Rectal prolapse


A rectal prolapse occurs when walls of the rectum have prolapsed to such a degree that they protrude out of the anus and are visible outside the body. However, most researchers agree that there are 3 to 5 different types of rectal prolapse, depending on whether the prolapsed section is visible externally, and whether the full or only partial thickness of the rectal wall is involved.
Rectal prolapse may occur without any symptoms, but depending upon the nature of the prolapse there may be mucous discharge, rectal bleeding, degrees of fecal incontinence, and obstructed defecation symptoms.
Rectal prolapse is generally diagnosed more commonly in elderly women, although it may occur at any age and any sex. It is very rarely life-threatening, but the symptoms can be debilitating if left untreated. Most external prolapse cases can be treated successfully, often with a surgical procedure. Internal prolapses are traditionally harder to treat and surgery may not be suitable for many patients.

Classification

The different kinds of rectal prolapse can be difficult to grasp, as different definitions are used and some recognize certain subtypes and not others do not. Essentially, rectal prolapses may be:full thickness, where all the layers of the rectal wall prolapse, or involve the mucosal layer only external if they protrude from the anus and are visible externally, or internal if they do notcircumferential, where the whole circumference of the rectal wall prolapses, or segmental if only parts of the circumference of the rectal wall prolapse
  • present at rest, or occurring during straining.
External rectal prolapse is
a full thickness, circumferential, true intussusception of the rectal wall which protrudes from the anus and is visible externally.
Internal rectal intussusception can be defined as a funnel shaped infolding of the upper rectal wall that can occur during defecation. This infolding is perhaps best visualised as folding a sock inside out, creating "a tube within a tube". Another definition is "where the rectum collapses but does not exit the anus". Many sources differentiate between [|internal rectal intussusception] and mucosal prolapse, implying that the former is a full thickness prolapse of rectal wall. However, a publication by the American Society of Colon and Rectal Surgeons stated that internal rectal intussusception involved the mucosal and submucosal layers separating from the underlying muscularis mucosa layer attachments, resulting in the separated portion of rectal lining "sliding" down. This may signify that authors use the terms internal rectal prolapse and internal mucosal prolapse to describe the same phenomena.
Mucosal prolapse refers to prolapse of the loosening of the submucosal attachments to the muscularis propria of the distal rectummucosal layer of the rectal wall. Most sources define mucosal prolapse as an external, segmental prolapse which is easily confused with prolapsed hemorrhoids. However, both internal mucosal prolapse and circumferential mucosal prolapse are described by some. Others do not consider mucosal prolapse a true form of rectal prolapse.
Internal mucosal prolapse refers to prolapse of the mucosal layer of the rectal wall which does not protrude externally. There is some controversy surrounding this condition as to its relationship with hemorrhoidal disease, or whether it is a separate entity. The term "mucosal hemorrhoidal prolapse" is also used.
Solitary rectal ulcer syndrome occurs with internal rectal intussusception and is part of the spectrum of rectal prolapse conditions. It describes ulceration of the rectal lining caused by repeated frictional damage as the internal intussusception is forced into the anal canal during straining. SRUS can be considered a consequence of internal intussusception, which can be demonstrated in 94% of cases.
Mucosal prolapse syndrome is recognized by some. It includes solitary rectal ulcer syndrome, rectal prolapse, proctitis cystica profunda, and inflammatory polyps. It is classified as a chronic benign inflammatory disorder.
Rectal prolapse and internal rectal intussusception has been classified according to the size of the prolapsed section of rectum, a function of rectal mobility from the sacrum and infolding of the rectum. This classification also takes into account sphincter relaxation:
  • Grade I: nonrelaxation of the sphincter mechanism
  • Grade II: mild intussusception
  • Grade III: moderate intussusception
  • Grade IV: severe intussusception
  • Grade V: rectal prolapse
Rectal internal mucosal prolapse has been graded according to the level of descent of the intussusceptum, which was predictive of symptom severity:
  • first degree prolapse is detectable below the anorectal ring on straining
  • second degree when it reached the dentate line
  • third degree when it reached the anal verge
The most widely used classification of internal rectal prolapse is according to the height on the rectal/sigmoid wall from which they originate and by whether the intussusceptum remains within the rectum or extends into the anal canal. The height of intussusception from the anal canal is usually estimated by defecography.
Recto-rectal intussusception is where the intussusception starts in the rectum, does not protrude into the anal canal, but stays within the rectum.. These are usually intussusceptions that originate in the upper rectum or lower sigmoid.
Recto-anal intussusception is where the intussusception starts in the rectum and protrudes into the anal canal
An Anatomico-Functional Classification of internal rectal intussusception has been described, with the argument that other factors apart from the height of intussusception above the anal canal appear to be important to predict symptomology. The parameters of this classification are anatomic descent, diameter of intussuscepted bowel, associated rectal hyposensitivity and associated delayed colonic transit:
  • Type 1: Internal recto-rectal intussusception
  • * Type 1W Wide lumen
  • * Type 1N Narrowed lumen
  • Type 2: Internal recto-anal intussusception
  • * Type 2W Wide Lumen
  • * Type 2N Narrowed lumen
  • * Type 2M Narrowed internal lumen with associated rectal hyposensitivity or early megarectum
  • Type 3: Internal-external recto-anal intussusception

Diagnosis

Medical history

Patients may have associated gynecological conditions which may require multidisciplinary management. History of constipation is important because some of the operations may worsen constipation. Fecal incontinence may also influence the choice of management.

Physical examination

Rectal prolapse may be confused easily with prolapsing hemorrhoids. Mucosal prolapse also differs from prolapsing hemorrhoids, where there is a segmental prolapse of the hemorrhoidal tissues at the 3, 7 and 11 o'clock positions. Mucosal prolapse can be differentiated from a full thickness external rectal prolapse by the orientation of the folds 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. Furthermore, in rectal prolapse, there is a sulcus present between the prolapsed bowel and the anal verge, whereas in hemorrhoidal disease there is no sulcus. Prolapsed, incarcerated hemorrhoids are extremely painful, whereas as long as a rectal prolapse is not strangulated, it gives little pain and is easy to reduce.
The prolapse may be obvious, or it may require straining and squatting to produce it. The anus is usually patulous, and has reduced resting and squeeze pressures. Sometimes it is necessary to observe the patient while they strain on a toilet to see the prolapse happen. A phosphate enema may need to be used to induce straining.
The perianal skin may be macerated and show excoriation.

Proctoscopy/sigmoidoscopy/colonoscopy

These may reveal congestion and edema of the distal rectal mucosa, and in 10–15% of cases there may be a solitary rectal ulcer on the anterior rectal wall. Localized inflammation or ulceration can be biopsied and may lead to a diagnosis of SRUS or colitis cystica profunda. Rarely, a neoplasm may form on the leading edge of the intussusceptum. In addition, patients are frequently elderly and therefore have increased incidence of colorectal cancer. Full length colonoscopy is usually carried out in adults prior to any surgical intervention. These investigations may be used with contrast media which may show the associated mucosal abnormalities.

Videodefecography

This investigation is used to diagnose internal intussusception, or demonstrate a suspected external prolapse that could not be produced during the examination. It is usually not necessary with obvious external rectal prolapse. Defecography may demonstrate associated conditions like cystocele, vaginal vault prolapse or enterocele.

Colonic transit studies

Colonic transit studies may be used to rule out colonic inertia if there is a history of severe constipation. Continent prolapse patients with slow transit constipation, and who are fit for surgery may benefit from subtotal colectomy with rectopexy.

Anorectal manometry

This investigation objectively documents the functional status of the sphincters. However, the clinical significance of the findings are disputed by some. It may be used to assess for pelvic floor dyssenergia,, and these patients may benefit from post-operative biofeedback therapy. Decreased squeeze and resting pressures are usually the findings, and this may predate the development of the prolapse. Resting tone is usually preserved in patients with mucosal prolapse. In patients with reduced resting pressure, levatorplasty may be combined with prolapse repair to further improve continence.

Anal electromyography/pudendal nerve testing

It may be used to evaluate incontinence, but there is disagreement about what relevance the results may show, as rarely do they mandate a change of surgical plan. There may be denervation of striated musculature on the electromyogram. Increased nerve conduction periods, this may be significant in predicting post-operative incontinence.

Complete rectal prolapse

Rectal prolapse is a "falling down" of the rectum so that it is visible externally. The appearance is of a reddened, proboscis-like object through the anal sphincters. Patients find the condition embarrassing. The symptoms can be socially debilitating without treatment, but it is rarely life-threatening.
The true incidence of rectal prolapse is unknown, but it is thought to be uncommon. As most affected people are elderly, the condition is generally under-reported. It may occur at any age, even in children, but there is peak onset in the fourth and seventh decades. Women over 50 are six times more likely to develop rectal prolapse than men. It is rare in men over 45 and in women under 20. When males are affected, they tend to be young and report significant bowel function symptoms, especially obstructed defecation, or have a predisposing disorder. When children are affected, they are usually under the age of 3.
35% of women with rectal prolapse have never had children, suggesting that pregnancy and labor are not significant factors. Anatomical differences such as the wider pelvic outlet in females may explain the skewed gender distribution.
Associated conditions, especially in younger patients include autism, developmental delay syndromes, and psychiatric conditions requiring several medications.

Signs and symptoms

Signs and symptoms include:
Initially, the mass may protrude through the anal canal only during defecation and straining, and spontaneously return afterwards. Later, the mass may have to be pushed back in following defecation. This may progress to a chronically prolapsed and severe condition, defined as spontaneous prolapse that is difficult to keep inside, and occurs with walking, prolonged standing, coughing or sneezing. A chronically prolapsed rectal tissue may undergo pathological changes such as thickening, ulceration and bleeding.
If the prolapse becomes trapped externally outside the anal sphincters, it may become strangulated and there is a risk of perforation. This may require an urgent surgical operation if the prolapse cannot be manually reduced. Applying granulated sugar on the exposed rectal tissue can reduce the edema and facilitate this.

Cause

The precise cause is unknown, and has been much debated. In 1912 Moschcowitz proposed that rectal prolapse was a sliding hernia through a pelvic fascial defect.
This theory was based on the observation that rectal prolapse patients have a mobile and unsupported pelvic floor, and a hernia sac of peritoneum from the Pouch of Douglas and rectal wall can be seen. Other adjacent structures can sometimes be seen in addition to the rectal prolapse. Although a pouch of Douglas hernia, originating in the cul de sac of Douglas, may protrude from the anus, this is a different situation from rectal prolapse.
Shortly after the invention of defecography, In 1968 Broden and Snellman used cinedefecography to show that rectal prolapse begins as a circumferential intussusception of the rectum, which slowly increases over time. 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 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 and downward displacement of the sigmoid and rectum
  • long rectal mesentery
  • a deep cul-de-sac
  • levator diastasis
  • a patulous, weak anal sphincter
Some authors question whether these abnormalities are the cause, or secondary to the prolapse. Other predisposing factors/associated conditions include:
The association with uterine prolapse and cystocele may suggest that there is some underlying abnormality of the pelvic floor that affects multiple pelvic organs. Proximal bilateral pudendal neuropathy has been demonstrated in patients with rectal prolapse who have fecal incontinence. This finding was shown to be absent in healthy subjects, and may be the cause of denervation-related atrophy of the external anal sphincter. Some authors suggest that pudendal nerve damage is the cause for pelvic floor and anal sphincter weakening, and may be the underlying cause of a spectrum of pelvic floor disorders.
Sphincter function in rectal prolapse is almost always reduced. This may be the result of direct sphincter injury by chronic stretching of the prolapsing rectum. Alternatively, the intussuscepting rectum may lead to chronic stimulation of the rectoanal inhibitory reflex. The RAIR was shown to be absent or blunted. Squeeze pressures may be affected as well as the resting tone. This is most likely a denervation injury to the external anal sphincter.
The assumed mechanism of fecal incontinence in rectal prolapse is by the chronic stretch and trauma to the anal sphincters and the presence of a direct conduit connecting rectum to the external environment which is not guarded by the sphincters.
The assumed mechanism of obstructed defecation is by disruption to the rectum and anal canal's ability to contract and fully evacuate rectal contents. The intussusceptum itself may mechanically obstruct the rectoanal lumen, creating a blockage that straining, anismus and colonic dysmotility exacerbate.
Some believe that internal rectal intussusception represents the initial form of a progressive spectrum of disorders the extreme of which is external rectal prolapse. The intermediary stages would be gradually increasing sizes of intussusception. However, internal intussusception rarely progresses to external rectal prolapse. The factors that result in a patient progressing from internal intussusception to a full thickness rectal prolapse remain unknown. Defecography studies demonstrated that degrees of internal intussusception are present in 40% of asymptomatic subjects, raising the possibility that it represents a normal variant in some, and may predispose patients to develop symptoms, or exacerbate other problems.

Treatment

Conservative

Surgery is thought to be the only option to potentially cure a complete rectal prolapse. For people with medical problems that make them unfit for surgery, and those who have minimal symptoms, conservative measures may be beneficial. Dietary adjustments, including increasing dietary fiber may be beneficial to reduce constipation, and thereby reduce straining. A bulk forming agent or stool softener can also reduce constipation.

Surgical

Surgery is often required to prevent further damage to the anal sphincters. The goals of surgery are to restore the normal anatomy and to minimize symptoms. There is no globally agreed consensus as to which procedures are more effective, and there have been over 50 different operations described.
Surgical approaches in rectal prolapse can be either perineal or abdominal. A perineal approach refers to surgical access to the rectum and sigmoid colon via an incision around the anus and perineum. Abdominal approach involves the surgeon cutting into the abdomen and gaining surgical access to the pelvic cavity. Procedures for rectal prolapse may involve fixation of the bowel, or resection, or both. Trans-anal procedures are also described where access to the internal rectum is gained through the anus itself.
Abdominal procedures are associated with lower risk of postoperative recurrence of the prolapse, compared with perineal procedures.
Abdominal procedures
The abdominal approach carries a small risk of impotence in males. Abdominal operations may be open or laparoscopic.
Laparoscopic procedures
Recovery time following laparoscopic surgery is shorter and less painful than following traditional abdominal surgery. Instead of opening the pelvic cavity with a wide incision, a laparoscope and surgical instruments are inserted into the pelvic cavity via small incisions. Rectopexy and anterior resection have been performed laparoscopically with good results.
Perineal procedures
The perineal approach generally results in less post-operative pain and complications, and a reduced length of hospital stay. These procedures generally carry a higher recurrence rate and poorer functional outcome. The perineal procedures include perineal rectosigmoidectomy and Delorme repair. Elderly, or other medically high-risk patients are usually treated by perineal procedures, as they can be performed under a regional anesthetic, or even local anesthetic with intravenous sedation, thus avoid the risks of a general anesthetic. Alternatively, perineal procedures may be selected to reduce risk of nerve damage, for example in young male patients for whom sexual dysfunction may be a major concern.
Perineal rectosigmoidectomy
The goal of Perineal rectosigmoidectomy is to resect or remove the redundant bowel. This is done through the perineum. The lower rectum is anchored to the sacrum through fibrosis in order to prevent future prolapse. The full thickness of the rectal wall is incised at a level just above the dentate line. Redundant rectal and sigmoid wall is removed and the new edge of colon is reconnected with the anal canal with stitches or staples. This procedure may be combined with levatorplasty, to tighten the pelvic muscles. A combined a perineal proctosigmoidectomy with anterior levatorplasty is also called an Altemeier procedure. Levatorplasty is performed to correct levator diastasis which is commonly associated with rectal prolapse. Perineal rectosigmoidectomy was first introduced by Mikulicz in 1899, and it remained the preferred treatment in Europe for many years. It was Popularized by Altemeier. The procedure is simple, safe and effective. Continence levatorplasty may enhance restoration of continence. Complications occur in less than 10% of cases, and include pelvic bleeding, pelvic abscess and anastomotic dehiscence, bleeding or leak at a dehiscence Mortality is low. Recurrence rates are higher than for abdominal repair, 16–30%, but more recent studies give lower recurrence rates. Additional levatorplasty can reduce recurrence rates to 7%.
Delorme Procedure
This is a modification of the perineal rectosigmoidectomy, differing in that only the mucosa and submucosa are excised from the prolapsed segment, rather than full thickness resection. The prolapse is exposed if it is not already present, and the mucosal and submucosal layers are stripped from the redundant length of bowel. The muscle layer that is left is plicated and placed as a buttress above the pelvic floor. The edges of the mucosal are then stitched back together. "Mucosal proctectomy" was first discussed by Delorme in 1900, now it is becoming more popular again as it has low morbidity and avoids an abdominal incision, while effectively repairing the prolapse. The procedure is ideally suited to those patients with full-thickness prolapse limited to partial circumference or less-extensive prolapse. Fecal incontinence is improved following surgery. Post operatively, both mean resting and squeeze pressures were increased. Constipation is improved in 50% of cases, but often urgency and tenesmus are created. Complications, including infection, urinary retention, bleeding, anastomotic dehiscence, rectal stricture, diarrhea, and fecal impaction occur in 6–32% of cases. Mortality occurs in 0–2.5% cases. There is a higher recurrence rate than abdominal approaches.
Anal encirclement
This procedure can be carried out under local anaesthetic. After reduction of the prolapse, a subcutaneous suture or other material is placed encircling the anus, which is then made taut to prevent further prolapse. Placing silver wire around the anus first described by Thiersch in 1891. Materials used include nylon, silk, silastic rods, silicone, Marlex mesh, Mersilene mesh, fascia, tendon, and Dacron. This operation does not correct the prolapse itself, it merely supplements the anal sphincter, narrowing the anal canal with the aim of preventing the prolapse from becoming external, meaning it remains in the rectum. This goal is achieved in 54–100% cases. Complications include breakage of the encirclement material, fecal impaction, sepsis, and erosion into the skin or anal canal. Recurrence rates are higher than the other perineal procedures. This procedure is most often used for people who have a severe condition or who have a high risk of adverse effects from general anesthetic, and who may not tolerate other perineal procedures.

Internal rectal prolapse

Internal rectal prolapse is a type of rectal prolapse where there is a telescopic, funnel-shaped infolding of the wall of the rectum that occurs during defecation. The term internal rectal prolapse is used when the prolapsed section of rectal wall remains inside the body and is not visible outside the body.
It may not cause any symptoms, or may cause obstructed defecation syndrome and/or fecal incontinence. The causes are not clear. It may represent the first stage of a progressive condition that eventually may result in external rectal prolapse, but this is uncommon. It is possible that chronic straining during defecation, connective tissue disorders, and anatomic factors are involved.
Diagnosis is by defecography. If internal rectal prolapse is causing symptoms, treatment is by various non surgical measures, or surgery. The most common surgical treatment is ventral rectopexy. Internal rectal prolapse is often associated with other conditions such as rectocele, enterocele, or solitary rectal ulcer syndrome. Internal rectal prolapse usually affects females who have given birth at least once, but it may sometimes affect females who have never given birth. About 10% of cases are in males. More severe forms of internal rectal prolapse are associated with older age.

Mucosal prolapse

Rectal mucosal prolapse is a sub-type of rectal prolapse, and refers to abnormal descent of the rectal mucosa through the anus. It is different to an internal intussusception or a complete rectal prolapse because these conditions involve the full thickness of the rectal wall, rather than only the mucosa.
Mucosal prolapse is a different condition to prolapsing hemorrhoids, although they may look similar.
Rectal mucosal prolapse can be a cause of obstructed defecation.

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:

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 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 by the orientation of the folds 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 of anorectum and banding of the mucosa with rubber bands.

Solitary rectal ulcer syndrome

Solitary rectal ulcer syndrome is a chronic disorder of the rectal mucosa. Symptoms are variable. There may be hematochezia, obstructed defecation, or no symptoms at all. Very often but not always SRUS occurs in association with varying degrees of rectal prolapse. The condition may be caused by different factors, such as long term constipation, straining during defecation, and dyssynergic defecation. Treatment is by normalization of bowel habits, biofeedback, and other non-surgical measures. In more severe cases, various surgical procedures may be indicated. The condition is relatively rare, affecting approximately 1 in 100,000 people per year. It affects mainly adults aged 30–50. Females are affected slightly more often than males. The disorder can be confused clinically with rectal cancer or other conditions such as inflammatory bowel disease, even when a biopsy is done.

Colitis cystica profunda

Another condition associated with internal intussusception is colitis cystica profunda, which is cystica profunda in the rectum. Cystica profunda is characterized by formation of mucin cysts in the muscle layers of the gut lining, and it can occur anywhere along the gastrointestinal tract. When it occurs in the rectum, some believe to be an interchangeable diagnosis with SRUS since the histologic features of the conditions overlap. Indeed, CCP is managed identically to SRUS.

Mucosal prolapse syndrome

A group of conditions known as Mucosal prolapse syndrome has now been recognized. It includes SRUS, rectal prolapse, proctitis cystica profunda, and inflammatory polyps. It is classified as a chronic benign inflammatory disorder. The unifying feature is varying degrees of rectal prolapse, whether internal intussusception or external prolapse.

Epidemiology

Rectal prolapse affects less than 0.5% of the general population. It affects women more commonly, with a female to male ratio of 9:1.

History

External rectal prolapse has been recognized since ancient times. The first written report is in the Ebers Papyrus. An Egyptian mummy from 400 to 500 BC was discovered to have rectal prolapse. In the Hippocratic Corpus there is a description of rectal prolapse and the following advice: "If there is a drop in the rectum, push it back in with a soft sponge, anoint it with snail medication, tie the person's hands and suspend him for a short time, and it will go in."
In 1831 British surgeon Frederick Salmon wrote a treatise on rectal prolapse, "Practical Observations on Prolapsus of the Rectum". What later became known as internal rectal prolapse was first described in 1888 in a textbook about diseases of the rectum. The author classified IRP as a variety of procidentia recti with the definition "the upper part of the rectum descends through the lower part, but does not appear outside the anus."

Society and culture

Rosebud pornography and prolapse pornography is an anal sex practice that occurs in some extreme anal pornography, wherein a pornographic actor or actress deliberately performs a rectal prolapse. "Rosebudding" is an example of producers making extreme content due to the easy availability of free pornography on the internet. Rosebudding is a way for pornographic actors and actresses to distinguish themselves. Some who participate in this form of pornography may be unaware of the consequences.

Etymology

Prolapse refers to "the falling down or slipping of a body part from its usual position or relations". It is derived from the Latin pro- - "forward" + labi - "to slide". Prolapse can refer to many different medical conditions other than rectal prolapse.
Procidentia has a similar meaning to prolapse, referring to "a sinking or prolapse of an organ or part". It is derived from the Latin procidere - "to fall forward". Procidentia usually refers to uterine prolapse, but rectal procidentia can also be a synonym for rectal prolapse.
Intussusception is defined as invagination, especially referring to "the slipping of a length of intestine into an adjacent portion". It is derived from the Latin intus - "within" and susceptio - "action of undertaking", from suscipere - "to take up". Rectal intussusception is not to be confused with other intussusceptions involving colon or small intestine, which can sometimes be a medical emergency. Rectal intussusception by contrast is not life-threatening.
Intussusceptum refers to the proximal section of rectal wall, which telescopes into the lumen of the distal section of rectum. What results is 3 layers of rectal wall overlaid. From the lumen outwards, the first layer is the proximal wall of the intussusceptum, the middle is the wall of the intussusceptum folded back on itself, and the outer is the distal rectal wall, the intussuscipiens.