What is the initial management for a patient presenting with abdominal pain and vomiting?

Initial Management of Abdominal Pain and Vomiting

Begin with immediate assessment of hemodynamic stability, followed by focused history for surgical red flags (bilious vomiting, prior abdominal surgery, peritoneal signs), physical examination for distension and peritonitis, and laboratory tests including lactate and blood gas analysis to detect bowel ischemia. 1

Immediate Assessment Priorities

Hemodynamic Evaluation

• Check vital signs for tachycardia, hypotension, fever, and tachypnea—these combinations predict serious complications including anastomotic leak, bowel ischemia, or sepsis 1
• Tachycardia alone is a critical warning sign in post-surgical patients and should trigger aggressive investigation 1
• Signs of shock (hypotension, tachycardia, decreased urine output) mandate immediate surgical exploration without delay 1

Critical History Elements

• Surgical history: Prior abdominal surgery has 85% sensitivity and 78% specificity for adhesive small bowel obstruction, which causes 55-75% of small bowel obstructions 1
• Vomiting characteristics: Bilious or feculent vomiting indicates mechanical obstruction and requires immediate nasogastric decompression and NPO status 1, 2
• Timing: Severe abdominal pain out of proportion to physical findings suggests acute mesenteric ischemia until proven otherwise 1
• Associated symptoms: The triad of abdominal pain, constipation, and vomiting (late sign) suggests sigmoid volvulus, particularly in elderly institutionalized patients on psychotropic medications 1

Physical Examination Red Flags

Signs Requiring Urgent Intervention

• Peritoneal signs: Rebound tenderness, guarding, or rigidity indicate possible perforation or bowel necrosis 1
• Abdominal distension with diminished bowel sounds: Classic for bowel obstruction 1
• Empty rectum on digital examination: Supports diagnosis of complete obstruction 1

Critical caveat: Absence of peritonitis does NOT exclude bowel ischemia—lactate and blood gas are essential 1

Mandatory Laboratory Tests

Initial Blood Work

• Complete blood count, electrolytes, renal function (vomiting causes dehydration and renal insufficiency in elderly patients) 1
• Blood gas and lactate levels: Essential for detecting bowel ischemia, though normal lactate does NOT exclude ischemia 1
• C-reactive protein and procalcitonin: Elevated CRP predicts postoperative complications 1
• Liver function tests and serum albumin in appropriate contexts 1

Important limitation: In pregnant post-bariatric surgery patients, white blood count is normal in 68.75% and lactate normal in 90% of internal herniation cases—do not rely on these alone 1

Diagnostic Imaging Approach

When to Image

• Plain abdominal radiograph is the initial test but has limited sensitivity—negative films do NOT exclude mesenteric ischemia or early obstruction 1
• CT abdomen/pelvis with IV contrast: The definitive test for identifying obstruction, transition points, bowel ischemia, and surgical causes 1
• CT helps distinguish mechanical obstruction from functional bloating and prevents unnecessary laparotomy 1

Initial Management Algorithm

Resuscitation Phase

1. IV fluid resuscitation: Aggressive crystalloid administration for dehydration from vomiting 1
2. NPO status: Stop all oral intake immediately if bilious vomiting or obstruction suspected 1, 2
3. Nasogastric tube decompression: Mandatory for bilious vomiting to decompress the stomach 1, 2
4. Antiemetic therapy: Ondansetron 0.15 mg/kg IV (maximum 4 mg) for persistent vomiting 2

Specific Clinical Scenarios

For suspected bowel obstruction (history of surgery, distension, vomiting):

• Obtain CT to identify transition point and assess for ischemia 1
• Serial abdominal exams every 4-6 hours to detect peritonitis 1

For suspected mesenteric ischemia (pain out of proportion to exam, atrial fibrillation, cardiac disease):

• Immediate CT angiography 1
• Surgical consultation without delay 1

For sigmoid volvulus (elderly, institutionalized, chronic constipation, massive distension):

• Plain radiograph may show characteristic findings 1
• CT confirms diagnosis 1
• Endoscopic decompression is first-line if no peritonitis 1

Common Pitfalls to Avoid

• Do not wait for peritoneal signs to develop before investigating—bowel ischemia can exist without peritonitis 1
• Do not dismiss normal lactate as excluding ischemia—clinical suspicion trumps laboratory values 1
• Do not delay imaging in patients with prior bariatric surgery—internal herniation presents with nonspecific symptoms and normal labs 1
• Do not perform "routine" laboratory screens—tailor investigations to clinical suspicion from history and exam 2