Solitary Rectal Ulcer Syndrome

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.

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