Thanks for writing in.
I suppose your brother in law must be suffering from acute renal failure
as a complication to his medical illnesses. This condition of 300 ml urine in a day is known as oliguria. Dialysis has been recommended because of raised blood urea and serum creatinine
. As you have not mentioned about the drugs and any possible nephrotoxicity
arising from it, its difficult to tell the exact problem.
You may seek guidance by discussing the case with a nephrologist
and taking along with yourself complete treatment details and reports.
Hope this helps.