Rectal discharge

Did You Know?

• Purulent rectal discharge usually indicates infection; the term mucopurulent discharge refers to a discharge containing both mucus and pus.
• Perianal discharge from fistulae or pilonidal disease can be misinterpreted as rectal discharge due to anatomical proximity.
• Perianal tumours may discharge when they fungate or become cystic or necrotic.

Mucous rectal discharge (mucinous rectal discharge, mucoid rectal discharge, muc

Mucus normally coats the colon wall as a protective barrier and to lubricate stool. Mucous discharges fall into three broad categories: normal physiological mucus; inappropriately expressed physiological mucus due to sphincter defects or lesions preventing closure; and mucus produced in pathological quantities from a lesion, generalized coloproctitis, or bacterial overgrowth. A mucous discharge may be blood-streaked, and in some conditions blood mixes homogenously with mucus to form a pink goo, such as the "red currant jelly" stools seen in intussusception, which contain sloughed mucosa, mucus, and blood. The noun "mucus" names the substance, while "mucous" is an adjective describing a discharge; "mucoid" means mucus-like, and "mucinous" often is used interchangeably with "mucous."

Differential diagnosis

The differential diagnosis for rectal discharge is extensive, with infection and inflammation as general etiological themes. Some lesions cause discharge by mechanically interfering with anal canal closure, allowing transit of liquid stool and mucus without intrinsically producing discharge. Common causes include haemorrhoids, proctitis, anal fissure, rectal prolapse, and perianal warts. Less common causes include colorectal carcinoma, irritable bowel syndrome, solitary rectal ulcer syndrome, anal fistulae, villous adenoma, and poor anal hygiene. Rare causes include sexually transmitted diseases such as syphilis, rectal gonorrhea, and chlamydia; anal carcinoma; AIDS; rectal foreign body; bowel obstruction; rectocele; enterocele; ulcerative colitis; bacterial colitis; anal or perianal tuberculosis; and ruptured perianal abscess. Perianal Crohn's disease is associated with fistulizing, fissuring, and abscess formation. After colostomy, the distal bowel continues to produce mucus, often resulting in mucinous discharge. Intestinal parasitic infection, such as whipworm, can occasionally present with discharge.

Causes

Proctitis, inflammation of the rectal lining including the distal 15 cm, has many causes. Common infectious causes include sexual intercourse with someone who has an STD, foodborne illness, and strep throat in children. Proctitis may also result from inflammatory bowel disease, radiation therapy, rectal or anal injury, or certain antibiotics. Tuberculosis proctitis can produce a mucous discharge. Anal warts, irregular verrucous lesions caused by human papilloma virus, are usually transmitted by unprotected anoreceptive intercourse; they may be asymptomatic or cause rectal discharge, anal wetness, rectal bleeding, and pruritus ani, especially when lesions occur within the anal canal. Chlamydia trachomatis causes trachoma and lymphogranuloma venereum; trachoma can cause asymptomatic proctitis, while lymphogranuloma venereum typically presents with pruritus ani, purulent rectal discharge, hematochezia, rectal pain, and diarrhea or constipation, and can lead to fistulas, strictures, and anorectal abscesses if untreated, sometimes mimicking Crohn's disease. Rectal gonorrhea, caused by Neisseria gonorrhoeae, is usually asymptomatic but may produce a brownish mucopurulent discharge, pruritus ani, tenesmus, and constipation, typically appearing 5–7 days post-exposure. Anorectal syphilis, from Treponema pallidum contracted through anoreceptive intercourse, causes minimal symptoms but may include mucous discharge, bleeding, and tenesmus. Diversion colitis can develop in bowel segments no longer exposed to stool after colostomy, due to lack of short-chain fatty acids from bacterial fermentation; symptoms include rectal bleeding, mucous discharge, tenesmus, and abdominal pain. Other causes include solitary rectal ulcer syndrome, colitis cystica profunda, internal intussusception, mucosal prolapse, and rectal prolapse.