A 28-year-old man is brought to the emergency department with a 4-day history of progressi… — USMLE Step 2 CK

A $28$ -year-old man is brought to the emergency department with a $4$ -day history of progressively worsening right-sided abdominal pain, nausea, and multiple episodes of bilious vomiting. He reports an inability to pass flatus or stool for the past $24$ hours. The patient was diagnosed with Crohn's disease $6$ years ago, which had been previously well-controlled on adalimumab. However, he discontinued all medications $1$ year ago due to a loss of insurance coverage.

Vital signs show a temperature of $38.6^\circ\text{C}$ ( $101.5^\circ\text{F}$ ), heart rate of $118/\text{min}$ , blood pressure of $105/65\text{ mm Hg}$ , and respiratory rate of $18/\text{min}$ . Physical examination reveals dry mucous membranes. The abdomen is moderately distended with high-pitched, tinkling bowel sounds. There is marked tenderness and a palpable, tender fullness in the right lower quadrant. No diffuse rebound tenderness or abdominal rigidity is appreciated.

Laboratory studies show:
Leukocyte count: $16,500/\text{mm}^3$ (with $85\%$ neutrophils)
Hemoglobin: $11.2\text{ g/dL}$
Platelets: $450,000/\text{mm}^3$
C-reactive protein: $145\text{ mg/L}$ (Normal: $<5\text{ mg/L}$ )
Lactate: $1.4\text{ mmol/L}$ (Normal: $0.5 - 2.2\text{ mmol/L}$ )

Computed tomography (CT) of the abdomen and pelvis with intravenous contrast reveals dilated loops of small bowel measuring up to $4.5\text{ cm}$ in diameter. A distinct transition point is seen in the terminal ileum, which exhibits severe transmural wall thickening and mucosal hyperenhancement. Immediately adjacent to this strictured segment, there is a $5.5\text{ cm}$ well-circumscribed, rim-enhancing fluid collection containing several small locules of gas. There is no evidence of free intraperitoneal air.

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

Percutaneous fluid drainage and intravenous antibioticsAnswer
B
Immediate exploratory laparotomy with ileocecal resection
C
Intravenous corticosteroids and nasogastric tube decompression
D
Broad-spectrum intravenous antibiotics and serial abdominal examinations
E
Colonoscopy with endoscopic balloon dilation of the terminal ileum

Answer

The most appropriate next step is percutaneous fluid drainage and intravenous antibiotics to achieve source control of the abscess while allowing the acute inflammation causing the obstruction to subside.

The correct answer emphasizes a step-up approach. This patient has a mechanical small bowel obstruction (SBO) caused by a Crohn's disease stricture and a concurrent

5.5\text{ cm}

intra-abdominal abscess. The standard initial management for a Crohn's abscess

>3\text{ cm}

is image-guided percutaneous drainage paired with intravenous antibiotics. This effectively achieves source control of the infection. Furthermore, draining the abscess often relieves the extrinsic compression and localized inflammatory edema on the adjacent bowel, thereby resolving the SBO without the need for emergent surgery. If surgery is ultimately required to resect the diseased bowel segment, doing so electively weeks later—after the acute infection and tissue friability have resolved—dramatically lowers the risk of anastomotic leak and the need for a temporary ostomy.

Step-by-Step Solution

Analyze the clinical presentation and laboratory data.

The patient presents with signs of a high-grade small bowel obstruction (obstipation, bilious vomiting, distension) combined with systemic inflammatory response syndrome (tachycardia, fever, leukocytosis).

Establishing the physiologic severity and primary syndrome narrows down the surgical vs. medical algorithms.

Interpret the radiological findings in the context of the patient's underlying disease.

The CT scan shows a small bowel obstruction transitioning at the terminal ileum, complicated by a 5.5 cm rim-enhancing fluid collection with gas locules (an intra-abdominal abscess).

In Crohn's disease, differentiating between an inflammatory/fibrotic stricture and penetrating disease (abscess/fistula) fundamentally alters the management pathway.

Determine the sequence of intervention for a Crohn's disease macro-abscess causing obstruction.

Select CT-guided percutaneous drainage and broad-spectrum IV antibiotics.

For Crohn's abscesses greater than 3 cm, percutaneous drainage is the standard first step. It controls the infection, decreases surrounding tissue edema (often relieving the obstruction), and converts a high-risk emergent operation into a safer elective procedure, reducing the risk of requiring a stoma.

Key Concept

In patients with Crohn's disease presenting with small bowel obstruction secondary to an intra-abdominal abscess, the initial standard of care is percutaneous drainage and intravenous antibiotics, rather than immediate surgery or immunosuppression.

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