Endoanal ultrasound in anal diseases

1. Endoanal ultrasound in anal diseases
Samir Haffar, M.D.

2. "It is necessary to see before reflecting,
to seize appearances before probing the causes;
and our ideas on any external object are vague
if they are not for us so many images.”
Xavier Bichat (1771 - 1802)
French anatomist and physiologist
Father of modern histology and
descriptive anatomy

3. (1) Normal ultrasound-anatomy of the anus
(2) Endoanal ultrasound (EAUS) in anal diseases:
- Anal sphincter lesions
- Perianal fistulas
- Anal canal tumors
- Miscellanous anal diseases
Endoanal ultrasound in anal diseases

4. (1) Normal ultrasound-anatomy of the anus

5. Coronal anatomy of the anal canal
Santoro JA & Di Falco G. Endosonographic anatomy of the normal anal canal.
In: Santoro JA & Di Falco G (eds), Benign anorectal diseases. Springer-Verlag, Italia, 2006.

6. Patient preparation
• Patients given routine cleansing enema 2 hours before examination
• Sedation not necessary
• Examination in left lateral decubitus position,
in knee-chest position
• Digital rectal exam before insertion of the probe into rectum:
Identify lesion size, location, & mobility of the tumor
Kim MJ. Ultrasonography 2015; 34:19-31.

7. Radial positions around the anus referenced with respect to a clock
Anterior anatomical structures at 12 o’clock side of the image
Patient’s left side at 3 o’clock & patient’s right side at 9 o’clock
Patient’s posterior side at 6 o’clock
Santoro JA & Di Falco G. Endosonographic anatomy of the normal anal canal.
In: Santoro JA & Di Falco G (eds), Benign anorectal diseases. Springer-Verlag, Italia, 2006.
Lesion localization with patient
in left lateral position

8. Layers Components
Subepithelium Moderately hyperechoic layer
Vascular channels may be seen at 6 & 12 o’clock
as low-reflective tubular structures running longitudinally
Internal anal sphincter Hypoechoic ring about 2 mm thick
Symmetric in thickness, best measured at either 3 or 9
Irregularity of last mm should not be taken for a tear
Longitudinal muscle
"Composite layer"
Smooth muscle from outer longitudinal layer of rectum
Striated muscle from puboanalis ( inner slip of PRM)
Fibroelastic tissue from endopelvic fascia
External anal sphincter
"3 parts"
1. Deep part: merges with puborectalis
2. Superficial part: ends at caudal extent of IAS
3. Subcutaneous part: curves inwards towards anal canal
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.
Four-layer structure of the anal canal

9. Subepithelium straight white arrows
Internal anal sphincter straight black arrows
Longitudinal muscle curved white arrows
External anal sphincter curved black arrows
Frudinger A et al. Radiology 2002; 224:417-423.
28-year-old nulliparous volunteer woman
Four-layer structure of the anal canal

10. Echogenicity of anal canal layers
• Puborectalis muscle Hyperechoic
• External sphincter
Deep part Hyperechoic - similar to PR
Superficial part Mixed echogenicity
Similar to proximal structures
Subcutaneous part Hyperechoic
• Internal sphincter Hypoechoic - more easily identifiable
• Longitudinal muscle Moderately echogenic
Abdool Z et al. Br J Radiol 2012; 85: 865–875.
Depends on muscle type, US beam angle & probe frequency

11. Longitudinal muscle (LM)
LMR: longitudinal muscle of rectum - MSA: muscularis submucosae ani
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.
Composite layer
- Smooth muscle from LMR
- Striated muscle from puboanalis (PA)
- Fibroelastic tissue from endopelvic fascia
- Slips from LM run through IAS to MMA
- Fibroelastic tissue through subcutaneous EAS
to peri-anal skin

12. Longitudinal muscle can be seen as a moderately echogenic structure
Santoro JA & Di Falco G. Endosonographic anatomy of the normal anal canal.
In: Santoro JA & Di Falco G (eds), Benign anorectal diseases. Springer-Verlag, Italia, 2006.
Longitudinal muscle

13. Levels of anal canal
Santoro JA & Di Falco G. Endoanal and Endorectal ultrasonography.
In: Santoro JA et al(eds), Pelviv floor disorders. Springer-Verlag, Italia, 2010.

14. • High anal canal At most cranial level of puborectalis
PRM is the landmark of high anal canal
Sling of PRM & deep part of external sphincter
• Mid anal canal Level where EAS forms a complete ring
Superficial part of EAS, IAS, perineal body,
& transverse perineii
Anococcygeal ligament post & vagina anteriorly
• Low anal canal Level below which the IAS terminate
Subcutaneous part of EAS
Levels of anal canal
Santoro JA & Di Falco G. Endosonographic anatomy of the normal anal canal.
In: Santoro JA & Di Falco G (eds), Benign anorectal diseases. Springer-Verlag, Italia, 2006.

15. (1) Fowler GE et al. BJOG 2008; cx 115:767-772.
(2) Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.
EAUS of the high anal canal
puborectalis muscle (PRM)
‘‘U’’-shaped PRM posteriorly (arrows)
Loss of EAS in midline anteriorly

16. Santoro JA & Di Falco G. Endosonographic anatomy of the normal anal canal.
In: Santoro JA & Di Falco G (eds), Benign anorectal diseases. Springer-Verlag, Italia, 2006.
EAUS of the high anal canal
In men In females
Thin arc of muscle from the deep part
of EAS can be seen anteriorly in males
Deep part of EAS not seen
anteriorly in females
Not to be taken for rupture

17. IAS: darker homogenous ring
EAS: white heterogeneous ring around IAS
(1) Fowler GE et al. BJOG 2008;115:767–772.
(2) AGA Review on Anorectal Testing Techniques. Gastroenterology 1999;116(3):735-760.
EAUS of the mid anal canal
IAS and EAS
Schematic representation1 Axial EAUS image2

18. • Central portion of perineum where EAS, transverse perineal
muscles and bulbospongiosus muscle meet
• Seen as complex structure of concentric rings with hypoechoic or
hyperechoic center
• Difficult to measure reliably because of lack of clear limits
Perineal body
mid anal canal
Santoro JA & Di Falco G. Endosonographic anatomy of the normal anal canal.
In: Santoro JA & Di Falco G (eds), Benign anorectal diseases. Springer-Verlag, Italia, 2006.

19. Bulbospongiosus muscle, TP & EAS
meet in perineal body
TP better defined in men
Join centre point of perineum
Creating gap between TP & EAS (arrow
In women, TP fuse into EAS
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.
Transverse perineii (TP)
mid anal canal - imaged at 11 & 1 o'clock
Schematic representation Transverse perineii in men

20. Anococcygeal raphe seen as posterior hypoechoic triangle
Santoro JA & Di Falco G. Endosonographic anatomy of the normal anal canal.
In: Santoro JA & Di Falco G (eds), Benign anorectal diseases. Springer-Verlag, Italia, 2006.
Axial EAUS at the mid anal canal
Anococcygeal ligament

21. Lower canal anal caudal to IAS termination
comprising the subcutaneous EAS (arrows)
Anococcygeal ligament posteriorly (arrowheads
Axial EAUS image2
Schematic representation1
EAUS of the low anal canal
Subcutaneous EAS
(1) Fowler GE et al. BJOG 2008;115:767–772.
(2) Engin G. J Ultrasound Med 2006; 25:57–73.

22. Normal measurements in EAUS
• Puborectalis muscle 6 ± 3 mm
• Subepithelium 2 ± 0.5 mm
• Internal anal sphincter 2.5 ± 0.5 mm - increased at older ages
• Longitudinal muscle (LM) 2 ± 0.5 mm
• External anal sphincter 4 ± 0.5 mm - decreased at older ages
Frudinger A et al. Radiology 2002; 224:417–423
150 asymptomatic nulliparous women (19 - 80 years – mean: 31)

23. Normal thickness of IAS
IAS not constant in thickness
• Neonates < 1 mm (very thin)
• Young adult 1-2 mm
• Middle age 2-3 mm
• Elderly 3-4 mm
Measurements taken at 3 & 9 o'clock positions in mid anal canal
IAS > 4 mm should be considered abnormal whatever the age
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.

24. Supralevator space Located superior to levator ani muscle
Intersphincteric space Between the IAS & the EAS
Ischioanal space Surrounds anal canal: pyramid shaped
Perianal space
Santoro JA & Di Falco G. Endosonographic anatomy of the normal anal canal.
In: Santoro JA & Di Falco G (eds), Benign anorectal diseases. Springer-Verlag, Italia, 2006.
Schematic representation of perianal spaces
Perianal spaces

25. (2) Endoanal ultrasound for anal lesions

26. Endoanal ultrasound for anal lesions
• Anal sphincter lesions Anal sphincter defect
Anal sphincter atrophy
Thick internal anal sphincter
• Peri-anal fistulas
• Anal canal tumors Squamous cell carcinoma: most frequent
Melanoma
Gastrointestinal stromal tumor (GIST)
• Miscellaneous lesions Endometriosis
Mucosal hemorrhoidal prolapse

27. Anal sphincter lesions

28. EAUS in fecal incontinence
• ERUS is the imaging examination of choice in fecal incontinence
• Differentiate between causes of incontinence:
Presence of anal sphincter defects
Features consistent with neurogenic cause:
- Sphincters appear normal or atrophic
- No EAS & PRM contraction during attempted contraction
(dynamic EAUS)
Kołodziejczak M & Sudoł-Szopińska I. Anal Incontinence.
In: Catto-Smith A (ed), Fecal incontinence. InTech, 2014.

29. Anal sphincter defect
• Obstetrical trauma: main indication of EAUS
Most common cause of fecal incontinence
Damage most frequent during first delivery & with forceps assistance
Affects only anterior portion: posterior injury due to other cause
Internal sphincter tears do not occur without EAS damage
Incidence: 27% of primiparous women after vaginal delivery in a MA 1
• Anorectal surgery: hemorrhoidectomy - anal fissure/perianal fistula
• Accidental injury: penetrating injury - road traffic accident
MA: meta-analysis
(1) Oberwalder M et al. Br J Surg 2003; 90: 1333-1337.
(2) Kołodziejczak M & Sudoł-Szopińska I. Anal Incontinence.
In: Catto-Smith A (ed), Fecal incontinence. InTech, 2014.

30. EAUS in sphincter defect
• Which muscle damaged Internal anal sphincter (IAS)
External anal sphincter (EAS)
Puborectalis muscle (PRM)
• Range of damage Circumference (mapped in hours)
Longitudinal extent
• Presentation of retained sphincters Muscle stumps
If defects are detected, one should determine
IAS: internal anal sphincter - EAS: external anal sphincter - PRM: puborectalis muscle
Kołodziejczak M & Sudoł-Szopińska I. Anal Incontinence.
In: Catto-Smith A (ed), Fecal incontinence. InTech, 2014.

31. Disruption of both IAS (small arrows) & EAS (large arrows)
Fibrotic tissue in disrupted areas (hypoechoic seg within sphincters)
Intact muscle stumps
AGA technical review on anorectal testing techniques. Gastroenterology 1999; 116(3): 735-760.
Obstetrical trauma
EAUS of the mid anal canal

32. Obstetrical trauma
EAUS at the high anal canal EAUS at the mid anal canal
Anterior tear
(30% of IAS circumference)
Normal retained muscles
Anterior tear
(50% IAS & EAS circumference)
Normal retained muscles
Kołodziejczak M & Sudoł-Szopińska I. Anal Incontinence.
In: Catto-Smith A (ed), Fecal incontinence. InTech, 2014.

33. Obstetrical trauma / cloacal-type defect
Axial EAUS image
Complete tear of perineum and sphincters
Only posterior halves of internal & external sphincters remaining
creating a cloacal-type defect
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.

34. Ano-vaginal fistula
frequently accompany obstetric defects
Axial EAUS image
Obstetric ano-vaginal fistula with air bubbles (arrow)
Anterior defect of 33% of IAS & EAS circumferences
Kołodziejczak M & Sudoł-Szopińska I. Anal Incontinence.
In: Catto-Smith A (ed), Fecal incontinence. InTech, 2014.

35. Sphincter defect / After hemorrhoidectomy
Axial EAUS image
57-year-old lady – fecal incontinence following haemorrhoidectomy
Defect between 3 to 5 o’clock positions (arrows)
Stretch procedure during operation or inadvertent division of sphincter
Camilleri-Brennan J. Anal injectables and implantables for feecal incontinence.
In: Catto-Smith A (ed), Fecal incontinence: causes, management and outcome. InTech, 2014.

36. Sphincter defect / After lateral sphincterotomy
Patient underwent lateral sphincterotomy for anal fissure
Axial EAUS at the level of high anal canal
Defect high in anal canal at level of puborectalis (arrows)
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.

37. Marked irregularity of sphincter thickness
Gross thinning of segment & fragmentation
with only irregular isolated remnants remain
Patient underwent manual dilatation for anal fissure
not performed as regularly as they were some years ago
Sphincter defect / After anal dilation
Santoro JA & Di Falco G. Three-dimensional endoluminal ultrasonography.
In: Santoro JA et al(eds), Pelviv floor disorders. Springer-Verlag, Italia, 2010.

38. Sphincter defect / After fistulectomy
Patient underwent fistulectomy for posterior transsphincteric fistula
EAUS at level of low anal canal EAUS at level of mid anal canal
30% of posterior circumference of EAS
Normal muscle stumps
50% of posterior aspect of IAS
Normal muscle stumps
Kołodziejczak M & Sudoł-Szopińska I. Anal Incontinence.
In: Catto-Smith A (ed), Fecal incontinence. InTech, 2014.

39. Partial rupture of sphincter with well-defined segmental scarring
and acoustic shadowing (arrows)
Young boy fell on a wooden stake
Sphincter defect / Traumatic injury
Axial EAUS image
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.

40. IAS degeneration
IAS is abnormally thin for the age (1.1 mm)
indicative of IAS degeneration
70-year-old man with passive fecal incontinence
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.

41. Koh CE et al. Dis Colon Rectum 2009; 52: 315-318.
Scleroderma
Study of 11 patients with scleroderma & fecal incontinence
Two distinct morphologic changes
Thinned, difficult to discern
& hyperechoic internal anal sphincte
Thickened, homogeneous,
& hypoechoic internal anal sphincter

42. External anal sphincter atrophy
Thin internal anal sphincter (< 2 mm)
Poorly defined interface between LM & EAI &outer border of EAS
making it impossible to assess thickness of EAS
Inability to recognize EAS border & thin IAS raise suspicion of atrophy
Middle-aged woman with fecal incontinence
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.

43. Thick internal anal sphincter
Disease Frequency of thick IAS
Solitary rectal ulcer syndrome 50% in one series1
Proctalgia fugax 30% in one series2
Uncomplicated constipation Occasionally3
Hereditary IAS myopathy Thick IAS in most patients4
(1) Sharma A et al. J Neurogastroenterol Motil 2014; 20(4): 531-538.
(2) Gracia Solanas JA et al. Rev Esp Enferm Dig 2005; 97: 491–496.
(3) Keshtgar AS et al. Pediatr Surg Int 2004; 20: 817-23.
(4) Kamm MA et al. Gastroenterology 1991; 100: 805-10.

44. Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.
Solitary rectal ulcer syndrome (SRUS)
Thick internal anal sphincter (4.3 mm)
36-year-old woman with SRUS
Axial EAUS image

45. Thick IAS in obstructed defecation
Damon H et al. Gastroenterol Clin Biol 2001; 25:35-44.
Axial EAUS at level of high anal canal
Thick internal anal sphincter (4.5 mm)
Male patient with obstructed defecation

46. Hereditary internal anal sphincter myopathy
"very rare disease"
• First described by Kamm in 1991
• Autosomal dominant inheritance with incomplete penetration
• Proctalgia fugax-type pain associated with thick IAS
• Physical examination: enlarged anal sphincter mimics anal tumor
• Improvement by medical/surgical therapy: Calcium antagonist
Complete sphincterotomy
Martorell P et al. Rev Esp Enferm Dig (Madrid) 2005; 97(7): 527-529.

47. Hereditary internal sphincter myopathy
Thick internal anal sphincter (7.6 mm)
76-year-old female – Long history of severe proctalgia fugax
Mother had similar history – daughter started having similar pain
Axial EAUS image
Bertram CI. Endoanal ultrasound.
In: Stoker J et al. Imaging pelvic floor disorders, 2nd edition. Springer-Verlag Berlin, 2008.

48. Perianal fistulas

49. Causes of perianal fistulas
• Idiopathic Most common – prevalence 1:10 000 – young adults
Cryptoglandular theorie: intersphincteric gland infection
• Crohn disease Complex & recurrent fistulas – perianal lesions
• Tuberculosis
• Pelvic infection
• Trauma
• Pelvic malignancy
• Radiation therapy
de Miguel Criado J et al. RadioGraphics 2012; 32:175–194.

50. Surgical anatomy of perianal fistulas
• Internal opening Usually at dentate line – 6-o'clock mostly
• Primary tract Penetrating anal sphincter & tissues
• Secondary tract Generally known as "extension"
• Collection Widening of primary or secondary track
considered as abscess
• External opening Fistula reach perianal skin by variety of routes
Fistulas classified according to the route taken by the
“primary tract” that links internal & external openings
Halligan S et al. Radiology 2006; 239(1): 18-33.

51. Parks classification of perianal fistula
Analysis of 400 patients referred to St Mark’s Hospital, London
• Intersphincteric fistula 45%
• Transsphincteric fistula 30%
• Extrasphincteric fistula 20%
• Suprasphincteric fistula 5%
Parks AG et al. Br J Surg 1976; 63:1-12.
Perianal fistulas divided into

52. AGA technical review on perianal Crohn’s disease. Gastroenterology 2003;125:1508–1530.
A. Superficial fistula
Underneath both perianal sphincter
B. Intersphincteric fistula
Track between IAS & EAS
C. Transsphincteric fistula
Track from intersphincteric space to EAS
D. Suprasphincteric fistula
From intersphincteric space to PRM
Penetrate levator muscle & down to skin
E. Extrasphincteric fistula
Track outside EAS to levator & rectum
Parks classification of perianal fistulas

53. Classification of perianal fistulas
American Gastroenterological Association
Simple
• Low origin
superficial, low transphinteric
• Single external orifice
• No pain or fluctuation
suggesting perianal abscess
• No rectovaginal fistula or
anorectal stenosis
Complex
• High origin
• Multiple external orifices
• Pain or fluctuation
suggesting perianal abscess
• +/- recto-vaginal fistulas,
stenosis, active rectal disease
AGA technical review on perianal Crohn’s disease. Gastroenterology 2003;125:1508–1530.

54. EAUS findings in perianal fistula
• Internal opening EAUS well suited to identify internal opening
Tract extends to anal mucosal surface rarely seen
Hypoechoic focus in intersphincteric space
abuts IAS, often with small defect in IAS
• Primary tract Hypoechoic tract with internal gas or debris
Gas in tract mimics extension
Active fistula: variable echogenic fluid/thick wall
Inactive fistula: tubular fibrotic bands – no fluid
• Secondary tract Side branches of primary track above IO
• Collection Widening of primary or secondary tracks
Hypoechoic fluid collection with gas & debris
IO: internal opening
Kim MJ. Ultrasonography 2015;34:19-31.

55. Primary opening in perianal fistula
• Criterion I
Rootlike budding formed by intersphincteric track that contacts IAS
• Criterion II
Rootlike budding with IAS defect
• Criterion III
Subepithelial breach connect to intersphincteric track through IAS
• Combination of these 3 criteria
94% sensitivity 87% specificity
Cho DY. Dis Colon Rectum 1999; 42:515–518.
Cho's criteria

56. Cho' criteria for primary opening in perianal fistula
Criterion I
Criterion II
Criterion III
Cho DY. Dis Colon Rectum 1999; 42:515–518.

57. Perianal fistula / Internal opening
dos Reis Lima DM et al. J Coloproctol (rio j) 2015;35(1):53–58.
Internal fistulous opening at 6 o’clock position (white arrow)
suggesting the presence of anal fistula (yellow arrows)
Axial EAUS at the mid anal canal

58. Intersphincteric fistula
Fistula with hypoechoic tract in intersphincteric plane between EAS/IAS
Internal opening correctly predicted at 6 o’clock posteriorly
because of radial position of fistula within the intersphincteric plane
Halligan S et al. Radiology 2006; 239(1): 18-33.
Axial EAUS at the mid anal canal

59. Intersphincteric inflammatory-infectious process (yellow arrows)
dos Reis Lima DM et al. J Coloproctol (rio j) 2015;35(1):53–58.
Axial EAUS at the mid anal canal
Intersphincteric fistula

60. Transsphincteric fistula
Halligan S et al. Radiology 2006; 239(1): 18-33.
Internal opening correctly predicted at 7-o’clock position
IAS relatively thin which is clue to site of IO but no tract to anal mucosa
Fistula (*) penetrate the EAS
Transverse EAUS at the mid anal canal

61. Perianal fistula
Hydrogen peroxide (H2O2) enhanced EAUS
Confirms presence of IO
White arrow: internal opening
Grey arrow: septic cavity
Black arrow: primary tract
IO: internal opening
Fernández-Frías AM et al. Rev Esp Enferm Dig 2006; 98(8): 573-581.
Transsphincteric fistula
White arrow: IO (indirect signs)
Grey arrow: septic cavity
Black arrow: primary track
Before H2O2 injection After H2O2 injection in external opening

62. • Ischioanal extension Commonest site for extension
• Supralevator pararectal extension From transsphincteric fistula
• Supralevator extension From intersphincteric fistula
• Horseshoes extensions Occurring in horizontal plane
Halligan S et al. Radiology 2006; 239(1): 18-33.
Secondary tracts (fistula extensions)
The more chronic the fistula, the more complicated the extensions
Missed extension is the commonest cause of recurrence (25% )

63. A Ischioanal fossa extension
From apex of transsphincteric fistula
B Supralevator pararectal extension
From apex of transsphincteric fistula
C Supralevator extension
From intersphincteric plane
D Horseshoe extension
Horizontal extension
Halligan S et al. Radiology 2006; 239(1): 18-33.
Secondary tracts (fistula extensions)
Coronal plane of fistula extensions

64. Ischio-rectal extension
Transsphincteric track (arrow)
Ischiorectal extension (arrowheads)
Buchanan GN et al. Radiology 2004; 233:674–681.
Axial EAUS at mid of anal canal
Confirms transsphincteric fistula (arrow
& ischiorectal extension (arrowhead)
Transverse MRI

65. Intersphincteric horseshoe extenstion
Halligan S et al. Radiology 2006; 239(1): 18-33.
Intersphincteric horseshoe extenstion
Gas in fistula causes acoustic shadowing (*)
which could be mistaken for transsphincteric tracts
EAUS at the upper anal canal

66. Extensive horseshoe extension
Halligan S et al. Radiology 2006; 239(1): 18-33.
Extensive hypoechoic horseshoe extension (i)
Difficult to determine if supra- or infralevator
(ERUS limited to transverse plane)
Supra- or infralevator extension is central to surgical management
EAUS at the upper anal canal

67. Perianal abscess (collection)
The perianal abscess is the most frequent & the supralevator the least
If abscess spreads partially circumferentially around the anus or rectum,
it is termed horseshoe abscess
https://www.fascrs.org/patients/disease-condition/abscess-and-fistula-expanded-information

68. Ischioanal abscess
(1) de Miguel Criado J et al. RadioGraphics 2012; 32:175–194
(2) Navarro A, Pando JA, and Ramírez JM. Atlas of anal endosonography, 2010.
Axial ERUS2Diaphragmatic representation1
Transsphincteric fistula with abscess or
secondary track in ischiorectal/ischioanal fossa

69. Supralevator abscess
(1) de Miguel Criado J et al. RadioGraphics 2012; 32:175–194
(2) Navarro A, Pando JA, and Ramírez JM. Atlas of anal endosonography, 2010.
Diaphragmatic representation1 Axial ERUS2
Left supralevator abscess with
left translevator fistula

70. Horseshoe abscess
Presence of horseshoe abscess (*) around the anal canal

71. Not all perianal abscess caused by perianal fistula
• Indected anal fissure
• Pilonidal sinus
• Verneuil’s disease
• Furoncle
• Infection associated with agranulocytosis: cellulitis without pus
• Suppuration associated with cancer: colloïdal rectal cancer
• Suppuration associated with Buschke-Loewenstein
Soudan D. Les différentes présentations cliniques des abcès et fistules.
In: Abramowitz L et al (eds), Fistules anales. Springer, Paris, 2010.

72. Perianal manifestations in Crohn's disease
• Skin lesion Anal plates - hemorrhoids
• Anal canal lesions Fissures - ulcers - anorectal stenosis
• Perianal fistula
• Recto-vaginal fistula
• Cancer
Variety of perianal manifestations

73. Frequency of perianal fistulas in Crohn's disease
• Patients with ileal disease 12%
• Patients with ileocolic disease 15%
• Patients with colon disease without rectal involvement 41%
• Patients with colon and rectal disease 92%

74. Complex fistula in a patient with Crohn's disease
http://www.grupuge.com.pt/ecoendoscopia/canal-anal.html

75. Active versus inactive Crohn's perianal fistula
Healed fistula
Scar tissue remains
at site of tract
Schwartz DA et al. Inflamm Bowel Dis 2005; 11:727–732.
15-year-old male with perianal pain and drainage
Initial ERUS
followed by seton placement
Posterior trans-
shincteric fistula
ERUS at week 16
Fistula inflammation improved
Air still seen within seton
Seton pulled after this ERUS
ERUS at week 30

76. Imaging of perianal Crohn's disease
• "Pelvic MRI is highly accurate non-invasive modality for
diagnosis & classification of perianal fistulas; therefore it is
considered gold standard imaging technique for perianal CD”
• "EUS with or without hydrogen peroxide is a useful alternative
to MRI in diagnosing perianal CD fistulas; however, accuracy
can belimited by its restricted view“
Gecse KB et al. Gut 2014; 63:1381–1392.
Global consensus on classification, diagnosis & multidisciplinary
treatment of perianal fistulising Crohn’s disease

77. • Primary opening
• Small intersphincteric abscess that might be difficult
to resolve by MRI
• Intramural rectal abscess
• Assess sphincter disruption after surgery for a fistula
Advantages of EAUS in anal fistula
Halligan S et al. Radiology 2006; 239(1): 18-33.

78. Disadvantages of EAUS in anal fistula
• Limited field of US view beyond EAS
Limited ability to resolve ischioanal & supralevator infections
• Difficulty in patients with recurrent disease
Distinction of infection from fibrosis: both are hypoechoic
• Inability to image in coronal plane
Difficulty to distinguish supra- from infra-levator extensions
Halligan S et al. Radiology 2006; 239(1): 18-33.
MRI is a superior technique overall and now
generally available

79. Respective role of EAUS & MRI
• Complex fistula
• Supralevator/ischioanal extension
• Anal canal stenosis
• Chronic/recurrent disease
• Primary opening
• Inter-sphincteric fistula
• Intramural rectal collection
• Evaluate anal sphincters
EAUS MRI

80. EAUS versus MRI for perianal fistula
Meta-analysis - 246 references - 4 studies - 241 patients
• MRI Combined sensitivity 0.87 (95% CI: 0.63-0.96)
Combined specificity 0.69 (95% CI: 0.51-0.82)
High degree heterogeneity between studies (df = 3, I2 =93%)
• EAUS Combined sensitivity 0.87 (95% CI: 0.70-0.95)
Combined specificity 0.43 (95% CI: 0.21-0.69)
High degree heterogeneity between studies (df =3, I2=92%)
Comparable Sen - Higher Sp for MRI - Both poor specificities
High degree of heterogeneity - Further studies needed
Sen: sensibility – Sp: specificity
Siddiqui MRS et al. Dis Colon rectum 2012; 55: 576–585.

81. Anal canal tumors

82. Histology of the anal canal
Upper part: covered by colorectal type mucosa
Middle part: covered by specialized epithelium
Lower part: covered by squamous epithelium
Santoro GA & Di Falco G. Endoanal ultrasonography in the staging of anal carcinoma.
In: Santoro GA et al (eds), Atlas of endoanal/endorectal ultrasonography. Springer, Italia, 2004.
Anal canal divided histologically into 3 zones

83. WHO histological classification of tumors of the anal canal
Origin of tumor Histologic type
Epithelial tumors Intraephitelial neoplasia Squamous or transitional epithelium
Glandular
Paget disease
Carcinoma SCC (most frequent)
Adenocarcinoma
Mucinous adenocarcinoma
Small cell carcinoma
Undifferentiated carcinoma
Carcinoid tumor
Malig melanoma
Non-epithelial
tumors
Secondary tumors
Santoro GA & Di Falco G. Endoanal ultrasonography in the staging of anal carcinoma.
In: Santoro GA & Di Falco G (eds), Atlas of endoanal & endorectal ultrasonography. Springer-

84. TNM Staging of anal cancer (American Joint Committee for Cancer)
TNM Explanation of Stage
Primary
tumor (T)
TX
T0
Tis
T1
T2
T3
T4
Primary tumor cannot be assessed
No evidence of a primary tumor
Carcinoma in situ
Tumor 2 cm or less in greatest dimension
Tumor > 2 cm but < 5 cm in greatest dimension
Tumor > 5 cm in greatest dimension
Tumor of any size invading adjacent organs
Regional
lymph nodes
(N)
NX
N0
N1
N2
N3
Regional nodes cannot be assessed
No regional node metastases
Metastasis in perirectal lymph node(s)
Metastasis in unilateral internal iliac &/or inguinal LNs
Metastasis in perirectal/inguinal LN &/or bilateral II LN
Metastasis
(M)
MX
M0
M1
Distant metastasis cannot be assessed
No distant metastasis
Distant metastasis present

85. uT1 anal SSC
tumor 2 cm or less in greater dimension
Hypoechoic mass invading IAS
Intact EAS
Santoro GA & Di Falco G. Endoanal ultrasonography in the staging of anal carcinoma.
In: Santoro GA et al (eds), Atlas of endoanal & endorectal ultrasonography. Springer, Italia, 2004.
Diaphragmatic representation Axial EAUS

86. Santoro GA & Di Falco G. Endoanal ultrasonography in the staging of anal carcinoma.
In: Santoro GA et al (eds), Atlas of endoanal & endorectal ultrasonography. Springer, Italia, 2004.
Anal carcinoma invading
subcutaneous part of EAS (arrows)
uT2 anal SSC
tumor > 2 cm but < 5 cm in greatest dimension
Diaphragmatic representation Axial EAUS
IAS
LM
EAS

87. Nearly circumferential anal lesion at PRM level
Thick area completely invading IAS
& extending through PRM
uT3 anal SSC
tumor > 5 cm in greatest dimension
Diaphragmatic representation Axial EAUS
Santoro GA & Di Falco G. Endoanal ultrasonography in the staging of anal carcinoma.
In: Santoro GA et al (eds), Atlas of endoanal & endorectal ultrasonography. Springer, Italia, 2004.

88. Santoro GA & Di Falco G. Endoanal ultrasonography in the staging of anal carcinoma.
In: Santoro GA et al (eds), Atlas of endoanal & endorectal ultrasonography. Springer, Italia, 2004.
Carcinoma extending outside EAS
(arrows) & infiltrating os coccyx
uT4 anal SSC
tumor of any size that invades adjacent organs
Diaphragmatic representation Axial EAUS

89. Melanoma of the anal canal / Rare
Very black tumor immediately
above anorectal junction
Berton F et al. AJR 2008; 190:1495–1504.
Axial EAUS image
Highly vascular tumor
Color Doppler image

90. Gastrointestinal stromal tumor of the anal canal
Posterior wall hypoechoeic nodule between IAS & EAS
Central calcification – Posterior enhancement
Local excision: gastrointestinal stromal tumor (GIST)
Carvalho N et al. World J Gastroenterol 2014; 7; 20(1): 319-322.
EAUS of mid anal canal

91. Miscellaneous anal lesions

92. Cystic lesion in the ischioanal space
Endometriosis in ischioanal space
Vieira AM et al. Rev Esp Enferm Dig (Madrid) 2010; 102(5): 308-313.
Axial EAUS image

93. Anal endometriosis / Rare
Bacher H et al. Dis Colon Rectum 1999; 42:680-682.
24-year-old female with fluctuating severe pain in
right anterior perianal region for 2 years
Radial EAUS image
Anechoic lesion (15.9 mm) in anterior EAS with dorsal enhancement
Lesion at distance of 4 mm from hypoechogenic line of IAS
Histology: endometrial glands with hemosiderin-laden macrophages

94. Mucosal hemorrhoidal prolapse
Increased thickness of subepithelial tissue
Measurements ˃3 mm may correspond to mucous-hemorrhoidal prolapse
Measurements obtained in middle & upper parts of anal canal
dos Reis Lima DM et al. J Coloproctol (rio j) 2015;35(1):53–58.
Axial EAUS image

95. Thank You