improved outcomes in colon and rectal surgery to more reliable and reproducible data, these catheters are more easily and reliably cleaned from patient to patient. Pressure data is recorded continuously to computer based software that assists in creating the interpretation and the report. One critical obser- vation of the water perfused systems is that the patient may react to the sensation of water dripping from the anus with increased tone. Scrupulous technique may avoid this. Because various technologies and methods exist for measur- ing anal canal pressures, no universally accepted set of normal values exist. Simpson et al. addressed this issue in a study com- paring five different catheters and techniques of manometry in both normal and incontinent patients.(6) Although their sample size was small, 10 normal and 11 patients with incontinence, the authors found no significant difference between five commonly employed devices. They were; a water perfused end-hole catheter, a catheter water perfused with four radially arranged side holes, water filled microballoon, microtransducer, and an air-filled port- able microprocessor controlled device. sphincter pressure measurement Although written consent is not required as the patient is fully awake, at our institution we obtain full informed consent and con- firmation of patient identity, condition being evaluated, and their understanding of the tests they are about to undergo. The patients take one or two small volume cleansing enemas at home before the exam. Anal canal pressures are measured with the patient lying comfortably in the left lateral decubitus position with knees as hips flexed 90°. Some emphasis is placed on comfort and relaxation as anxiety, talking and anything that increases the intraabdominal pressure may affect the results. We employ a stationary pull through technique. The catheter is placed transanally with the measuring points (balloons, holes or microtransducers) to a distance of 6 cm above the anal verge. Measurements are taken in the anterior, pos- terior, left, and right lateral positions. (Figure 10.2c) Pressures are recorded at relaxation and at maximum “squeeze” for 10 seconds. The patient must be instructed to try to isolate squeeze of the anus and not employ the gluteal or any other accessory muscles. The Figure 10.1 Typical Anorectal Physiology Lab with Manometry, Transanal ultrasound, Pudendal Nerve Terminal Motor Latency testing, Biofeedback, storage and equipment for sterilization. (a) (b) (C) Figure 10.2 (A) Manometry Catheter, with balloon. (B) Manometry Catheter, detail microtransducers. (C) Manometry tracing, computer display. limitations of anorectal physiology testing catheter is repositioned 1 cm distally and the process is repeated. The process is repeated in step-wise fashion until the entire canal had been tested. An alternative to this “station pull out” technique is recording pressures during a continuous pullout of the catheter at a controlled steady rate. The following parameters are recorded: length of the anal high pressure zone, mean resting tone, maximum squeeze pressure. In an effort to study the symmetry and detailed overall pressure profile of the anal sphincter, pressure vectography, a technique that provides graphical representation of radial pressure profile of anal canal, was developed. the recto-anaL inhibitory refLex The presence or absence of the Recto-Anal inhibitory reflex (RAIR) is identified by rapid distention of the rectum by insuf- flation of the balloon at the tip of the catheter with 10 cc of air. Simultaneous recording taken in the middle of the anal canal high pressure zone are made for 10 seconds. If the RAIR is present, a reflex relaxation of internal sphincter and resultant decrease in anal canal pressure should be observed. Balloon insufflation may be repeated with more air at 10 cc increments up to 60 cc until a reflex is observed. rectaL capacity and sensation The balloon at the end of the catheter may also be filled with water in an incremental fashion to assess rectal sensation and compliance. Measurements are made at the minimum volume of first rectal sensation, the volume required to produce a sustained feeling of the need to defecate and a maximum volume that cre- ates significant discomfort or an irresistible need to defecate. vaLue and Limitations of manometry for incontinence Anal manometry has become a staple in the evaluation of fecal incontinence. Though routinely performed in many centers, man- ometry lacks standardization of technique, data collection, and methods of interpretation. This makes it extremely difficult to compare data obtained at different centers. The range of accepted normal values is wide varying for gender, parity, age, and numer- ous other factors. Despite the fact that the newer catheters are more comfortable and easier to maintain, the test remains mildly invasive and uncomfortable for the patient. There are several technical caveats that may lead to consider- able alteration in results. Patients with megarectum may require a higher volume to illicit RAIR and may be falsely labeled as RAIR negative if the usual volume of 30–40 cc is used to illicit RAIR.(7) The balloon material can influence the results as latex balloons tend to deform along their axis, resulting in a falsely elevated rectal compliance.(8) Rectal compliance testing depends entirely upon patient’s input, thus patient’s psychological status plays a very important role in data acquisition during this test. (7) Furthermore the results of rectal compliance may differ if the test is performed on “prepared”, i.e., after enema evacuation vs. unprepared rectum.(7) The rate at which water is injected into the balloon may also affect the rectal sensitivity testing.(9) Thus, it is recommended that slow filling should be accomplished at a rate of 1 ml/second.(7) Whatever the method used, the same technique should be applied to all patients in order to obtain reproducible and comparable results. Caution should be exercised while making treatment decisions based on manometric findings as normal or abnormal values in incontinent patients do not necessarily correlate with severity of symptoms. In a large prospective study Lieberman et al. evaluated 90 incontinent patients, including 6 males with a specific goal at determining what impact physiology testing including manom- etry had on treatment and outcome. After appropriate history and physical exam patients were selected for medical or surgical management. Following this determination they underwent anal physiology testing including manometry, pudendal nerve termi- nal motor latency (PNTML), and anal ultrasound (AUS). Overall only 9 (10%) had a change in their management plan. Based on the results of these tests, 5 of 45 patients initially assigned to medical management were offered surgery instead. On the other hand, 3 of 45 patients assigned to undergo surgical treatment were switched to the medical group. Almost all of these alterations in manage- ment were based on AUS. Manometry was found to be abnormal in one-third of both management groups and there was no correla- tion between manometric results and change in management plan. There did not appear to be an association between manometry, AUS and PNTML results.(10) In an elaborate study of 350 patients including 80 controls, Felt-Bersma et al. found that the most sig- nificant difference between continent and incontinent patients was maximum squeeze pressure.(11) However, the authors surmised that continent function could not be predicted based on anal man- ometry alone and suggested that these results should only be inter- preted in conjunction with other tests. Although it creates a rather striking and impressive graphical representation of anal canal pressure profile, pressure vector dia- grams have been shown to be of questionable clinical value for sphincter evaluation.(12) A study by Yang et al. could not demon- strate any correlation when vectoral analysis was compared to nee- dle electromyography (EMG) and ultrasonography.(12) With the increased use of AUS the utility of vectogrpahy has been negated. Anorectal manometry remains of value for objective preopera- tive documentation of anal tone function or muscle weakness. It is also helpful in excluding patients from surgery.(2) Perhaps the biggest merit of manometry is its role as the initial diagnostic test for short segment Hirschsprung’s disease where the presence of an RAIR effectively rules out the disease. eLectromyography EMG is the measurement of the electrical activity generated by mus- cle fibers during contraction or at rest. In 1930 Beck first described anal sphincter EMG.(13) Specifically, the EMG measures activity in a motor group or those muscle cells innervated by a single axon. Muscles whose nerves have been damaged will demonstrate altered activity. Myography has been used to map the perianal area for muscular activity and thereby detect sphincter defects. EMG is also used to demonstrate nerve conduction and appropriate activation and relaxation used in biofeedback therapy. Concentric Needle EMG A concentric needle electrode is two insulated electrodes, one within the other. With the needle inserted into the muscle to 0 improved outcomes in colon and rectal surgery be observed, in this case the external sphincter or the pelvic floor, the electrical potential from one electrode to the other is recorded. Information collected includes amplitude, duration and frequency, as well as the number of phases. Amplitude is proportional to the number of muscle fibers activated. Normal values are an amplitude of <600 μV and duration <6 μs.(14, 15) Longer duration or spreading of the signal can indicate dis- persion of the motor unit potential (MUP). This may repre- sent denervation or demyelination, or simply aging. The sum of the activity of many muscle cells creates a shape to the MUP. Normal MUPs are bi- or triphasic. In general, more phases within the action potential indicated denervation and rein- nervation. However four or more phases have been reported in normal muscle in up to ¼ of the time. Single Fiber EMG Individual muscle fiber action potentials can be recorded with a single fiber EMG. The recording area of the needle is much smaller, 25 μm. In normally innervated external anal sphinc- ter muscle only a few fibers will be activated by a single motor group axon. However, when damage occurs denervated muscle fibers are recruited by surviving axons. The number of muscle fibers and thereby signal density within the recording area of the needle increases, resulting in a more polyphasic signal. The test is performed by taking multiple readings requiring multiple skin punctures around the anus. Surface EMG/biofeedback Measurement of muscular activity through the insulation of the skin is far more imprecise but less painful than needle EMG. Surface EMG is valuable for documentation of overall activity, especially during attempted voluntary rest, inhibition, or contrac- tion of a muscle. Surface EMG is helpful to document paradoxical sphincter activity as part of the diagnosis of disordered defecation. Two self-adhering surface electrodes can be applied on opposite sides of the anus over the subcutaneous portion of the external sphincter, with a grounding electrode placed at a distance on the patient. Alternatively, a plug electrode is employed within the anal canal (Figure 10.3). Surface measurement of muscle activity is more valuable if the muscle is being artificially activated by stimu- lating the nerve. When the time of nerve stimulation is known and time of muscle activity measured, nerve conduction velocity can be assessed. A specific application of nerve stimulation and surface EMG is measurement of the PNTML. pudendaL nerve terminaL motor Latency The pudendal nerve arises from the second, third and fourth sac- ral nerve roots bilaterally and passes along the inferior pubic rami through Alcock’s canal. Prolonged labor or the use of forceps for delivery may injure the pudendal nerve as it exits from the canal. The conduction time of the nerve can be measured by stimu- lating the nerve transrectally and observing the time to electri- cal activity of the external anal sphincter. A St. Marks electrode attached to a gloved finger provides both stimulation and meas- urement (Figure 10.4a,b). An absent trace may indicate injury to the nerve whereas a prolonged PNTML is interpreted to indicate nerve injury and repair. Figure 10.3 Surface EMG electrode. (a) (b) Figure 10.4 St. Marks electrode. 1 limitations of anorectal physiology testing Limitations of eLectomyography in incontinence The EMG delineation of anatomic sphincter defect has been largely supplanted by imaging studies such as ultrasound and pelvic mag- netic resonance imaging (MRI). Concentric needle EMG and single fiber EMG testing is uncomfortable, or in some cases, frankly pain- ful for the patient. The equipment is expensive and difficult to mas- ter. Results are variable based on the cooperation of the patient, the experience of the examiner, and the patience of both.(16) Surface EMG is mildly uncomfortable to the patient and technically chal- lenging to perform. Identification of the nerve tracing can be sub- jective. Pudendal nerve latency testing is operator dependent. Since PNTML measures the fastest remaining fibers, a normal latency time does not exclude injury. The latency values obtained are also affected by the distance between the electrode and the pudendal nerve; shortest latencies being obtained by placing the electrode as close to the nerve as possible.(9) This is usually accomplished with subtle movements of the electrode bearing finger inside the anal canal while observing waveforms for the shortest latency thus gen- erated in response to repeated electrical stimuli. This method may result in significant patient discomfort in some cases. There is some bilateral crossover innervation of the sphincter therefore a unilat- erally abnormal test does not preclude normal function. Earlier studies indicated that significantly abnormal bilateral results were predictive of poor outcome with sphincter repair.(17–19) However, other authors have not found PNTML to be helpful in this regard. (10, 20) Increased pudendal nerve terminal velocities have been previously associated with patients with idiopathic incontinence. (21) Newer literature, however, suggests that this association might not be entirely true. Ricciardi et al. showed that only a small per- centage of patients with idiopathic fecal incontinence had associ- ated pudendal neuropathy.(22) Anal Ultrasonography High quality circumferential images of the anal sphincter complex can be obtained using anal ultrasonography (AUS). Although a number of probes are available, the most commonly used for evalu- ation of the anal sphincter is a rotating probe that creates a 360°, two-dimensional transverse image. The transducer generally used is a combined 7 or 10 MHz transducer, rotating within a water-filled rigid cap covered with a balloon or condom. Newer probes are fully self-contained. They still require protection with a condom and some type of interface media such as gel or water.(Figure 10.5) In many outpatient anorectal physiology labs the procedure is performed in the left lateral decubitus position in conjunc- tion with anal manometry. For a patient scheduled to undergo multiple anorectal physiology studies the same day, we follow a policy of performing manometry initially followed by other investigations as the sphincter stretch induced by 12 mm son- ogram probe may produce erroneous manometric findings. As such, the patient may have had limited preparation with a small volume enema. This is not required for AUS alone. Some authors prefer the prone or lithotomy positions feeling that the lateral position deforms the anatomy.(23) The clinical signifi- cance of this is unclear. AUS can distinguish the internal and external sphincters individually, with an intact internal sphinc- ter representing a continuous hypoechoic band. The external sphincter is more heterogenous but distinctly more hyperechoic. Although images can be taken throughout the anal canal, images are traditionally documented and preserved at proximal, mid and, distal anal canal. Defects in either the internal or external sphincters are identified as a disruption in the continuous ring. The external sphincter naturally splits proximally as it extends to the levator sling and the pelvic floor musculature. Disrupted tissue heals with a scar which appears amorphous, more echo- genic than internal sphincter, but less so than external. It is seen bridging the gap in the defect between the disrupted ends of the sphincters. The presence of a sphincter defect on AUS cor- relates well with a history of obstetrical trauma, as well as with physical exam findings and manometric findings.(10, 20, 24) Interobserver agreement is excellent and when an anatomic defect is present AUS sensitivity approaches 100%, specifically for internal anal sphincter defects in the mid anal canal.(25) Different techniques have been employed to either improve or make easier definition of the anal anatomy. Some authors claim anal squeeze, and relaxation improves the yield of sonographic exam while others have no benefit.(23) A finger placed in the posterior wall of the vagina used to measure the thickness of the perineal body has been shown to aid in the evaluation of anterior sphincter defects.(25) Figure 10.5 St. Marks electrode attached to glove. improved outcomes in colon and rectal surgery Global deficiencies or thinning of the sphincters rather than defects are more difficult to define with AUS. The internal sphincter is normally between 2 to 4 mm. Since it is more distinct on AUS, excessive thickness or thinness can be identified. One elusive objective is to identify atrophy of the external sphincter as this correlates with poor outcome from sphincter repair.(26) Three dimensional axial endosonography is now available. The probe spirals and moves through the sphincter at a fixed rate collecting a three dimensional block of echo-data that can be represented on a computer screen and evaluated through any plane through the block. In a study involving 33 women with sus- pected sphincter injury, two different observers compared 2-D AUS with 3-D evaluation. There was an identifiable improvement in the confidence of the examiner in detecting sphincter defects with 3-D evaluation over 2-D images. Interobserver correlation was also improved by 3-D evaluation but not to a significant degree.(27) Nevertheless, 3-D AUS has not been indisputably demonstrated to be more sensitive or specific, than transverse planar AUS. Limitations of uLtrasound in incontinence Ultrasound is the most important test in the evaluation of fecal incontinence with few limitations. Anorectal ultrasound entails a significant learning curve (28) and results are operator and experi- ence dependent. The external sphincter is less distinct than internal sphincter and smaller, <90°, defects are harder to demonstrate. (29) Patients with minimal symptoms and limited defects may not require surgery; therefore the clinical significance of a defect is determined by the combination of physical exam, anorectal physiology (ARP) testing, and AUS (Figure 10.4). The presence of atrophy of the external sphincter is similarly hard to prove. This is due to the fact that atrophic external sphincter becomes replaced with fat making sonographic delineation of the sphincter from the surrounding fat tissue more difficult.(30) Many investigators believed that 3-D ultrasound, by virtue of its superior resolu- tion, may result in improved identification of external sphincter atrophy. However a comparative study showed no correlation between 3-d AUS and MRI in 18 incontinent women with MRI evidence of sphincter atrophy.(31) Biofeedback for fecal incontinence Biofeedback is a process by which the patient is given an audi- tory or visual representation of anorectal information, pres- sure or muscle activity, which they cannot otherwise perceive or correctly interpret. Techniques of biofeedback have successfully used in the treatment of fecal incontinence for over 25 years. The practice parameters of the American Society of Colon and Rectal Surgeons (ASCRS) give a grade “B” recommendation for its use as a first line therapy and in patients that have incomplete success after sphincter repair.(2) Limitations of biofeedback for incontinence Despite some encouraging earlier reports describing success of biofeedback in the management of incontinence, the Cochrane system review of treatments for incontinence in 2006 did not support its use.(32) The authors reported, “The 11 trials reviewed were of very limited value because they were generally small, of poor or uncertain quality, and compare different combinations of treatments”. Overall success with biofeedback varies from 65% to 89%.(2, 33, 34) Two large randomised controlled trials include more than 100 subjects. Both concluded that biofeedback pro- vided no additional benefit over office counseling therapy such as advice, education, dietary modification, digital guidance, and medication. Despite the lack of demonstrated benefit, both trials showed improvement in severity of symptoms, fecal incontinence scores, and quality of life.(35–37) These benefits were seen in both the treatment and control groups indicating the role of patient motivation and ongoing medical involvement in the treatment of fecal incontinence. The most important predictors of success were completion of the program, and age over 60 years. Higher body mass index was associated with a worse outcome. Summary: Value and limitations of ARP testing for evaluation of fecal incontinence The perceived value of ARP testing in the evaluation and man- agement of fecal incontinence varies greatly on the perspective of the examiner and the expectations of the patient. The most fre- quently employed test include anal manometry, transanal ultra- sound, and pudendal nerve terminal motor latency. Techniques and normal values are not universally accepted. Abnormal results do not equate with specific disease, injury, or symptomatology. Transanal ultrasonography and MRI provide excellent anatomic definition to aid in the planning of surgical intervention. At best manometry serves for documentation of preoperative function and may assist in patient selection for surgery. PNTML is still controversial as to its role in the treatment of fecal incontinence. investigations for constipation and disordered defecation Constipation is one of the common ailments presented to the color- ectal surgeon. It usually entails unsatisfactory defecation resulting from decreased frequency of defecation of difficulty in passing stools or both. Prevalence in the general population in United States has been reported to be as high as 2–15%.(38, 39) Women are affected 2–3 times more commonly with incidence increasing with age. As with incontinence, the etiology is multifactorial and complex. Etiological factors associated with constipation include lifestyle issues and medications; especially narcotics, antidepres- sants, and calcium channel blockers. Pelvic outlet obstruction (puborectalis dysfunction, rectocele) is also a common underlying abnormality. Other causes include neurological or endocrine dys- function for example, Parkinson’s disease, diabetes mellitus, and hypothyroidism. Finally, dysfunction of enteric nervous system seen in Hirschsprung’s and Chagas disease and psychological factors may also play an important role in the pathogenesis. Refractory constipation that fails to respond to dietary modifi- cation and conservative management warrants a formal work-up. From management perspective, constipation is usually referred to as either slow transit constipation or obstructed defecation. The initial history and physical examination, in most cases, is able to indicate if the patient is experiencing slow transit con- stipation vs. obstructed defecation. Colonic transit studies are usually the first tests to be ordered in cases where slow transit is suspected to be the underlying etiology whereas in patients limitations of anorectal physiology testing with obstructed defecation, a defecogram should be offered as the initial diagnostic study. However, studies have shown that there is little, if any, correlation between these two diagnostic modalities and clinical picture does not necessarily reciprocate the radiological findings.(40) defecography Since the 1960s, continuously recorded fluoroscopy has been used to evaluate the dynamic function of the pelvic floor. Defecating proctography or ciné defecography is a method whereby semi-solid radiopaque contrast material is placed retrograde into the rectum and lateral images are obtained in real time. Creating a realistic “pseudo stool” has been a challenge. A commercially available prod- uct was available but was transiently taken off the market. Many institutions create there own contrast as needed using a combina- tion of barium and potato starch. At the authors institution we use a unique recipe based on breadcrumbs. The material must be thick enough to simulate stool but able to be passed transanally. Once the enema is administered the subject is seated in a lat- eral orientation on a radiolucent commode. Before defecation measurements are made of the angles of the proximal and distal rectum. In women the vagina may be delineated with a tampon soaked with water soluble contrast, and in certain circumstances the small bowel is opacified with oral contrast. If further deline- ation is required sterile water soluble contrast can be placed intraperitoneally to define the lower peritoneal reflection, fur- thermore, in patients with suspected cystocele, instillation of dye into the bladder may increase the diagnostic yield of the study. The anorectal angle is created in part by the tone and function of the puborectalis muscle. Measurements are taken as the patient is sit- ting at rest, during forced contraction, straining without defecation (Valsalva maneuver), and during defecation. Perineal decent is defined as the change in distance of the line drawn perpendicularly from the anorectal junction to the pubococcygeal line. This line is drawn from the tip of the coccyx to the posterior-inferior margin of the pubic ramus. In addition perianal skin can be marked with a metal marker and the motion or decent of the perineum measured. Normal reported values vary widely. One author offers a broad range, 70°–140° at rest, 100° to 180° defecating, and 75° to 90° squeezing (41, 42), where another is more specific 92° +/- 1.5° resting and 137° +/- 1.5° straining (5). The change in the angle may be more important than the absolute numbers. In our prac- tice the test is of most value if the surgeon reviews the study with the radiologist while the test is being performed. Abnormal findings include perineal descent of more than 3 cm while resting or more than 3 cm while straining. Paradoxical con- traction of the puborectalis and disordered defecation is indicated by an observed ascent of the perineum or a static or more acute anorectal angle during attempted defecation. Additional findings may include internal intussusception to frank prolapse, rectocele, or enterocele. Small, <2 cm rectoceles, are commonly seen in asymptomatic patients and are regarded as a normal finding. Limitations of defecography in constipation It must be remembered that defecography is not a “physiological” study as the study is not performed in response to a natural desire to defecate, instead patients are asked to evacuate in a rather alien, uncomfortable environment. Amongst other criticisms regarding defecography are poor interobserver agreement.(43, 44) To com- plicate issues further, abnormal defecographic findings are com- mon in asymptomatic patients.(45, 46) The significant degree of overlap between defecographic findings in patients with con- stipation and asymptomatic controls raises questions regarding the cause and effect relationship between clinical symptoms and defecographic findings. One of the radiological signs frequently documented during these studies is contrast retention within the rectoceles. The clinical significance of this “Barium trapping” seen has also been questioned.(47) In a study by Shorvon et al. one half of asymptomatic subjects had some aspect of mucosal prolapse and intussusception, 17 of 21 women demonstrated some degree of rectocele.(48) In addition, before that work, no work had employed normal, healthy volun- teers as controls and “normal” was determined retrospectively by lack of anatomic abnormality. Other studies were performed in patients undergoing barium enemas for other, nonanorectal condi- tions.(48, 45, 49) Anorectal angle assessment and its interpretation should be performed with utmost caution. As alluded to earlier, there is a wide variation in normal values for anorectal angle and many investigators believe that it is the change in angle rather than the absolute values that serves as a useful guide to therapy.(7) Patients with urge incontinence may frequently show increased threshold for urge to defecate. It is unclear if this finding is the result rather than the cause of constipation (9) and the clinical implication of this finding remains uncertain. Abnormal pub- orectalis function noted at defecography has also been a topic of considerable debate. Many normal individuals have been shown to have puborectalis abnormalities on defecograms (50), thus the clinical relevance of these findings are questionable and thera- peutic decisions should be based on clinical rather than mere abnormal findings on radiological studies. coLonic transit studies (sitz marker®) Colonic transit studies play a pivotal role in the assessment of con- stipation. Majority of colorectal surgeons agree that transit studies supply the most pertinent information out of all the physiology testing modalities available for constipation.(51) The most widely accepted technique involves ingestion of 24 radio-opaque rings followed by X-ray at days 1,3 and 5. A normal study entails passage of more than 80% of the rings. A quick way to help evaluate the patient for the presence of gastroparisis as well as small dysmotily is to make sure that they take the sitzmaker pill right before bed and have the day one x-ray as early in the morning as possible. While not useful in evaluating colonic transit, all of the makers should be out of the upper GI tract. The mean colonic time has been shown to 31 hours in males and 39 hours in females.(15) Based on the location of retained rings, abnormal studies may be labeled as “outlet obstruction” if 20% or more rings are retained at day 5 in the rectosigmoid region or “colonic inertia” if more than 20% rings are dispersed throughout entire colon. Clinical effi- cacy of colonic transit studies to detect segmental bowel motility remains controversial.(9) No bowel prep is administered before the study and patients are directed to avoid using laxatives and promotility agents including dietary fiber for at least a week before the study and during the duration of the study. improved outcomes in colon and rectal surgery smaLL boweL transit studies Since it is generally accepted that slow transit constipation is over- whelmingly attributed to colonic dysfunction, small bowel transit studies are infrequently requested. However when clinical suspicion exists, such as patients with gastroparesis and dilated small bowel on plain x-rays, small bowel motility studies should be undertaken before undertaking a surgical intervention. Several techniques are available to assess small bowel transit. Nondigestible carbohy- drates are broken down into hydrogen and fatty acids upon reach- ing the colon. Hydrogen and fatty acids are then absorbed into the blood stream. Therefore interval between ingestion of substrate and increments in exhaled hydrogen levels estimate small bowel transit. Similarly, orally administered sulfasalazine is broken down by colonic bacteria into mesalazine and sulfapyridine and then absorbed. Colonic transit can be measured by serum detection of sulfapyridine. Radio nucleotide scintigraphy has also been used to assess small bowel transit function. However, the clinical applica- tion of these tests is limited by their complexity and variation in bacterial flora in different subjects. mri Magnetic Resonance Imaging (MRI) of the pelvic floor is the newest addition to the diagnostic armamentarium available for pelvic floor evaluation. MRI obviates the exposure to radiation. Technique involves filling rectum with ultrasound gel. Images can be obtained in “static” manner or in the form of dynamic pelvic MRI which involves patient to perform maneuvers that are simi- lar to those performed during conventional defecography. During these maneuvers, multiple images are obtained which are then viewed as a cine loop. MRI provides excellent spatial orientation of the sphincter complex and provides superior delineation of the surrounding structures. MRI appears to be superior to ultra- sonography in discerning external sphincter abnormalities.(30) Additionally, dynamic MRI defecography appears to be supe- rior to conventional defecography in the evaluation descending perineum syndrome as it provides excellent spatial assessment of pelvic floor musculature.(52) Limitations of MRI in constipation Dynamic pelvic floor MRI shares similar limitations as conven- tional MRI: cost, claustrophobia, and availability. There are how- ever, some specific limitations related to the diagnostic modality. Studies comparing dynamic MRI with conventional defecography have yielded conflicting results. Healy et al. (53) found significant correlation between dynamic MRI findings and defecography in ten patients examined employing both techniques. On the con- trary, Matsouka et al. (54), in their study of 22 patients, reported defecography to be more sensitive than dynamic MRI and recom- mended against the routine use of this expensive modality. Most centers perform pelvic floor imaging with patient in supine posi- tion. Patients are asked to strain in a position which is far from physiologic and raises concerns regarding the reliability of the test. The influence of patient positioning has been investigated. Bertschinger et al. (55) performed a prospective comparison of 38 patients who underwent closed MRI in supine position fol- lowed by open MRI in a sitting position. Four rectal descents, two enteroceles, four small cystoceles, and four small anterior rectoceles were missed at supine MRI. The clinical significance of these findings, however, remains questionable. As mentioned earlier, the lack of “normal controls” makes it difficult to assess the efficacy of this test. baLLoon expuLsion test Balloon expulsion test is an infrequently used method to test motor defecatory function of the rectum. There is complete lack of standardization of methods used in various anorectal manom- etry laboratories.(55A) Various size balloons have been used for this purpose. Commonly 50–100 cc deformable balloons are used. Alternatively, smaller, more rigid balloons may also be employed. The impact of size and compliance of balloon on the final inter- pretation of test is unclear. In general, it is easier to evacuate larger balloons.(56) Many investigators believe that volume of balloon should be individualized to induce a constant desire to defecate. Consequently, use of lower volumes may result in false positive results.(57) There is a wide variation in what is considered to be a normal test. Inability to expel balloon in a sitting position within 30–60 seconds is considered abnormal in most centers. Balloon expulsion has been shown to be of importance in differentiating between constipation caused by slow transit from that caused by pelvic floor dyssynergia.(57) biofeedback for constipation Biofeedback training is widely utilized to teach relaxation of the pelvic floor in patients with pelvic floor dyssynergia. A critical review of the available literature by Heymen et al. (58) includ- ing thirty eight studies showed that mean success rate with pres- sure biofeedback was 78% compared to mean success rate of 70% seen with electromyography feedback. The authors surmised that despite the reported success rates, quality research is lacking. The most controversial area involving biofeedback training for constipation is questionable longevity/sustainability of the results. Ferrara et al. (59) reported a clear loss of benefits over time despite initial success. patients perspective Inherent to the evaluation of fecal incontinence is patients’ feel- ings of shame, embarrassment and discomfort. These sensations are felt by the incontinent patient resulting in depression and social isolation. A number of quality of life tools have been devel- oped to quantify the results of evaluation and treatment of fecal incontinence. No one tool is universally accepted and these tools have been difficult to validate.(60, 61) In addition the testing incontinent patients are subjected to may be embarrassing and uncomfortable. Deutekom et al. con- ducted a cohort study of 240 consecutive patients undergoing evaluation of fecal incontinence in 16 Dutch centers. Each patient underwent manometry, defecography, AUS, PNTML, and MRI. Two hundred forty of the 270 self-administered questionnaires were returned. Patients were asked to evaluate anxiety, discom- fort, embarrassment, and pain. Answers were scaled from 1(not 0), none to 5, severe. Results were also summarized as total test burden. Overall test results were surprisingly low, with aver- age scores in each category not exceeding 2. Overall MRI was the most preferred and least uncomfortable test. Defecography limitations of anorectal physiology testing was the most inconvenient and uncomfortable. Anorectal com- bined testing; manometry, PNTML, and AUS, also scored low for discomfort and overall test burden but more so than MRI.(62) concLusion Physiological studies of anorectal function can provide valuable information in carefully selected cases. While performing these studies, one should be cognizant of the fact that these procedures can be embarrassing, and at best are far from patient’s usual habits. It is unnerving for many patients to perform the act of defecation in the presence of an audience and it is conceivable that “perform- ance anxiety” may lead to results which may not be truly repre- sentative of actual patient status. Thus, these studies should be interpreted with a grain of salt. Despite the plethora of literature available, the clinical usefulness of these tests remains vague and there is limited evidence that anorectal imagining guides man- agement in pelvic floor disorders.(63) There are multiple well- designed studies, which unfortunately report conflicting results. We therefore recommend that the most decisive factor govern- ing treatment decisions is history and physical exam. Physiology testing should always be used as an adjunct rather than a primary determinant. references 1. Whitehead WE, Wald A, Norton NJ. Treatment options for fecal incontinence. Dis Colon Rectum 2001; 44: 131–42. 2. Tjandra JJ, Dykes SL, Kumar RR et al. 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Recent advances in assessing anorectal structure and functions. Gastroenterology 2007; 133(4): 1069–74. 11 Limitations of colorectal imaging studies Travis J Blanchard, Wilson B Altmeyer, and Charles C Matthews CHALLENGING CASE A 53 year-old woman presents to the emergency room with fever, left lower quadrant abdominal pain, and tenderness. Her tem- perature is 39 degrees Centigrad and her white blood cell count is 17,000 cells per cubic milliliter. What is the best radiologic test to confirm her diagnosis? CASE MANAGEMENT A CT scan of the abdomen and pelvis will evaluate her to con- firm the diagnosis of acute diverticulitis. In the absence of acute diverticulitis it may very well provide anothe explanation for her symptoms. INTRODUCTION Years of technical developments, organizational changes, and educational advances have inexorably altered the nature and com- position of colorectal imaging. Conventional radiology or “plain films” and barium fluoroscopy studies are still important, but the developments of CT, US, MRI, nuclear medicine, and interven- tional radiology have greatly expanded the scope of radiology. This chapter will discuss the various imaging modalities, focusing on the capabilities and limitations of each modality to diagnose various disease processes important to the colorectal surgeon. ABDOMINAL RADIOGRAPHY (PLAIN FILMS) Abdominal radiography typically consists of a single-view abdom- inal x-ray of the kidneys, ureters, and bladder (KUB) or an acute abdominal series (AAS). An AAS includes an upright chest radiograph, as well as upright and supine radiographs of the abdomen. An AAS can identify large masses, radiopaque for- eign bodies, and radiopaque densities (including gallstones and kidney stones). Pneumoperitoneum As little as 1–2 cc of pneumoperitoneum (free intraperitoneal air) can be seen on an upright chest (Figure 11.1) or lateral decubitus film.(1) Postoperative pneumoperitoneum usually resolves in 3 to 7 days. Failure of progressive resolution or an increase in the amount of air present suggests a bowel anastomosis leak or abscess/sepsis. Signs of pneumoperitoneum (Figure 11.2) on supine radiographs include the “Rigler” sign or “double lumen” sign (gas on both sides of the bowel wall), and gas outlining the falciform ligament.(2) Bowel Obstruction and Dilatation The 3, 6, 9 rule can be used to identify bowel dilatation. The small bowel is dilated when its diameter is 3 cm; the colon when it is 6 cm, and the cecum when it is 9 cm. Abdominal plain films can diagnose small bowel obstruction (SBO), in 50–60% of cases with approximately 20% false-negative rate.(3) SBO can be com- plete/high grade or partial. Dilated loops of small bowel, air-fluid Figure 11.1 Pneumoperitoneum. Upright radiograph of the abdomen demonstrates a collection of air within the peritoneal space between the liver and the diaphragm. Figure 11.2 Pneumoperitoneum. Plain radiograph demonstrates the “Rigler” sign or “double lumen” sign (gas on both sides of the bowel wall). . is two insulated electrodes, one within the other. With the needle inserted into the muscle to 0 improved outcomes in colon and rectal surgery be observed, in this case the external sphincter. glove. improved outcomes in colon and rectal surgery Global deficiencies or thinning of the sphincters rather than defects are more difficult to define with AUS. The internal sphincter is. 1567–74. 11. Felt-Bersma RJ, Klinkenberg-Knol EC, Meuwissen SG. Anorectal function investigations in incontinent and con- tinent patients. Differences and discriminatory value. Dis Colon Rectum