scandinavian Journal of Gastroenterology.2025; 60(4): 307. CrossRef
Anal sphincter reconstruction for fecal incontinence: Techniques, outcomes, and future directions
Hai-Liang Li, Hao-Ran Zhang, Yuan Wu, Kai-Qiang He, Tian-Jie Chen, Jing Wang
World Journal of Gastrointestinal Surgery.2025;[Epub] CrossRef
Tissue engineering and regenerative medicine approaches in colorectal surgery
Bigyan B. Mainali, James J. Yoo, Mitchell R. Ladd
Annals of Coloproctology.2024; 40(4): 336. CrossRef
3D spheroids versus 2D-cultured human adipose stem cells to generate smooth muscle cells in an internal anal sphincter-targeting cryoinjured mouse model
Iltae Son, Minsung Kim, Ji-Seon Lee, Dogeon Yoon, You-Rin Kim, Ji Hye Park, Bo-Young Oh, Wook Chun, Sung-Bum Kang
Stem Cell Research & Therapy.2024;[Epub] CrossRef
Differentiation of Adipose-Derived Stem Cells into Smooth Muscle Cells in an Internal Anal Sphincter-Targeting Anal Incontinence Rat Model
Minsung Kim, Bo-Young Oh, Ji-Seon Lee, Dogeon Yoon, You-Rin Kim, Wook Chun, Jong Wan Kim, Il Tae Son
Journal of Clinical Medicine.2023; 12(4): 1632. CrossRef
Improving Efficiency and Accuracy in English Translation Learning: Investigating a Semantic Analysis Correction Algorithm
Lingmei Cao, Junru Fu
Applied Artificial Intelligence.2023;[Epub] CrossRef

Original Articles

Clinical Significance of the Pecten Band in Hemorrhoids.: Lee, Je Seung , Ahn, Byeong Yul , Lee, Han Il; J Korean Soc Coloproctol. 2006;22(1):8-14.

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Abstract PDF: PURPOSE
The pecten band can be defined as a fibrous tissue on the lowermost part of internal anal sphincter and may cause anal outlet obstruction, but its role is debatable. We evaluated the functional roles of the pecten band in hemorrhoids patients.
METHODS
Three hundred sixteen hemorrhoids patients who underwent operations from January 1998 to April 2003 were analyzed for anal function according to presence or absence of a pecten band by using anorectal manometry and the constipation score.
RESULTS
The numbers of males and females were 167 and 149. The overall pecten band positive was 63.6% (201/316), and pecten band positive was 84.6% (33/39) in patients who had previous anal surgery while it was 60.6% (168/277) in patients who had no history of surgery (P= 0.002). Pure hemorrhoids patients showed an 18.3% positive rate while patients with hemorrhoids and other conditions, such as anal fissure, fistula, or stricture, showed a 95.7% positive rate (P=0.00). Maximal resting anal pressures (mmHg, Mean+/-SD) and constipation score were 78.9+/-24.7 and 7.88+/-3.8 in the positive group and 67.1+/-22.2 and 4.55+/-2.8 in the negative group (P=0.00, 0.00). Postoperatively, the constipation score decreased significantly from 7.25 to 2.82 (P=0.003).
CONCLUSIONS
The pecten band seems to be associated with anal outlet obstruction, and a pecten band releasing operation may be considered according to its presence or absence.

Anal Endosonographic Findings of Internal Anal Sphincter in Normal Adult Korean.: Kim, Kyung Jong , Kim, Cheong Yong , Jang, Jeong Hwan , Kim, Kweon Cheon , Min, Young Don; J Korean Soc Coloproctol. 1998;14(2):217-224.

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Abstract PDF: PURPOSE
To describe the appearance and average thickness of the internal anal sphincter with anal endosonography in healthy Korean adults. MATERIAL AND METHODS: 184 subjects(male: 96, female: 88) with no history of anorectal disease or surgery were studied with anal endosonography. The average thickness of internal sphincter was meas ured at the mid-anal canal. For the internal sphincter, which is often asymmetric, the thickness of each 4 part(12, 3, 6 and 9 o'clock direction) were measured in left lateral decubitus position.
RESULTS
The anal wall was well visualized in 5 layers(mucosa, submucosa, internal anal sphincter, intersphincteric plane, external anal sphincter) with anal endosonography. The anal endosonogram showed the internal anal sphincter as a homogenous, well-defined, hypoechoic, circular band, and slightly asymmetric. The average thickness of the internal anal sphincter in the area of mid-anal portion was 2.0 0.3 mm(range: 1~3 mm). There was no sexual difference; however, a significant positive correlation with age was found in average thickness of the internal anal sphincter. The correlation with lean body mass was not found.
CONCLUSION
The internal anal sphincter is well-visualized, best defined structure by anal endosonography. Average thickeness of the sphincter in Korean appeared to be the same as in the Western.

The Effect of Intraoperative Anal Sphincter Injection of Ketorolac Tromethamine for Pain Control after Hemorrhoidectomy.: Park, Jea Kun , Kim, Nam Kyu , Sohn, Seung Kook , Min, Jin Sik; J Korean Soc Coloproctol. 2000;16(5):296-301.

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Abstract PDF: PURPOSE
An adequate pain control is one of important factors for obtaining good outcomes in the ambulatory basis of hemorrhoidectomy. There have been many methods for pain control after hemorrhoidectomy such as narcotics, various kinds of analgesics, etc. The aim of this study is to compare intraoperative internal anal sphincter injection of Ketorolac tromethamine and other two conventional methods for pain control.
METHODS
A total of 56 patients with hemorrhoid grade III or IV underwent surgery between May and October 1999, and prospectively assigned to three groups in the consecutive order. The group was divided in Group 1: [Ketorolac tromethamine (Tarasyn) 60 mg intrasphincteric injection intraoperatively and 30 mg IM/prn?10 mg po/6hrs], Group 2: [No intraoperative injection and maintain pain control with Tarasyn 30 mg IM/prn/10 mg po/6hrs], and Group 3: [No intraoperative injection and maintain pain control with Pethidine (Demerol) 50 mg IM/prn and Ibuprofen 400 mg/Paracetamol 500 mg/Codeine 20 mg (Myprodol) po/8hrs]. The post operative data and pain scoring was performed on the questionnaire with Point box scale (BS-11) and Behavioral rating scale (BRS-6) each 24 hours during 5 days after surgery.
RESULTS
There are 22 patients in the Group 1, 16 in the Group 2 and 18 patients in the Group 3. The median age of the Group 1 is 42.5, Group 2, 44.5 and Group 3, 45 years. The pain score on the first day after surgery in group 1 was significantly lower than group 2 (p<0.05) in the both pain scoring scale but was no differences between group 1 and 3. On the fifth day after surgery group 3 was significantly lower than both group 1 and 2 in the point box scale (p<0.05). The urinary retention rate and the day of first bowel movement after surgery show no differences among three groups (p>0.05).
CONCLUSIONS
Intraoperative internal anal sphincter injection of Ketorolac tromethamine shows a better pain control than conventional methods in early postoperative period. Therefore it might be helpful for patients to go home on the day after surgery, and strong pain killer to control pain after discharge will be needed.

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