Procedure name

Clinical history

Technique

Comparison studies

Findings

Posterior compartment

Rectum

Mesorectal fascia

Pelvic floor

Middle compartment

Uterus

Cervix

Vagina

Ovaries and paraovarian spaces

Anterior compartment

Distal ureters

Bladder

Urethra

Other findings:

Vasculature

Bowel

Lymph nodes

Peritoneum and peritoneal space

Skeleton and body wall

Or

Findings

GU

Distal ureters

Bladder

Urethra

Uterus

Cervix

Vagina

Ovaries and paraovarian spaces

GI

Small bowel

Rectum

Mesorectal fascia

Vasculature

Nodes

Peritoneum

Posterior compartment

Middle compartment

Anterior compartment

Skeleton and body wall

Buzz words and concepts

Mention areas of fibrosis/invasion caused by endometriosis:

• uterosacral ligaments

• torus uterinus

• rectal and vaginal invasion

Notes:

• Pertinent lesion diameters can be provided

• mr O-RADS scores are provided when pertinent

• Average female pelvis MR report length:  300 words

• Volumes are not provided in standard reports; however, ARA can provide volumes and other pertinent post-processing for a mutually agreed per-exam service fee (~ $700/hour) paid to ARA by the office of the ordering provider.

• 3 main morphologic patterns of endometriosis:

  • Ovarian endometriomas

  • Superficial endometriosis 

    • No subperitoneal extension at histopathologic exam

  • Deep endometriosis 

    • Subperitoneal extension seen at histopathologic exam

    • Manifest as fibrotic and desmoplastic plaques, glandular components, mass formation, polypoid lesions

• Surgery appearance:

  • White, red, or black peritoneal lesions

  • Ovarian endometriomas

  • Dense fibrosis

  • Filmy adhesions

US EVALUATION

• US diagnosis of endometriosis encompasses direct and indirect observations. 

  • The most common direct observations (ie, evidence of ectopic endometrial-like tissue) include ovarian endometrioma, USL, rectosigmoid, uterine serosal, vaginal, and bladder DE implants (Fig 2). 

  • Indirect observations (ie, a fibrotic reaction induced by endometriosis) include fixed uterine retroflexion, bowel tethering to the posterior uterus, posterior malposition of one or both ovaries, and ovarian immobility. 

  • Other associated observations are hydrosalpinx and diffuse adenomyosis. Hematosalpinx is an infrequent isolated associated observation that must be distinguished clinically from pyosalpinx.

• The absence of a normal posterior uterine sliding sign has a strong correlation with a pouch of Douglas obliteration and is associated with a higher incidence of rectosigmoid DE. 

  • The posterior uterine sliding sign is acquired with transducer pressure to demonstrate the presence (nml) or absence (abnormal) of sliding motion b/n the posterior uterocervical junction and adjacent rectum.

• Ovarian endometriomas 

  • Typically unilocular cysts with a ground-glass appearance with homogeneous low-level echoes, which can have punctate wall echogenic foci and mild to no peripheral vascularity. 

  • Solid-appearing areas can develop with debris and should be evaluated with color Doppler US. 

  • The combination of premenopausal status, ground-glass echogenicity, one to four locules, and absent color Doppler flow within papillary projections yields a specificity of greater than 98% for endometrioma.

  • Kissing ovaries refers to ovaries that abut one another posterior to the uterus and is associated with  advanced-stage endometriosis. 

  • Ovarian mobility, evaluated by using transducer or bimanual pressure techniques, may demonstrate adhesions, especially posteromedial to the uterus. 

• USL, Uterine, Vaginal involvement

  • The USLs are the most common location of DE, accounting for 69% of DE implants. 

  • The USL may be identified by placing the transducer in the posterior vaginal fornix and rotating the transducer up to 45° until an echogenic band is observed coursing laterally from or just inferior to the posterior uterocervical junction. 

  • DE implants of the USL are typically moderately hypoechoic to the echogenic ligament and may be smooth or spiculated, nodular, or plaque-like, often with echogenic punctate foci.

  • DE most commonly affects the uterus along the posterior serosal surface, typically by extension of DE originating on the USL. Manifests as an adenomyosis-like hypoechoic infiltration of the myometrium, with an outside to inside pattern of involvement sparing the inner myometrium. 

  • Vaginal involvement usually manifests as moderately hypoechoic infiltration of the posterior vaginal fornix, sometimes with cystic spaces, often associated with USL and rectal or rectovaginal septum DE, creating an hourglass configuration.

• Bowel and Rectovaginal Septum 

  • Transvaginal US of the rectosigmoid colon has sensitivity and specificity approaching 100%, particularly after bowel preparation, which emphasizes the superiority of this method in detecting and characterizing multiple bowel lesions. 

  • The mid to upper rectum is the most common location of bowel endometriosis, and the sigmoid colon, lower rectum, and rectovaginal septum are less commonly involved. 

  • DE observations are reported based on the distance of the caudal end from the anal verge and whether they extend into the rectovaginal septum. 

  • Transvaginal US defines the normal bowel wall layers, allowing for assessment of even small infiltrations of the muscularis propria. 

  • DE induces hypertrophy of the muscularis propria, resulting in very hypoechoic thickening, usually obliterating the connective tissue layer, and occasionally exhibiting internal echogenic foci. Lesions typically are elliptical with tapered ends. 

  • The induction of surrounding fibrosis may result in C- or Ω-shaped nodules. Curved measurement ensures accurate prediction of the affected colon length.

• Urinary Tract Endometriosis 

• DE may involve the urinary bladder along its posterior peritoneal surface, often at the dome. 

• Nodules are typically isoechoic to mildly hypoechoic compared with the detrusor muscle and may contain cystic components. 

• Ureteral involvement is less common, usually as extrinsic involvement from spread of retrocervical DE, typically when the primary DE nodule exceeds 3 cm.

MRI EVALUATION

T2-weighted MRI Evaluation for Disease Presence,  Extent, and Phenotypes 

• DE on T2-weighted images manifests as irregular, linear, stellate, or nodular T2-hypointense (relative to muscle signal intensity) thickening that corresponds to fibrosis and stroma. 

• Regions of most frequent involvement include the USL, torus uterinus, parametrium, and the rectovaginal space. 

• Variable degrees of cystic change can be present. 

• Architectural distortion from repeated bleeding, inflammation, and fibrosis leads to deviation of the uterus from the midline (marked retroflexion or deviation into the right and/or left pelvis), abnormal ovarian position posterior or lateral to the uterine body with medial contact (kissing ovarian configuration), nonvisualization of the anterior or posterior cul-de-sac, obliteration of the hypointense signal of the fibromuscular stroma of the cervix or vaginal wall, or abrupt angulation of the bowel (small or large) toward a focal point in the pelvis. 

T1-weighted MRI Evaluation for Hemorrhagic Disease 

• After assessing disease presence and location on T2-weighted images, T1-weighted imaging with fat saturation is a critical sequence in the evaluation of characteristic T1-hyperintense blood products seen in ovarian endometriomas, and variably within superficial and deep endometriotic deposits. 

• DE implants comprise predominantly chronic stromal and/ or fibrotic components surrounding areas of active glandular elements, which can appear T1 hyperintense because of hemorrhagic contents. 

  • The T1 signal within DE implants is variable, as the hemorrhagic elements can become suppressed in patients using oral contraceptives or hormonal therapy or who are pregnant. 

  • DE is also less likely to contain T1 hyperintense foci compared with endometriomas due to the surrounding fibrous reaction and smooth muscle proliferation, which minimize cyclical bleeding of the glandular components. 

• Although the sensitivity for hemorrhagic foci is reportedly high, the lack of T1-hyperintense foci does not exclude endometriosis, and in fact, DE can occur without any T1 hyperintensity.

Ovarian endometriomas 

• The best known manifestations of endometriosis. 

• These are unilocular or multilocular cystic lesions containing blood products of varying age from repetitive, cyclical hemorrhage. Once identified, this should trigger further evaluation for DE.

• Hemorrhage causes endometriomas to be T1 hyperintense and T2 hypointense, also called T2 shading (ie, signal loss at T2-weighted MRI). 

• Other T2-weighted imaging features include a hypointense thickened rim due to fibrous tissue and hemosiderin-laden macrophages in the wall of the endometrioma and the T2 dark spot sign, thought to represent a chronic retractile blood clot. 

• However, the presence of an enhancing mural nodule is often a marker of malignancy, and this assessment is best evaluated at postcontrast subtraction MRI. 

• Endometriomas are a marker for severe disease and can be multiple and/or bilateral. Superficial implants on the serosal surface or peritoneum of the ovarian fossa become detectable most commonly when they are T1 hyperintense.

Fallopian Tubes, Broad and Round Ligaments

• Fallopian tube endometriosis may manifest as hematosalpinx with intrinsic T1-hyperintense contents or mild salpingitis with T1- and/or T2-hypointense, enhancing tubal wall thickening and occasionally diffusion restriction. 

• Broad ligament DE manifests as T2-hypointense implants between the uterus and lateral pelvic sidewalls. 

• Paraovarian endometriomas can also be located in the broad ligaments. 

• The round ligaments of the uterus arise from the anterolateral uterine fundus, course through the broad ligaments laterally to the pelvic side walls, anterior to the external iliac vessels, into the inguinal canals, and terminate in the labia majora. 

• DE of the intrapelvic portion most commonly occurs adjacent to the uterus and can be seen with morphology and signal changes, nodularity, cysts, deviation, or shortening.

USL, Parametrial, and Uterine and/or Vaginal Invasion 

• The USLs are fibrous bands extending from either side of the posterior uterocervical junction (torus uterinus) to the sacrum, suspending and stabilizing the uterus and vagina. 

• They are the most common site of DE, seen in 60%–85% of patients at laparoscopy, usually involving the proximal third of the ligament. 

• Typical torus uterinus and/or USL DE is fibrotic, appearing as stellate or nodular T2-hypointense tissue with tethering of surrounding structures and variable active glandular components. 

• MRI criteria for USL endometriosis are still debated, with one study suggesting spiculated and/or retracted, nodular, irregular, or smooth thickening greater than 5 mm or hemorrhagic implant regardless of thickness as diagnostic features. 

• A bat wing USL appearance on MRI scans has been associated with posterior cul-de-sac obliteration.

• When severe, USL and/or torus uterinus DE can extend cranially to involve the posterior uterine wall, resulting in pronounced retroflexion, or caudally to involve the vagina, tethering the posterior fornix.

• Reporting the depth of myometrial and vaginal invasion is important for surgical planning, as the former may impact fertility preservation and the latter may require a deeper, subperitoneal dissection for complete resection. 

• Posterior extension of USL and/or torus uterinus DE across the rectouterine space is a conduit for involvement of structures such as the rectovaginal septum, rectosigmoid colon, posterior compartment nerves, and the ureters.