Intestinal Endometriosis: An Unusual Cause of a Rectal Mass

A 33-year-old woman with altered bowel habits for 5 months presented for a gastroenterology evaluation.She also reported pain in her lower back and sacrum.Other symptoms included constipation with less frequent loose stools with urgency and sensation of incomplete emptying.She stopped caffeine and tried a "squatting potty" with no improvement in symptoms.There was no rectal bleeding, but some intermittent abdominal cramping pain.without specific aggravating factors.The pain did not respond to over-the-counter medications.Past medical history included acne vulgaris.She was on topical benzoyl peroxide-erythromycin and clindamycin swabs.She did not smoke, use drugs or drink significant amounts of alcohol.She had no personal or family history of gastrointestinal malignancies or other gastrointestinal disorders.Laboratory evaluation included normal complete blood count, comprehensive metabolic panel and TSH.Celiac panel was also negative.Colonoscopy revealed a 15 mm nodular sessile lesion in the distal rectum with active oozing (Figure 1).Multiple biopsies revealed histology consistent with endometriosis (Figure 2).