A 59-year-old male seeks medical attention complaining of general malaise, evening fever (38,5°C) and suprapubic pain - more intense to the left, which started 3 days ago. He also reports lack of appetite, nausea and a constipated bowel habit, interspersed with occasional episodes of diarrhea. On physical examination: abdominal pain in the left flank and hypogastrium, with voluntary defense, without peritoneal irritation or palpable masses. Laboratory tests showed leukocytosis with left shift and no changes in routine urinalysis. A computed tomography scan of the abdomen and pelvis without contrast was requested (Images 1 to 4).

Question:
Considering the images and the clinical data, which is the most likely diagnosis?