Diffuse abdominal pain

Background

• Diffuse (generalized) abdominal pain suggests a process affecting multiple quadrants or a non-localizing etiology
• Key EM concern: diffuse pain with peritoneal signs suggests perforation, mesenteric ischemia, or diffuse peritonitis — all surgical emergencies
• Diffuse pain may also represent early appendicitis (before localizing to RLQ), early small bowel obstruction, or extra-abdominal causes
• Consider metabolic and extra-abdominal sources (DKA, uremia, adrenal crisis)

Classification by Abdominal pain location

Side-by-side comparison of quadrants and regions.

Chart of commonly reported referred pain sites.

RUQ pain	Epigastric pain	LUQ pain
Flank pain	Diffuse abdominal pain	Flank pain
RLQ pain	Pelvic pain	LLQ pain

Clinical Features

History

• Onset, character, duration, progression
• Associated symptoms: nausea/vomiting, diarrhea/constipation, fever, last bowel movement/flatus
• Prior abdominal surgeries (adhesive small bowel obstruction)
• Medications: NSAIDs, anticoagulants, immunosuppressants
• Medical history: diabetes (DKA), atrial fibrillation (mesenteric ischemia), vascular disease
• Social history: alcohol use, recent travel

Physical Exam

• Assess for peritoneal signs: rigidity, rebound tenderness, guarding, involuntary guarding
• Abdominal distension (obstruction, ileus, ascites)
• Bowel sounds: absent (ileus, late obstruction), high-pitched/tinkling (early obstruction)
• Hernial orifices (incarcerated hernia)
• Rectal exam: occult blood, rectal mass
• Skin: jaundice, rash (vasculitis), livedo reticularis

Red Flags

• Hemodynamic instability
• Rigid abdomen (peritonitis — surgical emergency)
• Diffuse pain out of proportion to exam (mesenteric ischemia — "pain out of proportion")
• Free air on imaging (perforation)
• Metabolic acidosis with diffuse pain (ischemia, DKA, toxic ingestion)
• Immunocompromised patient with abdominal pain (broad differential, atypical presentations)

Differential Diagnosis

Diffuse Abdominal pain

• Abdominal aortic aneurysm
  • Aortocaval fistula
• Acute gastroenteritis
• Aortoenteric fisulta
• Appendicitis (early)
• Bowel obstruction
  • Large bowel obstruction
    • Ogilvie's syndrome
  • Small bowel obstruction
  • Malignant bowel obstruction
• Bowel perforation
• Diabetic ketoacidosis
• Gastroparesis
• Hernia
• Hypercalcemia
• Inflammatory bowel disease
• Mesenteric ischemia
  • Mesenteric vein thrombosis
• Pancreatitis
• Peritonitis
• Sickle cell crisis
• Spontaneous bacterial peritonitis
• Volvulus

Extra-abdominal Sources of Abdominal pain

• MI
• Aortic Dissection
• PNA
• PE
• Testicular Torsion
• Herpes Zoster
• Muscle spasm
• Spinal pathology
• Strep Pharyngitis (peds)
• Mononucleosis
• DKA
• ETOH Ketoacidosis
• Uremia
• Sickle Cell Crisis
• SLE
• Vasculitis
• Glaucoma
• Hyperthyroidism
• Methanol Poisoning
• Heavy Metal toxicity
• Addison's disease
• Porphyria
  • Acute intermittent porphyria
• Paroxysmal nocturnal hemoglobinuria
• Black widow spider bite

Must Not Miss

• Mesenteric ischemia: elderly, atrial fibrillation, pain out of proportion to exam
• Perforated viscus: free air, peritonitis
• Small bowel obstruction: vomiting, distension, prior surgery
• Ruptured AAA: elderly, hypotensive, pulsatile abdominal mass
• Diabetic ketoacidosis: may present with severe abdominal pain as chief complaint

Evaluation

Laboratory

• CBC, BMP
• LFTs, lipase
• Urinalysis
• Urine pregnancy test (females of reproductive age)
• Lactate: elevated in mesenteric ischemia, sepsis, shock
• ECG: rule out MI in older patients (can present as epigastric/diffuse abdominal pain)
• Blood gas: metabolic acidosis (ischemia, DKA, toxic ingestion)
• Lipase: pancreatitis
• Blood cultures if febrile
• Stool guaiac

Imaging

• CT abdomen pelvis with IV contrast: most useful single test for diffuse abdominal pain (identifies obstruction, perforation, ischemia, abscess, appendicitis)
• Upright CXR or abdominal X-ray: free air under diaphragm (perforation), air-fluid levels (obstruction)
• POCUS: free fluid, AAA, hydronephrosis, gallbladder
• CT angiography: if mesenteric ischemia suspected
• KUB (abdominal X-ray): obstruction pattern, foreign body

Management

• IV access, fluid resuscitation
• Analgesia: appropriate pain control does NOT mask important findings and should not be withheld — opioids may actually improve physical exam by allowing patient to cooperate
• NPO if surgical abdomen suspected
• NG tube for decompression in obstruction with vomiting
• Emergent surgical consultation for: peritonitis, free air, suspected mesenteric ischemia, ruptured AAA, SBO with signs of strangulation
• Broad-spectrum IV antibiotics if perforation, peritonitis, or intra-abdominal sepsis suspected
• Treat metabolic cause (DKA, adrenal crisis) if identified

Disposition

• Admit: peritonitis, bowel obstruction, mesenteric ischemia, perforation, intra-abdominal abscess, pancreatitis requiring IV management, GI bleeding with hemodynamic changes
• Observation: undifferentiated abdominal pain with concerning features but negative initial workup — serial exams
• Discharge: benign etiology identified, pain resolving, tolerating oral intake, reliable follow-up in 24-48 hours
• Return precautions: worsening pain, vomiting, fever, inability to eat/drink, blood in stool

See Also

• Abdominal Pain
• Abdominal Pain (Peds)
• Mesenteric ischemia
• Small bowel obstruction