Rectosigmoid junction

The rectosigmoid junction, formerly the rectosigmoid sphincter or sphincter of O'Beirne, is the junction of the sigmoid colon and the rectum.

Hypothesized sphincter

The rectosigmoid sphincter, also known as the sphincter of O'Beirne, was hypothesized as an anatomical structure located between the sigmoid colon and rectum. The structure was first proposed by the 19th-century Irish surgeon James O'Beirne. Its existence, structure and function has been a matter of long-standing medical controversy. The Latin names sphincter ani tertius and pylorus sigmoidrectalis also been used.

As of 2025, the existence of some form of distinct contractile anatomical structure at the rectosigmoid junction, if not an actual sphincter, in many people is acknowledged in numerous articles in the medical literature.

The junction is made up of circular and longitudinal muscle fascia. Like many of our other digestive system’s sphincters: Upper esophageal sphincter (UES) , pyloric sphincter , sphincter of Oddi; this junction may have a high-pressure zone mimicking our digestive systems’ sphincter-like functions .The RSJ may also play a role in regulating stool passage by increasing rectal pressure and thereby preventing premature reflux of rectal contents back into the sigmoid colon. However, this functional role of the rectosigmoid junction is yet to be considered as a distinct anatomical sphincter.

Molecular signature of rectosigmoid junction cancer

A 2023 study suggested that cancers of the rectosigmoid junction exhibit different chemical signatures from either cancers of the colon or cancers of the rectum.

Clinical Significance

The junction is important in clinical practices, especially in the classification and management of colorectal diseases and colorectal cancer. Due to its variable definition of sigmoid and rectal pathology of whether to classify tumors in this region as colorectal cancer or rectal cancer, it may complicate diagnostic approaches and treatments in cancer .

The taenia coli of the colon spreads out to form a continuous longitudinal muscle layer around the rectum, approximately 12-15 cm from the anal verge.

Research indicates that RSJ cancers can have a higher propensity for synchronous liver metastasis and lymphovascular invasion when compared to tumors in the sigmoid or upper rectum.

In a retrospective cohort study, the five-year survival rate for patients with carcinomas as the RSJ was significantly lower than that of patients with tumors in the sigmoid colon or upper rectum. However, other large-scale registry data show that when adjusted for comorbidities in patients, RSJ and rectal cancers could have slightly better survival chances than proximal colon cancers in specific demographics.

References

  1. 1 2 3 4 Ballantyne, G. H. (August 1986). "Rectosigmoid sphincter of O'Beirne". Diseases of the Colon and Rectum. 29 (8): 525–531. doi:10.1007/BF02562612. ISSN 0012-3706. PMID 3525042.
  2. ↑ Chen, Ji-Hong; Nirmalathasan, Sharjana; Pervez, Maham; Milkova, Natalija; Huizinga, Jan D. (October 2021). "The Sphincter of O'Beirne - Part 1: Study of 18 Normal Subjects". Digestive Diseases and Sciences. 66 (10): 3516–3528. doi:10.1007/s10620-020-06657-w. ISSN 1573-2568. PMID 33462748.
  3. 1 2 Steele, Scott R.; Hull, Tracy L.; Hyman, Neil; Maykel, Justin A.; Read, Thomas E.; Whitlow, Charles B. (2021-11-20). The ASCRS Textbook of Colon and Rectal Surgery. Springer Nature. p. 18. ISBN 978-3-030-66049-9.
  4. ↑ "sphincter ani tertius". Farlex Partner Medical Dictionary. Retrieved 2025-10-30.
  5. ↑ Trzpis, Monika; Sun, Ge; Chen, Ji-Hong; Huizinga, Jan D.; Broens, Paul (January 2023). "Novel insights into physiological mechanisms underlying fecal continence". American Journal of Physiology. Gastrointestinal and Liver Physiology. 324 (1): G1–G9. doi:10.1152/ajpgi.00313.2021. hdl:11370/f16949ad-100a-4bba-8267-9948d15e0234. ISSN 0193-1857. PMID 36283962.
  6. ↑ Shafik, Ahmed; Mostafa, Randa M.; Shafik, Ali A. (2002). "Electrophysiological study of the rectosigmoid canal: evidence of a rectosigmoid sphincter". Journal of Anatomy. 200 (5): 517–521. doi:10.1046/j.1469-7580.2002.00049.x. ISSN 1469-7580. PMC 1570712. PMID 12090397.
  7. ↑ Shafik, A.; Doss, S.; Asaad, S.; Ali, Y. A. (November 1999). "Rectosigmoid junction: anatomical, histological, and radiological studies with special reference to a sphincteric function". International Journal of Colorectal Disease. 14 (4–5): 237–244. doi:10.1007/s003840050217. ISSN 0179-1958. PMID 10647633.
  8. ↑ Shafik, Ahmed; Asaad, Soheir; Doss, Sameh (March 2003). "Identification of a sphincter at the sigmoidorectal canal in humans: histomorphologic and morphometric studies". Clinical Anatomy. 16 (2): 138–143. doi:10.1002/ca.10054. ISSN 0897-3806. PMID 12589668.
  9. ↑ Shafik, Ahmed; Shafik, Ali A.; Sibai, Olfat El; Ahmed, Ismail; Mostafa, Randa M. (2006-01-01). "Role of the Rectosigmoidal Junction in Fecal Continence: Concept of the Primary Continent Mechanism". Archives of Surgery. 141 (1): 23–26. doi:10.1001/archsurg.141.1.23. ISSN 0004-0010. PMID 16415407. Archived from the original on 2023-06-10.
  10. ↑ Shafik, A. (April 1997). "The hypertonic rectosigmoid junction: description of a new clinicopathologic entity causing constipation". Surgical Laparoscopy & Endoscopy. 7 (2): 116–120. doi:10.1097/00019509-199704000-00009. ISSN 1051-7200. PMID 9109239.
  11. ↑ Massalou, Damien; Moszkowicz, David; Mariage, Daniela; Baqué, Patrick; Camuzard, Olivier; Bronsard, Nicolas (2018-04-01). "Is it possible to give a single definition of the rectosigmoid junction?". Surgical and Radiologic Anatomy. 40 (4): 431–438. doi:10.1007/s00276-017-1954-4. ISSN 1279-8517. PMID 29218384.
  12. ↑ Mittal, Ravinder K. (2011), "Upper Esophageal Sphincter", Motor Function of the Pharynx, Esophagus, and its Sphincters, Morgan & Claypool Life Sciences, retrieved 2026-03-27
  13. ↑ "Pylorus", Wikipedia, 2025-07-06, retrieved 2026-03-27
  14. ↑ Shafik, Ahmed; Mostafa, Randa M.; Shafik, Ali A. (2002). "Electrophysiological study of the rectosigmoid canal: evidence of a rectosigmoid sphincter". Journal of Anatomy. 200 (5): 517–521. doi:10.1046/j.1469-7580.2002.00049.x. ISSN 1469-7580. PMC 1570712. PMID 12090397.
  15. ↑ Ballantyne, G. H. (August 1986). "Rectosigmoid sphincter of O'Beirne". Diseases of the Colon and Rectum. 29 (8): 525–531. doi:10.1007/BF02562612. ISSN 0012-3706. PMID 3525042.
  16. ↑ Zhu, Qiuwei; Zhu, Chenyang; Zhang, Xiaotao; Zhu, Xiaodan; Chen, Zhe; Gu, Dejian; He, Yuange; Jin, Chunhui (2023-06-30). "Comprehension of rectosigmoid junction cancer molecular features by comparison to the rectum or sigmoid colon cancer". Journal of Gastrointestinal Oncology. 14 (3): 1307–1319. doi:10.21037/jgo-23-120. ISSN 2078-6891. PMC 10331759. PMID 37435233.
  17. ↑ D'Souza, Nigel; de Neree tot Babberich, M.P.M; Lord, Amy; Shaw, Annabel; Abulafi, Muti; Tekkis, Paris; Wiggers, Theo; Brown, Gina (September 2018). "The rectosigmoid problem". Surgical Oncology. 27 (3): 521–525. doi:10.1016/j.suronc.2018.06.005. PMID 30217314.
  18. ↑ Wang, Yun Hwa W.; Wiseman, Jeffrey (2026), "Anatomy, Abdomen and Pelvis, Rectum", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30725930, retrieved 2026-04-05
  19. 1 2 Falch, Claudius; Mueller, Sven; Braun, Manuel; Gani, Cihan; Fend, Falko; Koenigsrainer, Alfred; Kirschniak, Andreas (2019-11-01). "Oncological outcome of carcinomas in the rectosigmoid junction compared to the upper rectum or sigmoid colon – A retrospective cohort study". European Journal of Surgical Oncology. 45 (11): 2037–2044. doi:10.1016/j.ejso.2019.06.024. ISSN 0748-7983. PMID 31239157.
  20. ↑ Yu, Shou-Chun; Liao, Kuang-Ming; Chou, Chia-Lin; Tian, Yu-Feng; Wang, Jhi-Joung; Ho, Chung-Han; Shiue, Yow-Ling (2022). "Impact of Tumor Location on Survival in Patients With Colorectal Cancer: A Retrospective Cohort Study Based on Taiwan's Cancer Registry Database". Clinical Medicine Insights. Oncology. 16 11795549221111713. doi:10.1177/11795549221111713. ISSN 1179-5549. PMC 9301104. PMID 35875416.

See also