Egg retention is a common reproductive disorder in birds characterized by the failure of an egg to pass through the oviduct within the expected period, leading to various clinical signs and complications. Egg retention is a prevalent yet underrepresented pathological reproductive disorder in waterfowl species, particularly within Anseriformes, with limited scientific literature addressing its pathophysiology and management. This case study describes a Toulouse goose (Anser anser domesticus) experiencing prolonged difficulty in laying an abnormall egg, leading to severe clinical complications. Over 17 days, the bird underwent comprehensive evaluation. The results described refer to the patient's return after an initial procedure of ovocentesis, in which the eggshells were not expelled. Subsequently, the bird returned presenting a serious condition and a second procedure was performed including physical exams, radiography (egg fracture and increased caudoventral volume relative to the coelomic cavity, secondary to an inflammatory process), ultrasonography (liquid content in the oviduct and structures consistent with eggshells), and blood tests showing significant leukocytosis, revealing monocytosis with 13.889 cells/mm3 (150 - 2000 cells/mm3), heterophilia with 50.654 cells/mm3 ( 3000-17.300 cells/mm3) and lymphocytes within the upper limit 17.157 cells/mm3 (7000-17.500 cells/mm3), indicating a serious inflammatory process. Despite medical interventions including fluid therapy, analgesia, antibiotic therapy, ovocentesis, oviduct disobstruction, the condition progressed, culminating in severe inflammation (peritonitis and celomitis) and death. This study highlights the critical importance of timely diagnosis and comprehensive management of egg retention and dystocia in waterfowl, while emphasizing significant diagnostic challenges and therapeutic limitations. The scarcity of detailed literature on egg retention in Anseriformes further impedes effective diagnosis and treatment, reinforcing the need for further studies and focused research. Moreover, the report identifies potential complications, including follicular rupture in post-mortem findings and secondary infections, reinforcing the necessity for specialized veterinary expertise to optimize outcomes in avian reproductive disorders.