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Endoanal ultrasound

Departments of ¹ Radiology and ² Surgery, Guy's and St Thomas' NHS Trust, Lambeth Palace Road, London SE1, UK

View larger version (170K): [in a new window]   Figure 1. Normal appearance of the male anal canal at the level of the puborectalis muscle. a, puborectalis; b, circular muscle of the rectum; c, prostate.

View larger version (181K): [in a new window]   Figure 2. Normal sphincter appearance in an adult male (mid anal canal). a, internal anal sphincter; b, longitudinal muscle; c, external anal sphincter.

View larger version (176K): [in a new window]   Figure 3. Normal sphincter appearance in an adult male (distal to the termination of the internal anal sphincter) demonstrating the normal subcutaneous portion of the external anal sphincter (arrow).

View larger version (184K): [in a new window]   Figure 4. Normal sphincter appearance in an adult female (mid anal canal). a, internal anal sphincter; b, longitudinal muscle; c, external anal sphincter. Note the poorer delineation between the external anal sphincter and the longitudinal layer than in the male patient in Figure 3.

View larger version (130K): [in a new window]   Figure 5. Prominent internal haemorrhoids. There is a hypoechoic focus in the subepithelial region (arrow) that should not be mistaken for a fistulous track.

View larger version (184K): [in a new window]   Figure 6. Marked thickening of the internal anal sphincter to 4.2 mm (arrow) in a 43-year-old patient with solitary rectal ulcer syndrome.

View larger version (200K): [in a new window]   Figure 7. Internal anal sphincter (IAS) atrophy in a 55-year-old man with passive incontinence. The IAS is thin but intact (arrow). The appearances are consistent with primary sphincter atrophy in the presence of normal pudendal nerve terminal motor latencies.

View larger version (193K): [in a new window]   Figure 8. Internal anal sphincter (IAS) disruption post anal stretch. The IAS is totally disrupted. The external anal sphincter is intact. Anal stretch procedures can produce single or multiple defects in the IAS.

View larger version (195K): [in a new window]   Figure 9. Internal anal sphincter (IAS) defect post surgery in a 27-year-old man with passive incontinence. There is a defect in the IAS between 6 O'clock and 11 O'clock (arrows) following surgery for haemorrhoids. The external anal sphincter is intact (arrowheads).

View larger version (178K): [in a new window]   Figure 10. Internal anal sphincter (IAS) defect post internal sphincterotomy. There is an IAS defect between 4 O'clock and 8 O'clock (arrow). The external anal sphincter appears attenuated but intact (arrowheads).

View larger version (164K): [in a new window]   Figure 11. Obstetric injury in a 32-year-old woman presenting with faecal urgency 6 months after a forceps delivery. There is a defect in the external sphincter between 1 O'clock and 3 O'clock (arrow). The normal external anal sphincter is shown (arrowhead).

View larger version (177K): [in a new window]   Figure 12. Severe obstetric trauma. There is a defect in the external anal sphincter between 9–12 O'clock and 2–3 O'clock (arrowheads). There is disruption of the internal anal sphincter (arrows).

View larger version (154K): [in a new window]   Figure 13. Obstetric injury and fistula formation. There is a defect in the anterior portion of the external anal sphincter with an anterior anal fistula (arrow). The tiny focus of increased reflectivity is from gas within pus in the fistula track.

View larger version (175K): [in a new window]   Figure 14. Obstetric injury, post repair. A defect in the internal anal sphincter remains between 10 O'clock and 3 O'clock. The external anal sphincter (EAS) has been repaired but there are still persistent changes in the EAS between 12 O'clock and 3 O'clock.

View larger version (160K): [in a new window]   Figure 15. Crohn's disease with recurrent fistula formation. There is disruption in the internal anal sphincter (arrow), which may be the result of previous sepsis compounded by surgery. There is evidence of an extra-sphincteric collection (arrowhead).

View larger version (187K): [in a new window]   Figure 16. Low intersphincteric collection between the internal and external anal sphincters (arrow).

View larger version (83K): [in a new window]   Figure 17. Low intersphincteric fistula in the (a) mid anal canal and (b) low anal canal. There is an intersphincteric collection low in the anal canal. The site of the internal opening is inferred by the point at which the collection enters the internal anal sphincter (a, arrow). The external anal sphincter appears intact.