The document discusses cesarean scar endometriosis, emphasizing its clinical presentation, imaging features, and the importance of MRI for diagnosis. It highlights that this condition is rare, primarily occurs in women of reproductive age, and often presents with abdominal wall lumps following cesarean sections. Treatment usually involves surgical excision, and MRI is crucial for accurate detection and surgical planning.

1. Cesarean scar endometriosis: Clinical presentation
and imaging features with a focus on MRI
Educational Exhibit at the European Congress of Radiology, Vienna, 2012
Authors: A. S. Dumitrescu, T. Herold; DOI: 10.1594/ecr2012/C-0505
Learning objectives
Endometriosis is a common and important clinical problem of women, predominantly
those in the reproductive age group. Endometriosis of the abdominal wall is less frequent
and is mostly associated with cesarean section scars. It can pose diagnostic difficulties
and should be in the differential diagnosis of abdominal wall lumps in females.
The purpose of this exhibit is:
1. to review the clinical presentation and imaging findings of abdominal wall
endometriosis with intramuscular as well as subcutaneous lesions following caesarian
section;
2. to discuss diagnostic strategies with a focus on MRI imaging;
3. to briefly review this condition's incidence, pathology and treatment.

2. Background
Endometriosis was first described by Rokitansky in 1860 and is defined as the presence
of endometrial glandular tissue outside of the uterus.
Clinical presentation
The most common symptoms are dysmenorrhea, dyspareunia, pelvic pain, and infertility,
although only a minority of patients present with all the symptoms and many patients are
Asymptomatic.
Localization
Frequent localizations in the pelvis include the ovaries, uterine ligaments, serosal
surfaces, cul-de-sac, fallopian tubes, rectosigmoid, and urinary bladder (Fig. 1). [3]
Extrapelvic endometriosis are bladder, kidney, bowel, omentum, lymph nodes,
lungs, pleura, extremities, umbilicus, hernial sacs, and the abdominal wall. [4]
Pathology
The foci of endometrial tissue are generally small (Fig. 2 on page 4). Typical
histopathologic features are endometrial glands, endometrial stroma and hemosiderin-
laden macrophages (Fig. 3).
Ectopic endometrial glandular
tissue is influenced by ovarian
hormones and undergoes cyclic
bleeding. Over time, the repeated
hemorrhaging can produce
extensive fibrosis surrounding the
endometrial tissue, which can
result in adhesions to neighboring
structures, e.g. adnexal structures,
peritoneum, bowel, depending on
the localization. [12]

3. Epidemiology
The prevalence of endometriosis is difficult to determine accurately; however, it has been estimated to
affect 5–10% of both symptomatic and asymptomatic women, the frequency being higher in women
with infertility and pelvic pain. [1]
Localization in the abdominal wall (Fig. 4) is comparatively rare and most frequently follows obstetrical
and gynecological surgeries. The actual incidence of abdominal wall endometriosis is unknown but
one series reported that only 6% of these were unrelated to scars. [6] In another series the prevalence
of surgically proven endometriosis in scars was 1.6%. [5]
Therapy
Treatment of endometriomas is most often surgical. Wide
excision of abdominal wall lesions may sometimes require
mesh placement. [21]
Medical treatment involves use of progestogens, oral
contraceptive pills, danazol, and gonadotrophin agonists.
[22] It provides only partial relief in symptoms with no
change in the lesion size and involves numerous side
effects such as amenorrhea, weight gain, hirsutism, and
acne.
Surgically treated patients need to be followed up because
of the chances of recurrence, which require re-excision. In
cases of continual recurrence the possibility of malignancy
needs to be ruled out.

4. Imaging considerations
Endometriosis, in patients with scars, is more common in the abdominal skin and subcutaneous tissue
compared to muscle and fascia. Endometriosis involving only the rectus muscle and sheath is very
rare. [7]
In this unusual localization, clinical as well as initial imaging findings are likely to be misinterpreted by
physicians and radiologists (e.g., as abscesses or malignant tumors). Along with the comparative rarity
of the disease this leads to frequent overlooking of the correct diagnosis. [8,9,10]
Usually, the initial imaging examination for suspected endometriosis is pelvic ultrasound. Magnetic
resonance imaging (MRI) provides superior anatomic detail and better defines abnormalities found
using ultrasonography. The multiplanar capability, high sensitivity for detection of blood products, and
ability to identify sites of disease hidden by dense adhesions have made MRI the noninvasive imaging
technique of choice for more accurate disease detection and staging. [13,14] It has been shown that
MRI has high accuracy in assessing the extension of the disease and assisting surgical treatment
planning. [15]
Most endometriomas have a relatively homogeneous high signal intensity on native T1-weighted images.
On T2-weighted scans, endometriomas often exhibit a phenomenon known as T2-shading, i.e. T2
shortening often associated with a dependent layering on T2-weighted scans reflecting the chronic
accumulation of blood degradation products resulting from repeated hemorrhaging over months and
years. [16,17]
Fat suppression narrows the dynamic signal range, thereby accentuating differences in tissue signal.
Thus, lesion conspicuity is improved. Furthermore, differentiation between hemorrhagic and fat
components is also facilitated. This has been shown to improve the sensitivity of MR imaging in the
detection of small lesions and to increase its specificity, since fat-containing lesions such as dermoids
are eliminated from the differential diagnosis. [18, 19, 20] Contrast-enhanced sequences are useful for
detection of very small endometrial implants associated with inflammatory reaction, as well as
assessing for malignant change. [23]

5. Sample case
A 33 years old female Caucasian patient was referred
to our department for imaging of a painful,
subcutaneous nodular lesion in the left lower
quadrant of the anterior abdominal wall situated at
the site of the cesarean section she had
undergone 2 years before.
Clinical examination at admission revealed a
palpable, hard nodule, sensitive to pressure. The
patient reported having noticed this some 18
months before, the nodule becoming
progressively painful over time.
Initial imaging involved ultrasound examination at
admission as well as contrast-enhanced CT of the
abdomen and pelvis in our department. The CT
scans revealed two adjacent solid nodular lesions,
each some 2 cm in size, one in the left rectus
abdominis muscle (Fig. 5) and another in the
corresponding subcutaneous fat (Fig. 6), along
with signs of a localized inflammatory reaction in
the surrounding fat tissue (Fig. 7).

6. The lesion's solid density and the absence of discernible gas inclusions virtually ruled out an abscess of the
abdominal wall. Rather, the findings were interpreted as pointing primarily towards a chronic inflammatory,
i.e. granulomatous lesion of as yet unclear aetiology, with a soft tissue tumor as a possible differential
diagnosis, possibly associated with a secondary hematoma of the abdominal wall.
Subsequently the patient was referred to MRI for further, more differentiated imaging. Here, renewed
questioning of the patient revealed that pain and swelling associated with the lesion showed a certain
periodicity and peaked at the time of menstruation.

7. The examination confirmed the presence of two neighboring foci in the left rectus abdominis muscle as well as
subcutaneous, with limited inflammation of the surrounding fat tissue. On the T1-weighted scans the lesions
showed slight hyperintensity, both native and fat saturated.

8. The T2-weighted scans showed low lesion signal, a phenomenon known as T2 shading [24]:

9. Furthermore, in all performed scans but especially in the inversion recovery scans (TIRM) the lesion showed small
signal-free dots characteristic of small hemosiderin inclusions.

10. After contrast injection the lesions showed marked enhancement:

11. The MRI appearance of the lesions ruled out an abscess
and confirmed the similarity of the intramuscular and
subcutaneous foci. It further suggested subacute and
chronic micro-hemorrhaging within the lesions, possibly
consistent with hypervascularized tumors such as
melanoma or soft tissue sarcoma but also with ectopic
endometrial tissue islands, i.e. endometriosis.
At this stage correlation with anamnestic data (especially
the fluctuation of symptoms with the menstrual cycle)
proved crucial, ultimately tipping the balance of evidence in
favor of endometriosis. This diagnosis was confirmed by
subsequent biopsy and surgical therapy was succesfully
performed.

12. Conclusion
Endometriosis is a common and important clinical problem of women, predominantly those in the
reproductive age group. The condition is associated with islands of ectopic endometrial tissue.
Localization in the abdominal wall as presented above is rare and mostly associated with a
cesarean section. Such lesions can mimic tumors of the soft tissue or hematomas of other origin.
It is important to keep this rare differential diagnosis in mind and to inquire about any association
of the clinical symptoms with the menstrual cycle, since the presence of cyclic pain in a cesarean
associated incisional mass is almost pathognomonic for the condition.
The noninvasive imaging method of choice is contrast-enhanced MRI. Biopsy is necessary to
confirm the diagnosis. Upon confirmation the lesions must be surgically removed, lest they lead
to significant reduction in quality of life and fertility. Here, MRI imaging is also important in surgical
treatment planning, especially in finding additional lesions that need to be treated.

13. References
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