Introduction: Giant Hydronephrosis (GH) is characterised by an extensive collection of urine in the kidney due to ureteral obstruction, often exceeding one litre or a kidney weighing more than 1.6% of total body weight. It is commonly seen in under-resourced areas and is usually caused by congenital Ureteropelvic junction (UPJ) obstruction. Symptoms include abdominal distention, flank pain, dyspnoea, constipation, fever, and sepsis. Progressive renal damage can occur due to increased intrapelvic pressure. Case Report: A 17-year-old male from a rural area presented with a massive abdominal distention that had been growing since birth. The patient had limited access to medical care, leading to the condition being neglected for years. Upon examination, the abdomen was enlarged but not tender, and vital signs were normal. Laboratory tests and imaging revealed a massive fluid-filled mass, suspected to be GH. Surgery confirmed a hydronephrotic cavity due to a PUJ obstruction. The patient underwent a left nephroureterectomy and was discharged after an uneventful recovery. Discussion: Congenital anomalies of the genitourinary tract (CAKUT) are a significant part of paediatric surgical cases worldwide. Early diagnosis and treatment are crucial to prevent irreversible renal damage. In under-resourced areas, a lack of awareness and constrained access to medical care can delay diagnosis and treatment. Conclusions: The reported case is notable for the large volume of urine retained in GH and the minimal symptoms, which delayed medical attention. A high index of suspicion is required for CAKUT in young patients. Early surgical management is recommended to preserve renal function.