9th June 2021

A 73-year-old man presents to A&E with severe back and abdominal pain

A 73-year-old man presents to A&E with severe back and abdominal pain, which came on around 12 hours ago, and has been constant and worsening since. He has not passed urine since the day previously, and on examination, his abdomen is grossly distended, with a palpable bladder. A PR examination is done, which demonstrates reduced perianal sensation. 

What investigation should be immediately performed?

Select the SINGLE most appropriate option from the list below. Select ONE option only.