The clinical evaluation of pelvic floor disorders hinges on patient history and physical examination. Standardized systems for the clinical assessment of pelvic organ prolapse, such as the Baden–Walker Halfway System1 or the Pelvic Organ Prolapse Quantification (POP-Q) System,2 enable clinicians to reliably and reproducibly describe the extent of prolapse in each vaginal compartment.3,4 However, the underlying defects that contribute to the symptomatology of pelvic floor disorders often elude visual inspection in the office. The organ lying behind each prolapsed vaginal segment varies5,6 and important defects in the levator ani musculature cannot be visualized.7,8 Pelvic floor clinicians and researchers abandoned the terms “cystocele” or “rectocele” in favor of anterior vaginal wall or posterior vaginal wall prolapse to reflect clinicians’ inability to reliably determine the organ lacking support behind the prolapsed vaginal wall.
Multiple studies report high rates of reoperation for pelvic floor disorders after initial pelvic floor surgery.9 Some experts believe that the unacceptably high reoperation rate for pelvic floor disorders may result from patients receiving an operation that is not tailored to the specific anatomic defects that lead to their symptomatology. Clinicians have used various techniques and maneuvers on physical examination to precisely identify each anatomic defect that may be responsible for a patient’s pelvic floor dysfunction.10,11 In 1976 Richardson et al. described a technique of supporting the lateral vaginal fornices with ring forceps to differentiate midline defects, which would persist despite fornix support, from lateral detachments of the paravaginal connective tissue from the arcus tendineus fascia pelvis.10 Similarly, pelvic floor surgeons describe identifying rectovaginal septal defects12 and levator ani defects during office examination. The straining q-tip test aims to discern stress urinary incontinence due to urethral hypermobility from intrinsic sphincter deficiency; and the dovetail sign is interpreted as an indication of anal sphincter disruption or dysfunction.
Despite attempts to uncover the specific defects responsible for pelvic floor dysfunction on physical examination, the pathophysiology of pelvic organ prolapse and urinary incontinence remains poorly understood. In an attempt to understand the underlying etiology of pelvic floor disorders, researchers have turned to static and dynamic imaging of pelvic soft tissues and viscera. The advantages, limitations, and clinical applications of pelvic imaging modalities will be discussed in this chapter.
Cystourethrography is a simple, inexpensive imaging modality that can be performed as a series of still images or can be used with fluoroscopy to obtain dynamic images. Because it employs plain radiography, it requires relatively small doses of ionizing radiation.13 To perform the test, a catheter is inserted into the bladder and used for instillation of contrast media.
Cystourethrography is used to diagnose urethral obstruction, such as from a tight sling, urethral fracture, or avulsion following trauma, especially if there is extravasation of contrast material outside of the urethra or bladder neck (Figure 15-1), or urethral strictures or fistulae, which can be seen in women following radiation therapy or urethral surgery. Globular filling defects within the urethra that are associated with a hard palpable mass on examination can represent urethral tumors. Urethral carcinoma is a rare malignancy, accounting for 0.01% of female cancers; however, it is four times more prevalent in women than in men and is found in 2.5% of women with urethral caruncles.14 If initially diagnosed with cystourethrography, urethral tumors are better characterized by CT or MRI, which provide information about the size of the tumor, extent of invasion, and the presence of lymphadenopathy.
To perform voiding cystourethrography, a transurethral catheter is used to fill the bladder with contrast material and, after the transurethral catheter is withdrawn, the patient voids under fluoroscopic observation. Fluoroscopy can also be used during the bladder-filling phase, enabling observations of bladder wall stability and contour. During normal voiding, the bladder neck becomes funnel shaped; absence of funneling can indicate bladder outlet obstruction, such as from prior surgery. The presence of vesicoureteral reflux is also diagnosed on voiding cystourethrography. Voiding cystourethrography can be combined with cystometry, allowing simultaneous visual observation along with bladder and urethral pressure data, which can be useful in the evaluation of complex patients, such as those with multiple prior surgical procedures or neuropathic disease.
Prior to advent of magnetic resonance (MR) imaging, double balloon cystourethrography was commonly used to diagnose urethral diverticulae. Urethral diverticulae may be congenital or acquired as a result of dilation or rupture of chronically infected or blocked periurethral glands. Rarely, diverticulae may undergo malignant degeneration with intraluminal adenocarcinoma.14 Diverticulae vary in size from an outpouching no larger than the diameter of the urethra to a large saddle diverticulum that surrounds the urethra and may be unilocular or multilocular, with the neck of the diverticulum usually arising from the posterior aspect of the urethra. Diverticulae are reported in 1.4% of women with stress urinary incontinence and less than 1% of women with recurrent urinary tract infections.14,15 The classic triad of symptoms associated with urethral diverticulae is known as the three D’s: dysuria, postvoid dribbling, and dyspareunia, although postvoid dribbling is present in only 25% of patients with diverticulum and dyspareunia only in 10%.16
Simple voiding cystourethrography is 65% sensitive for detecting urethral diverticula, missing many diverticula with a narrow or kinked neck.14 At least 10% of diverticula are complicated by infection or stone formation, which can occlude the neck of the diverticulum, making it unlikely for contrast material to opportunistically enter the ostium during voiding. Double balloon, or positive pressure, urethrography employs a catheter with one proximal and one distal balloon and an injection port between the balloons. The catheter is inserted through the urethra, the proximal balloon is inflated in the bladder neck, and the distal balloon is inflated just outside the urethral meatus, thus creating a closed pressure urethral system. Contrast material is then instilled through the injection port and can be forced into narrow or kinked diverticular ostia, improving diagnostic sensitivity.17,18 The disadvantage of positive pressure urethrography is that it causes significant patient discomfort and hinges on establishing and maintaining a closed pressure system within the urethra for diagnostic accuracy. For this reason, it is rarely performed in current clinical practice and is largely replaced by MR and ultrasound imaging.
Evacuation proctography, also known as defecography, is a radiographic technique used for imaging of the posterior compartment at rest and during straining or defecation. The rectum is opacified with barium paste until the patient feels a sense of fecal urgency. The patient is then placed on a commode and instructed to evacuate while a series of lateral films or continuous fluoroscopy records the process of rectal evacuation. Typically, images are obtained at rest, with voluntary squeezing of the anal sphincter and/or levator ani, with Valsalva, and during defecation. Evacuation proctography is limited by cumbersomeness required to provide small bowel and rectal contrast and allow patients to defecate in the radiology suite. As a result, other imaging modalities are more commonly used to identify position of the pelvic organs in women with pelvic floor disorders. However, Kelvin et al. compared evacuation proctography with evacuation MR and concluded that proctography was superior to supine MR for detecting rectal intussusception.19
Parameters assessed on defecography include pelvic floor descent with straining, the rectal diameter, anorectal angle at rest and with straining, and rectal intussusception. There are specific characteristics associated with successful evacuation in patients without pelvic floor dysfunction. At rest, the external anal sphincter and the puborectalis muscle are contracted, creating an impression on the rectum that is visualized on lateral imaging as the anorectal angle, measured from the axis of the anal canal to a line through the central axis of the rectum (Figure 15-2A). The anorectal angle in normal subjects is about 90°, ranging from 70° to 135°.20,21 When the patient is asked to squeeze the anal sphincter and contract her pelvic floor, the anorectal junction is elevated, resulting in a decrease in the anorectal angle to approximately 75° (Figure 15-2B). With straining, the pelvic floor should descend on average 2 to 3 cm; descent should not exceed 4.5 cm in a patient without pelvic floor dysfunction.22 During defecation, the anorectal impression formed by the puborectalis should disappear allowing the anorectal angle to widen and the rectum to descend, assuming a continuous, funnel-shaped configuration with the anal canal23.
FIGURE 15-2
Defecography. A. The puborectalis muscle encircles the rectum, forming an impression that is identified as the anorectal angle (white arrow). The vagina has been filled with contrast (black arrow). B. Voluntary contraction of the pelvic floor engages the puborectalis muscle, accentuating the anorectal angle.
Defecography studies of normal volunteers also describe the position of the anterior rectal wall during defecation.24 Not surprisingly, the anterior rectal wall protrudes up to 2 cm during defecation in normal women, suggesting small rectoceles are probably a normal anatomic finding.
Studies performed on asymptomatic nulliparous women describe a wide range of findings.20,21 This may be a reflection of variation in normal anatomy, a lack of standardization of imaging technique, and the unnatural circumstances under which the patient is asked to defecate. Barium paste consistency also likely plays a role in study results, as thick, more solid paste is more difficult to evacuate than a more liquid suspension and, therefore, may be more sensitive for detecting defecatory dysfunction. As a result, it is difficult to reliably correlate radiographic findings on defecography studies with specific pathologic conditions, and the role of defecography in clinical practice continues to be uncertain. However, certain conditions are associated with specific findings, which are described below.
Posterior vaginal wall prolapse is thought to result from inadequate support by the rectovaginal septum, either due to general laxity in the endopelvic connective tissue or due to site-specific breaks in this connective tissue. The relationship between the position of the posterior vaginal wall and anterior rectal wall (rectocele) is complex as is the relationship between posterior vaginal wall prolapse and patient symptoms. Posterior vaginal wall prolapse can be associated with symptoms of only a bulge or defecatory dysfunction, including distal stool trapping.25 This complex relationship between anatomy and function makes it difficult to counsel patients about postsurgical outcomes of rectocele repair. Defecography depicts rectoceles as outpouchings in the anterior rectal wall with straining or defecation (Figure 15-3). Imaging not only is useful for visualization of rectocele size but can also reveal barium trapping within the rectocele, which can be a reflection of incomplete evacuation. Proctography studies of patients with rectal symptoms indicate that virtually all of them have a rectocele identifiable on imaging and that large rectoceles (larger than 4 cm in diameter) are more likely to retain barium.23 However, asymptomatic women are also known to retain barium on defecography, making barium retention a difficult result to interpret.26 Similarly, investigators found that grade of posterior vaginal wall prolapse was not associated with rectocele on defecography; likewise, contrast retention was not associated with clinical symptoms of incomplete evacuation.27 Therefore, whether retention is an artifact of the imaging modality or whether it is the first demonstrable defecatory abnormality that can be visualized prior to the development of defecatory symptoms is unclear.
Enteroceles are often confused for rectoceles as a cause of posterior wall prolapse. They can be difficult to determine on physical examination and difficult to differentiate from rectocele or sigmoidocele. Evacuation proctography is useful in identifying enteroceles if the small bowel is opacified by orally ingested barium. After performing fluoroscopy, including small bowel opacification, on 62 women prior to pelvic floor surgery, Altringer et al. concluded that evacuation proctography was superior to physical examination for diagnosing enterocele in women with prolapse, detecting enteroceles unsuspected on physical examination in 46% of patients.28 A widened rectovaginal space (>2 cm) on imaging suggests that there is a potential space for the appearance of an enterocele, but definitive diagnosis requires the visualization of small bowel loops within the rectovaginal space (Figure 15-4).
Similar to enterocele, sigmoidocele can be difficult to differentiate from rectocele and/or enterocele using just physical examination findings and patient symptoms; however, sigmoidocele is easily identified from its swan’s neck appearance on evacuation proctography. One study using evacuation proctography with small bowel, rectal, and vaginal contrast reported a 4% incidence of sigmoidocele in women undergoing pelvic floor surgery.29 Surgeons did not identify any of the sigmoidoceles on physical examination.
As previously mentioned, functional defecation requires the obliteration of the anorectal angle by means of voluntary relaxation of the external anal sphincter and the puborectalis muscle in response to rectal distension by stool or contrast media. Descriptive studies identified a group of patients who are unable to relax the levator ani, including the puborectalis, during defecation.30 Electromyographic studies of the puborectalis muscle in patients who fail to increase their anorectal angle on evacuation proctography confirm paradoxic myotonic activity during straining.31 This syndrome is referred to by a variety of names, including pelvic floor outlet obstruction, pelvic floor dyssynergia, anismus, and dyskinetic puborectalis, and is experienced by patients as chronic constipation requiring straining and/or digitation to complete rectal evacuation. Chronic straining commonly results in rectoceles in patients with a spastic pelvic floor. In this group of patients, performing rectocele repair without addressing their levator ani dysfunction is unlikely to resolve their defecatory symptoms. Thus, defecography can influence the management of patients with constipation and rectocele by elucidating the underlying dysfunction that resulted in rectocele formation.
Rectal prolapse occurs when a portion of the rectal mucosa protrudes beyond the anal verge, resulting in irritation, ulceration, and bleeding. It is thought to be preceded by rectal intussusception, an anterior or annular infolding of the rectum inside itself that originates 6 to 8 cm proximal to the anus but can progress to complete eversion of the rectum.32 Real-time defecography is used to demonstrate the progression of intussusception to complete rectal prolapse on straining. It is the study of choice for detecting rectal prolapse and sigmoidocele, both of which require surgical correction with rectopexy or sigmoidopexy, respectively, to achieve a favorable treatment outcome. However, the finding of isolated intussusception on evacuation proctography without signs or symptoms of an associated rectal prolapse is difficult to interpret clinically, as it is unknown what proportion of intussusceptions will progress to clinically significant prolapse.
Whereas imaging is certainly not required to make the diagnosis of fecal incontinence, it can shed light on the underlying mechanism behind the incontinence. External and internal anal sphincters cannot be visualized on defecography; ultrasound and MR imaging studies are much better suited for observation of sphincter anatomy and disruption. Sphincter function is better assessed by anal manometry or anal sphincter electromyography. However, defecography is an inexpensive and readily available tool that can provide general information about sphincter function. The thickness of barium paste can be manipulated to resemble fecal material that is most likely to elicit fecal incontinence, based on patient report. Barium leakage at rest implicates the internal anal sphincter, whose smooth muscle should be under involuntary continuous contraction maintaining continence at rest. A patient’s inability to decrease the anorectal angle with squeezing can be a reflection of levator ani denervation or avulsion, leading to a loss of function of the puborectalis sling. However, due to a limited treatment repertoire, information regarding fecal incontinence provided by defecography is generally unlikely to influence clinical or surgical management.
