Surgical consultation is requested for a 58-year-old male inpatient whose clinical status … — USMLE Step 2 CK

Surgical consultation is requested for a 58-year-old male inpatient whose clinical status acutely deteriorated on the seventh day following an elective open right hemicolectomy for a large cecal adenoma. His recovery was initially unremarkable; he tolerated a liquid diet and passed flatus on the fourth day after surgery.

Over the past 8 hours, the patient developed sudden-onset, severe, and continuous abdominal pain. He reports the pain is agonizing and poorly relieved by intravenous morphine. He has had two episodes of non-bilious emesis.

Vital signs:

Parameter	Value
Temperature	$38.3^\circ\text{C}$ ( $100.9^\circ\text{F}$ )
Blood Pressure	$102/64\text{ mm Hg}$
Heart Rate	$118/\text{min}$
Respiratory Rate	$24/\text{min}$
SpO $_2$	$96\%$ on room air

Physical examination reveals a moderately distended abdomen. The midline surgical incision is clean and intact without erythema or fluctuance. Palpation elicits mild diffuse tenderness but no rebound, guarding, or rigidity. Bowel sounds are hypoactive.

Laboratory evaluation:

Test	Result	Reference Range
Leukocytes	$18,200/\text{mm}^3$ ( $16\%$ bands)	$4,000-11,000/\text{mm}^3$
Hemoglobin	$13.8\text{ g/dL}$	$13.5-17.5\text{ g/dL}$
Serum Sodium	$138\text{ mEq/L}$	$136-145\text{ mEq/L}$
Serum Potassium	$4.2\text{ mEq/L}$	$3.5-5.0\text{ mEq/L}$
Serum Bicarbonate	$14\text{ mEq/L}$	$22-28\text{ mEq/L}$
Serum Lactate	$5.2\text{ mmol/L}$	$0.5-2.2\text{ mmol/L}$

Arterial blood gas analysis on room air shows a pH of $7.27$ , PaCO $_2$ of $32\text{ mm Hg}$ , and PaO $_2$ of $88\text{ mm Hg}$ .

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

A
Placement of a nasogastric tube and administration of intravenous fluids
B
Collection of blood cultures followed by empiric broad-spectrum antibiotics
Immediate exploratory laparotomyAnswer
D
Computed tomography of the abdomen and pelvis with intravenous contrast
E
Intravenous infusion of sodium bicarbonate

Answer

Immediate exploratory laparotomy

Immediate exploratory laparotomy is correct because this patient is exhibiting the classic triad of acute bowel ischemia/strangulation: severe continuous abdominal pain out of proportion to physical exam findings, systemic inflammatory response (fever, extreme leukocytosis with a left shift), and severe metabolic derangement (high anion gap metabolic acidosis with hyperlactatemia). In the post-operative setting, this is most commonly caused by an internal hernia or a closed-loop small bowel obstruction. When clinical and laboratory signs strongly point to bowel necrosis, the definitive and life-saving step is immediate surgical exploration. Delaying for imaging or attempting medical management drastically increases mortality.

Step-by-Step Solution

Analyze the patient's timeline and clinical symptoms.

The patient developed sudden, severe, continuous abdominal pain on postoperative day 7 that is 'out of proportion' to the physical exam findings (lack of overt peritonitis).

Differentiating severe acute catastrophic events from expected postoperative pain or simple ileus is critical.

Evaluate the vital signs and laboratory data.

Findings show borderline hypotension, tachycardia, fever, marked leukocytosis with bandemia, and a severe high anion gap metabolic acidosis (pH 7.27, bicarbonate 14 mEq/L) driven by hyperlactatemia (lactate 5.2 mmol/L).

Identifies the presence of systemic toxicity and critical tissue hypoperfusion.

Synthesize the clinical and laboratory picture to form a diagnosis.

The combination of severe continuous pain out of proportion to exam findings and lactic acidosis strongly indicates acute bowel ischemia, likely from a strangulated internal hernia or closed-loop obstruction.

These are the hallmark signs of bowel necrosis, distinguishing it from an uncomplicated post-operative ileus or simple obstruction.

Determine the most appropriate definitive management.

The patient must undergo an immediate exploratory laparotomy.

Ischemic bowel is a surgical emergency; delaying for advanced imaging or attempting conservative medical management leads to rapid clinical deterioration and high mortality.

Key Concept

Diagnosis and management of postoperative bowel ischemia and strangulating obstruction.

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