An otherwise healthy 48-year-old female presents to the surgical assessment unit with a 24… — USMLE Step 2 CK

An otherwise healthy $48$ -year-old female presents to the surgical assessment unit with a $24$ -hour history of intermittent, crampy abdominal pain. She reports three episodes of bilious vomiting and states she has not passed flatus or stool since the pain began. Her surgical history is significant for a total abdominal hysterectomy performed five years ago for uterine fibroids.

Vital signs include a blood pressure of $122/78$ mmHg, heart rate of $82$ /min, respiratory rate of $14$ /min, and temperature of $37.0^\circ$ C ( $98.6^\circ$ F). Physical examination reveals a moderately distended abdomen with high-pitched, 'tinkling' bowel sounds. The abdomen is softly to moderately tender diffusely, but there is no rigidity, guarding, or rebound tenderness.

Laboratory studies show a leukocyte count of $8,200$ /mm $^3$ and a serum lactate level of $1.1$ mmol/L. A computed tomography (CT) scan of the abdomen and pelvis with intravenous contrast demonstrates dilated loops of small bowel measuring up to $4.2$ cm with multiple air-fluid levels and a discrete transition point in the mid-ileum. The distal small bowel and colon are collapsed. There is no evidence of pneumatosis intestinalis, mesenteric fat stranding, or free intraperitoneal fluid.

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

Nasogastric tube decompression and intravenous fluidsAnswer
B
Immediate exploratory laparotomy
C
Intravenous broad-spectrum antibiotic therapy
D
Colonoscopy with endoscopic decompression
E
Administration of intravenous metoclopramide

Answer

The correct answer is nasogastric tube decompression and intravenous fluids.

The correct answer is nasogastric tube decompression and intravenous fluids. This patient presents with a classic adhesive small bowel obstruction, likely secondary to her prior abdominal hysterectomy. Crucially, she lacks any clinical or radiographic signs of bowel ischemia, strangulation, or perforation. She is hemodynamically stable, afebrile, has no peritonitis on physical examination, and her laboratory markers (leukocyte count, lactate) are within normal limits. Furthermore, her CT scan lacks 'red flags' such as pneumatosis intestinalis, mesenteric fat stranding, or free intraperitoneal fluid. Therefore, the standard of care is a trial of conservative (non-operative) management. This regimen consists of intravenous fluid resuscitation (to correct third-spacing losses), bowel rest (nothing by mouth), and nasogastric tube placement to decompress the stomach and proximal bowel, which reduces distension and the risk of aspiration.

Step-by-Step Solution

Analyze the patient's clinical presentation, history, and imaging findings.

The patient has cardinal signs of a small bowel obstruction (colicky pain, bilious vomiting, obstipation, distension, and prior abdominal surgery) confirmed by a clear transition point on the CT scan.

Accurate diagnosis of the etiology and location of the obstruction is required to guide therapy.

Assess for signs of complications such as bowel strangulation, ischemia, or perforation.

The patient is hemodynamically stable and afebrile. She has a normal leukocyte count, normal lactate, no peritoneal signs on examination, and no concerning CT findings (e.g., pneumatosis intestinalis or free fluid).

The presence or absence of ischemic 'red flags' strictly dictates whether management should be surgical or conservative.

Determine the appropriate initial management pathway based on the absence of complications.

Because this is an uncomplicated partial or complete adhesive small bowel obstruction, the patient should initially be managed conservatively with bowel rest, gastric decompression, and fluid resuscitation.

A significant percentage of adhesive small bowel obstructions will resolve with conservative management alone, avoiding the morbidity of recurrent abdominal surgeries.

Key Concept

Patients presenting with an uncomplicated small bowel obstruction (characterized by the absence of fever, tachycardia, leukocytosis, metabolic acidosis, peritoneal signs, or ischemic changes on imaging) should initially undergo a trial of conservative management consisting of nasogastric tube decompression, intravenous fluids, and bowel rest.

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