NON-COMMUNICATING HYDROCOELE OF THE CANAL OF NUCK: A RARE FINDING IN A RURAL-DWELLING NIGERIAN WOMAN.

She is a 34-year-old woman, trader and farmer who lives in Ago-are area of Oyo State in western Nigeria. She presented to a surgical outreach with complaints of progressive painless swelling in the left groin. Symptoms were said to have been noticed after a left inguinal repair which she had three months earlier at a secondary health facility for an inguinal hernia. The procedure was said to be largely uneventful. There was no family history suggestive connective tissue disorder and she neither takes alcohol nor smoke cigarette. There is no history of chronic cough, constipation, or abdominal swelling. There were no features suggestive of intestinal obstruction. On general examination, she was not found to be obese, no swelling on the right groin region, the left groin revealed a previous well-healed scar, no positive cough impulse, an irreducible left Inguinolabial swelling, with soft consistency and non-tender, measuring approximately 10 × 4 centimeters. Transillumination was unremarkable and vital signs were within normal limits. A preoperative clinical diagnosis of Left Recurrent Irreducible Inguinolabial hernia was made. (Figure 1 ). Laboratory investigations done were within normal limits. The patient was prepared for surgery as per the routine for groin swellings and consents were obtained. A left groin exploration was done under a sub-Arachnoid block type of anaesthesia. The findings of dilated left canal of Nuck with a cystic swelling containing serous fluids (Figures 2 ) were in keeping with a left non-communicating hydrocele of the canal of Nuck (Type 3). 7 This cystic lesion extended up to the deep ring, (Figure 3 ) and this was excised after high ligation of the sac with Vicryl 2/0 suture and the external oblique aponeurosis, subcutaneous layer of the surgically created groin wound were repaired with non-absorbable suture. The immediate post-operative period was uneventful. The patient was discharged on the second postoperative day. A follow-up visits to the clinic in the second and sixth post operative weeks showed satisfactory wound healing.

Hydrocele of the canal of Nuck is an uncommon condition seen in the female adult population. It is an anatomical extension of the parietal peritoneum that has developed into an analogous entity, and when it fails to obliterate, hydrocele could develop. 1 - 3 . Hydrocele of the canal of Nuck was first described by Anton Nuck in the seventeenth century, and the fluid filled processus vaginalis (Hydrocoele) within the inguinal canal of the female is named after him. 4 . The incidence of a patent processus vaginalis decreases with age. In newborns, 80-94% have patent processus vaginalis. 5 As many as 30% of adults are discovered to have a patent processus vaginalis at autopsy. Why all patient with patent processus vaginalis do not develop into hydrocoele is not well understood. Hydrocoele of the canal of Nuck occurs more in adult females and less in infants and girls. 6 We report a case of an adult female who initially was thought to have a left recurrent irreducible Inguinolabial Hernia status post a previous left groin hernia repair. She had groin exploration with finding of a left cystic swelling within the canal of Nuck. The aim of this report is to draw the attention of practitioners to the occurrence of this rare finding, and to make them raise their index of suspicion and consider this as a possible differential diagnosis in young females who present to them with inguinolabial swelling especially after previous groin surgery.

Hydrocoele of the canal of Nuck though rare, should be considered as one of the differential diagnoses of groin swelling in females. The outcome of management is comparable to other groin surgeries especially in the absence of preoperative ultrasonographic imaging as was the case in our index patient. Practitioners in resource-poor settings should therefore consider an intra-operative diagnosis when such a case is suspected even in the face of near-absence hi-tech diagnostic facilities.

Inguinal hernia is the commonest presentation of Inguinal and Inguino-labial swellings in females; however, differential diagnoses do exist though rare. As we tend to see in males with encysted hydrocele of the spermatic cord, hydrocele of the canal of Nuck is an analogous entity in females. 2 , 3 Huang et al., reported that the incidence of the hydrocoele of the canal of Nuck in female children was 1% (only 6 cases out of 580) female inguinal hernia cases admitted in Chang Gung Children’s Hospital, Taiwan over a 6-year period.8 The Dutch anatomist, Anton Nuck in the seventeenth century (1691), who described the fluidfilled processus vaginalis in the inguinal canal had this named after him.4 During embryogenesis, the processus vaginalis, which is an extension of the parietal peritoneum, accompanies the round ligament up to the labia majora and is usually obliterated within the first year of life. Failure to obliterate, results in the formation of hydrocele of the canal of Nuck. The development of hydrocoele of the canal of Nuck can result following trauma, filariasis and majorly idiopathic however, it is a very rare occurrence following a previous groin surgery. 2 , 9 This was the finding in our patient. Anatomically, there are three types of hydroceles of the canal of Nuck described in the literature. Type 1 is like encysted hydrocele, which is noncommunicating with the peritoneal cavity and is the most common type. Type 2 is freely communicating with the peritoneal cavity and resembles congenital hydrocele in males, which may have associated indirect hernia. Type 3 is the rarest form, accounting for less than 1% of cases, which occurs owing to partial constriction at the deep ring that allows the distal part to descend into the inguinal canal, with the proximal part being retroperitoneal 7 , 10 Type 1 is like encysted hydrocele, which is noncommunicating with the peritoneal cavity and is the most common type. Type 2 is freely communicating with the peritoneal cavity and resembles congenital hydrocele in males, which may have associated indirect hernia. Type 3 is the rarest form, accounting for less than 1% of cases, which occurs owing to partial constriction at the deep ring that allows the distal part to descend into the inguinal canal, with the proximal part being retroperitoneal 7 , 10 Our index patient presented with one of the rarest types – Type 3, and probably the first of its kind because it followed a previous left inguinal herniorrhaphy. Clinically, hydrocele of the canal of Nuck usually presents with swelling in the inguinal area extending up to the labia majora, it is cystic and non-reducible, features which characterizes hydrocele. The cyst may or may not be trans-illuminant. There may be no features of intestinal obstruction except there is a communicating hydrocele with a dilated internal ring or there is a co-exiting hernia component. 2 Sometimes, the cystic swelling may be confused with components of endometriosis if it is communicating with the peritoneal cavity through the fallopian tube and the deep ring, 11 however that was not the case here as there was no such communication. As a superficial lesion, groin ultrasonography can complement the clinical diagnostic acumen of the physician with findings of a well-defined hypoechoic or anechoic, sausage- or comma-shaped cystic mass lying superficial and medial to the pubic bone in the inguinal canal, with posterior acoustic enhancement through translucency. 12 Magnetic Resonance Imaging (MRI) is also helpful with the findings of a well-defined, thin-walled, sausage-shaped cystic lesion, which is hyperintense on T2 - weighted image and hypointense on T1 – weighted image in the inguinal area. 13 However, preoperative radiological investigations such as ultrasonography and MRI could not be performed in this case because of the non-availability in this remote, rural and resource-poor setting. As per our protocol, these investigations are not mandatory for clinically diagnosed cases such as hernia or hydrocele. The definitive management includes open groin exploration surgery, which serves as a final diagnosis and treatment. However, laparoscopic excision of a cyst with associated hernia repair has been documented in the literature with a rewarding outcome. 14 As it is commonly associated with inguinal hernia, dissection must be carried out to the deep inguinal ring 5 , along with high ligation of the neck of the peritoneal pouch and this were the operative details in this patient. 15 Hydrocoele of the canal of Nuck may be misdiagnosed as inguinal hernia because of its rarity, lack of adequate knowledge regarding this entity and paucity of literature on the subject matter, furthermore at least a third of the cases are associated with inguinal hernia. 16 This typifies our experience.