Diagnostic ultrasound and intraoperative findings on canal of Nuck hernia with ovary

A 1-month-old girl was brought to the emergency department with a bulge on the left inguinal region, increasing with crying and with no inflammatory signs. Clinical inspection revealed a left inguinal swelling compatible with an irreducible inguinal hernia. An ultrasound was advised for further evaluation.

A left inguinal hernia was observed, apparently indirect and with a 10 mm neck. At the distal end of the hernial sac, a peri centimetric oval structure of poly-follicular aspect could be identified, suggesting the presence of an ovary. Although there was no reduction with instrumental compression, findings that suggested vascular distress were not present, as free fluid or changes in the echogenicity of the surrounding tissues. The right ovary appeared with multiple follicles, in a normal location. Uterus was seen as normal in size, shape, and location.

Ultrasound diagnosis was confirmed by surgery. A Marcy herniorrhaphy was performed and the ovary was spared. Post-operative occurred without complications.

Female inguinal hernias are rare and most common in the first year of life. The main cause is a failure of obliteration of the canal of Nuck [1].

Embryologically, the feminine inguinal canal development involves the gubernaculum, a fibromuscular ligament. Its proximal third inserts in the uterus to prevent the ovaries from penetrating the inguinal canals, and the distal part inserts in the labium major. The vaginal process, a peritoneal recess, herniates through the defect in the anterior abdominal wall previously created by the gubernaculum. This recess obliterates in a craniocaudal direction between the seventh gestation month to the first year of life. A permeable vaginal process in girls is called the canal of Nuck, and coupled with a failure of attachment of the proximal gubernaculum to the uterus, provides the defect necessary for this patient’s condition [1-4].

These hernias often contain peritoneal fat and are treated with elective surgery [4]. However, 15-20% of them contain ovaries, sometimes with other pelvic organs (including ectopic testis, which is a typical presentation of androgen insensitivity syndrome). If so, urgent management is needed [1-5].

Incarceration is frequent and manifests with a nonreducible tender groin lump. Local inflammatory signs may be missing [3,4]. There can be torsion of the ovarian pedicle at any time after incarceration which constitutes a genuine risk of necrosis [3].

Ultrasound with a high-frequency transducer is the preferred modality for initial imaging. When an intra-pelvic structure is identified in the canal of Nuck, as an ovary-like structure, no additional differential is needed [1,3]. A patent canal of Nuck can have a linear, round, or heart shape, located in the subcutaneous fat, anterolateral to pubic bones, and is easier to identify in a comparative axial plane [3]. Ultrasound can depict other conditions involving this area [3,4]. MRI is only considered when ultrasound is inconclusive [4].

The main ischemia sign is an enlarged ovary, with thickened stroma and peripheral follicles (not valuable in neonates). Other characteristics include heterogeneous, hypoechoic stroma compared with adjacent fat and absent or decreased vascularization of the ovary, although normal vascularization cannot exclude torsion. The surrounding tissues may have blurred margins [3].

Ovarian incarceration can lead to torsion at any time, and signs of normal vascularization cannot exclude it, making the prognosis falsely reassuring. This means that ovary incarceration alone can lead to loss of the organ. Due to this potential complication, radiologists should fully understand the canal of Nuck’s ultrasound anatomy as prompt diagnosis is essential [4].