Soru

An independent $72$-year-old male presents to the acute care clinic with a $6$-hour history of severe, crampy left-sided abdominal pain and two episodes of bright red blood per rectum. Over the preceding three days, he experienced a viral gastroenteritis characterized by frequent watery stools and poor oral intake, which caused him to feel lightheaded upon standing. His past medical history includes heart failure with preserved ejection fraction, hypertension, and hyperlipidemia. His current medications are lisinopril, metoprolol, and atorvastatin.

Vital signs are heart rate $112\text{/min}$, blood pressure $105/65\text{ mm Hg}$, respiratory rate $18\text{/min}$, and oxygen saturation $96\%$ on room air. Physical examination shows dry mucous membranes and decreased skin turgor. The abdomen is soft but moderately tender to palpation in the left lower quadrant. There is no rebound tenderness, rigidity, or guarding. Bowel sounds are diminished.

Laboratory studies show:
Leukocyte count: $10,500\text{/mm}^3$
Hemoglobin: $14.2\text{ g/dL}$
Creatinine: $1.4\text{ mg/dL}$ (baseline $0.9\text{ mg/dL}$)
Lactic acid: $1.6\text{ mmol/L}$ (normal: $0.5-2.2\text{ mmol/L}$)

A CT scan of the abdomen with intravenous contrast reveals edema and thickening of the colonic wall isolated to the splenic flexure and descending colon. There is no evidence of pneumatosis intestinalis or free intraperitoneal air.

Which of the following is the most appropriate next step in management?