Endometriosis is the presence of uterine tissue foci, composed of endometrial and stromal glands, beyond the uterine cavity. It belongs to non-malignant lesions. The most typical sites are the ovaries, with as many as 80% of cases. Other possible sites mainly include: the fallopian tubes, the pouch of Douglas, the peritoneum, the uterine ligaments, laparotomy scars, particularly caesarean section scars, the umbilicus, the vulva, the vagina and the cervix uteri. As for the gastrointestinal tract, the disease usually develops within the appendix. It is rarely observed in the chest, e.g. in the lungs (1). Endometriosis is said to affect 10% of fertile women (2).

The pathogenesis of the phenomenon remains unclear. A possible cause is tissue implantation during surgery, but this hypothesis does not explain the occurrence of endometriosis in patients with no history of abdominal surgery. It is thought that implantation is the most likely during episiotomy in childbirth or during pelvic surgery. Numerous authors support the regurgitation theory, which involves retrograde flow of endometrial fragments during menstruation through the fallopian tubes to the peritoneal cavity. This is where implantation and tissue growth occurs. Other possible causes are haematogenous or lymphatic dissemination and metaplasia of cells lining the abdominal cavity (3). Endometriosis is also sometimes considered an autoimmune disease caused by immune system disorders.

A 42-year-old patient reported to the Emergency Department with severe abdominal symptoms and faecal incontinence in August 2018. Pain had persisted for two weeks. On the day of admission, the symptoms exacerbated significantly with additional nausea. On physical examination, the abdomen was particularly painful in the left epigastric region. The peristalsis was periodically inaudible; there were numerous sloshing sounds. There were no clinical signs of peritonitis. Inflammatory markers were normal. Plain abdominal X-ray showed dilated loops of the small intestine in the mid-abdomen and the epigastric region on the left side with the presence of fluid-air levels reaching the width of approximately 90 mm. There were no signs of free fluid under the diaphragm domes. Abdominal US revealed significant dilatation of the small intestinal loops with pendular movement. The gallbladder was non-dilated and thin-walled. It contained two stones measuring approximately 17 and 18 mm, respectively. Additionally, there was some interloop fluid reaching the width of approximately 15 mm. The examinations led to a diagnosis of mechanical bowel obstruction of unknown aetiology. The patient was admitted to the surgical ward where conservative treatment was initially implemented, but caused no pain relief. That is why the patient was sent for an emergency exploratory laparotomy. During the surgery, turbid fluid was found, and some samples were collected for bacteriology. The small bowel was significantly distended. Approximately 15 cm before the Bauhin’s valve, there was an annular endophytic tumour that completely occluded the intestine. The mesenteric lymph nodes were noticeably enlarged. No other significant pathology within the remaining abdominal organs was found on palpation. Due to a family history of bowel cancer and the intraoperative macroscopic image of the tumour, the lesion was suspected of being malignant (adenocarcinoma). A decision was made to excise the tumour with a margin of the small intestine and with right hemicolectomy. The terminal 40 cm of the small intestine with the tumour, ascending colon and the right half of the transverse colon were removed. The ileum was joined with the transverse colon using a stapler (end-to-side anastomosis). The excised bowel fragment was sent for a histopathological examination. Two pathogens were cultured from the peritoneal fluid collected intraoperatively: Escherichia coli and Enterobacter cloacae AL PAT. The histopathological report described reactive, probably inflammatory mesenteric lymph nodes of typical structure. The middle part of the terminal ileum, the subperitoneal tissue and mucosa presented numerous foci of endometriosis, creating the tumour mass. Apart from this, the mucosa was normal. The remaining material sent for examination contained no pathology.

Parenteral nutrition was started on the day of surgery and continued for 4 days. Subsequently, liquid diet was introduced and gradually expanded. Before and directly after the surgery, the patient received two broad-spectrum antibiotics, which occurred to be appropriate as per the obtained antibiograms. On day 6 after the surgery, the patient was discharged in a good overall condition, with a normally healing abdominal wound. A surgical follow-up appointment was ordered.