Table 1.

Comparison of the Cyst of the canal of Nuck and possible differential diagnosis.

Differential Diagnosis	Symptoms	Physical Examination	Imaging
Cyst of the canal of Nuck	Cysts of the canal of Nuck present as an inguinal or genital, painless or painful swelling with no gastrointestinal symptoms.	On clinical examination, an inguinal or genital swelling is palpable. This mass shows no increase in volume by performing the Valsalva maneuver, and may is manually reducible.	On ultrasound, an anechoic or hypoechoic lesion without changes in the Valsalva maneuver and without vascular flow can be detected. Computed tomography (CT) imaging shows the cyst of the canal of Nuck as a homogeneous fluid-filled lesion along the round ligament. On magnetic resonance imaging (MRI), it shows as a thin-walled lesion, which appears hypointense on T1-weighted and hyperintense on T2-weighted sequences.
Inguinal hernia [34,35,36,37]	Inguinal hernias may be asymptomatic or symptomatic along with swelling, discomfort, or pain in the groin. Activities that increase intra-abdominal pressure may increase these symptoms. Sudden severe pain, nausea and vomiting indicate possible incarceration of organs in the hernia sac.	The gold standard for hernia diagnostics is clinical examination, although diagnosis is more difficult in women. A female inguinal hernia is confirmed if a bulge is palpable with the open hand over the groin during a Valsalva maneuver.	Although it is rarely necessary, imaging may be useful in unclear situations. Ultrasound is a highly sensitive method of identifying hernias. While the herniating fat appears hyperechoic on ultrasound, the bowel may show peristalsis. Valsalva maneuver is an important examination during the sonography, to increase the swelling and show characteristic movement of the herniating tissues. When ultrasound is not sufficient, a dynamic MRI or CT can be considered. On MRI, hernias present as pathological widening of the anteroposterior inguinal canal and/or protrusion of gastro-enteric content within the inguinal canal.
Lymph-adenopathy [38,39]	Localized inguinal lymphadenopathy is typically caused by infection, while malignancy rarely presents itself solely in the inguinal lymph nodes.	Inguinal lymph node size over 1.5 cm should be suspected as pathological. Pain and tenderness on a lymph node is a non-specific finding. Lymphadenopathies resulting from infections are usually free moving. Acute inflammation makes nodes tauter with concomitant tenderness, while chronic inflammation leads to hard nodes. Painless and adamantine nodes, which are fixed to the surrounding tissues are usually caused by metastatic cancer or granulomatous diseases. Rubbery mobile nodes are typical of lymphoma.	On ultrasound, benign lymphadenopathies emerge as ovoid lesions with various borders, inconspicuous hilum, and isoechoic internal echogenicity, while neoplastic disorders present as round lesions with a sharp border, no hilum and a hypoechoic internal echogenicity. Most benign lymphadenopathies present as ovoid lesions with a central fatty hilum on CT and MRI. Round morphology in addition to changes in size, signal intensity, and dynamic gadolinium contrast enhancement are typical for malignant lesions.
Bartholin cysts [40,41,42]	Bartholin cyst can be asymptomatic or symptomatic, associated with painful swelling in not only the genital but also the inguinal region.	During examination small asymptomatic cysts may be observed as small masses, while larger cysts and abscesses are associated with cellulitis, severe pain and swelling. In addition, a Bartholin gland abscess presents with erythema, edema and sometimes ruptured skin.	On ultrasound, a Bartholin cyst is a central hypoechoic to anechoic lesion, surrounded by a stronger reflective cystic wall, which presents as increased echo enhancement on the posterior side. On MRI, it shows as a small cystic mass with a high signal intensity on T2-weighted sequences and also, depending on the mucoid content, on T1-weighted ones.
Endometriosis of the round ligament [43,44]	If endometriosis affects the extra pelvic portion of the round ligament it may present as a painful, palpable groin mass with or without menstrual variation.	On examination, the endometriosis of the round ligament presents as groin mass without fluctuation, which is non-reducible and possibly partially tender. There are no changes through straining, coughing or adjustments in the patient’s position.	On sonographic examination, endometriosis of the round ligament shows as an inhomogeneous hypoechoic lesion with poorly defined boundaries. On MRI scans, endometriosis of the round ligament, which usually presents as a thin hypointense structure, appears thickened, shortened and irregular. While pure fibrous lesions are hypointense on T1- and T2- weighted sequences, hemorrhagic lesions are hyperintense on T1-weighted images.
Ganglion cysts [45,46]	Ganglion cysts of the hip joint are usually asymptomatic but may cause pain through compression of nerves and vessels. They may present as swelling of the groin or genital region, when they become larger.	On clinical examination, ganglion cysts show as tender, non-pulsatile masses, which may limit the range of motion of the hip joint. Deeper cysts are more difficult to palpate and usually a radiological imaging is necessary to detect them.	Ganglion cysts present on ultrasound as a hypoechoic lesion without the ability to identify the exact joint connection. On CT, ganglion cysts show lower attenuation than muscles, but higher ones than fat. After contrast administration, a rim enhancement may be observed. MRI can show round or ovoid cystic masses with low signal intensities on T1- and high ones on T2-weighted sequences. Similar to CT, a rim enhancement can be observed on T1-weighted MRI sequences, after contrast administration.
Lipomata [47]	Lipoma presents as a painless soft-tissue mass. Deeper ones may be larger and present as asymmetrical.	On palpation, lipomata are freely movable doughy subcutaneous masses. Deeper ones, namely intramuscular lipomata move simultaneously with muscle contraction.	On ultrasonography, lipomata present as homogenous hyperechogenic masses. MRI is necessary for any deeper lipomas or lesion bigger than 5 cm. Lipomata show as homogenous lesions, isointense to fat and may contain thin fibrous septae, on MRI. CT is only the second choice, when patients are inept for MRI due to medical reasons.
Leiomyomata [48,49,50]	Leiomyomata may arise in unusual regions such as the vulva. Clinically, these vulvar leiomyomata usually present as painless swellings of the genital region.	On palpation a vulvar leiomyoma shows as a partially mobile mass, which is non-tender in most cases. In certain superficial lesions, a peduncle is sometimes palpable.	On ultrasound leiomyomata present as well-defined, solid, concentric, hypoechoic masses. Due to its bad soft-tissue contrast, CT has a minor role in diagnostics. Vaginal Leiomyomata are isotense to muscles on T1-weighted MRI sequences and enhance homogenously after contrast administration. On T2-weighted sequences, vulvar leiomyomata show a low signal intensity similar to that of smooth muscles.
Varicosity of the round ligament [51,52,53,54,55]	Varicosity of the round ligament is a further rare condition, which commonly occurs as painful or painless inguinal swelling. In most common cases, the occurrence is associated with pregnancy.	On physical examination, varicosity of the round ligament occurs as a soft groin mass. Some authors describe an increase in size of the mass in standing position and on Valsalva maneuver.	The sonographical characteristics of the round ligament varicosities are dilated veins that appear as multiple echo free serpentine tubes, some of which drain into the inferior epigastric artery, with no herniated bowel or lymphadenopathy. Doppler sonography reveals hypervascularity with a venous flow pattern which increases during Valsalva-maneuver. On both MRI and CT, the varicosity of the round ligament appears as a well-defined serpentine structure extending along the inguinal course of the round ligament of the uterus. In the case of thrombosis, the MRI will show a high T1 and a low T2 signal.