This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Musculoskeletal  disorders, Subject name: Pediatrics
A child presented with decreased S.Calcium, increased S.Phosphorus and decreased urinary calcium and phosphorus. These are seen in which condition? 
Select and explain. 
A. Renal tubular acidosis, B. Chronic Renal failure, C. Nutritional rickets, D. Coeliac rickets
B: Chronic Renal failure
Answer: B: Chronic Renal failure 
Explanation: Decreased sr. Calcium and increased S . phosphorus and decreased urinary phosphate and calcium excretion occurs in chronic renal failure . At first with the reduction of renal function phosphate balance is initially maintained by increased excretion from normal nephrons . However when gfr falls <25 % blood phosphate level rises and urinary phosphate decreased. Ref : Ghai pediatrics eighth edition pg no 495 - 496