Four family cases of acute renal failure: question

An 11 year-old boy was referred and admitted to our institution for acute kidney injury (AKI). He had no significant past medical events and no family history of kidney disease. Before his admission, he had experienced vomiting and diarrhea for 4 days, leading to oliguria. Because these symptoms were shared with his parents and grandparents, acute viral gastroenteritis was clinically suspected and symptomatic treatment was started. Despite this symptomatic treatment, vomiting and diarrhea persisted. The child was referred to the pediatric emergency department of our hospital. At the time of admission, his physical examination was normal. He had no fever or edema, and his blood pressure was 142/ 72 mmHg. Urinary tests showed microscopic hematuria and proteinuria <1 g/L. His laboratory results were as follows: serum creatinine 12.9 mg/dl (1,137 μmol/L); sodium (Na) 123 mmol/L; potassium (K) 9.1 mmol/L; bicarbonate (HCO3 ) 13 mmol/L. His electrocardiogram