This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Renal involvement in multiple myeloma is characterized by 
Select and explain. 
A. Nitrogen retention, B. Hypertension, C. Edema, D. Haematuria
A: Nitrogen retention
Answer: A: Nitrogen retention 
Explanation: It is due to the accumulation of light chain immunoglobulins, which here can be referred by nitrogen retention.