On the sixth day following an open sigmoid colectomy for complicated diverticulitis, a 64-… — USMLE Step 2 CK

On the sixth day following an open sigmoid colectomy for complicated diverticulitis, a 64-year-old male patient is assessed for sudden clinical deterioration. The nursing staff reports that over the previous 24 hours, the patient developed progressive abdominal distension alongside multiple episodes of bilious emesis. He has had no return of bowel function since the operation. Initially, he described the abdominal pain as crampy and intermittent, but over the last 4 hours, the pain has transitioned into a severe, unremitting, and continuous ache.

Current vital signs are:
* Temperature: $38.7^\circ\text{C}$ ( $101.7^\circ\text{F}$ )
* Pulse: $122/\text{min}$
* Blood pressure: $98/60\text{ mm Hg}$
* Respirations: $24/\text{min}$

Physical examination reveals a markedly distended, tympanic abdomen. Deep palpation elicits diffuse tenderness, though distinct rebound tenderness and involuntary guarding are absent. Bowel sounds are undetectable. The midline abdominal incision appears well-approximated with no exudate or surrounding erythema.

Pertinent laboratory results are as follows:

Laboratory Parameter	Result
Leukocyte count	$17,500/\text{mm}^3$ (with $12\%$ bands)
Serum bicarbonate	$15\text{ mEq/L}$
Serum creatinine	$1.4\text{ mg/dL}$
Venous lactate	$4.8\text{ mmol/L}$

An urgent abdominal plain film exhibits several distended loops of small bowel with prominent air-fluid levels, without visible colonic gas or free intraperitoneal air.

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

Urgent exploratory laparotomyAnswer
B
Insertion of a nasogastric tube and serial abdominal examinations
C
Intravenous piperacillin-tazobactam and continuation of bowel rest
D
Abdominal and pelvic computed tomography with oral contrast
E
Administration of intravenous neostigmine

Answer

Urgent exploratory laparotomy

The correct intervention is urgent exploratory laparotomy. This patient is presenting with a small bowel obstruction (SBO), which is a common postoperative complication. However, his clinical picture has evolved to demonstrate classic signs of bowel strangulation (ischemia). While uncomplicated SBO typically presents with colicky, intermittent pain and is managed conservatively with nasogastric decompression, the transition to severe, continuous pain is a cardinal sign of compromised intestinal blood flow. Furthermore, systemic inflammatory signs including fever, tachycardia, leukocytosis with a left shift (bandemia), and lactic acidosis strongly point to necrotic bowel. In this clinical scenario, even if classic peritonitis (rigid abdomen, rebound guarding) is not yet fully pronounced, the objective markers of tissue ischemia mandate immediate operative exploration to resect the dying bowel segment.

Step-by-Step Solution

Identify the primary clinical syndrome from the patient's presentation and imaging.

The patient has a mechanical small bowel obstruction (SBO), evidenced by abdominal distension, bilious emesis, obstipation, and plain film showing dilated small bowel loops with air-fluid levels.

Recognizing the mechanical nature of the obstruction is the first step in differentiating it from postoperative ileus, which typically presents with less severe pain and gas present throughout the large and small bowel.

Assess for 'red flag' signs of bowel ischemia, necrosis, or strangulation.

The patient demonstrates multiple red flags: a change in pain character from crampy to continuous/unremitting, fever, tachycardia, marked leukocytosis with a left shift, and lactic acidosis.

Uncomplicated SBO is managed conservatively, but strangulated SBO is a surgical emergency. The presence of metabolic acidosis (high lactate, low bicarbonate) indicates tissue hypoperfusion and active bowel necrosis.

Select the definitive management strategy based on the patient's stability and tissue viability.

Urgent exploratory laparotomy is chosen.

When signs of bowel strangulation are present, immediate surgical exploration is mandatory to resect ischemic bowel segments and re-establish continuity before catastrophic perforation and septic shock occur. The lack of overt rebound tenderness does not override the objective laboratory markers of ischemia.

Key Concept

Patients with a small bowel obstruction who develop continuous pain, fever, leukocytosis, or metabolic acidosis (lactic acidosis) have a strangulated obstruction and require immediate exploratory laparotomy, rather than conservative management.

Estimated Time:1m 30s

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