MRI of Endometriosis

Authors: Kristine Burk, MD, Leslie Lee, MD

Date: May 11, 2020

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Superficial Endometriosis Implants (SIE)

  • <5 mm of peritoneal invasion
  • MRI appearance:
    • T1 hyperintense foci on peritoneal/serosal surfaces without T2 correlate
    • SIE disease burden underestimated by MRI

Superficial Endometriosis Implants:

T1 Sagittal

 

Deep Infiltrating Endometriosis (DIE)

  • >5 mm of peritoneal invasion
  • Two morphologic subtypes, often seen in

(1) Active glandular morphology

  • Hemorrhagic glandular +/- cystic tissue predominates
  • MRI appearance:
    • T1 hyperintense/T2 hypointense hemorrhagic glandular tissue +/- T1 hypointense/T2 hyperintense cysts  
Active Glandular Deep Infiltrating Endometriosis:

T2 Axial
T1 Axial

(2) Chronic stromal fibrotic morphology

  • Smooth muscle hypertrophy and fibrosis predominates
  • MRI appearance:
    • T1 hypointense/T2 hypointense, linear or stellate shapes
    • May cause tethering or obliteration of spaces (fibrotic scarring across a peritoneal or retroperitoneal space bringing adjacent organs into fixed contact with one another)

Chronic Stromal Fibrotic Deep Infiltrating Endometriosis:

T2 Aixal

 

Endometriomas

  • Thick walled ovarian or paraovarian cysts containing blood of varying age
  • Most common manifestation of endometriosis
  • MRI appearance:
    • Homogenously T1 hyperintense / Heterogeneously T2 hypointense (T2 shading)
    • Paraovarian location, multilocular appearance, angled margins, fluid-fluid levels, and internal restricted diffusion are all possible
  • Pearls:
    • Compared to hemorrhagic cysts,
      • T2 signal is darker and more heterogenous & T1 signal is brighter and more homogenous
      • “T2 dark spot sign” (T2 hypointense/T1 hyperintense nodule) is most specific finding of endometrioma
    • Kissing Ovaries” = medialized and tethered together by paraovarian DIE
      • Indicates moderate to severe (stage III-IV) endometriosis
    • Consider malignant transformation if: enhancing nodule (most sensitive sign), nodule > 3 cm, lesion growth, loss of T2 shading from fluid produced by tumor cells
Endometrioma with T2 Dark Spot Sign (arrow)

T2 Axial
T1 Axial
Kissing Ovaries:

T2 Axial
T1 Axial

Anterior Compartment Contents

  • Prevesical space
  • Round ligaments
  • Bladder
  • Distal ureters
  • Vesicouterine/cervical/vaginal spaces

 

Middle Compartment Contents

  • Vagina
  • Uterus
  • Fallopian tubes
  • Broad ligaments
  • Ovaries

 

Posterior Compartment Contents

  • Rectouterine space
  • Rectocervical/vaginal spaces
  • Uterosacral ligaments
  • Rectosigmoid colon
  • Presacral space

Anterior Compartment

Bladder

  • Most often involves posterior wall
  • Typically T1 isointense, T2 hypointense, demonstrates increased and delayed enhancement compared to the normal surrounding detrusor muscle
  • Report should describe:
    • Lesion size
    • Location
    • Depth of detrusor muscle invasion
    • Distance form ureterovesicular junctions (UVJs)

Active Glandular DIE of the Bladder:

T2 Sagittal T1 Sagittal

Ureters

  • Distal 3-4 cm most common site of involvement. Left more common than right.
  • Two subtypes:
    • Extrinsic – abuts the ureter resulting in tethering, angular deviation, and compression (75-80% of cases of ureteral involvement)
    • Intrinsic – invades the ureter resulting in luminal narrowing and hydroureteronephrosis (20-25% of cases of ureteral involvement)
  • Report should describe:
    • Lesion size/length of ureter involved
    • Extrinsic versus intrinsic subtype
    • Absence or presence of hydroureteronephrosis
    • Location and distance from UVJ
    • Depth of invasion

Intrinsic Chronic Stromal Fibrotic DIE of the Ureter with Mild Hydroureteronephrosis:

T2 Coronal Ureter T2 Coronal Kidney
 
T2 Axial  

Vesicouterine Space

  • Most common site of anterior compartment involvement
  • Causes pronounced uterine anteversion/anteflexion
  • Report should describe:
    • Lesion size
    • Presence or absence of space obliteration since this impedes laparoscopic evaluation

Chronic Stromal Fibrotic DIE with Obliteration of the Vesicouterine Space:

T2 Axial

 

Middle Compartment

Vagina

  • Most often involves posterior fornix
  • Can appear as nodular thickening of the vaginal wall or as a polypoid mass extending into the lumen
  • Report should describe:
    • Lesion size
    • Location
    • Depth of invasion
    • Vaginal cuff tethering, if present

Active Glandular DIE of the Posterior Vaginal Forinx:

T2 Sagittal T1 Saggital

Fallopian Tubes

  • Hematosalpinx, a dilated fallopian tube filled with hemorrhagic products, may be the only finding of endometriosis
  • Appears as a T2 hypointense/T1 hyperintense tubular structure in the adnexa

Hematosalpinx:

T2 Axial T1 Axial

Uterus

  • Uterine version and flexion can be exaggerated by DIE
  • Torus uterinus (junction of the uterine corpus and the cervix along the posterior serosa/origin of the uterosacral ligaments) is a very common site of involvement
  • Report should describe:
    • Uterine version (angle of the uterus relative to the angle of the vagina)
    • Uterine flexion (angle of the uterine body relative to the angle of the cervix)
    • Lesion size
    • Lesion location
    • Depth of invasion from the serosa into the myometrium
    • Distance from innermost point of invasion to the endometrium

Mixed Active Glandular and Chronic Stromal Fibrotic DIE of the Torus Uterinus:

T2 Sagittal T1 Sagittal

 

Posterior Compartment

Rectouterine/Cervical Space

  • Causes pronounced uterine retroversion/retroflexion
  • Report should describe:
    • Lesion size
    • Presence or absence of space obliteration since this impedes laparoscopic evaluation
    • If rectovaginal disease is present, since this is extraperitoneal and requires a deeper dissection during laparoscopy

Chronic Stromal Fibrotic DIE of the Rectocervical Space:

T2 Sagittal T2 Axial

Uterosacral Ligaments

  • Extends from the torus uterinus towards the sacrum
  • Most common site of posterior compartment involvement 
  • Appears as asymmetric thickening, nodularity, and shortening
  • Report should describe:
    • Whether thickening appears smooth or irregular/nodular
T2 Axial

Rectosigmoid Colon

  • Rectum & sigmoid colon account for 90% of bowel endometriosis
  • Terminal ileum is the most common location of small bowel involvement
  • Can appear as:
    • Wall thickening or a mass
    •  “Mushroom cap” of muscularis propria hypertrophy surrounding a serosal DIE implant
  • Treatment:
    • discoid resection if < 50% circumference involved
    • segmental resection if > 50% of circumference involved, liminal narrowing, or multifocal
  • Report should describe:
    • Lesion location
    • Lesion size
    • Depth of invasion
    • % of circumference involved (> or < 50%)
    • Length of bowel involved
    • Distance between nodules (if multifocal)
    • Relationship to the peritoneal reflection
    • Distance to anal verge

Chronic Stromal Fibrotic DIE of the Rectum

T2 Sagittal T1 Sagittal
Wall Thickening Mushroom Cap Sign
T2 Axial T2 Sagittal

Key sequences:

  • To evaluate for SEI = T1 weighted fat-saturated axial and sagittal
  • To evaluate for DIE = T2 weighted non-fat-saturated axial, sagittal, and coronal
  • To evaluate for endometriomas = Both listed above
  • To evaluate for malignancy or infection: DWI/ADC and contrast enhanced T1 weighted images

Additional considerations:

  • Use of an anti-peristaltic agent is highly recommended to minimize bowel motion artifact
    • 0.5-1 mg glucagon, either IM or injected IV over 1 minute
    • Hyoscyamine sulfate SL can be used in patients with a glucagon contraindication
  • Vaginal distention with 60 cc of ultrasound gel is conditionally recommended
    • typically injected by the patient
  • Rectal distension 60-180 cc of ultrasound gel is conditionally recommended
    • typically injected by a physician or other trained medical personnel
  • Moderate bladder distension is conditionally recommended

Describe the following:

  • Uterus:
    • Version and flexion (always)
    • Adenomyosis or adenomyoma (if present)
  • Adnexa:
    • Location in the pelvis (always)
      • Are the ovaries tethered or displaced?
    • Endometrioma (if present)
    • Hydrosalpinx or hematosalpinx (if present)
  • Superficial endometriosis implants (if present)
    • Compartment and location
  • Deep endometriosis implants (if present)
    • Compartment and location
    • Morphology (active glandular or chronic stromal fibrotic)
    • Size of implant
    • Space obliteration/tethering of adjacent organs (if present)
    • Organ invasion (if present, with individual organ considerations as detailed above)
  • Superficial endometriosis implant – endometriosis implant with < 5 mm of peritoneal invasion
  • Deep infiltrating endometriosis – endometriosis implant with > 5 mm of peritoneal invasion
  • Active glandular DIE – morphology of deep infiltrating endometriosis in which hemorrhagic glandular and cystic tissue predominates
  • Chronic stromal fibrotic DIE – morphology of deep infiltrating endometriosis in which fibrosis and smooth muscle hypertrophy predominates
  • Tethering/obliteration – fibrotic scarring across a peritoneal or retroperitoneal space, bringing adjacent organs into fixed contact with one anothe
  • Endometrioma – thick walled ovarian or paraovarian cyst containing blood of varying age
  • Extrinsic ureteral involvement – DIE that abuts the ureter causing tethering and a resultant angulated course, but no invasion
  • Intrinsic ureteral involvement – DIE that invades the wall of the ureter resulting in luminal narrowing and obstruction/hydroureteronephrosis
  • Uterine version – angle of the uterus relative to the angle of the vagina: anteversion or retroversion
  • Uterine flexion – angle of the uterine body relative to the angle of the cervix: anteflexed or retroflexed
  • Torus uterinus – junction of the uterine corpus and the cervix along the posterior serosa/origin of the uterosacral ligaments
  • Vaginal Fornix – most superior reflection of the vaginal wall/recess of the vaginal lumen, formed by the protrusion of the cervix into the vaginal vault 
  • Hematosalpinx – a Fallopian tube filled with hemorrhagic products, implies the presence of endometriosis implants within the tube, tough these are not always seen

The Signs:

  • T2 Shading – decreased signal seen within an endometrioma on T2 weighted images, may or may not have a layered appearance
  • T2 dark spot sign – T2 dark/T1 bright nodule of inspissated blood products that may be found at the edge of an endometrioma
  • Kissing ovaries – medialization and tethering of the ovaries together, usually in the rectouterine space though can also occur in the vesicouterine space, implies paraovarian chronic stromal fibrotic DIE
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