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: Surgery
60 yrs old male with poor stream of urine, post void residual urine is 400m1, bA hydronephrosis and prostate weighing 70 g. His urea is 120 and creat 3.5. Ideal "next immediate" step : 
Select and explain. 
A. Catheterize with Foley catheter, B. bA PC Nephrostomies, C. CT to rule out ca, D. MRI pelvis
A: Catheterize with Foley catheter
Answer: A: Catheterize with Foley catheter 
Explanation: Catheterize with Foley catheter [Ref: Bailey and Love 25/e p1316, 1349; CSDT I 3/e p922/ "Catheterization is mandatory for acute urinary retention. Spontaneous voiding may return, but a catheter should be left indwelling.for 3 days while detruson tone returns."- CSDT I 3/e This is a case of bladder outlet obstruction most likely due to BHP (can also he due to ca). So the immediate next step is to drain the bladder a transurethral Foley catheter. If this fails suprapubic drainage can be done