What is the initial workup for a patient with acute abdomen?

From the Guidelines

The initial workup for a patient with acute abdomen should begin with a thorough history and physical examination, followed by laboratory tests and imaging studies, with abdominal CT suggested as the initial imaging modality for adults with suspected acute appendicitis, as recommended by the 2024 clinical practice guideline update by the Infectious Diseases Society of America 1. The workup should include obtaining vital signs, such as temperature, heart rate, blood pressure, respiratory rate, and oxygen saturation, to assess for signs of shock or systemic inflammatory response.

• Laboratory tests should include:
  • Complete blood count to evaluate for leukocytosis
  • Comprehensive metabolic panel to assess liver and kidney function
  • Lipase to rule out pancreatitis
  • Urinalysis to exclude urinary causes
  • Pregnancy test for women of childbearing age
• Blood cultures should be drawn if infection is suspected. Initial imaging typically includes:
• An upright chest X-ray to look for free air under the diaphragm
• An abdominal X-ray to evaluate for obstruction or perforation
• Abdominal ultrasound is useful for biliary pathology
• CT scan with intravenous contrast is the gold standard for most acute abdominal conditions, as it can identify other potential causes of abdominal pain, such as colon cancer, which are more likely to be seen in adults 1. Pain management should be provided with intravenous opioids, such as morphine 2-4 mg or hydromorphone 0.5-1 mg every 2-4 hours as needed, and fluid resuscitation with isotonic crystalloids should be initiated at 1-2 L bolus followed by maintenance rates based on the patient's hemodynamic status. A step-up approach for diagnosis should be used and tailored to the clinical setting, resources, and patient’s age, beginning with clinical and laboratory examination and progressing to imaging examinations 1. In immunocompromised patients, a reliable diagnosis may be reached only by combining signs, symptoms, patient history, and radiological evaluation, and contrast-enhanced CT scan is the most reliable exam to diagnose intrabdominal disease 1.

From the Research

Initial Workup for Acute Abdomen

The initial workup for a patient with acute abdomen involves a combination of clinical history, physical examination, laboratory tests, and imaging studies. The goal is to quickly and efficiently diagnose the underlying cause of the abdominal pain and initiate appropriate treatment.

Clinical Evaluation

• A thorough clinical history is essential to identify the onset, location, and characteristics of the pain, as well as any associated symptoms such as nausea, vomiting, or fever 2, 3.
• Physical examination should include assessment of vital signs, abdominal tenderness, guarding, and rebound tenderness 2, 4.
• Laboratory tests such as complete blood count, C-reactive protein, hepatobiliary markers, electrolytes, creatinine, glucose, urinalysis, lipase, and pregnancy testing may be ordered to help diagnose the underlying cause of the abdominal pain 3.

Imaging Studies

• Imaging studies such as ultrasonography, computed tomography (CT) scan, and magnetic resonance imaging (MRI) may be ordered to help diagnose the underlying cause of the abdominal pain 2, 5, 3.
• Ultrasonography is often the first-line imaging modality for patients with right upper quadrant pain or suspected gallbladder disease 5, 3.
• CT scan with intravenous contrast media is often chosen for generalized abdominal pain, left upper quadrant pain, and lower abdominal pain 3.
• Point-of-care ultrasonography can aid in the prompt diagnosis of several etiologies of acute abdominal pain, including cholelithiasis, urolithiasis, and appendicitis 6, 3.

Diagnostic Approach

• A step-by-step diagnostic approach has been shown to be efficient in evaluating patients with acute abdomen, with advanced diagnostic measures reserved for patients who require them 2.
• The choice of diagnostic tests and imaging studies should be guided by the clinical presentation and suspected underlying cause of the abdominal pain 2, 3.
• In patients with undifferentiated abdominal pain, a positive point-of-care ultrasonography can rule in acute appendicitis, but a negative result cannot rule it out 6.

Special Considerations

• In patients with female reproductive organs, diagnoses such as ectopic pregnancy, pelvic inflammatory disease, and adnexal torsion should be considered 3.
• In pregnant patients, magnetic resonance imaging is preferred over computed tomography when available 3.
• In patients with atypical symptoms or uncertain diagnosis, laparoscopy may be considered as a diagnostic and potentially therapeutic option 4.