British Journal of Radiology (2007) 80, e205-e208
© 2007 British Institute of Radiology
doi: 10.1259/bjr/52038548
Paraovarian adrenal rest with MRI features characteristic of an adrenal adenoma
F Ors, MD
A Lev-Toaff, MD
P O'Kane, MD
N Qazi, MD
and
D Bergin, MB, Bch, BAO FRCR
Thomas Jefferson University Hospital, 111 South 10th Street, Philadelphia, PA, USA
Correspondence: Dr Diane Bergin, Thomas Jefferson University Hospital, 111 South 10th Street, Philadelphia, PA, USA. E-mail: diane.bergin{at}jefferson.edu
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Abstract
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We report MR and sonographic imaging features of an incidentally detected paraovarian adrenal rest in a 44-year-old woman who was being evaluated for menorrhagia. This is the first report of chemical shift imaging identifying the presence of lipid within an adrenal rest as well as rapid washout of contrast. Both of these MR characteristics are typically seen with an adrenal adenoma.
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Case report
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A 44-year-old woman with a history of menorrhagia and an enlarged uterus on clinical examination was referred by her gynaecologist for endovaginal ultrasound. The patient had a history of two ectopic pregnancies and a tubal ligation. Endovaginal ultrasound with a 9 MHz transducer revealed two leiomyomas less than 2 cm in size in the uterus. The right and left ovaries were normal in appearance. There was a well-defined mass with colour flow measuring 2.2 cm by 2.4 cm in the right adnexa between the right ovary and the uterus but separate from both. The patient was referred for MR imaging to further characterize this adnexal mass.
MR imaging of the pelvis was performed with a 1.5 T unit (Signa; GE Medical Systems, Milwaukee, WI) with a dedicated pelvic coil (Medrad, Indianola, PA) using a 24 cm field of view. Sequences performed were coronal T2 single shot fast spin echo (TR/TE effective 2500/180, bandwidth 31, matrix 256x256, 5 mm slice thickness, signal 0.5), axial T2 FSE (TR/TE effective 4000/100, bandwidth 15, matrix 256x256, 7 mm slice thickness, signal 2), sagittal T2 weighted fast spin echo (TR/TE effective 2500/80, bandwidth 31, matrix 256x192, 6 mm slice thickness, signal 1) with fat suppression, axial T1 gradient echo opposed-phase (TR/TE 175/2.4), in-phase (TR/TE 175/5) and fat suppressed three-dimensional gradient echo imaging (TR/TE/flip angle 6/2/15, 4 mm slice thickness) before and after the intravenous administration of contrast (0.1 mmol L–1 per kilogram of body weight of gadopentate dimeglumine, Magnevist; Berlex Laboratories, Wayne, NJ). Delayed post-contrast sagittal two-dimensional spoiled gradient fat-suppressed T1 weighted images (TR/TE 21/2.2/30, 5 mm slice thickness) were also obtained.
MR imaging showed a well-defined 2.2 cm by 1.7 cm mass in the right adnexa between the right ovary and uterus. This was isointense to muscle on T1 weighted images, hyperintense to muscle on T2 weighted images and had a central component, which dropped in signal on opposed-phase gradient echo T1 weighted imaging (Figure 1
). This mass enhanced greater than muscle on initial post-contrast images but demonstrated rapid washout of contrast relative to muscle on delayed imaging (Figure 2). From these findings, MR interpretation was of a solid adnexal mass of indeterminate aetiology.
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Figure 1. AxialT2 FSE (a): Right adnexal mass (arrow) hyperintense to muscle. Axial T1 gradient echo in phase (b) and opposed phase (c) images shows drop in signal of right adnexal mass (arrow) on opposed phase images consistent with intracellular lipid.
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Figure 2. (a) Axial T1 weighted fat-suppressed 3D gradient echo images pre (a) and immediate post gadolinium (b) demonstrate enhancement of the right adnexal mass greater than muscle (arrow) on early post contrast images. On delayed post contrast sagittal 2D gradient echo images (c), the right adnexal mass (arrow) washes out faster than muscle.
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Laparoscopic resection of this right adnexal mass and distal salpingectomy was performed. At surgery, a 2 cm right paraovarian mass was identified, separate from the right ovary but attached to the distal segment of the right fallopian tube. Pathological evaluation revealed an adrenal rest tumour. The patient did not show endocrine abnormalities clinically; therefore, preoperative hormonal screening was not performed. A subsequent postoperative hormonal screen revealed normal serum cortisol, androstenedione, oestrogen and progesterone levels.
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Discussion
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Adrenal rests, or ectopic adrenal tissue, can be found in many different parts of the abdomen or pelvis [1–3]. The adrenal cortex develops from the coelomic mesoderm in the fourth to sixth week of gestation as a cluster of cells between the root of the mesentery and the genital ridge [1]. Ectopic adrenal tissue can migrate with gonadal tissue [2]. Therefore, adrenal rests may be found anywhere along the path of embryogenic migration, including kidney, periadrenal and retroperitoneal fat, in proximity to pelvic organs such as ovary, uterus, broad ligament, spermatic cord and vessels, as well as testes. Adrenal rest tumours in the broad ligament or mesovarium are considered to occur as a result of aberrant embryologic development, as the adrenal cortex is derived from coelomic epithelium immediately adjacent to the developing Mullerian duct [1]. Less common sites include pancreas, liver, transverse colon, retroperitoneum and hernial sacs. The incidence of adrenal rests may be as high as 50% in children, but these rests generally undergo atrophy and disappear within a few years [3]. In male patients with congenital adrenal hyperplasia (CAH), testicular adrenal rests are relatively common [4]. Testicular adrenal rest tumours in CAH can impair both spermatogenesis and endocrine testicular function. The preferred method of treatment is glucocorticoid therapy with partial orchidectomy reserved for adrenal rests resistant to medical therapy. Ovarian rest tumours are exceedingly rare, even in female patients with CAH [4].
Few reports have described the imaging characteristics of adrenal rests [3, 4]. Avila et al [4] described the MR and sonographic findings of testicular adrenal rest tissue in CAH. The MR features of testicular adrenal rest tissue were similar to those of normal adrenal gland: isointense to muscle on T1 weighted and T2 weighted images. On sonography, testicular adrenal rest tissue masses were commonly hypoechoic. Neither the sonographic nor the MR imaging findings were specific. Chemical shift imaging and enhancement characteristics of adrenal rests have not been described [5]. In our patient, the adnexal mass identified had MR imaging characteristics of an adrenal adenoma; isointense to muscle on T1 weighted images with drop in signal on opposed-phase imaging. This mass enhanced rapidly on immediate post-contrast images. Washout of contrast material was faster than muscle. A drop in signal on opposed-phase images indicates the presence of intracellular lipid within this mass. These features, as well as the rapid washout of contrast, are MR characteristics classically associated with an adrenal adenoma [6–8].
Chemical shift imaging is an MR technique used to detect intracellular lipid within tissue. It is commonly used to differentiate adrenal adenoma, which has intracellular lipid from metastases [6, 7]. Chemical shift imaging relies on the different resonance frequency rates of protons in fat and water molecules. Fat protons because of their molecular structure are more shielded than water protons, experience less magnetic field and therefore resonate at a slower frequency. It is this difference in resonance of protons in fat and water that is exploited in chemical shift imaging. The net effect is that there is cancellation of the signal between lipid and water protons when they occur within the same voxel. Therefore, tissues with intracellular lipid and water have signal loss (i.e. appear darker) on opposed-phase imaging. The amount of signal drop-out depends on the amount of lipid in the tissue [8].
In summary, we present the sonographic and MR imaging features of an incidentally found non-functioning paratubal adrenal rest tumour. Although sonographic features are non-specific, the MR features are notable. If an adnexal mass with imaging features similar to an adrenal adenoma is detected on MR, ectopic adrenal rest should be strongly considered. Further studies are needed to determine whether this characteristic may be helpful in the assessment of testicular masses in patients with CAH.
Received for publication February 20, 2006.
Revision received June 15, 2006.
Accepted for publication June 16, 2006.
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References
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- Lack EE. Pathology of the adrenal cortex. New York: Churchill Livingstone, 1990
- Avila NA, Premkumar A, Merke DP. Testicular adrenal rest tissue in congenital adrenal hyperplasia: Comparison of MR imaging and sonographic findings. AJR Am J Roentol 1999;172:1003–6.
- Sasano H, Sato S, Yajima A, Akama J, Nagura H. Adrenal rest tumor of the broad ligament: case report with immunohistochemical study of steroidogenic enzymes. Pathol Int 1997;47:493–6.[Medline]
- Avila NA, Premkumar A, Shawker TH, Jones JV, Louisa Laue RNC, Cutler GB. Testicular adrenal rest tissue in congenital adrenal hyperplasia: findings at gray-scale and color Doppler US. Radiology 1996;198:99–104.[Abstract/Free Full Text]
- Stikkelbroeck NMML, Hermus ARMM, Schouten D, Suliman HM, Jager GJ, Braat DDM, et al. Prevalence of ovarian adrenal rest tumours and polycystic ovaries in females with congenital adrenal hyperplasia: results of ultrasonography and MR imaging. Eur Radiol 2004;14:1802–6.[Medline]
- Dunnick NR, Korobkin M. Imaging of adrenal incidentalomas: current status. AJR Am J Roentol 2002;179:559–8.
- Ichikawa T, Ohtomo K, Uchiyama G, Fujimoto H, Nasu K. Contrast enhanced dynamic MRI of adrenal masses: classification of characteristic enhancement patterns. Clin Radiol 1995;50:295–300.[CrossRef][Medline]
- Mitchell DG, Crovllo M, Matteucci T, Pterson Ro, Miettinen MM. Benign adrenocortical masses:diagnosis with chemical shift MR imaging. Radiology 1992;185:345–51.[Abstract/Free Full Text]
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Abstract
Case report
