Canal of Nuck cyst (hydrocele)
The canal of Nuck in females corresponds to the processus vaginalis in males. It results from developmental protrusion of the parietal peritoneum through the inguinal ring down into the inguinal canal together with the round ligament of the uterus. Failure of complete obliteration of the canal of Nuck may result in a hernia or hydrocele 1,2.
Canal of Nuck hydrocele is a cystic collection which results from the imbalance between fluid production and absorption by the peritoneum 3. It is a disorder of female infants and childhood, however may present in adults 4.
On clinical examination, a swelling at the inguinal/labia is noted. Being irreducible differentiates it from an inguinal hernia. Also Valsalva maneuver is done to help to differentiate, where a hernia is expected to enlarge while a hydrocele does not 3,4.
Imaging is primarily done using ultrasound. It is simple, noninvasive, and radiation-free. It identifies the contents of the swelling with real time imaging to help differentiate it from herniating bowel or pelvic organs. Canal of Nuck hydrocele appears as anechoic thin walled cyst connected to the inguinal canal 3,4.
Cross sectional imaging: preferably magnetic resonance imaging (MRI) to help evaluate deeper intrapelvic component, and to accurately identify the components of the swelling and signs of complications in cases of inflammation/infection 3. Computed Tomography (CT) is not preferred for purpose of radiation protection, especially when imaging infants.
In the presented case, CT images were unfortunately the only available images. However, it is recommended to do MRI if the diagnosis is still doubtful with US. In this case, the cyst was surgically removed.