Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Endorectal endoscopic ultrasound in the evaluation of fecal incontinence

David A Schwartz, MD
Maurits J Wiersema, MD
Section Editor
Douglas A Howell, MD, FASGE, FACG
Deputy Editor
Kristen M Robson, MD, MBA, FACG


Fecal incontinence is one of the most devastating of all physical disabilities since it affects self-confidence and personal image, and can lead to social isolation. Previously, the evaluation of fecal incontinence was largely limited to anal manometry, electromyography (EMG), and studies of pudendal nerve latency. Although helpful, these tests provide no direct structural evidence of sphincter injury. Imaging of the anal sphincter is helpful in all patients with fecal incontinence to assess the structure and integrity of the sphincters. Newer imaging modalities, such as endorectal ultrasound (which can be performed with a transrectal ultrasound probe or with endoscopic ultrasonography) and MRI, have added to the diagnostic tools available to clinicians for the evaluation of fecal incontinence. Ultrasound imaging of the anal sphincter provides complementary structural information to the functional information that can be obtained with manometry and should be performed in combination with this test. This topic review will focus on the use of endorectal endoscopic ultrasound (EUS) in the evaluation of fecal incontinence. An overview of fecal incontinence is presented separately. (See "Fecal incontinence in adults: Etiology and evaluation".)


The normal ultrasound appearance of the anorectum has been well delineated in several studies performed on normal subjects [1-8]. Two discrete rings of tissue can be seen when using a radial scanning echoendoscope to examine the anorectum (image 1). The inner hypoechoic ring of tissue represents the internal anal sphincter (IAS), which is formed by the thickened continuation of the circular smooth muscle of the rectum. The outer hyperechoic ring of tissue represents the longitudinal muscle and the external anal sphincter (EAS), which is formed by the downward extension of the skeletal muscle of the puborectalis. The normal IAS is between 2 to 3 mm thick [2,5] and the normal EAS is between 7 to 9 mm thick [2,6,9]. The IAS becomes thicker and more hyperechoic with age, probably reflecting collagen replacement of the IAS [5]. Conversely, the EAS tends to become thinner with age [6]. The perineal body is not clearly defined with ultrasound [9,10]. The anal canal length varies from 25 mm for women to 33 mm for men [11].

There is a different configuration of the anterior part of the EAS in men and women [12]. The anterior part of this sphincter seems to be shorter and slopes downward in women. This can make demonstrating a complete 360 degree ring of the EAS in one plane difficult [9]. It is essential to recognize this variation so that one does not incorrectly diagnose an anterior sphincter defect where one does not exist. The anococcygeal ligament appears as a hypoechoic triangular structure posteriorly and can be confused as a sphincter defect in this location.


Before the development of endosonography, electromyography (EMG) was used to assess the integrity of the EAS. However, EMG studies were poorly tolerated since they required insertion of needles directly into the muscle. The first reports on the use of ultrasound to study the anal sphincter came from St. Mark's Hospital in the late 1980s and early 1990s. A study comparing electromyography (EMG) with ultrasound in 15 patients with fecal incontinence showed that endosonography could accurately identify EAS defects [13]. The correlation between EMG and ultrasound was 0.96. In addition, ultrasound was better tolerated. A follow-up study of 45 patients found that ultrasound agreed with EMG assessment of the external sphincter in all patients studied [14]. In a separate study, the same group used endosonography to direct EMG needle placement into the sphincter defect seen on ultrasound [15]. In all of the patients where EMG was technically successful, EMG showed no evidence of electrical activity, thus confirming the accuracy of endosonography. It is largely because of these studies that endosonography has replaced EMG as the investigation of choice to identify sphincter defects.


A number of studies have reported the utility of endosonography in identifying sphincter injuries in patients with fecal incontinence (image 2) [16-33]. Several of these reports have compared the ultrasound findings to the results of surgery (sphincteroplasty). Sensitivity exceeded 90 percent in most reports; specificity is hard to determine from these studies since patients in whom a tear was not strongly suspected may not have been operated on. However, false positive results have been described. The following illustrate the range of findings:

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Aug 22, 2016.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Marzio L, Ciccaglione FA, Falcucci M, et al. Relationship between anal canal diameter and pressure evaluated simultaneously by endosonography and manometry in normal human subjects. Int J Colorectal Dis 1998; 13:21.
  2. Nielsen MB, Hauge C, Rasmussen OO, et al. Anal sphincter size measured by endosonography in healthy volunteers. Effect of age, sex, and parity. Acta Radiol 1992; 33:453.
  3. Nielsen MB. Endosonography of the anal sphincter muscles in healthy volunteers and in patients with defecation disorders. Acta Radiol Suppl 1998; 416:1.
  4. Gantke B, Schäfer A, Enck P, Lübke HJ. Sonographic, manometric, and myographic evaluation of the anal sphincters morphology and function. Dis Colon Rectum 1993; 36:1037.
  5. Burnett SJ, Bartram CI. Endosonographic variations in the normal internal anal sphincter. Int J Colorectal Dis 1991; 6:2.
  6. Papachrysostomou M, Pye SD, Wild SR, Smith AN. Anal endosonography in asymptomatic subjects. Scand J Gastroenterol 1993; 28:551.
  7. Sultan AH, Nicholls RJ, Kamm MA, et al. Anal endosonography and correlation with in vitro and in vivo anatomy. Br J Surg 1993; 80:508.
  8. Wong RF, Bonapace ES Jr, Chung CY, et al. Simultaneous endoluminal sonography and manometry to assess anal sphincter complex in normal subjects. Dig Dis Sci 1998; 43:2363.
  9. Sultan AH, Kamm MA, Hudson CN, et al. Endosonography of the anal sphincters: normal anatomy and comparison with manometry. Clin Radiol 1994; 49:368.
  10. Falk PM, Blatchford GJ, Cali RL, et al. Transanal ultrasound and manometry in the evaluation of fecal incontinence. Dis Colon Rectum 1994; 37:468.
  11. Gold DM, Bartram CI, Halligan S, et al. Three-dimensional endoanal sonography in assessing anal canal injury. Br J Surg 1999; 86:365.
  12. Oh C, Kark AE. Anatomy of the external anal sphincter. Br J Surg 1972; 59:717.
  13. Law PJ, Kamm MA, Bartram CI. A comparison between electromyography and anal endosonography in mapping external anal sphincter defects. Dis Colon Rectum 1990; 33:370.
  14. Law PJ, Kamm MA, Bartram CI. Anal endosonography in the investigation of faecal incontinence. Br J Surg 1991; 78:312.
  15. Burnett SJ, Speakman CT, Kamm MA, Bartram CI. Confirmation of endosonographic detection of external anal sphincter defects by simultaneous electromyographic mapping. Br J Surg 1991; 78:448.
  16. Damon H, Henry L, Valette PJ, Mion F. [Incidence of sphincter ruptures in anal incontinence: ultrasound study]. Ann Chir 2000; 125:643.
  17. Sailer M, Leppert R, Fuchs KH, Thiede A. [Endo-anal sonography in diagnosis of fecal incontinence]. Zentralbl Chir 1996; 121:639.
  18. Farouk R, Bartolo DC. The use of endoluminal ultrasound in the assessment of patients with faecal incontinence. J R Coll Surg Edinb 1994; 39:312.
  19. Roche B, Marti MC. [Value of endo-anal ultrasonography in the assessment of anal incontinence]. Schweiz Med Wochenschr Suppl 1996; 79:64S.
  20. Eckardt VF, Jung B, Fischer B, Lierse W. Anal endosonography in healthy subjects and patients with idiopathic fecal incontinence. Dis Colon Rectum 1994; 37:235.
  21. Rieger NA, Sweeney JL, Hoffmann DC, et al. Investigation of fecal incontinence with endoanal ultrasound. Dis Colon Rectum 1996; 39:860.
  22. Karoui S, Savoye-Collet C, Koning E, et al. Prevalence of anal sphincter defects revealed by sonography in 335 incontinent patients and 115 continent patients. AJR Am J Roentgenol 1999; 173:389.
  23. Liberman H, Faria J, Ternent CA, et al. A prospective evaluation of the value of anorectal physiology in the management of fecal incontinence. Dis Colon Rectum 2001; 44:1567.
  24. Voyvodic F, Rieger NA, Skinner S, et al. Endosonographic imaging of anal sphincter injury: does the size of the tear correlate with the degree of dysfunction? Dis Colon Rectum 2003; 46:735.
  25. Fowler AL, Mills A, Virjee J, et al. Comparison of ultrasound and manometric sphincter length and incontinence scores. Dis Colon Rectum 2003; 46:1078.
  26. Damon H, Henry L, Barth X, Mion F. Fecal incontinence in females with a past history of vaginal delivery: significance of anal sphincter defects detected by ultrasound. Dis Colon Rectum 2002; 45:1445.
  27. Martínez Hernández Magro P, Villanueva Sáenz E, Jaime Zavala M, et al. Endoanal sonography in assessment of fecal incontinence following obstetric trauma. Ultrasound Obstet Gynecol 2003; 22:616.
  28. Tankova L, Draganov V, Damyanov N. Endosonography for assessment of anorectal changes in patients with fecal incontinence. Eur J Ultrasound 2001; 12:221.
  29. Barthet M, Bellon P, Abou E, et al. Anal endosonography for assessment of anal incontinence with a linear probe: relationships with clinical and manometric features. Int J Colorectal Dis 2002; 17:123.
  30. Beer-Gabel M, Teshler M, Barzilai N, et al. Dynamic transperineal ultrasound in the diagnosis of pelvic floor disorders: pilot study. Dis Colon Rectum 2002; 45:239.
  31. Williams AB, Spencer JA, Bartram CI. Assessment of third degree tears using three-dimensional anal endosonography with combined anal manometry: a novel technique. BJOG 2002; 109:833.
  32. Shobeiri SA, Nolan TE, Yordan-Jovet R, et al. Digital examination compared to trans-perineal ultrasound for the evaluation of anal sphincter repair. Int J Gynaecol Obstet 2002; 78:31.
  33. Gravante G, Giordano P. The role of three-dimensional endoluminal ultrasound imaging in the evaluation of anorectal diseases: a review. Surg Endosc 2008; 22:1570.
  34. Sentovich SM, Blatchford GJ, Rivela LJ, et al. Diagnosing anal sphincter injury with transanal ultrasound and manometry. Dis Colon Rectum 1997; 40:1430.
  35. Meyenberger C, Bertschinger P, Zala GF, Buchmann P. Anal sphincter defects in fecal incontinence: correlation between endosonography and surgery. Endoscopy 1996; 28:217.
  36. Deen KI, Kumar D, Williams JG, et al. Anal sphincter defects. Correlation between endoanal ultrasound and surgery. Ann Surg 1993; 218:201.
  37. Sultan AH, Kamm MA, Talbot IC, et al. Anal endosonography for identifying external sphincter defects confirmed histologically. Br J Surg 1994; 81:463.
  38. Schäfer R, Heyer T, Gantke B, et al. Anal endosonography and manometry: comparison in patients with defecation problems. Dis Colon Rectum 1997; 40:293.
  39. Papachrysostomou M, Pye SD, Wild SR, Smith AN. Significance of the thickness of the anal sphincters with age and its relevance in faecal incontinence. Scand J Gastroenterol 1994; 29:710.
  40. Rociu E, Stoker J, Eijkemans MJ, et al. Fecal incontinence: endoanal US versus endoanal MR imaging. Radiology 1999; 212:453.
  41. Malouf AJ, Williams AB, Halligan S, et al. Prospective assessment of accuracy of endoanal MR imaging and endosonography in patients with fecal incontinence. AJR Am J Roentgenol 2000; 175:741.
  42. Cazemier M, Terra MP, Stoker J, et al. Atrophy and defects detection of the external anal sphincter: comparison between three-dimensional anal endosonography and endoanal magnetic resonance imaging. Dis Colon Rectum 2006; 49:20.
  43. Felt-Bersma RJ, Cuesta MA, Koorevaar M. Anal sphincter repair improves anorectal function and endosonographic image. A prospective clinical study. Dis Colon Rectum 1996; 39:878.
  44. Ternent CA, Shashidharan M, Blatchford GJ, et al. Transanal ultrasound and anorectal physiology findings affecting continence after sphincteroplasty. Dis Colon Rectum 1997; 40:462.
  45. Savoye-Collet C, Savoye G, Koning E, et al. Anal endosonography after sphincter repair: specific patterns related to clinical outcome. Abdom Imaging 1999; 24:569.
  46. Hill K, Fanning S, Fennerty MB, Faigel DO. Endoanal ultrasound compared to anorectal manometry for the evaluation of fecal incontinence: a study of the effect these tests have on clinical outcome. Dig Dis Sci 2006; 51:235.
  47. Sultan AH, Kamm MA, Bartram CI, Hudson CN. Anal sphincter trauma during instrumental delivery. Int J Gynaecol Obstet 1993; 43:263.
  48. Fynes M, Donnelly V, Behan M, et al. Effect of second vaginal delivery on anorectal physiology and faecal continence: a prospective study. Lancet 1999; 354:983.
  49. Abramowitz L, Sobhani I, Ganansia R, et al. Are sphincter defects the cause of anal incontinence after vaginal delivery? Results of a prospective study. Dis Colon Rectum 2000; 43:590.
  50. Burnett SJ, Spence-Jones C, Speakman CT, et al. Unsuspected sphincter damage following childbirth revealed by anal endosonography. Br J Radiol 1991; 64:225.
  51. Frudinger A, Bartram CI, Halligan S, Kamm M. Examination techniques for endosonography of the anal canal. Abdom Imaging 1998; 23:301.
  52. Sultan AH, Loder PB, Bartram CI, et al. Vaginal endosonography. New approach to image the undisturbed anal sphincter. Dis Colon Rectum 1994; 37:1296.
  53. Poen AC, Felt-Bersma RJ, Cuesta MA, Meuwissen GM. Vaginal endosonography of the anal sphincter complex is important in the assessment of faecal incontinence and perianal sepsis. Br J Surg 1998; 85:359.
  54. Stewart LK, Wilson SR. Transvaginal sonography of the anal sphincter: reliable, or not? AJR Am J Roentgenol 1999; 173:179.
  55. Frudinger A, Bartram CI, Kamm MA. Transvaginal versus anal endosonography for detecting damage to the anal sphincter. AJR Am J Roentgenol 1997; 168:1435.
  56. Gold DM, Halligan S, Kmiot WA, Bartram CI. Intraobserver and interobserver agreement in anal endosonography. Br J Surg 1999; 86:371.