You are seeing a 45-year-old male in A&E who has present with abdominal pain. On questioning, the patient reports that the pain came on suddenly several hours ago and is on the left side of his abdomen radiating to the testicular area. He also reports that the pain lasts minutes and occurs in spasms however between the spasms there is a dull ache in the same area. He is also complaining of pain when passing urine. You do some basic observations and they are as follows: BP 130/80, HR 90, RR 17, O2 saturations 100% on room air and a temperature of 38.3 degrees. What is the most likely diagnosis?