Introduction
The canal of Nuck is the female equivalent to the male patent processus vaginalis. Embryologically this accompanies the gubernaculum and develops as a result of an evagination of the parietal peritoneum accompanying the round ligament through the inguinal canal at its insertion into the labia majora [
1,
2].
Usually the processus vaginalis obliterates within the first year of life. Failure to do so may result in either an indirect inguinal hernia, or if the processus vaginalis remains completely patent, a communicating hydrocele. Hydrocele of the canal of Nuck remains a rare occurrence.
Herein the authors describe a case of hydrocele of the canal of Nuck in a young patient and the subsequent management.
Case presentation
A previously fit and well 38-year-old female presented to the acute surgical admissions unit with a one day history of a swelling in her right groin. It was associated with constant pain but no other symptoms were described.
On examination there was a small irreducible tender swelling in her right groin, below and lateral to the pubic tubercle. It was soft on palpation. There were no changes to the overlying skin and no skin lesions on her legs to account for a pathological lymph node.
The differential diagnosis included a reactive lymph node versus a femoral hernia. To avoid potentially unnecessary surgical intervention an ultrasound scan was ordered urgently.
This was reported as showing a 1.5 cm×1.8 cm septated fluid collection along the line of the canal of Nuck (Fig. 1). There was no discernible connection with the peritoneal cavity. Radiologically this was in keeping with a hydrocele of the canal of Nuck.
The patient was offered the choice of aspiration, accepting that there may be a risk of recurrence, or surgical excision. She opted for the latter.
Under general anesthesia a small incision was made over the lump and upon further dissection revealed a cystic lesion distal to the superficial inguinal ring (Fig. 2). This was excised and the inguinal canal deliberately not opened so as not to weaken it. The wound was closed in layers using absorbable sutures.
Following surgery, the patient was pain free, eating and drinking and discharged home the following day.
Histopathological examination of the specimen confirmed the suspected diagnosis.
Discussion
The canal of Nuck was first described by Anton Nuck in 1691 [
3]. It is a pouch of peritoneum in the female which extends across the inguinal canal accompanying the round ligament. It is the female equivalent to the processus vaginalis, which in males accompanies the testes in their descent into the scrotum, following the gubernaculum. It usually obliterates within the first year of life.
Failure of obliteration results in a communication of the peritoneal cavity to the labia majora. The failure may result in either an indirect inguinal hernia, or a persistent communication of fluid in the sac resulting in a hydrocele.
There are three main patterns of hydroceles of the canal of Nuck depending on the degree and location of obliteration [
4]. They include:
(1) Obliteration of the processus vaginalis proximal to the deep ring, resulting in no communication with the peritoneal cavity, but instead resulting in an encysted hydrocele anywhere along the tract of descent, from deep ring to labia (as in our case).
(2) Persistent communication with the peritoneal cavity — resulting in a congenital hydrocele and possible inguinal hernia.
(3) A combination of the above, due of the deep ring compressing the hydrocele, resulting in partial communication with the peritoneal cavity and a part enclosed sac. This results in a bi-locular hour glass type of sac.
Hydrocele of the canal of Nuck usually presents in young girls with a painless inguinal swelling. It is a rare occurrence.
Clinically other commoner differentials for lumps in the groin include femoral neuromas, true or false femoral artery aneurysms, saphena varix, inguinal or femoral hernias, lymphadenopathy, as well as soft tissue lesions such as lipoma or abscess. Bartholin’s cyst and abscess should also be considered. There are a wide variety of differentials of groin pain [
5].
Investigations are tailored to answer the clinical question and refine the differential. Ultrasound is a popular first line investigation, due to the superficial nature of groin lesions, lack of radiation, cost and general ease of access. One main disadvantage with sonography is that it is highly operator dependent.
The ultrasound findings in hydrocele of the canal of Nuck are those of a well-defined hypoechoic or anechoic comma shaped mass [
6], which can be cystic in appearance or with septations [
7], as in our patient. MRI has also been used.
Clearly surgical excision of the sac is the only definitive management of hydrocele. However sonographically guided aspiration of the hydrocele is an option, which can offer symptomatic relief and obviate the need for surgery, accepting that as the mesothelial cyst lining remains, so does a risk of recurrence.
In this case, once radiology confirmed no communication with the inguinal canal a local excision was made and the external oblique aponeurosis was not opened, so as to not weaken the inguinal canal. We hypothesize that in this patient the persistent processus vaginalis had partially obliterated and left a small distal sac which may have become infected.
In conclusion, we feel that this pathological entity, rare as it is, is easily understood through a clear understanding of the embryology and hence it is of relevance to all general surgeons and abdominal/pelvic radiologists. Despite its rarity, its presentation is common to a variety of other causes and hence must be considered in the differential diagnosis.
Higher Education Press and Springer-Verlag Berlin Heidelberg
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