A rare variant of dysontogenesis of the embryonic diaphragm in children is Morgagni–Larrey hernia and hypoplasia of the muscular layer of the diaphragm. The low frequency of these malformations, which ranges from 1 : 2000 to 1 : 4000 newborns, and the nonspecific clinical manifestations of the disease explain the limited experience of specific specialists in diagnostics, features of surgical treatment, and early postoperative rehabilitation of children with these anomalies.

Aim. To analyze the features of the clinical course, diagnosis, and surgical treatment of a rare diaphragmatic malformation in a child, Morgagni–Larrey hernia combined with hypoplasia of the right diaphragmatic dome, using an original case as an example.

Clinical case. A 13-year-old boy K., who was undergoing inpatient treatment in the surgical department of Zaporizhzhia Regional Children’s Clinical Hospital, was diagnosed with a large congenital hernia of the anterior part of the right diaphragmatic dome based on clinical complaints and results of laboratory and instrumental examinations. Following a comprehensive clinical and laboratory evaluation, the child underwent surgery, including right-sided anterolateral thoracotomy, plastic repair of the right diaphragmatic dome, removal of the congenital Morgagni–Larrey hernia with defect repair using a polypropylene anti-adhesive mesh (Peters Surgical, France), and pleural cavity drainage using the Bülau technique. Intraoperatively, a large congenital hernia of the anterior diaphragm (measuring 17 × 15 × 12 cm) and hypoplasia of the right diaphragmatic dome muscular part were identified. The hernial sac contents were adherent to the greater omentum. Postoperative diagnosis: congenital diaphragmatic defects, including hypoplasia of the right diaphragmatic dome and Morgagni–Larrey hernia. The postoperative period was uneventful with the wound healing by primary intention. Pleural cavity drainage was removed on day 3, and the patient was discharged home on day 10. Follow-up examinations at 6 months and 1 year revealed the patient remained asymptomatic with no complaints or functional impairments.

Conclusions. Morgagni–Larrey diaphragmatic hernia combined with hypoplasia of the right diaphragmatic dome remained asymptomatic in the patient for an extended period. The gradual increase in hernia size led to compression of the right lung and nonspecific clinical manifestations, including coughing attacks. The most effective diagnostic method, beyond chest radiography, was computed tomography. The transthoracic surgical approach was the most appropriate, enabling the elimination of the significant hernial process and plastic repair of the right diaphragmatic dome.