Chapter 15 — Rectal Intussusception

Rectal intussusception means the rectal wall folds inward on itself. It does not come out through the anus. This is why it is sometimes called internal prolapse. This chapter explains rectal intussusception in full. It covers presentation, examination, differential diagnosis, investigations, and management. This is the same pattern used for every disease chapter in this manual.

15.1 What Is Rectal Intussusception

Chapter 14 introduced rectal prolapse. In a full prolapse, the rectum comes out through the anus. In intussusception, the rectal wall folds inward instead. The upper part of the rectum slides down into the lower part, like one part of a telescope sliding into another.

This folding can stay high inside the rectum. It can also travel further down, into the anal canal. It does not pass through the anus itself. This is the key difference from the full-thickness prolapse described in Chapter 14.

Intussusception is common. Many people have some degree of it on imaging, without any symptoms at all. It only becomes a clinical problem when it causes symptoms, or blocks normal defecation.

15.2 Why It Happens

The causes overlap closely with rectal prolapse, described in Chapter 14. A weak pelvic floor is the main factor. Long-standing straining adds to this weakness over time.

Excess laxity of the rectal wall itself also plays a role. The wall becomes loose. It folds instead of staying taut during defecation. Age, childbirth, and chronic straining all contribute to this laxity.

15.3 Classification and Defecographic Grading

Rectal intussusception is graded by how far the fold travels, and by imaging during defecation. Defecography, described further in Chapter 8, is the main tool used for this grading.

High rectal intussusception — the fold stays within the rectum itself. It does not reach the anal canal. Low rectal intussusception — the fold reaches the upper anal canal, but does not enter it fully. High anal intussusception — the fold enters the anal canal, but stays in its upper part. Low anal intussusception — the fold reaches the lower anal canal. This is the most advanced internal grade, just short of a full external prolapse.

This grading matters for two reasons. It predicts how likely the condition is to progress to a full external prolapse. It also guides the choice between conservative and surgical treatment, discussed later in this chapter.

15.4 Presentation

Follow the history-taking method described in Chapter 2. The symptoms of intussusception are often less obvious than full prolapse, since nothing is visible outside the anus.

A sense of incomplete emptying after defecation. This is the most common symptom. A need to strain hard, or for a long time, to pass stool. A feeling of a blockage or obstruction inside the rectum during defecation. Some patients use digital support, pressing on the perineum or inside the vagina, to help complete defecation. Mucus discharge, in some patients, from chronic irritation of the folded rectal wall. Mild faecal incontinence, in some patients, though this is less common than with full prolapse.

Ask specifically about straining and incomplete emptying. These symptoms overlap closely with obstructed defecation syndrome, covered in Chapter 16. The two conditions often coexist.

15.5 Examination

Follow the sequence from Chapter 3. Intussusception is much harder to detect on simple examination than full prolapse, since nothing protrudes through the anus.

See Chapter 4 for the inspection method. Inspection is usually normal, even during straining. This is the main clinical clue that distinguishes intussusception from full external prolapse.

Digital rectal examination may feel a mass of folded rectal wall on straining, high inside the rectum. This finding is subtle. It is easy to miss without a deliberate, careful examination during active straining.

Proctoscopy may show redundant, folding mucosa. It cannot reliably grade the intussusception. Imaging is needed for that, as described below.

15.6 Differential Diagnosis

Several conditions can cause similar symptoms of straining and incomplete emptying.

Rectocele — a bulge of the rectal wall into the vagina. Chapter 16 covers this in detail. Obstructed defecation syndrome, from other causes — such as pelvic floor dyssynergia. Chapter 16 covers this separately. Slow transit constipation — a whole-colon problem, rather than a rectal one. Investigations help distinguish the two. Full rectal prolapse — should already be excluded by inspection, as described in Chapter 14.

Intussusception often coexists with these other conditions, rather than replacing them. A full assessment considers all of them together, rather than stopping once one diagnosis is found.

15.7 Investigations

Defecography is the key investigation for rectal intussusception. It shows the rectum during active straining and defecation. This is the only reliable way to grade the condition, as described in section 15.3.

MRI defecography is a modern alternative. It avoids radiation exposure, and can show the pelvic floor and other pelvic organs at the same time.

Colonoscopy is advisable in an older patient, or in any patient with red flag symptoms, to exclude another cause of the symptoms.

Anorectal manometry, described in Chapter 8, can help assess overall pelvic floor function. It does not replace defecography for grading the intussusception itself.

15.8 Principles of Management

Most patients with rectal intussusception do not need surgery. Many have no symptoms at all, and need no treatment beyond reassurance.

Conservative treatment is the correct first step for almost every symptomatic patient. This includes dietary fibre, adequate fluid intake, and correcting any straining habit.

Pelvic floor physiotherapy, including biofeedback training, can help many patients. It teaches better coordination during defecation, and reduces the need to strain.

15.9 The Conservative-Versus-Surgical Threshold

Deciding when to move from conservative treatment to surgery is one of the most difficult judgements in this condition. The grade of intussusception alone does not decide this. Symptoms matter more than the imaging findings.

A patient with a high-grade intussusception on defecography, but few symptoms, is usually best managed conservatively. Surgery carries real risks. It should not be offered simply because imaging looks abnormal.

A patient with a lower-grade intussusception may still benefit more from surgery than one with worse imaging. This is true if their symptoms are severe and persistent, and a full conservative trial has already failed. Symptoms guide the decision, not the grade alone.

As a practical guide, surgery is considered when three things are all true. The symptoms are significant and persistent. A fair trial of conservative treatment and pelvic floor therapy has failed. The intussusception is clearly the main cause of the symptoms, rather than a coexisting problem such as slow transit constipation.

15.10 Surgical Techniques

Ventral mesh rectopexy is described in Chapter 14. It is the main surgical option for a symptomatic, high-grade intussusception. It supports the rectum from the front, and corrects the folding pattern.

The same caution on synthetic mesh, discussed in Chapter 14, applies here. This remains an evolving area, and should be discussed openly with the patient as part of consent.

Stapled transanal procedures, used mainly for obstructed defecation syndrome, are covered in Chapter 16. They are sometimes used for intussusception with a coexisting rectocele.

Surgery for intussusception alone, without a clear symptom benefit expected, should be avoided. The threshold described in section 15.9 applies strictly here.

15.11 Special Situations

Intussusception with rectocele — needs assessment of both problems together. Treating one alone may not resolve the symptoms. Chapter 16 covers this overlap. Intussusception with slow transit constipation — needs careful distinction, since surgery for the intussusception will not fix a whole-colon transit problem. Progression to full prolapse — a small number of patients progress from intussusception to full external prolapse over time. Warn the patient of this possibility, and arrange appropriate follow-up. Young patient with mild symptoms — conservative treatment and pelvic floor therapy should be tried thoroughly before any consideration of surgery.

15.12 Complications of Treatment

Conservative treatment carries very little risk. The risks below apply mainly to surgery.

Recurrence of symptoms, even after successful surgery. New or worsened constipation, particularly after certain rectopexy techniques. Mesh-related complications, as described in Chapter 14, when mesh is used. Persistent symptoms, if the intussusception was not the true cause of the patient's complaints.

15.13 Common Mistakes to Avoid

Offering surgery based on imaging grade alone, without matching it to the severity of symptoms. Missing a coexisting rectocele or pelvic floor dyssynergia, and treating the intussusception in isolation. Failing to try a full, structured course of conservative treatment before considering surgery. Assuming every case of straining and incomplete emptying is due to intussusception, without excluding other causes.

15.14 Recording and Follow-Up

Record the grade of intussusception on defecography, the main symptoms, and the treatment plan chosen. For example: "High-grade rectal intussusception on defecography. Symptoms: straining, incomplete emptying. Plan: pelvic floor physiotherapy, review in 12 weeks." Arrange follow-up to check symptom response before considering any surgical referral.

15.15 Why This Chapter Matters

Rectal intussusception sits between normal anatomy and full rectal prolapse. Most cases need no more than reassurance and simple measures. A careful few need surgery, chosen for the right reason. The next chapter turns to obstructed defecation syndrome, which often overlaps closely with the condition described here.