It is different to an internal intussusception (occult prolapse) or a complete rectal prolapse (external prolapse, procidentia) because these conditions involve the full thickness of the rectal wall, rather than only the mucosa (lining).Mucosal prolapse is a different condition to prolapsing (3rd or 4th degree) hemorrhoids, although they may look similar. Rectal mucosal prolapse can be a cause of obstructed defecation (outlet obstruction). and rectal malodor. Symptoms
Symptom severity increases with the size of the prolapse, and whether it spontaneously reduces after defecation, requires manual reduction by the patient, or becomes irreducible. The symptoms are identical to advanced hemorrhoidal disease, and include:

Fecal leakage causing staining of undergarments
Rectal bleeding
Mucous rectal discharge
Rectal pain
Pruritus ani

Cause
The condition, along with complete rectal prolapse and internal rectal intussusception, is thought to be related to chronic straining during defecation and constipation. Mucosal prolapse occurs when the results from loosening of the submucosal attachments (between the mucosal layer and the muscularis propria) of the distal rectum. The section of prolapsed rectal mucosa can become ulcerated, leading to bleeding. Diagnosis
Mucosal prolapse can be differentiated from a full thickness external rectal prolapse (a complete rectal prolapse) by the orientation of the folds (furrows) in the prolapsed section. In full thickness rectal prolapse, these folds run circumferential. In mucosal prolapse, these folds are radially. The folds in mucosal prolapse are usually associated with internal hemorrhoids. Treatment
EUA (examination under anesthesia) of anorectum and banding of the mucosa with rubber bands.
The leading edge of the intussusceptum may be located at 6–8 cm or at 15–18 cm from the anal verge. This proved an older theory from the 18th century by John Hunter and Albrecht von Haller that this condition is essentially a full-thickness rectal intussusception, beginning about 3 inches above the dentate line and protruding externally.Since most patients with rectal prolapse have a long history of constipation, it is thought that prolonged, excessive and repetitive straining during defecation may predispose to rectal prolapse. Since rectal prolapse itself causes functional obstruction, more straining may result from a small prolapse, with increasing damage to the anatomy. This excessive straining may be due to predisposing pelvic floor dysfunction (e.g. obstructed defecation) and anatomical factors:
Abnormally low descent of the peritoneum covering the anterior rectal wall
poor posterior rectal fixation, resulting in loss of posterior fixation of the rectum to the sacral curve
loss of the normal horizontal position of the rectum with lengthening (redundant rectosigmoid) and downward displacement of the sigmoid and rectum
long rectal mesentery
a deep cul-de-sac
levator diastasis
a patulous, weak anal sphincterSome authors question whether these abnormalities are the cause, or secondary to the prolapse. Other predisposing factors/associated conditions include:

pregnancy (although 35% of women who develop rectal prolapse are nulliparous) (have never given birth)
previous surgery (30-50% of females with the condition underwent previous gynecological surgery)
pelvic neuropathies and neurological disease
high gastrointestinal helminth loads (e.g. Whipworm)
COPD
cystic fibrosis The association with uterine prolapse (10-25%) and cystocele (35%) may suggest that there is some underlying abnormality of the pelvic floor that affects multiple pelvic organs.