Simulated stool for assessment of anorectal physiology.

Fecal continence is maintained by several mechanisms including anatomical factors, anorectal sensation, rectal compliance, stool consistency, anal muscle strength, mobility, and psychological factors. The homeostatic balance is easily disturbed, resulting in symptoms including fecal incontinence and constipation. Current technologies for assessment of anorectal function have limitations. Overlap exist between data obtained in different patient groups, and there is lack of correlation between measurements and symptoms. This review describes a novel technology named Fecobionics for assessment of anorectal physiology. Fecobionics is a simulated stool, capable of dynamic measurements of a variety of variables during defecation in a single examination. The data facilitate novel analysis of defecatory function as well as providing the foundation for modeling studies of anorectal behavior. The advanced analysis can enhance our physiological understanding of defecation and future interdisciplinary research for unraveling defecatory function, anorectal sensory-motor disorders, and symptoms. This is a step in the direction of improved diagnosis of anorectal diseases.

Rectal diameter assessment in enuretic children-exploring the association between constipation and bladder function.

OBJECTIVES: Detrusor overactivity and constipation often co-exist in children with enuresis. Constipation is known to be linked to detrusor overactivity. The voiding chart is the best non-invasive way to investigate bladder function, whereas the ultrasonographical detection of rectal dilatation is the best way to objectify constipation. We wanted to investigate a possible relationship between the rectal diameter and voiding chart data in enuretic children. METHODS: Children with therapy-resistant enuresis were retrospectively evaluated. All had completed a voiding chart for at least 48 h. The rectal diameter was assessed ultrasonographically. The cutoff for rectal dilatation was set at 30 mm. RESULTS: We evaluated 74 patients (12 girls) aged 10.2 ± 2.8 years, 35 of whom had rectal dilatation. No significant differences in voiding chart parameters were found between children with normal versus dilated rectum. Neither did urgency or a history of daytime incontinence differ between the groups. Boys were more likely to have rectal dilatation than girls (p = 0.02). CONCLUSIONS: The absence of differences regarding voiding chart data may be explained as two mechanisms neutralizing each other: behavioral factors may make the constipated children void seldom and with large volumes, whereas detrusor overactivity caused by rectal compression of the bladder may have the opposite effect. Another option may be that the voiding chart is too blunt an instrument to detect detrusor overactivity. Constipation, and thus presumably bladder dysfunction, seems to be more important in enuretic boys than girls.

Virtual reality training and assessment in laparoscopic rectum surgery.

BACKGROUND: Virtual-reality (VR) based simulation techniques offer an efficient and low cost alternative to conventional surgery training. This article describes a VR training and assessment system in laparoscopic rectum surgery. METHODS: To give a realistic visual performance of interaction between membrane tissue and surgery tools, a generalized cylinder based collision detection and a multi-layer mass-spring model are presented. A dynamic assessment model is also designed for hierarchy training evaluation. RESULTS: With this simulator, trainees can operate on the virtual rectum with both visual and haptic sensation feedback simultaneously. The system also offers surgeons instructions in real time when improper manipulation happens. The simulator has been tested and evaluated by ten subjects. CONCLUSIONS: This prototype system has been verified by colorectal surgeons through a pilot study. They believe the visual performance and the tactile feedback are realistic. It exhibits the potential to effectively improve the surgical skills of trainee surgeons and significantly shorten their learning curve.

SVM-MRF segmentation of colorectal NBI endoscopic images.

In this paper we investigate a method for segmentation of colorectal Narrow Band Imaging (NBI) endoscopic images with Support Vector Machine (SVM) and Markov Random Field (MRF). SVM classifiers recognize each square patch of an NBI image and output posterior probabilities that represent how likely the given patch falls into a certain label. To prevent the spatial inconsistency between adjacent patches and encourage segmented regions to have smoother shapes, MRF is introduced by using the posterior outputs of SVMs as a unary term of MRF energy function. Segmentation results of 1191 NBI images are evaluated in experiments in which SVMs were trained with 480 trimmed NBI images and the MRF energy was minimized by an α - ß swap Graph Cut.

Imaging paradigms in assessment of rectal carcinoma: loco-regional and distant staging.

The role of imaging in the management of rectal malignancy has progressively evolved and undergone several paradigm shifts. Unlike a few decades ago when the role of a radiologist was restricted at defining the longitudinal extent of the tumour with barium enema, recent advances in imaging techniques permit highly accurate locoregional and distant staging of the disease as well as prognostication on those who are likely to have a postoperative recurrence. Computed tomography (CT) has always been the mainstay of imaging when evaluating for distant metastasis, with the advent of positron emission tomography/CT improving its specificity. In rectal malignancy, it is the local extent of the disease that often influences the surgical decision making and need for neoadjuvant therapy. Although endoscopic ultrasound has been the traditional technique for determining the depth of tumour invasion, over the last decade magnetic resonance imaging (MRI) has emerged as a very effective tool for accurate T-staging. This review intends to address the status of various imaging modalities and their advantages and limitations in detection, pretreatment staging, and assessment of therapeutic efficacy in rectal cancer, with emphasis on MRI of high spatial resolution.

Assessment of bladder motion for clinical radiotherapy practice using cine-magnetic resonance imaging.

PURPOSE: Organ motion is recognized as the principal source of inaccuracy in bladder radiotherapy (RT), but there is currently little information on intrafraction bladder motion. METHODS AND MATERIALS: We used cine-magnetic resonance imaging (cine-MRI) to study bladder motion relevant to intrafraction RT delivery. On two occasions, a 28 minute cine-MRI sequence was acquired from 10 bladder cancer patients and 5 control participants immediately after bladder emptying, after abstinence from drinking for the preceding hour. From the resulting cine sequences, bladder motion was subjectively assessed. To quantify bladder motion, the bladder was contoured in imaging volume sets at 0, 14, and 28 min to measure changes to bladder volumes, wall displacements, and center of gravity (COG) over time. RESULTS: The dominant source of bladder motion during imaging was bladder filling (up to 101% volume increase); rectal and small bowel movements were transient, with minimal impact. Bladder volume changes were similar for all participants. However for bladder cancer patients, wall displacements were larger (up to 58 mm), less symmetrical, and more variable compared with nondiseased control bladders. CONCLUSIONS: Significant and individualized intrafraction bladder wall displacements may occur during bladder RT delivery. This important source of inaccuracy should be incorporated into treatment planning and verification.

Assessment of rectal distention in radiotherapy of prostate cancer using daily megavoltage CT image guidance.

PURPOSE: Assessment of rectal distention in a group of patients who are not receiving daily rectum emptying procedures during a course of prostate cancer radiotherapy to investigate which patients could benefit from daily rectum emptying. METHODS AND MATERIALS: Eighteen patients underwent daily megavoltage CT (MVCT) scanning with positioning based on bony anatomy. Emptying the rectum was only performed before planning CT and not during the actual treatment. The rectal average cross-sectional area (CSA) was determined on the MVCTs. The relative CSA (CSA(rel)) was defined as CSA on MVCT / CSA on planning CT. Additional prostate soft tissue matching was performed to verify the influence of rectal distention on prostate motion. RESULTS: Two distinct subgroups could be defined a posteriori. One group had a limited and stable rectal distention with a CSA (mean+/-SD) of 6.6+/-2.1cm(2), in contrast with a second group with large and variable rectal filling with a CSA of 9.5+/-3.7cm(2) (p<0.01). Mean anterior-posterior prostate displacement was 0.4+/-2.4 mm in the stable group versus -2.4+/-6.1 mm in the unstable group (p<0.01). A mean CSA(rel) of 1.35 of the first 3 days as cut-off value allowed for a correct a priori classification of 90% and 85% of the patients from groups 1 and 2, respectively. CONCLUSION: Based on a few measurements of the CSA by daily MVCT imaging at the first days of treatment, rectum emptying may be omitted in part of the patients.

[Morphologic evaluation of fecal incontinence by magnetic resonance imaging in patients with corrected anal atresia]. / Valoración morfológica mediante resonancia magnética de la incontinencia fecal en pacientes con atresia anal corregida.

PURPOSE: To describe the findings obtained with magnetic resonance imaging (MRI) in patients with ano-rectal atresia, after treatment by posterior sagittal anorectoplasty (PSARP), who have fecal incontinence and to describe its usefulness in the evaluation of causes of incontinence. SUBJECT AND METHODS: Twelve patients, 9 men and 3 women, with anorectal atresia were examined with 0.5T MRI after performing PSARP for imperforate anus. The study included T1-weighted, T2-weighted and proton-density, axial, sagittal and coronal planes. The location of descended neorectus and the degree of development of pelvic musculature were evaluated. RESULTS: Normal development of anus levator muscles and sphincterian complex were observed in six patients, with correct situation of neorectus between anus levator muscles and sphincterian complex in five of them and eccentric in the other one. Diverse grades of striate muscular complex underdevelopment were showed in the other six cases, moderate grade in four of them and severe hypoplasia in the other two. Spinal and urogenital congenital anomalies were found in these patients. Sagittal and coronal T1-weighted MR images were the most useful planes in evaluating the relationship between anus levator muscles and sphincterian complex and axial T1-weighted MR images in the evaluation of the level of development of striated muscle complex in the evaluation of patients. CONCLUSIONS: MRI is useful in the evaluation of patients with fecal incontinence after performing PSARP for anorectal atresia. Unsuitable neorectus position or striated muscle complex hypoplasia are causes of postoperative incontinence in these patients.

The mesorectum: morphometric assessment with magnetic resonance imaging.

The purpose of the present study was to assess the size and configuration of the perirectal fatty tissues using magnetic resonance imaging, including the volume occupied by the rectum itself, and to establish a simple method by which such analysis could be derived. Included in the study were 25 consecutive patients without any large pelvic tumor (diameter of potential pelvic tumor less than 3 cm in any plane) referred for high-resolution pelvic MR imaging. The volume and cross-sectional parameters based on the amount of mesorectum to different sides of the rectum, and the total area occupied, including the rectum, were retrospectively measured using a transaxial three-dimensional T1-weighted gradient-echo sequence. The mesorectum, including the rectum within, occupied an axial area ranging from 320 to 5992 mm(2), and a total volume of 54-323 ml. There was a good correlation between anteroposterior diameter of the perirectal fat at 4 cm below S1-2 and the left-to-right diameter 7 cm below S1-2, and the total volume. Furthermore, the form of mesorectal tissue differed significantly between male and female subjects. In male subjects, measurements in the anteroposterior dimension accurately reflected the volume of mesorectal tissue, while in women, assessment of both the anteroposterior and the size parameters of the mesorectum from the left to right were required for the best evaluation of the volume of mesorectal tissue. The amount of fat posterior to the rectum was significantly more in men than in women, with or without consideration of length of the pelvis. Finally, the contour of the mesorectal fascia was subject to impression by other nearby visceral organs. There is a great individual variation in the amount of mesorectal fat, and in morphometric parameters between the two sexes. The morphological variations of the mesorectum can be assessed by magnetic resonance imaging using a formula based on two simple measurements of the anteroposterior and left-to-right dimensions.

Magnetic resonance assessment of prostate localization variability in intensity-modulated radiotherapy for prostate cancer.

PURPOSE: To measure prostate motion with magnetic resonance imaging (MRI) during a course of intensity-modulated radiotherapy. METHODS AND MATERIALS: Seven patients with prostate carcinoma were scanned supine on a 1.5-Tesla MRI system with weekly pretreatment and on-treatment HASTE T2-weighted images in 3 orthogonal planes. The bladder and rectal volumes and position of the prostatic midpoint (PMP) and margins relative to the bony pelvis were measured. RESULTS: All pretreatment positions were at the mean position as computed from the on-treatment scans in each patient. The PMP variability (given as 1 SD) in the anterior-posterior (AP), superior-inferior (SI), and right-left (RL) directions was 2.6, 2.4, and 1.0 mm, respectively. The largest variabilities occurred at the posterior (3.2 mm), superior (2.6 mm), and inferior (2.6 mm) margins. A strong correlation was found between large rectal volume (>95th percentile) and anterior PMP displacement. A weak correlation was found between bladder volume and superior PMP displacement. CONCLUSIONS: All pretreatment positions were representative of the subsequent on-treatment positions. A clinical target volume (CTV) expansion of 5.3 mm in any direction was sufficient to ascertain a 95% coverage of the CTV within the planning target volume (PTV), provided that a rectal suppository is administered to avoid rectal overdistension and that the patient has a comfortably filled bladder (<300 mL).

Assessment of pelvic organ descent by use of functional cine-MRI: which reference line should be used?

BACKGROUND AND AIMS: So far there is no agreement between clinical and radiological measurements and reference points for the quantification of pelvic organ descent in women. The aim of this study was to find out which of three reference lines on functional cine-magnetic resonance imaging (MRI) correlates best with the respective clinical diagnoses. METHODS: We retrospectively evaluated the functional cine-MRI studies of 41 asymptomatic volunteers. Our golden standard was the results of the clinical examination using the International Continence Society (ICS)-score. On MRI, we measured the distance of the bladder-neck, distal edge of cervix/posterior fornix, and the most ventrocaudal point of the ventral rectal wall, respectively, to the pubococcygeal line (PCL), the horizontal tangent of the inferior rim of the pubic bone, and the line drawn through the long axis of the pubic bone. The results were correlated with the respective clinical findings using descriptive analysis alone. RESULTS: The volunteers either showed a Stage 0 (16 cases), Stage I (12 cases), or a Stage II (13 cases) organ descent on clinical examination with 10 women (24.4%) having a pathological ICS-score in the anterior, 15 women (36.1%) in the superior, and 4 women (9.8%) in the posterior compartment. On functional MRI the best correlation with the clinical results was achieved using the PCL for the anterior compartment (22.0%), the PCL with an offset of +3 cm for the superior (36.6%), and the hymenal line (HL) for the posterior compartment (9.8%). CONCLUSIONS: Organ descent on functional cine-MRI cannot be described using only one reference line. In order to optimize clinical exploitation of functional MRI of the pelvic floor a consensus regarding imaging protocols and evaluation criteria should be aimed for.

A model to simulate day-to-day variations in rectum shape.

PURPOSE: To develop a model that predicts possible rectum configurations that can occur during radiotherapy of prostate cancer on the basis of a planning CT scan and patient group data. MATERIALS AND METHODS: We used a stochastic shape description model with a limited number of parameters (area, area difference, and curvature) on a slice-by-slice basis to simulate rectum motion. The probability distributions of the chosen parameters were obtained from a group of 9 reference patients, who each received 15-17 repeat CT scans. We used a Monte Carlo technique to generate different rectum configurations from the probability distributions. We verified the model by comparing dose-wall histograms (DWHs) of the originally delineated rectal contours and simulated rectums for a three-field treatment technique with a prescription dose of 78 Gy. The 15-17 sets of rectal contours of each patient are regarded as the golden standard and provide a good estimate of the actual dose received during the treatment. We determined the equivalent uniform dose (EUD) for a quantitative comparison between the actual dose, the dose predicted on the basis of the simulations, and the dose predicted on the basis of a single planning CT scan. RESULTS: The simulated rectum configurations yield a better estimate of the actual dose in the rectal wall than the rectum in the planning CT scan alone. The differences between the EUD based on the planning CT scan and the actual EUD ranged between -1.1 Gy and 2.1 Gy, with respect to a mean actual EUD of 69.8 Gy. This range is smaller for the EUD based on the simulated rectums, namely -0.4 Gy to 0.6 Gy. Furthermore, the simulation generates a set of rectum configurations that provides an estimate of the variation in DWHs during the course of the treatment. This estimate can be used in addition to the DWH of the planning CT scan in the analysis of gastrointestinal toxicity. CONCLUSIONS: To simulate rectum shapes, we have developed a model that can be used in addition to the information available in the planning CT scan in the analysis of the received dose to the rectal wall during radiotherapy of prostate cancer.

Pelvic floor function/dysfunction and electrodiagnostic evaluation.

The pelvic floor provides support for the bladder, rectum, and genital systems, as well as proper positioning and orientation of the urethral and anal sphincters. Impairment may result in prolapse, urinary and fecal incontinence, and sexual dysfunction. The impact is enormous in terms of personal, social, and financial burden. Pertinent anatomy is presented, followed by an overview of available electrodiagnostic techniques and a description of pudendal nerve conduction studies, sacral reflex testing and selected electromyographic techniques. Clinical applications are discussed throughout the text and the need for further research is addressed.

Vaginal endosonography in the assessment of the anorectum.

Endosonography from within the anus has been used to image the anorectum and its associated musculature. A 5.0-MHz endovaginal probe was inserted vaginally, and longitudinal and cross-sectional views of the anorectum were obtained. We were able to measure rectal length and diameter, puborectalis thickness and angle, thickness of internal and external anal sphincter, and the curvature of the anal canal. We visualized defects in the internal and external anal sphincters. Suitable images were obtained from 70 subjects. Muscle thicknesses were within previously published ranges. Twenty-five of 70 subjects (36%) had defects of the internal anal sphincter, and 19 of 65 subjects (29%) had defects of the external anal sphincter.

Assessment of the reproductive system of the female ruminant.

In summary, a thorough physical examination of the reproductive tract includes a complete history, general physical examination, and evaluation of the external and internal genitalia. Ancillary tests that can be applied to this system include uterine culture, biopsy, cytology, and lavage.

Videoproctographic assessment after restorative proctocolectomy.

Videoproctography was performed in 40 patients after restorative proctocolectomy to evaluate pouch emptying, anopouch angle, and pelvic floor movement in relationship to functional outcome. Results were compared between the two different pouch designs tested and a control group of 26 patients who had an intact rectum. There was no difference in emptying between the two pouch designs or compared with the control subjects. Emptying did not influence either the frequency of defecation or patient soiling rate. The presence of an anal stricture was associated with poor emptying in each case in the pouch group. Anorectal angle was no different between the different pouch designs or compared with the control group at rest, during pelvic floor contraction, or attempted defecation. A similar finding was obtained with anorectal angle position and movement during pelvic floor contraction and attempted defecation in both pouch design groups and when compared with normal rectum. This study shows that the only factor that is consistently associated with poor pouch emptying is the presence of an anal stricture.