Endometriosis: A Masquerade

KR is a 31 year-old woman with past medical history significant for an atrial septal defect who first presented in August 2016 with constant lower abdominal cramping with nausea, diarrhea, and vaginal bleeding during her usual menstrual cycle. The patient's menstrual cycles had been painful prior and she had been on an oral contraceptive (OCP) for 13 years though had stopped 3 months prior to presentation. Upon presentation, the patient's physical exam was notable for guarding and diffuse tenderness along both lower abdominal quadrants. The patient's pregnancy testing was negative and urinalysis unremarkable. Initial labs were notable only for mild leukocytosis and endovaginal ultrasound was unremarkable. On CT of the abdomen/pelvis, a right lower quadrant soft tissue mass was identified - perhaps an inflamed appendix. The plan was for non-operative management with pain control and antibiotics as the patient completed 7 days of Levaquin and Flagyl. Upon discharge and after completion of antibiotics, the patient felt better. However, in October, the patient presented once more with right lower quadrant abdominal pain - again during menses. Upon re-imaging, CT was unchanged and MRI demonstrated the same soft tissue mass at the ileocecal valve. Given no improvement in symptoms, the patient was planned for open ileocectomy and concurrent diagnostic laparoscopy. Upon laparoscopy, midline endometrial implants were noted scarring the cul-de-sac as well as the anterior bladder. A specimen obtained from the terminal ileum demonstrated full-thickness endometriosis and was, in fact, not a phlegmon. Endometriosis, affecting 10-15% of women of reproductive age, most frequently affects ovaries, the cul-de-sac, and the uterosacral ligaments. Under rarer circumstances, it has been noted to involve the GI tract. Notably, GI involvement by endometriosis has been noted to occur in 3-7% of menstruating women and ileal localization is even rarer - noted in 1-7% of all cases. Given the rarity of such a presentation, it is easy to commit diagnostic errors and consider more common pathologies such as abscesses. One such case discussed a similar diagnostic dilemma to ours in which the only means by which diagnosis of endometriosis was made was via histopathology. This information highlights the uniqueness of our case and adds perspective to a differential diagnosis we often consider when evaluating abdominal pain in the menstruating woman.Figure: CT imaging demonstrating RLQ mass in August 2016.Figure: CT imaging demonstrating RLQ mass in September 2016 upon repeat.Figure: MR imaging demonstrating RLQ mass upon second presentation in October 2016.