Cyst of the canal of Nuck: an atypical course with cyclic changing of size
- Helen Bumann and
- Stefano Corrà
- Center Da Sanadad Savognin, Savognin, Switzerland
- Correspondence to Dr Helen Bumann; hmbumann@gmail.com
Abstract
As the canal of Nuck normally obliterates before birth, a patent canal is a rare anatomic variant in adult women analogue to the patent processus vaginalis in men. In a patent canal of Nuck, pathologies such as hernias and cyst can build within time. Such cysts themselves are so uncommon that they are mostly described in case reports. Normally, cysts of the canal of Nuck present as a consistent, inguinal swelling with or without pain. Interestingly, in our case, the painful swelling was cyclic changing from the size of a plum to being clinically undetectable within the course of a day. To the best of our knowledge, this is the first description of such an unusual course. The cyst was removed operatively via an open approach. The spasms declined shortly after the operation. At 1 year postoperatively, the patient was still asymptomatic.
Background
The canal of Nuck is an anatomic variant only present in some adult women. Through the descent of the peritoneum through the inguinal canal, the canal of Nuck is formed, representing the equivalent of the processus vaginalis in men.1 The canal of Nuck accompanies the round ligament of the uterus, which origins at the uterine horns close to the tubouterine junction.1 Its distal insertion is often said to end in the labia majora.2 However, a cadaver study from Bellier et al could show that the round ligament of the uterus has a variable distal insertion in adult women.3 According to their study, the round ligament of the uterus most commonly ends at the external inguinal ring. Alternatively, the ligament inserts at the internal inguinal ring or the downstream pubis bone, but no insertion at the labia majora could be shown.3
As the canal of Nuck normally obliterates before birth, a patent processus vaginalis is fairly rare.1 If the canal stays patent, pathologies like hernias, herniation of uterus and ovarian, endometriosis or cysts can build.4 Due to the rarity of the patent canal itself, all pathologies are very uncommon and mostly described as case reports or case series in literature.5
Depending on the location and configuration of the cyst, three subtypes are classified6:
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Type 1: no communication between hydrocele/cyst and peritoneal cavity. It mostly appears as an encysted mass without hernia defect in children.7
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Type 2: the hydrocele communicates with the peritoneal cavity, thus mostly resulting in an indirect hernia.7
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Type 3: combined type has an encysted part that does not communicate with the peritoneal cavity and another that does. Its appearance resembles an hourglass and commonly causes a hernia. It is the rarest of the three subtypes.7
Case presentation
A female patient in her 40s presented at our clinic with lower left abdominal pain and inconsistent swelling of the groin region for about 4–6 months prior to her first consultation. The pain was spasmodic with peaks multiple times per week. There were no menstruation-dependent patterns. The patient described pain during her periods, but those were unchanged to previous decades and clearly distinguishable from the spasmodic pain she had recently experienced. The swelling was, however, frequently varying in size, being visible and palpable at some times, while being neither palpable nor visible at others. Quite often, the size of the swelling would change from the size of a plum to clinically undetectable within the course of a day. Even though the size of the mass was very variable from day to day, the size was overall slowly increasing. The patient had undergone appendectomy 30 years ago and diagnostic laparoscopy for fertility clarification 25 years ago. A hysterosalpingography at that time showed tubal infertility. Current gynaecological examination showed cystic ovaries on both sides. Other than that, there are no medical conditions. There were neither cases of cysts of the canal of Nuck nor unclear abdominal pain in her close family.
Investigations
On her first consultation with her general practitioner, there was a palpable, irreducible mass in the left inguinal area. Same-day sonography revealed a hypointense tumour of 2 × 4 cm(figure 1). Due to the unusual location of the mass, an MRI was ordered and performed within a week. The MRI showed a multilobulated cystic formation of 3.6 × 3.6 × 4 cm reaching from the inner inguinal canal towards the insertion of the round ligament of the uterus, which itself was noticeably distended. The right side did not show any abnormalities.
Sonography of the left inguinal region showing a lobulated, hypointense structure with a diameter of 3.73 cm.
Differential diagnosis
Femoral/inguinal hernia: Without proper imaging, the swelling could be mistaken as a hernia.5 However, if proper imaging is done, the differentiation between hernia and cyst of the canal of Nuck is apparent.
Endometriosis/irritable bowel syndrome: Due to the spasmic character of our patient’s pain as well as the cyclic presence of the swelling, the disease could be mistaken for a variety of other causes of spasmic, irregular lower abdominal pain such as endometriosis or irritable bowel syndrome. As this kind of clinical presentation of the cyst of Nuck has not yet been described in literature, misdiagnosis could be more frequent than with classical presentation of the disease. To avoid this kind of misdiagnosis, it is crucial to listen to the patient’s history carefully and to perform imaging only in symptomatic periods.
Treatment
As the patient was symptomatic with painful cramps with a pain score 7/10, surgery was scheduled. The extirpation of the cyst was performed via an open approach to the inguinal canal. The cyst, which was lying partially within the inguinal canal, was dissected from the round ligament of the uterus and the internal oblique muscle. Subsequently, the mass could be removed in toto.(figure 2) After excision of the cyst, the posterior wall of the inguinal canal was reconstructed. Since the fascia was of good quality, an additional net mesh implantation could be waived. Histology confirmed a cyst of the canal of Nuck.
The excised cyst.
Outcome and follow-up
The postoperative course was without any complications. Initially, the patient needed painkillers, which could be waived within 2 weeks. The spasmodic pain described above was immediately gone after the excision of the cyst and did not reappear during 18 months of follow-up.
Discussion
The cyst of the canal of Nuck is a rare condition mainly described by case reports.1 2 4 Comparing the cases, there is variety in the presentation, such as size, level of pain, age of the patients or duration of symptoms.1–8 However, a consistency in swelling within the cases was described in all cases.1–8 To the best of our knowledge, a cyclic changing of size has not yet been described, certainly not such a fast change as within the course of a day. Due to the rarity of the disease, there are no clear management guidelines for cyst of the canal of Nuck. There is consensus that operative excision is the best treatment option in symptomatic patients.1 3 8 In literature, there are different surgical approaches described, including both open and laparoscopic surgeries with no obvious benefit for either of them.7 In a case report and review in 2020, Prodromidou et al analysed 16 cases. Surgical excision was performed in all cases, 13 cases were performed with an open surgical approach and 3 cases with laparoscopic approach. As the cyst of the canal of Nuck can be associated with inguinal hernia and the extent of the disease is different from case to case, they suggest to choose the surgical approach depending on those parameters.8 Thus, we agree that the best surgical solution such as laparoscopic versus open approach, mesh placement versus direct closure of the fascia and additional hernia repair or reconstruction of the inguinal canal if needed should be tailored according to the preoperative imaging, concomitant pathologies and extent of the cyst. In our case, there were no concomitant pathologies, but since the mass was extensive, an open approach was performed.
Learning points
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As a rare condition, a cyst of a patent canal of Nuck should be considered as a differential diagnosis in inguinal masses.
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As our case could demonstrate eminently, clinical presentation can also be atypical with frequent change of size and symptoms. Thus, we recommend to also list the disease as a rare differential diagnosis to lower abdominal pain.
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In case of clinical suspicion, a cyst of Nuck must be ruled out in a patient describing inguinal swelling with or without inguinal/lower abdominal pain.
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If confirmed, surgical removal is recommended. The surgical technique may vary between open, minimally invasive or laparoscopic approaches depending on the specific position of the cyst.
Ethics statements
Patient consent for publication
Footnotes
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Contributors The article was written by HB and edited/supervised by SC.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
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Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.
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