Our study series focused on about twenty patients whose age range varies between 26 and 52 years.
Deep pelvic endometriosis was the most prominent form (17 cases) and included a large variety of lesions (small infiltrating implants and nodules,
deep pelvic ligamentous adhesions and solid visceral infiltrating endometriosis).
The most affected locations were the Fallopian tubes,
pelvic Peritoneum,
Pouch of Douglas or Cul-de-Sac, Rectal-vagina septum and the Uterosacral ligaments.
The ovaries represent also a frequent location of endometriosis (12 cases) with lesions wich are often multiple and bilateral.
Some cases of extrapelvicendometriosis were noted such abdominal wall,
perineal region or Caesarian-section scars.
- Review the anatomy of the female pelvis and MRI findings:
MRI features of endometriotic foci with histopathologic correlation:
Since endometriotic lesions consist of functional endometrial tissue,
they respond to the hormonal changes of the menstrual cycle.
Thus they may appear as foci of variable signal intensity on T2- and T1-weighted images,depending on the age of hemorrhage.
Three main aspects can be described:
- Endometriotic implants with subacute bleeding stigma appear in very high signal intensity on T1-weightedimages,
which is usually more conspicuous on images withfat suppression,
and relatively low signal intensity on T2-weighted images.
- Fibrotic and retractiel endomtriosis masses,
present with an irregular spiculated contour and relatively low sig-nal intensity on both T1- and T2-weighted images.
They have a variable enhancement on MRimages obtained after intravenous administration of gadolin-ium chelate.
- Mixed implants appearing as fibrous masses containing punctiform lesions in hypersignal T1 and T2.
Also three main topographic and macroscopic entities have been described : superficial peritoneal endometriosis,
ovarian and deep endometriosis (DE).
In fact the histopathology of endometriosis reflects a continuum of lesions:
1-Superficial peritoneal implants wich are difficult to identify in MRI and are better recognized at laparoscopy.
2-Adhetions that maybe seen,
as low signal intensity bands on T2-weighted images of variable thickness,
extending between pelvic organs.
Sometimes,
they may be too thin to be visualized on MRI; indirect signs, such as distorted anatomy (e.g.
uter-ine retraction),
dilated tubes,
peritoneal inclusion cysts or bowel angulation may suggest the presence of pelvic adhesions
3- Deeply infiltrating endometriosis (DE) defined as subperitoneal invasion at the depth of more than 5 mm and and is well studied in MRI offering a detailed cartography. they appear as thickening,
nodules and tissue masses.
The pooled sensitivity and specificity for DE diagnosis regardless of their locations was 94% and 77%,
respectively,
whatever protocol or device (1.5T or 3.0T) was used.(Meta-analyse de Nisenblat and al.)
Fig. 2: Summary diagram showing the contribution of the couple imaging-laparoscopy in the endometriosis diagnosis
References: Hôpital Charles Nicolle-Tunis
In order to simplify and optimize our lesion mapping of pelvic endometriosis in MRI,
we adopted a subdivision of the pelvis in three compartments in the sagittal plane: Fig. 3
- Anterior compartment
- Medium compartment
- Posterior compartment
Fig. 3: Sagittal MR T2 Weighted image shows deep pelvis compartments : anterior (blue), medium (red) and posterior (green).
1: endometrium / 2:Transitional zone TZ / 3:myometrium.
References: Hôpital Charles Nicolle-Tunis
Anterior compartment:
- Anatomy:
It includes :
- Prevesical space and vesico-uterine pouch (VUP): the dome of the bladder is covered by peritoneum,
creating with the pelvic wall an anterior fold,
the prevesical space,
and with the uterus a posterior fold,
known as vesico-uterine pouch (VUP),
the latter being a common location of deeply infiltrating endometriosis.
- Bladder: T1 sequences and ultrasound are very useful for the study of parietal infiltration of the bladder.
- The round ligaments.
- Terminal portion of the ureters
- Vesico-vaginal Septum
-Pathological aspects:
The estimated prevalence of such locations is low,
at 2% to 8.4%.
- Lesions include usually nodules or masses usually located at the level of the vesico-uterine pouch Fig. 4 ,
forming an obtuse angle with the wall of the bladder.
Fig. 4: Sagittal T2 Weited image (a) Sagittal T1 Weighted and Fat supressed image(b)show nodules of the vesico-uterine pouch with stigmata of sub-acute bleeding (hypersignal T1 W) associated with fibrous thickening of the bladder dome.
References: Hôpital Charles Nicolle-Tunis
Extension through bladder wall involving muscular layer (obliteration of
hypointense signal of wall on T2W),
or protruding into lumen with invasion of the mucosal layer.
Fig. 5
Fig. 5: Infiltrating endometriosis of the vesicouterine pocket.
Coronal T2 MR Weighted image (a) and axial T1 fat-supressed and injected image (b) showing irregular nodular thickening of the ceiling of the bladder associated with an endomatriosic mass projecting into the lumen(blue star).
References: Hôpital Charles Nicolle-Tunis
-The involvement of ureters can cause ureterohydronephrosis (utility of uro-MRI sequences).
-The vesico-vagianl septum is better studied after vaginal opacification; Its involvement appears as a nodule or a mass often of fibrous nature in hyposignal T2,
or of mixed component with a hemorrhagic portion in hypersignal T1.
-The involvement of the round ligament is rare and it shows a fibrous
thickening (generally > 1 cm) compared to the contralateral round
ligament,
with regular or irregular margins and occasionally a nodular
appearance.
Medium compartment:
- Anatomy:
It contains the female genital organs,
including the ovaries, uterine tubes,
uterus,
and vagina.
The broad ligaments are peritoneal folds between the uterus and the lateral walls of the pelvis and are also a part of the rectouterine and vesicouterine folds.
-Pathological aspects:
- Endometriomas:
Endometriotic cysts (or endometriomas) are localized forms of ovarian endometriosis.
The adnexa is the most common location of endometriosis (50%).
they can be solitary ormultiple,
unilateral or,
in almost 42% of women with endometriosis,
bilateral.
As the MRI has a high specificity(>90%),
endometriomas is easily recognizable.
They are characterized by a thick wall with blood products related to cyclic bleeding.
Typically,
present with bright signal intensity on T1-weighted images (T1 shortening is due to the presence of subacute hemorrhage and high protein content) and homogenously low signal intensity on T2-weighted images (T2 shading—caused by accumulation of iron and protein due to repeated bleeding).
As shading in T2 is visible in other bleeding adnexal lesions (the main differential diagnosis of endometriomas),
its specificity remains low (45%) but its sensitivity is high (93%).
In such cases,it may be helpful to look for the T2 dark spot sign which consists of small- usually multiple- foci of very low signalintensity on T2-weighted images within the cyst but not inits wall.
A low signal intensity peripheral rim on T2-weighted images,
caused by hemosiderin-ladden macrophages within the wall of the lesion and fluid-fluid levels,
due to recent bleeding,
may also be seen on T2-weighted images.
Multiple bilateral endometriomas (50%) with coexisting adhesions cause retraction of the ovaries which come to about each other,
the so-called kissing ovaries.
2.
Adénomyosis:
It is defined by the presence of ectopic endometrial glands and stroma within the myometrium.
It is characterized by:
- An enlarged and globular uterus with regular contours.
- Thickening of junctional zone >12 mm.
- The ratio of junctional zone thickness and myometrium thickness > 40 -50%
- Junctional zone with ill-defined area and foci of high T1 and/or T2 signal correspending on dilated endometrial glands +/-hemorrhage.
3.
Follopian tubes:
Almost 30% of women with endometriosis present with fallopian tube involvement at laparoscopy.
Howerver is most often asymptomatic,
discovered during the exploration of infertility or an ectopic pregnancy.
Recurrent hemorrhage within the ectopic glands results in the formation of adhesions,
obstruction and finally tubal dilatation.
MRI can show a hematosalpinx with an enlarged fallopian tube and a high T1 signal that persists on the fat suppression sequences.
Posterior compartment:
It shows the most frequent location of DE +++(90-95%)
- Anatomy:
It includes :
- The rectovaginal septum Fig. 3 : a thin membrane that contains fat and is located between the posterior wall of the vagina and the anterior wall of the rectum.Vaginal distension with gel allows better assessment of the wall,
with a thickness of 3 mm
- The rectum: Digestive wall is in hyposignal T2 and the depth of its infiltration is better appreciated by the endorectal ultrasound.
- Cul-de-sac or pouch of Douglas: It is the lowest portion of the peritoneal cavity,
covering part of the vagina and rectum and located between the two rectouterine folds.
- Retrocervical septum includes: *The torus: it is the posterior area of the isthmus formed by the union of the utero-sacral ligaments. *USL: The uterosacral ligaments are bilateral fibrous bands,
which attach the lateral edges of the cervix to the anterior surface of the sacrum Fig.
8 .
They appear in hyposignal T 1 and T2
- Pathologic aspects:
- The rectocervical region Fig. 3 :
It is commonly affected by deeply infiltrating endometriosis,
and is frenquently associated with vaginal and intestinal lesions.
USL presents the most frequent location and appears when it bears a nodule or shows fibrotic thickening in hyposignal T1 and T2 compared to the contralateral USL,
with regular or irregular margins.
When bilateral,
involvement is usually associated with the torus uterinus which is the seat of stellar and retractile fibrous plaques ; that is termed an arciform abnormality.
Therefore uterine angulation with retroversion can be seen
2.
Pouch of Douglas:
Lesion appears as a fibrous nodule or of mixed composition.
Sometimes it causes a rectal wall infiltration with a partial or a complete obliteration the Douglas cul-de-sac.
It is frequently associated with digestive involvement.
3.digestive involvement:
Bowel endometriotic involvement is usually seen in the rectosigmoid colon
Bowel preparation is advocated as ‘best practice’ that helps to detect deep infiltrating lesions.
Important points have to be mentioned :the portion of the circumference that is affected,
the distance from the inferior margin of the lesion to the anal verge and the degree of stenosis.
In fact the examination must include a determination of which layers of the bowel wall are affected.
The pooled sensitivity and specificity of MRI for rectosigmoid endometriosis were 92% and 96%,
respectively.
The latter presents the most frequent intestinal location and represents 75-90%.
Involvement is suspected in the disappearance of adipose tissue located between the uterus and the rectum / sigmoid colon,
replaced by a tissue mass forming an obtuse angle with the wall of the rectosigmoid.
Multifocality is noted in 10% of cases.
MRI enterography is a good indication in that case.
Fig. 7: 45 year old woman consults for recurrent pelvic pain.
Axial T2 MR Weighed images (a,b,c) and T1 MR Wighted Fat-supressed image (d) showing the recto cervical involvement with a stellar and retractile fibrous plaque of the torus uterinus lateralised on the right (Red arrow)invading the homolateral mesorectal fascia with slight rectal attachement and retraction (blue arrow) and associated with bilateral thickening of th USL(Blue stars).
Infracentimetric focus in hypersignal T1 (d) framing with internal adenomyosis (Red circle)
References: Hôpital Charles Nicolle-Tunis
Fig. 6: Same patient ; Axial T2 MR Weighted image(a) and axial T1 MR Weighted image Fat-supressed (b).
Bilateral ovarian endometrioma with hypersignal T1W Fat-suppressed image contrasting with an hyposignal T2W and reflecting repeated episodes of chronic bleeding :'shading sign '.
References: Hôpital Charles Nicolle-Tunis
Fig. 8: 36 year old women etiological investigation of infertility and pelvic pain.
Axial T2 Weighted images and sagittal T2 MR Weighted image: nodular and fibrous thickening of the uterine torus (Blue arrow).
Discret thichneneing of the left USL (Blue star) responsible for climbing the vaginal fornix (Red arrow)
Left hydrosalpinx (Red star) associated with a blade of effusion at the Douglas cul de sac (curved blue arrow).
References: Hôpital Charles Nicolle-Tunis
Fig. 9: Axial T2 MR Weighted image (a) / Sagittal T2 MR Weighted image
Thickening of the right USL(Red arrow) associated with adhesion next to the rectal wall (Blue arrow).
References: Hôpital Charles Nicolle-Tunis
Endometrial Implants in cutaneous scars:
Frequently ,
foci of endometriosis are simultaneously observed at different sites.
In fact woman may present palpable nodules or masses with cyclic episodes of pain that coincide with menstruation.
They are usually located within scars from Cesarean Section and Laparoscopy .
However endometriosis has been described in several other locations : vagina,
ischioanal fossa,
chest,
skull ,
cutaneous scars...
Usually, these masses appear as fibrous and retractile nodules with spots in hypersignal T1 that are almost pathognomonic of their endomatriotic origin.
Fig. 10: Axial T1 Weighted images before (a) and after fat-suppression (b).
Retractile and fibrotic endometriotic mass (red star) of the anterior abdominal wall at the level of the caesarean section scar with intermingled high signal intensity foci (blue arrow).
References: Hôpital Charles Nicolle-Tunis
Fig. 11: Axial T1 MR Weighted Fat-supressed image.
Perineal nodule with high signal intensity foci of subacute hemorrhage.
Histopathological analysis of biopsy specimen revealed endometriosis
References: Hôpital Charles Nicolle-Tunis
2.
MRI protocol:
Based on a manuscript recently published by the European Society of Urogenital Radiology(ESUR) reporting specific guidelines of patient preparation,
optimal MRI sequences and precising criteria for the evaluation of patients with endometriosis ,
it is recommanded:
- Fasting (at least 4—6 h prior to the examination).
- Adadministration of antiperistaltic agents (intramuscularly orintravenously) for better image quality.
Fig. 12
- Bladder moderately filled.
- An abdominal stapping in order to reduce artefact caused by respiratory movement.
- Vaginal and/or rectal opacification in the presence of symptoms suggestive of rectal or vaginal involvement,
such as constipation,
painful defecation,
dypareunia...
Both 1.5T and 3.0T seem valuable for the evaluation of deep pelvicendometriosis (DPE).
Pelvic phased array coils are recommended in the evaluation of DPE at both 1.5T and 3.0T.
The timimg of MRI examinantion was not proposed but it is preferable to perform the MRI during a painful period at the beginning of the cycle due to the possibility of spontaneous T1W -signal intensity of blood.
Fig. 12: Sagittal 2D T2-weighted MR images performed at 1.5
Tesla showing the benefits of antiperistaltic agents on image
quality. Imaging performed in the same patient before (a) and after
(b) administration of glucagondemonstrating a dramatic improvement in image quality.
References: Bazot M. Ed. Lavoisier-Paris 2016
Sequences:
Basic sequences :
- High resolutionT2-weighted series without fat-supression at least two orthogonal T2W planes.
- The use of thin sections-oblique 2D-T2W imaging improves assessment of uterosacral and parametrial endometriosis
- T1-weighted without fat suppression and fat-suppressed T1-weighted series in transverse plane
Optionnal sequences:
- Intravenous injection of Gadolinium is not systematic,
fat-suppressed T1-
- weighted series
- Diffusion Weighted MRI
- T2W MR sequences without fat-suppression technique are
the best sequences for detecting pelvic endometriosis due to its excellent contrast resolution.
-T1-weighted images with and without fat-suppression are helpful for depicting ovarian endometri-omas and detection of peritoneal lesions.
-Gadolinium-enhanced fat-saturated T1-weighted sequences allow the study of active inflammatory lesions,
detect infiltration of the digestive walls and provide useful information in cases of atypical adnexal lesions (e.g.
cysts with mural nodules).