Proctoscopy has an important role in the evaluation of fecal incontinence. It can be performed independently or during colonoscopy, ﬂexible sigmoidoscopy, and the ﬂat tire test. Proctoscopy can detect anorectal pathology, such as prolapsing hemorrhoids, intussusception, ulcerative or radiation proctitis, or a solitary rectal ulcer. The ﬂat tire test is added when a rectovaginal or colovaginal fistula is suspected but cannot be visualized on routine office evaluation. This test usually is performed under anesthesia but can also be done in the office setting. Saline or water is placed in the vagina with the patient in Trendelenburg position. Using a proctoscope or rigid sigmoidoscope, air is instilled into the rectum. Vaginal retractors provide visualization of the posterior vaginal epithelium and vaginal apex. Observation of bubbling into the vaginal ﬂuid confirms the diagnosis and location of a rectovaginal or colovaginal fistula. The rectal site of the fistula usually is identifiable, depending on the size and location of the fistula as well as the quality of the bowel preparation.
Sitzmark Study Colonic transit studies are performed using ingested radiopaque markers followed by serial abdominal radiography. Patients are asked to follow a high-fiber diet over the test period and avoid the use of laxatives, suppositories, or enemas. A capsule containing 20 to 24 markers is ingested initially, and abdominal radiography is performed either daily or on the fourth day, the seventh day, and every 3 days thereafter until all the markers are gone. Segmental transit times are then calculated using a mathematical formula. Colonic transit study results are used to classify patients with constipation into delayed transit, normal transit, and outlet obstruction. After day 6, there should be fewer than five markers remaining in the colon. With slow transit, more than five markers are scattered throughout the colon. With outlet obstruction, more than five markers are in the rectosigmoid region, and transit is normal throughout the rest of the colon.
Pelvic ﬂuoroscopy permits radiological evaluation of pelvic ﬂoor and anorectal anatomy and physiology. It is particularly useful in obstructive defecation disorders, such as intussusception, rectocele, enterocele, anismus, and perineal descent. The patient is placed on a radiolucent commode, and contrast material is instilled into the rectum. The addition of vaginal, bladder, and oral contrast material is helpful diagnostically when multicompartmental prolapse is suspected. A series of lateral still images or continuous imaging using videography are made with ﬂuoroscopy while the patient is at rest, during defecation, and with contraction of the anal sphincter. Similar films can be obtained for evacuation of the bladder. Pelvic ﬂuoroscopy has many names, including defecography, defecating proctography, defecating cystoproctography, and colpocystoproctography, depending on the technique used. The measurements obtained include size of the rectal ampulla, length of the anal canal, anorectal angle, puborectalis motion, and pelvic ﬂoor descent. Severity of prolapse and pelvic ﬂoor descent is quantified in relation to the pubococcygeal line. Pelvic ﬂuoroscopy is superior to physical examination for diagnosing enterocele, and this technique has the advantage of being able to distinguish enteroceles from sigmoidoceles (90). Rectosphincteric dyssynergia may be present when the patient experiences incomplete relaxation of the puborectalis muscle during rectal evacuation, the anorectal angle is preserved, and there is incomplete emptying. Pelvic ﬂuoroscopy is considered the definitive test for diagnosing intussusception, and it is the preferred technique for quantifying perineal descent (91).
Dynamic MRI with luminal contrast is an imaging modality similar to pelvic ﬂuoroscopy.