Introduction

Solitary rectal ulcer syndrome (SRUS) is a chronic benign disorder of the rectum and pelvic floor that produces ulcerated and polypoid areas in the rectal wall. Although some patients have a single rectal ulcer, the term is misleading because the ulcers sometimes are multiple and extensive, and at times no ulcers are present but the rectal wall has a polypoid appearance (colitis cystic profunda). The condition predominantly affects young adults with equal gender incidence. SRUS causes significant symptoms associated with disordered defecation, and it can be diagnosed via a biopsy according to its specific histologic features. Its annual incidence is estimated to be 1 in 100,000 population. In this chapter, current thoughts about the cause, presentation, and treatment of SRUS will be discussed.

Cause

Although poorly understood, the cause of SRUS is thought to be disordered rectal evacuation associated with straining. Complete satisfactory rectal evacuation requires the coordinated and integrated normal function of the rectum, anus, and pelvic floor, including the reflex arcs and the voluntary responses to rectal filling that control them. Failure of this complex mechanism may result in a spectrum of problems ranging from minor mucus seepage to incontinence and obstructed defecation. A degree of rectal prolapse or intussusception and outlet obstruction attributed either to the redundant rectal wall, paradoxical contraction of puborectalis, or both is common to patients diagnosed with SRUS. It is likely that the individual presentation of each affected patient is determined by the degree of prolapse, the redundancy of tissue, and the strength of straining as patients seek to defecate and satisfy the urge they are feeling.

Pathophysiology

A paradoxical contraction of the puborectalis upon straining is not unique to SRUS; it also is a common cause of outlet obstruction to defecation in patients who do not have SRUS. However, it is the combination of rectal prolapse and paradoxical contraction of the puborectalis that seems to generate the ulceration seen in persons with SRUS. Persistent and prolonged straining pushes the prolapsing rectum against a closed pelvic floor and results in mucosal ischemia, trauma, and ulceration through compressive and shear forces. When the puborectalis muscle relaxes normally, a prolapsing rectal wall or mucosa may impact against the top of the anal canal, blocking evacuation. This type of trauma, which is less severe than that causing the ulcerated type of SRUS, is likely to produce the polypoid appearance that is sometimes seen. Patients experience a sense of rectal fullness as a result of retained stool and the presence of redundant prolapsing rectum. More straining may exacerbate the prolapse, which then worsens the feeling of incomplete emptying, thus producing further straining in a vicious cycle.

Clinical Features

The clinical presentation of SRUS is nonspecific, and the differential diagnosis includes a spectrum of disorders. Frequent unproductive straining is almost universal because of a constant desire to defecate and feelings of incomplete evacuation. Bleeding and passage of mucus occur in almost all cases. The bleeding sometimes leads to anemia and on rare occasions is massive. Difficulty initiating defecation is common. Most patients report tenesmus, and 20% of patients have a deep-seated pelvic ache. About 50% of patients have some degree of fecal incontinence. There is an association with the abdominal symptoms of irritable bowel syndrome and a high prevalence of psychoneurosis.

The rectal prolapse associated with SRUS takes time to develop, and patients often have a long history of unsatisfactory evacuation, chronic straining, and pelvic fullness.

Apart from an occasional patient with mildly abnormal perineal descent, few external physical signs are present. Digital rectal examination may reveal anterior rectal wall nodularity, friability, and erythema. Upon performing a sigmoidoscopy, excess rectal mucus is frequently noted with localized mucosal edema and reddening. Ulceration is usually seen on the lead point of the prolapsing bowel. Ulcers or polypoid changes are anterior in more than 90% of cases and are usually around 7 to 10 cm from the anal verge.

Some debate exists regarding the relationship between SRUS and colitis cystica profunda syndrome (CCP). The syndromes share common clinical presentations, underlying pathogenesis, and some endoscopic features, although in persons with CCP the endoanal ultrasound will show multiple submucosal cysts and intervening echorefringent fibrosis. Endoscopically, both SRUS and CCP can be mistaken for a neoplasm. A biopsy is the key to making the diagnosis. Samples should be taken from the edge of the ulcer and ideally should include submucosa. SRUS has the following microscopic features:

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  Eroded hyperplastic mucosa

  
  
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  Thickened muscularis mucosa

  
  
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  Fibromuscularization of the lamina propria

  
  
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  Hyperplastic glandular changes

  
  
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  Collagen infiltration

  
  
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  Polymorph infiltrate

  
  
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  Diamond-shaped crypts are also a characteristic diagnostic finding

These findings, often termed “mucosal prolapse syndrome,” are characteristic of mucosal prolapse found anywhere in the large intestine. It is sometimes found in the sigmoid colon, where polypoid, erythematous mucosal polyps are the result of prolapse engendered by the strong peristalsis.

In persons with SRUS, histologically, ectopic mucosal glands in the submucosa may be confused with the invasion that is the hallmark of an adenocarcinoma; the pathologist and surgeon should be aware of this potential for confusion. The lack of a desmoplastic reaction around the glands is an important clue to the absence of cancer.