Intraabdominal infection and acute abdomen

A 57-year-old man presents to the emergency department complaining of severe, cramping abdominal pain that has significantly worsened in the past 7 hours. The pain has been continuous and gradually worsening since its onset over the past 72 hours. The pain is localized to the left lower quadrant and is associated with nausea and vomiting. He felt feverish but did not take his temperature.

He reports a history of hypertension and hypercholesterolemia, but denies any significant gastrointestinal problems prior to this episode, except some slight constipation and occasional dyspepsia after heavy meals.

His family history is negative for gastrointestinal disorders, and he denies any trauma.

What will be your diagnostic approach?
15 /min
108 /min
98 %
146/92 (110) mmHg
Patient is alert with GCS 15. On examination, he is in obvious pain, lying still, has a fever of 38,6 °C, and tachycardia. His abdominal exam shows absent bowel sounds, diffuse tenderness, rigidity on palpation, and pain on percussion.