Endometriosis

Endometriosis is defined as the presence of secretory endometrial glands and stroma outside endometrium or myometrium 

It affects aprox 10% of women, principally in active reproductive life.  Clinical signs usually consist of dysmenorrhea, dysparaeunia and pelvic pain, menstrual irregularity, and infertility in 30-40%.  Symptoms may be cyclical and oestrogen dependent. 

It may occur in ovaries (up to 50% bilateral), uterine ligaments, rectovaginal septum, pelvic peritoneum, and laparotomy scars.   A closely related disorder, adenomyosis, is defined as the presence of endometrial tissue within the myometrium.

<1% rate of complicating malignancy, usually in large endometriomas (>15cm), rarely in peritoneal endometriosis. 

Laparoscopy is the standard of reference for the diagnosis and staging  
of endometriosis, and should be the first-line investigation. Imaging  
should be reserved for the following situations:  
To detect and characterise clinically suspected adnexal masses. 
To visualise laparoscopic 'blind spots' (extraperitoneal sites such as  
the rectum, vagina and bladder, areas hidden by dense adhesions)

To aid surgical planning in women with known endometriosis 

The commonest imaging finding is of an endometrioma - a thick walled, complex cyst ("chocolate cyst") with internal haemorrhagic debris, found on the ovary or elsewhere within the pelvis (and rarely in extraperitoneal sites such as lungs or CNS).Typical ultrasound appearance - diffuse, low level homogenous internal echoes with no internal doppler flow.

Other manifestations include peritoneal plaques which may be vascular, typically in the cul de sac bridging uterus to rectosigmoid, diffuse peritoneal foci, and adhesions and tethering of organs. 

      MRI (for indeterminate findings at ultrasound) is over 90% specific, detecting blood products of endometriomas or plaques.

Neither ultrasound nor MRI are 100% sensitive, particularly for diffuse low volume peritoneal deposits or plaques, but MRI is more specific as a problem solving modality. 

Hysterosalpingography is usually performed following specialist referral for investigation of infertility.  This can demonstrate tubal occlusion, hydrosalpinx, and peritubal 'clumping' of contrast, all due to scarring. 

CT is not used for investigation - may show a non specific complex pelvic mass or plaque.