Rectal Prolapse - Classification

Classification

The different kinds of rectal prolapse can be difficult to grasp, as different definitions are used and some recognize some subtypes and others do not. Essentially, rectal prolapses may be

• full thickness (complete), where all the layers of the rectal wall prolapse, or involve the mucosal layer only (partial)
• external if they protrude from the anus and are visible externally, or internal if they do not
• cicumfrential, where the whole circumference of the rectal wall prolapse, or segmental if only parts of the circumference of the rectal wall prolapse
• present at rest, or occur during straining.

External (complete) rectal prolapse (rectal procidentia, full thickness rectal prolapse, 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 (occult rectal prolapse, internal procidentia) can be defined as defined as a funnel shaped infolding of the upper rectal (or lower sigmoid) 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 (partial rectal 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 (3rd or 4th degree) hemorrhoids (piles). However, both internal mucosal prolapse (see below) and circumferential mucosal prolapse are described by some. Others do not consider mucosal prolapse a true form of rectal prolapse.

Internal mucosal prolapse (rectal internal mucosal prolapse, RIMP) 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 hemmorhoidal disease, or whether it is a separate entity. The term "mucosal hemorrhoidal prolapse" is also used.

Solitary rectal ulcer syndrome (SRUS, solitary rectal ulcer, SRU) 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 (MPS) 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 (anismus)
• 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 predicitive 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 (high) intussusception (intra-rectal intussusception) is where the intussuscetption starts in the rectum, does not protrude into the anal canal, but stays within the rectum. (i.e. the intussusceptum originates in the rectum and does not extend into the anal canal. The intussuscipiens includes rectal lumen distal to the intussusceptum only). These are usually intussusceptions that originate in the upper rectum or lower sigmoid.

Recto-anal (low) intussusception (intra-anal intussusception) is where the intussusception starts in the rectum and protrudes into the anal canal (i.e. the intussusceptum originates in the rectum, and the intussuscipiens includes part of 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