What Vital Signs Indicate Second Opinion Needed?

Second opinion needed? - what vital signs indicate

1) You are invited to assess a patient in oliguria lower unit. The patient is TURP day two years. The reports of the nurse, was the straw-colored urine, no blood clots in the last layer. Currently, no irrigation once 100 cc of sterile Foley. The patient is alert and reported no discomfort. The bug report indicates that the patient had an episode of hypotension, but vital signs remained unchanged since then. How prerenal oliguria vs. intrarenal better differentiate?

a) the administration of a bolus of 500 cc NSS 0.9% and monitor response
b) applying a surcharge of 50 cc of sterile irrigation Foley
c) receive a kidney ultrasound
d) First of sodium in urine and calculation FENA +