Solitary rectal ulcer syndrome

# Overview
Solitary rectal ulcer syndrome (SRUS, SRU), is a disorder of the rectum and anal canal, caused by straining and increased pressure during defecation. This increased pressure causes the anterior portion of the rectal lining to be forced into the anal canal (an internal rectal intussusception). The lining of the rectum is repeatedly damaged by this friction, resulting in ulceration. SRUS can therefore considered to be a consequence of internal intussusception (a sub type of rectal prolapse), which can be demonstrated in 94% of cases. It may be asymptomatic, but it can cause rectal pain, rectal bleeding, rectal malodor, incomplete evacuation and obstructed defecation (rectal outlet obstruction).

# Epidemiology and Demographics
The condition is thought to be uncommon. It usually occurs in young adults, but children can be affected too.

# Causes
- The essential cause of SRUS is thought to be related to too much straining during defecation.
- Overactivity of the anal sphincter during defecation causes the patient to require more effort to expel stool. This pressure is produced by the modified valsalva manovoure (attempted forced exhalation against a closed glottis, resulting in increased abdominal and intra-rectal pressure). Patiest with SRUS were shown to have higher intra-rectal pressures when straining than healthy controls. SRUS is also associated with prolonged and incomplete evacuation of stool.
- More effort is required because of concomitant anismus, or non-relaxation/paradoxical contraction of puborectalis (which should normally relax during defecation). The increased pressure forces the anterior rectal lining against the contracted puborectalis and frequently the lining prolapses into the anal canal during straining and then returns to its normal position afterwards.
- The repeated trapping of the lining can cause the tissue to become swollen and congested. Ulceration is thought to be caused by resulting poor blood supply (ischemia), combined with repeated frictional trauma from the prolapsing lining, and exposure to increased pressure are thought to cause ulceration. Trauma from hard stools may also contribute.
- The site of the ulcer is typically on the anterior wall of the rectal ampulla, about 710 cm from the anus. However, the area may of ulceration may be closer to the anus, deeper inside, or on the lateral or posterior rectal walls. The name "solitary" can be misleading since there may be more than one ulcer present. Furthermore, there is a "preulcerative phase" where there is no ulcer at all.
- Pathological specimens of sections of rectal wall taken from SRUS patients show thickening and replacement of muscle with fibrous tissue and excess collagen.
 Rarely, SRUS can present as polyps in the rectum.
- SRUS is therefore associated and with internal, and more rarely, external rectal prolapse. Some believe that SRUS represents a spectrum of different diseases with different etiologies.
- Another condition associated with internal intussusception is colitis cystica profunda (also known as CCP, or proctitis 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.
- Electromyography may show pudendal nerve motor latency.

# Differentiating Solitary Rectal Ulcer Syndrome from other Diseases
The differential diagnosis of SRUS (and CCP) includes:
- polyps
- endometriosis
- inflammatory granulomas
- infectious disorders
- drug-induced colitis
- mucus-producing adenocarcinoma

# Natural History, Complications and Prognosis
Complications are uncommon, but include massive rectal bleeding, ulceration into the prostate gland or formation of a stricture.  Very rarely, cancer can arise on the section of prolapsed rectal lining.

# Diagnosis

## History and Symptoms
Symptoms include:
- Straining during defecation
- Mucous rectal discharge
- Rectal bleeding
- Sensation of incomplete evacuation (tenesmus)
- constipation, or more rarely diarrhea
- fecal incontinence (rarely)

## Laboratory Findings
- SRUS is commonly misdiagnosed, and the diagnosis is not made for 57 years. Clinicians may not be familiar with the condition, and treat for Inflammatory bowel disease, or simple constipation.
- The thickened lining or ulceration can also be mistaken for types of cancer.
- Defecography, sigmoidoscopy,  transrectal ultrasound, mucosal biopsy, anorectal manometry and electromyography have all been used to diagnose and study SRUS.  Some recommend biopsy as essential for diagnosis since ulcerations may not always be present, and others state defecography as the investigation of choice to diagnose SRUS.

# Treatment
Although SRUS is not a medically serious disease, it can be the cause of significantly reduced quality of life for patients. It is difficult to treat, and treatment is aimed at minimizing symptoms.
- Stopping straining during bowel movements, by use of correct posture, dietary fiber intake (possibly included bulk forming laxatives such as psyllium), stool softeners (e.g. polyethylene glycol, and biofeedback retraining to coordinate pelvic floor during defecation.
- Surgery may be considered, but only if non surgical treatment has failed and the symptoms are severe enough to warrant the intervention. Improvement with surgery is about 55-60%.
- Ulceration may persist even when symptoms resolve.