Anatomy of Rectal Prolapse in Older Women
Rectal prolapse is a circumferential, full-thickness protrusion of all layers of the rectal wall through the anal canal, resulting from progressive weakening of the pelvic floor support structures due to chronic straining, denervation injury, and age-related deterioration of fascial attachments. 1, 2
Anatomical Pathophysiology
The anatomical basis of rectal prolapse involves multiple structural failures:
Pelvic floor muscle weakness and denervation injury increase stress on the fascia and lead to progressive weakening of support structures, particularly in women over 60 who have undergone menopause and vaginal multiparity 1
Chronic increases in intra-abdominal pressure from repetitive straining during defecation cause mechanical stretching and eventual failure of the rectovaginal septum, levator ani muscles, and endopelvic fascia 1
The rectum loses its normal sacral fixation and descends through a patulous pelvic floor, creating the characteristic circumferential protrusion 2, 3
Associated Anatomical Defects
Rectal prolapse in older women rarely occurs in isolation:
Concurrent pelvic organ prolapse is common, including cystocele, enterocele, uterovaginal prolapse, and bladder prolapse, reflecting global pelvic floor failure 4, 5
Anal sphincter damage develops from mechanical stretching over time as the prolapsed rectum repeatedly passes through the anal canal, explaining why fecal incontinence is the predominant symptom 6
Enteroceles and rectoceles frequently coexist, with small bowel sometimes prolapsing between the rectum and vagina, compressing the anterior rectal wall 7
Imaging Anatomy
When clinical examination is inadequate or surgical planning is needed:
Dynamic cystocolpoproctography (CCP) demonstrates the functional anatomy during defecation in physiologic upright positioning, with 88% sensitivity for detecting internal rectal prolapse and excellent visualization of full-thickness prolapse, rectoceles, and peritoneoceles 4
Contrast-enhanced CT of abdomen and pelvis should be performed in complicated cases (irreducible or strangulated prolapse) to detect bowel obstruction, perforation, prolapse of other pelvic organs, and to rule out colorectal malignancy, which has a 4.2-fold increased relative risk in patients with rectal prolapse 4
MRI defecography can reveal enteroceles and small bowel prolapsing between rectum and vagina that may not be apparent on physical examination 7
Critical Anatomical Pitfall
The presence of rectal prolapse mandates colorectal cancer screening, as rectosigmoid cancer prevalence is 5.7% in patients with rectal prolapse compared to 1.4% in age-matched controls, representing a significantly elevated risk that should not be overlooked 4