title: Endosonographic imaging of anal sphincter injury: does the size of the tear correlate with the degree of dysfunction?
abstract: OBJECTIVE
  This study was designed to test the hypothesis that the extent of anal sphincter muscle injury as graded at endosonography correlates with the degree of functional impairment.
  
  
  METHODS
  Three hundred and thirty adults presenting for evaluation of fecal incontinence were recruited. Ultrasound was performed with a 7.5-MHz radial rotating axial endoprobe in the left lateral position. Anal sphincter muscle tears were graded on the basis of the degree of circumferential involvement (< or >25 percent) and by an assessment of the superoinferior longitudinal extent of an external anal sphincter tear. Muscles that demonstrated multiple tears, poor visualization, or fragmentation were classed as fragmented. Sphincter injuries were correlated with basal and squeeze pressures at manometry, pudendal nerve terminal latencies, and the severity of symptoms using the Parks-Browning clinical score.
  
  
  RESULTS
  Patients with an intact external anal sphincter had a higher squeeze pressure (mean, 162.6 cm H(2)O) than those with a partial- (mean, 125.7 cm H(2)O) or full-length tear (mean, 124.9 cm H(2)O; P < 0.0001). There was no significant difference in squeeze pressure between those with partial- vs. full-length external anal sphincter tears nor between circumference tears < or >25 percent. Basal pressure was significantly lower in those with a full-length external anal sphincter tear (47.8 cm H(2)O) vs. an intact external anal sphincter (65.7 cm H(2)O; P < 0.001). The basal pressure in those with an intact internal anal sphincter was not significantly different from those with clearly defined internal anal sphincter tears, and the degree of circumferential involvement was also not important in this regard. However, those with a fragmented internal anal sphincter had a significantly lower basal pressure than other subgroups of internal anal sphincter injuries (P < 0.001). There was no association between external or internal anal sphincter status and the mean pudendal nerve terminal motor latency, suggesting the patient groups were neurologically similar. There was no significant association between external or internal anal sphincter status and the severity of reported symptoms.
  
  
  CONCLUSIONS
  Correlations between the presence or absence of muscle tears and reduced manometric function have been identified. Further grading of tears was of less importance. No relationship between muscle injuries and the severity of clinical symptoms could be elicited.
authors.affiliation: Division of Medical Imaging, Flinders Medical Centre and Flinders University, Bedford Park, South Australia, Australia.
authors.forename: Frank
authors.initials: F
authors.lastname: Voyvodic
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Rieger
authors.forename: Sarah
authors.initials: S
authors.lastname: Skinner
authors.forename: Ann C
authors.initials: AC
authors.lastname: Schloithe
authors.forename: Gino T
authors.initials: GT
authors.lastname: Saccone
authors.forename: Michael R
authors.initials: MR
authors.lastname: Sage
authors.forename: David A
authors.initials: DA
authors.lastname: Wattchow
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000000981:diagnostic imaging* / Q000293:injuries* / Q000503:physiopathology; D004576:Electromyography; D019160:Endosonography; D005242:Fecal Incontinence / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D012189:Retrospective Studies