F/39 CC : Defecation difficulty D : 1mo

Sigmoidoscopy (10.3.2)

CT Colonography (10.3.5)

Rectum, Low anterior resection ( )  Endometriosis  Size: 5.5x4cm  Location  Rectum  Involving serosa, proper muscle and submucosa  Resection margin  Proximal: Absence of endometriosis  Distal: Absence of endometriosis  Proximal, separately sent: Absence of endometriosis  Distal, separately sent: Absence of endometriosis

Endometriosis  Definition  The presence of functional endometrial glands and stroma outside the uterine cavity  Epidemiology  In women of childbearing age  Mean age at diagnosis  25–29 years  Deep pelvic endometriosis  Endometriotic lesion penetrating into the retroperitoneal space or the wall of the pelvic organs to a depth of at least 5 mm  In most cases of severely infiltrating disease, surgery is the final solution

Pathogenesis  Metastatic theory  Retrograde menstrual implantation ☆  Vascular and lymphatic spread  Intraoperative implantation  Metaplastic theory  Induction theory

Endometriotic implants of the GI tract  Occur in 12%–37% of patients with endometriosis  Most commonly affects those segments of bowel in the dependent portion of the pelvis  Rectosigmoid > appendix > cecum > distal ileum  Usually serosal but can eventually erode through the subserosal layers and cause marked thickening and fibrosis of the muscularis propria  Inflammatory response to cyclic hemorrhage  Lead to adhesions, bowel stricture, and GI obstruction  Differential diagnosis  Primary colon cancer  Metastatic disease  The CT and US appearances of endometriosis involving the bowel are nonspecific and usually do not help differentiate masses  CT finding of endometrioma  Hyperattenuating area suggesting hemorrhage within the cyst

Endometriotic implants of the GI tract

 MR imaging characteristics  Depend on the type of lesions  Infiltrating small implants  Mainly located in the posterior cul-de-sac involving the uterosacral ligaments  T1WI : Low to intermediate SI with punctate regions of high SI  Represent regions of hemorrhage surrounded by solid fibrotic tissue  T2WI : Uniform low SI and enhancement, corresponding to the abundant fibrous tissue  Visceral endometriosis  Involving the bladder and rectal wall  Rectal involvement  Thickening of the rectal wall in association with specific symptoms  Low SI on T2-weighted images and sometimes the presence of punctate hyperintense foci of hemorrhage Endometriotic implants of the GI tract

 MR imaging  T2WI : “Shading” (Loss of signal within the lesion)  Reflects the chronic nature of an endometrioma  Result of cyclic bleeding accumulating over months to years  Very viscous, with extremely high concentrations of iron and protein Endometriotic implants of the GI tract