MR defecography for obstructed defecation syndrome

Abstract

Patients with obstructed defecation syndrome (ODS) form an important subset of patients with chronic constipation. Evaluation and treatment of these patients has traditionally been difficult. Magnetic resonance defecography (MRD) is a very useful tool for the evaluation of these patients. We evaluated the scans and records of 192 consecutive patients who underwent MRD at our center between January 2011 and January 2012. Abnormal descent, rectoceles, rectorectal intussusceptions, enteroceles, and spastic perineum were observed in a large number of these patients, usually in various combinations. We discuss the technique, its advantages and limitations, and the normal findings and various pathologies.

Keywords: Chronic constipation; magnetic resonance defecography; obstructed defecation syndrome; pelvic floor.

Figure 1(A-D)

Normal MR defecogram. Normal position of the anorectal junction at rest (arrow in a) with mild pelvic floor lift on squeeze (B) On straining (C) and defecation (D) there is mild descent of the anorectal junction, with the rectum and anal canal aligned in almost a straight line. The broken white line in (D) is the pubococcygeal line. The broken black line is the “H line” corresponding to the anteroposterior dimension of the hiatus. The solid black line is the “M line” which is the perpendicular distance between the pubococcygeal line and the posterior anorectal junction

Figure 2(A-D)

Severe descent of the anorectal junction with moderate anterior rectocele. Normal position of anorectal junction at rest (A) with normal alignment on straining (B). During defecation (C and D), there is severe descent of the anorectal junction which is located approximately 7 cm below the pubococcygeal line (line 1 in d). Also, note the moderate anterior rectocele measuring approximately 3 cm in length. The descent and the rectocele are measured as shown in (D)

Figure 3(A-C)

Moderate descent of anorectal junction and bladder with moderate anterior rectocele. Normal positions at rest (A) with moderate anorectal and bladder descent on defecation (B). Moderate anterior rectocele is also seen. The bladder and anorectal descents are measured as the respective perpendicular distance below the pubococcygeal line, while the rectocele is measured as the maximum depth of protrusion of the rectal wall beyond its expected normal contour as shown in (C)

Figure 4(A-D)

Retained contents in large anterior rectocele. Normal position at rest (A). On defecation (B-D), there is moderate anorectal descent (5.3 cm) and mild bladder descent (1.2 cm) with a large anterior rectocele (4.1 cm). The rectocele showed retained contents at the end of the defecating effort, (D) shows the measurements with line 1 representing the pubococcygeal line, lines 2 and 4 representing the anorectal and bladder descents, respectively, and line 3 representing the length of the rectocele

Figure 5(A-D)

Rectorectal intussusception. Normal position at rest (A) with moderate anorectal descent on defecation (B). There is evidence of telescoping of the proximal rectum into the distal rectum representing rectorectal intussusception (C and D). Note the classical “arrowhead” configuration of the intussusception

Figure 6(A-E)

Rectal prolapse. Normal position at rest (A). During defecation (B-E), there is a rectorectal intussusception which progressively descends and eventually causes a rectal prolapse with mucosal outpouching through the anal verge (open arrow in E)

Figure 7(A-D)

Spastic pelvic floor syndrome. Normal position at rest (A). During straining (B) and defecation (C), there is persistent prominent indentation of the puborectalis sling on the posterior rectal wall with an acute anorectal angle. (D) shows the acute anorectal angle of approximately 44° (measured between the posterior rectal and anal walls) during defecation. Compare with the normal defecogram in Figure 1

Figure 8(A-C)

Enterocele. Normal position at rest (A). During defecation (B and C), there is descent of the peritoneal sac with small bowel loops along the anterior rectal wall representing an enterocele. Also note the bladder and anorectal descent, anterior rectocele, and rectorectal intussusception

Figure 9(A-D)

Descending perineum on tricompartmental defecogram. Normal position at rest (A). Note the opacification of the vaginal vault by T2-hyperintense jelly improving its visualization. During straining (B) and defecation (C), there is significant descent of all the three compartments (i.e. urinary bladder, vaginal vault, and anorectal junction). The descents are measured below the pubococcygeal line as shown in (D). A small anterior rectocele is also seen

Figure 10(A-E)

Delayed rectorectal intussusception. Normal position at rest (A). During early defecation (B), no obvious abnormality was detected. However, during later stages of defecation, undulations appeared in the anterior rectal wall (C) with progressive development of rectorectal intussusception (D and E). This emphasises the need to run the dynamic sequence long enough to detect these delayed abnormalities which manifest on prolonged straining effort

Figure 11(A-C)

Pre- and post-operative MRD. Pre-operative MRD images (A and B) show significant bladder, vault, and anorectal descent with moderate anterior rectocele. The patient underwent anterior and posterior colporrhaphy and sacrospinous ligament fixation with trans-obturator band. Defecation phase of postoperative MRD (C) shows complete resolution of the bladder and vault descent and the anterior rectocele. The patient also showed symptomatic improvement