Question Of The Day #35

This patient presents to the emergency department with generalized abdominal pain, nausea, vomiting, and constipation. The physical exam demonstrates tachycardia and a distended and diffusely tender abdomen. The patient has three prior abdominal surgeries. The upright abdominal X-ray shows multiple dilated loops of small bowel with air-fluid levels. The information provided by the history, physical exam, and diagnostic imaging collectively supports a diagnosis of small bowel obstruction.

Small bowel obstruction (SBO) is a mechanical blockage to forward flow through the intestines. The majority of SBOs are caused by post-operative scar tissue formation (adhesions), but other causes include hernias, intra-abdominal malignancies, foreign bodies, and Crohn’s disease. Symptoms include intermittent colicky abdominal pain, abdominal distension, nausea and vomiting, and constipation. Some patients may be able to pass stool and flatus early in the timeline of an SBO or if the obstruction is partial, rather than complete. Typical exam findings in SBO are a diffusely tender abdomen and high-pitched bowel sounds. Findings of abdominal rigidity, guarding, or fever should raise concern about possible intestinal perforation, peritonitis, or intestinal necrosis. Diagnosis is made clinically in combination with diagnostic imaging, such as abdominal X-rays, CT scanning, or ultrasound. CT scans have better sensitivity and specificity in diagnosing an SBO than Xray. Abdominal ultrasound is more sensitive and specific in diagnosing SBO than CT scan, but this test requires a skilled practitioner to get high-quality results. Treatment of SBO involves IV hydration, surgical consultation for possible operative intervention, pain medications, antiemetics, and electrolyte repletion. Nasogastric tube placement for gastric decompression is helpful in patients who have marked abdominal distension, intractable vomiting, or have risks for aspiration (i.e. altered mental status).

The most common cause of SBO is adhesions (Choice B), not malignancy (Choice A). Diabetic ketoacidosis (Choice C) can present with abdominal pain, nausea, and vomiting. However, DKA becomes more likely when the glucose is elevated over 250mg/dL. The presence of air-fluid levels and dilated small bowel on X-ray imaging also supports SBO over DKA. Delayed gastric emptying (Choice D) is the cause of gastroparesis, a diagnosis that can also present as nausea and vomiting. The other signs, symptoms, and imaging results make SBO a more likely diagnosis than gastroparesis.