This prospective study included 30 patients with ano-rectal dysfunction, from May 2015 till October 2015, [12 males, 18 females, age range 20–77 years, mean age 48.5 ± 15.7] and control group included 10 healthy adults having normal bowel habit [4 males and 6 females, age range 25–62 years; mean age 43.5 ± 13.7]. Inclusion criteria include adult patients with chronic constipation for at least 3 months fulfilling at least 2 of the following according to “Rome Diagnostic Criteria III” for functional constipation [10], less than 3 motions per week, straining, hard stools, sensation of incomplete evacuation, sensation of ano-rectal obstruction, and manual assistance needed for defecation. Exclusion criteria were patients with 2ry constipation due to bad dietary habits, structural cause; as colonic strictures, tumors or volvulus, systemic diseases including metabolic and endocrinal disorders as diabetes mellitus, hypothyroidism, hyperparathyroidism, pregnancy, hypokalemia, or hypercalcemia. Neurologic disorders as stroke, head injury, spinal injury, multiple sclerosis, or Parkinson disease. Also, Hirschsprung disease and connective tissue disorders as amyloidosis and scleroderma.
Clinical assessment
Clinical evaluation was done to all patients by detailed history taking and physical assessment of abdomen and anal examination. Colonoscopy was done to all patients to exclude any obstructing cause like stricture, tumor or polyp. Also, Colon transit time was done to exclude patients with colonic inertia. Medical treatment was given to patients with ano-rectal dysfunction for 3 months in the form of bulk forming laxatives, and the patients that responded to the medical treatment were excluded from the study.
MR defecography was done to all patients needing no patient preparation with the explanation of the procedure done to the patients prior to the procedure to ensure their cooperation throughout the scanning. Consent was taken from all the patients along with human ethics committee approval from the institutional review board of the private hospital where the study took place.
Image acquisition
MR defecography was performed on 1.5 Tesla closed MR scanner “MAGNETOM Avanto, Siemens, Germany,” using a body-array-surface coil. First, the patient was on the left lateral decubitus to insert 300 ml ultrasound gel through a rectal tube then the examination was done while he/she was in the supine position with the hips and knee flexed, stimulating physiological defecation position. Initially static imaging was done to evaluate pelvic anatomical details by axial and coronal T2-weighted turbo spin-echo sequence with the following parameters: TR/TE 4000/100, matrix size 256 × 256, FOV 25 mm–35 mm with RFOV 100%, slice thickness 4 mm, then dynamic imaging was performed using T2-weighted multiphasic 2D steady-state free precession sequence [SSFP] in the mid-sagittal plane through the anal canal with the following parameters: TR/TE 5.3/2.4, matrix size 320 × 220, FOV 40 mm, slice thickness 10 ml; this sequence was running for 2 min while the patient was instructed to strain till defecation occurs, acquiring about 250 images [2 image/s] and was repeated for another 2 min if the patient failed to defecate.
Image analysis
Images were analyzed by two different radiologists [4-year experience in reading MRD, and the findings were recorded by consensus of both] on a PACS workstation [SECTRA IDS7 Sweden]; first, static images were reviewed to detect any pelvic floor abnormality then dynamic mid-sagittal images were evaluated in the two phases: rest and defecation in cine loop mode.
Normally at rest, all the pelvic organs, namely urinary bladder base, vaginal vault, and peritoneal cavity [omental fat-small bowel-sigmoid colon] should be above the pubococcygeal line (PCL) which is the line joining the inferior border of the symphysis pubis and the last coccygeal joint. Also, at rest, the ano-rectal angle (ARA) which is formed between the posterior border of the rectum and the central axis of the anal canal is between 65 and 100° with no noticeable differences between males and females [11]; in straining the ARA increases and the perineum descends, its landmark is ano-rectal junction (ARJ) and it is considered normal when caudal migration is less than 2 cm relative to the resting position (Fig. 1). During defecation as a result of relaxation of the puborectalis muscle and anal sphincter, rectum and anal canal are in alignment causing more widening of the ARA [12]. Increase of the ARA less than 15–20° is considered abnormal [13].
Presence of organ descent was measured as the perpendicular distance of ARJ (rectal descent), bladder base (cystocele), vaginal vault (uterine prolapse), and omental fat-small bowel-sigmoid colon (enterocele) below PCL [14]. Its grading was as follows: mild 2–< 3 cm, moderate from 3 to < 6 cm, and severe = > 6 cm [15]. Also, detection of associated findings, like rectocele, rectal intussusception, and paradoxical puborectalis, was documented. Rectocele which is defined as anterior rectal wall protrusion beyond the rectal wall during defecation, and it is graded as follows: mild (< 2 cm), moderate (2–4 cm), and large (> 4 cm) [4]. Rectal intussusception which is internal invagination of the rectal wall, and it is classified according to the location into intra-rectal, intra-anal, and according to thickness into mucosal or full thickness [16]. Paradoxical puborectalis is detected when there is failure of puborectalis muscle to relax during defecation with an increase of the ARA less than 15–20° or even decrease [11].
Statistical analysis
IBM SPSS statistics (V. 25.0, IBM Corp., USA, 2017–2018) was used for data analysis. Data were expressed as mean ± SD for quantitative parametric measures in addition to both number and percentage for categorized data. Comparison between two dependent groups [clinical findings and MRD results] for parametric data using Z test was used. The probability of error at 0.05 was considered significant, while at 0.01 and 0.001 are highly significant.