This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney & Ureturs, Subject name: Surgery
A 60-year-old male with poor stream of urine, post void residual urine is 400 mL, bilateral hydronephrosis and prostate weighing 70 g. His urea is 120 and creatinine 3.5. Ideal "next immediate" step: 
Select and explain. 
A. Catheterize with Foley catheter, B. Bilateral PC nephrostomies, C. CT to rule out carcinoma, D. MRI pelvis
A: Catheterize with Foley catheter
Answer: A: Catheterize with Foley catheter 
Explanation: Ans. (a) Catheterize with Foley catheterCauses of bilateral hydronephrosis:* Posterior urethral valves* Urethral atresia* BPH/ cancer prostate* Bladder neck stricture* Urethral stricture* PhimosisThe immediate next step in those cases is to put a Foley's catheter if possible.