A 25-year-old woman with a 4-year history of ileocolonic Crohn disease is evaluated in the… — USMLE Step 2 CK

A $25$ -year-old woman with a $4$ -year history of ileocolonic Crohn disease is evaluated in the hospital on day $4$ of her admission. She originally presented with fever, right lower quadrant abdominal pain, and leukocytosis. A computed tomography scan of the abdomen on admission revealed acute terminal ileitis complicated by a $4.5\text{-cm}$ adjacent fluid collection. She was empirically started on intravenous piperacillin-tazobactam, and a percutaneous drain was successfully placed by interventional radiology on hospital day $1$ .

Today, the patient feels much better. She is tolerating a low-residue diet and her abdominal pain has largely resolved. Her temperature is $37.3^\circ\text{C} (99.1^\circ\text{F})$ , pulse is $82/\text{min}$ , and blood pressure is $118/76\text{ mm Hg}$ . Her leukocyte count has decreased from $16,000/\text{mm}^3$ to $8,200/\text{mm}^3$ . The percutaneous drain has output only $5\text{ mL}$ of serous fluid over the past $24$ hours. Abscess fluid cultures have finalized, growing *Escherichia coli* and *Bacteroides fragilis*. Susceptibility testing demonstrates that both organisms are susceptible to amoxicillin-clavulanate. The *E. coli* isolate is susceptible to ciprofloxacin and ceftriaxone, and the *B. fragilis* isolate is susceptible to metronidazole.

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

Remove the percutaneous drain and transition to oral amoxicillin-clavulanateAnswer
B
Remove the percutaneous drain and continue intravenous piperacillin-tazobactam via a midline catheter
C
Remove the percutaneous drain and transition to oral ciprofloxacin monotherapy
D
Retain the percutaneous drain and initiate intravenous infliximab therapy
E
Refer for exploratory laparotomy and ileocecal resection

Answer

Remove the percutaneous drain and transition to oral amoxicillin-clavulanate.

This patient with Crohn disease developed an intra-abdominal abscess that was successfully managed with percutaneous drainage and empiric intravenous antibiotics. She is now clinically stable, afebrile, and tolerating a diet. Furthermore, her drain output is minimal (

<10\text{ mL/day}

), indicating that the abscess cavity has collapsed and adequate source control has been achieved. Therefore, the correct next step is to remove the drain and transition to a targeted oral antibiotic regimen. The culture results demonstrate *Escherichia coli* and *Bacteroides fragilis*, both of which are susceptible to amoxicillin-clavulanate. This single agent provides the necessary aerobic and anaerobic coverage for safe outpatient completion of therapy.

Step-by-Step Solution

Evaluate the patient's clinical trajectory and drain output.

The patient is afebrile, tolerating a diet, and the drain output is minimal (<10 mL/day).

These findings indicate that the abscess cavity has successfully collapsed and source control has been achieved, permitting drain removal.

Analyze the abscess culture and susceptibility results.

The culture grew both an aerobe (E. coli) and an anaerobe (B. fragilis). Both are susceptible to amoxicillin-clavulanate.

Intra-abdominal abscesses are polymicrobial. It is necessary to transition from empiric broad-spectrum intravenous therapy to targeted therapy based on these results.

Determine the optimal route and regimen for completing therapy.

Transition to oral amoxicillin-clavulanate.

The patient's gastrointestinal tract is functional (tolerating diet), allowing for highly bioavailable oral antibiotics, which minimizes the risks associated with prolonged intravenous access.

Key Concept

Management of complicated Crohn disease abscesses involves percutaneous drainage followed by a transition to targeted oral antibiotics once source control is achieved and the patient is clinically stable.

Estimated Time:1m 30s

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