A 58-year-old man presents to the emergency department with a 4-day history of progressive… — USMLE Step 2 CK

A $58$ -year-old man presents to the emergency department with a $4$ -day history of progressively worsening left lower quadrant abdominal pain, subjective fever, and decreased appetite. He has no prior history of similar episodes. His temperature is $38.7^\circ\text{C}$ ( $101.7^\circ\text{F}$ ), blood pressure is $130/80\text{ mmHg}$ , and pulse is $98\text{/min}$ . Physical examination demonstrates marked focal tenderness and voluntary guarding in the left lower quadrant, but no generalized rigidity. Laboratory evaluation reveals a leukocyte count of $16,500\text{/mm}^3$ . Intravenous fluid resuscitation and broad-spectrum antibiotics are initiated.

Assume the patient's clinical course progresses appropriately through standard management. Arrange the following steps in the most appropriate chronological sequence for the optimal diagnosis and long-term management of this patient.

1Perform a computed tomography (CT) scan of the abdomen and pelvis with contrast.
2Perform percutaneous image-guided drainage of a $5.5$ -cm pericolic fluid collection.
3Perform a full colonoscopy to evaluate the colonic mucosa and rule out malignancy.
4Perform an elective sigmoid colectomy with primary anastomosis.

Answer

The correct sequence is to first confirm the diagnosis with a CT scan, followed by percutaneous drainage of the large abscess, then a delayed colonoscopy (

6

8

weeks later) to rule out malignancy, and finally an elective sigmoid colectomy.

The correct sequence for managing a patient presenting with complicated diverticulitis featuring a macro-abscess requires a stepwise approach designed to minimize morbidity. The initial step is a CT scan of the abdomen and pelvis to confirm the diagnosis and identify the size and location of the abscess. Once a large (

>3

cm) abscess is identified, the standard acute management is intravenous antibiotics and percutaneous image-guided drainage. This approach controls the sepsis while avoiding an emergency laparotomy, which would likely necessitate a temporary colostomy (Hartmann procedure). After the acute episode resolves and the colon heals (typically

6

8

weeks), a colonoscopy is mandatory. This is because a perforated colon cancer can clinically and radiologically mimic complicated diverticulitis, and the colon must be evaluated to rule out malignancy. Colonoscopy is contraindicated during the acute phase due to a high risk of iatrogenic perforation. Finally, once cancer is ruled out, an elective sigmoid colectomy is recommended. Patients with a history of complicated diverticulitis are at high risk for recurrent, potentially life-threatening episodes, and interval elective surgery allows for a primary anastomosis without a stoma.

Step-by-Step Solution

Diagnose the acute condition using cross-sectional imaging.

A CT scan of the abdomen and pelvis is performed.

CT scan is highly sensitive and specific for diverticulitis and can identify complications such as an abscess, while avoiding the perforation risks associated with endoscopy in the acute setting.

Manage the acute complication (large abscess) non-operatively.

Percutaneous image-guided drainage is performed.

For diverticular abscesses larger than

3

cm in hemodynamically stable patients, percutaneous drainage combined with intravenous antibiotics is the standard of care, avoiding the morbidity of emergency surgery and a potential colostomy.

Rule out underlying colorectal malignancy once acute inflammation resolves.

A diagnostic colonoscopy is performed after

6

8

weeks.

Colorectal cancer can present with localized microperforation mimicking diverticulitis. Colonoscopy is essential but must be delayed until the colonic wall has healed to minimize the risk of iatrogenic perforation.

Prevent future complicated episodes.

An elective sigmoid colectomy with primary anastomosis is performed.

Patients who have survived an episode of complicated diverticulitis are at high risk for recurrence. Elective resection is recommended and can usually be done with a primary anastomosis, avoiding a stoma. This requires prior colonoscopy to ensure an oncologic resection is not needed instead.

Key Concept

The sequential management of complicated acute diverticulitis with a large abscess involves CT diagnosis, percutaneous drainage, delayed colonoscopy, and subsequent elective resection.

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