Soru

A $47$-year-old man with a history of ulcerative colitis, chronic obstructive pulmonary disease (COPD), and hypothyroidism is evaluated in the intensive care unit. He was admitted $2$ days ago for a severe ulcerative colitis flare characterized by $>10$ bloody bowel movements per day and was started on intravenous methylprednisolone. Over the past $12$ hours, his diarrhea has abruptly ceased, but he has developed severe, diffuse abdominal pain and progressive distension.

Vital signs:
- Temperature: $39.3^\circ\text{C}$ ($102.7^\circ\text{F}$)
- Blood pressure: $84/52 \text{ mm Hg}$
- Heart rate: $136/\text{min}$
- Respiratory rate: $28/\text{min}$

Physical examination reveals a markedly distended abdomen with diffuse rebound tenderness and rigidity. Bowel sounds are absent. Lung auscultation reveals faint, scattered expiratory wheezes bilaterally.

Laboratory studies:
- Leukocytes: $25,500/\text{mm}^3$
- Bicarbonate: $13 \text{ mEq/L}$
- Arterial blood gas (on room air): pH $7.24$, $PaCO_2$ $30 \text{ mm Hg}$, $PaO_2$ $68 \text{ mm Hg}$
- TSH: $0.1 \mu\text{U/mL}$ (Normal: $0.4$-$4.0$)
- Free T4: $0.5 \text{ ng/dL}$ (Normal: $0.9$-$1.7$)
- Lactic acid: $7.2 \text{ mmol/L}$ (Normal: $0.5$-$2.2$)

An upright abdominal radiograph shows a continuous column of gas in the transverse colon measuring $8.5 \text{ cm}$ in diameter with a loss of normal haustral markings. No free air under the diaphragm is visualized.

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