Abdominal Pain: Causes, Differential Diagnosis by Region, and When to Go to the Emergency Room

What Is Abdominal Pain?

Hello, I am Dr. Emre Gecer. Abdominal pain is pain felt in the region between the lower border of the rib cage and the groin. It accounts for about 5-10% of emergency department visits and is one of the most common complaints across all age groups. To understand the causes of abdominal pain, one must first know how the pain arises.

The abdomen contains many organs, including the stomach, intestines, liver, gallbladder, pancreas, spleen, kidneys, bladder and reproductive organs. Disease in any of these organs can cause abdominal pain. However, the source of abdominal pain can sometimes also be extra-abdominal organs (lung, heart); this is an important point that makes diagnosis difficult.

Types of Abdominal Pain: Visceral, Parietal and Referred Pain

According to Harrison's Principles of Internal Medicine, abdominal pain arises by three main mechanisms, and understanding these mechanisms helps identify the source of the pain:

1. Visceral Pain

Visceral pain results from stretching, contraction or ischemia of the internal organs (viscera). Arising from the organs themselves, this pain is dull, throbbing and poorly localized. It tends to be felt in the midline of the abdomen. For example, early appendicitis pain begins as a vague pain around the umbilicus because visceral pain signals from the inflamed appendix are transmitted via the T10 dermatome. Nausea, vomiting and sweating frequently accompany it.

2. Parietal (Somatic) Pain

Parietal pain develops as a result of inflammation, infection or mechanical irritation involving the parietal peritoneum (the lining of the abdominal cavity). Unlike visceral pain, it is sharp, well-localized and severe. It is worsened by movement, coughing and deep breathing. In appendicitis, localization of the pain to the right lower quadrant indicates spread of inflammation to the parietal peritoneum. Abdominal rigidity (guarding) and rebound tenderness are findings of peritonitis.

3. Referred Pain

Referred pain is pain originating from one organ that is felt in a different area innervated by the same spinal segment. Classic examples include gallbladder pain referred to the right shoulder and below the scapula (via the phrenic nerve), pain referred to the left shoulder in splenic rupture (Kehr's sign), and a sense of epigastric pain in myocardial infarction. Referred pain can be misleading in diagnosis and must be considered by experienced clinicians.

Abdominal Pain Causes by Region

The location of abdominal pain is the most important clue for narrowing the list of possible causes. Let us consider the abdomen as four quadrants plus the epigastric region:

Epigastric Region (Upper Middle Abdomen)

• Gastritis and peptic ulcer: Burning, gnawing pain; related to meals (worse with food in gastric ulcer, relieved by food in duodenal ulcer)
• Gastroesophageal reflux (GERD): A burning sensation radiating to the chest
• Acute pancreatitis: Severe, band-like pain radiating to the back; relieved by leaning forward
• Myocardial infarction: Inferior MI in particular may present with epigastric pain; chest pain, shortness of breath and sweating may accompany it
• Aortic aneurysm: Severe pain accompanied by a pulsatile mass

Right Upper Quadrant (Right Hypochondrium)

• Acute cholecystitis: Severe pain in the right upper quadrant after a fatty meal, Murphy's sign positive; fever and nausea accompany it
• Biliary colic: Sudden, colicky pain caused by a gallstone obstructing the bile duct
• Hepatitis: Dull pain due to stretching of the liver capsule; jaundice may accompany it
• Liver abscess: Fever, chills and right upper quadrant tenderness
• Pneumonia/pleurisy: Right lower-lobe pneumonia can mimic right upper quadrant pain

Left Upper Quadrant

• Splenic pathologies: Splenomegaly, splenic infarction, splenic rupture
• Peptic ulcer (gastric ulcer): Pain localized to the left upper quadrant
• Pancreatitis: Band-like pain radiating to the left side
• Left kidney pathologies: Pyelonephritis, kidney stone
• Left lower-lobe pneumonia

Right Lower Quadrant

• Acute appendicitis: The most common surgical emergency! Pain beginning around the umbilicus and localizing to the right lower quadrant, loss of appetite, nausea, low-grade fever. Tenderness at McBurney's point and Rovsing's, psoas and obturator signs
• Mesenteric lymphadenitis: Can mimic appendicitis, especially in children and young adults
• Crohn's disease: Right lower quadrant pain, diarrhea and weight loss with terminal ileum involvement
• Ovarian cyst rupture or torsion: Sudden, severe pain in women
• Ectopic pregnancy: An emergency in women of reproductive age; missed menstrual period and vaginal bleeding may accompany it
• Cecal diverticulitis: Right lower quadrant pain and fever

Left Lower Quadrant

• Sigmoid diverticulitis: Also known as 'left-sided appendicitis'. Left lower quadrant pain, fever, leukocytosis
• Irritable bowel syndrome (IBS): Chronic, crampy pain; relieved by defecation
• Ulcerative colitis: Left lower quadrant pain with bloody-mucous diarrhea
• Left ovarian pathologies: Cyst, torsion, endometriosis
• Left ureteral stone: Severe colicky pain that may radiate to the groin and genital area

Periumbilical Region (Around the Navel)

• Early appendicitis: Vague pain around the umbilicus during the visceral pain phase
• Small bowel obstruction: Colicky pain, vomiting, distension, inability to pass gas or stool
• Mesenteric ischemia: Sudden, severe abdominal pain in the elderly; typically the pain is disproportionate to physical examination findings
• Abdominal aortic aneurysm: A pulsatile mass may be palpable
• Gastroenteritis: Crampy pain, diarrhea and vomiting

Diffuse Abdominal Pain

• Peritonitis: Inflammation of the peritoneum; severe diffuse pain, board-like rigidity of the abdomen
• Intestinal obstruction: Diffuse pain and distension in advanced stages
• Diabetic ketoacidosis: A metabolic emergency; abdominal pain, nausea, vomiting, Kussmaul breathing
• Sickle cell anemia crisis: A hematologic emergency
• Spontaneous bacterial peritonitis: In patients with ascites

Common Emergencies

Acute Appendicitis

One of the most common surgical emergencies. According to Tintinalli's Emergency Medicine, the classic presentation is: pain that starts around the umbilicus and within 6-12 hours localizes to the right lower quadrant, loss of appetite, nausea and low-grade fever. However, approximately 30-40% of patients may have an atypical presentation. The main diagnostic tools are physical examination, leukocytosis and abdominal CT. Delayed diagnosis can result in perforation and peritonitis.

Acute Cholecystitis

Acute inflammation that develops when a gallstone obstructs the cystic duct. The typical presentation is severe, continuous pain in the right upper quadrant hours after a fatty meal, with fever, nausea and vomiting. On ultrasonography, gallbladder wall thickening, pericholecystic fluid and a positive Murphy's sign are diagnostic findings.

Acute Pancreatitis

Characterized by severe, band-like pain that begins suddenly in the epigastric region and radiates to the back. The most common causes are gallstones (40%) and alcohol use (30%). Serum amylase and lipase levels rise to more than three times normal. The clinical spectrum ranges from mild to necrotizing pancreatitis.

Peptic Ulcer Perforation

Perforation of a gastric or duodenal ulcer into the abdominal cavity causes sudden, severe 'knife-like' epigastric pain. The patient develops board-like abdominal rigidity (guarding) and signs of peritonitis. It is a surgical emergency, and according to Sabiston Surgery, early intervention significantly reduces mortality.

Diagnostic Approach to Abdominal Pain

A systematic approach is vitally important in the evaluation of abdominal pain:

History (Anamnesis)

• Onset of pain: Sudden (perforation, rupture) or gradual (inflammation)?
• Character: Colicky (wave-like), continuous, burning, knife-like?
• Location and radiation: In which region, where does it radiate to?
• Duration and course: How long has it lasted, is it worsening?
• Aggravating and relieving factors: Relationship with meals, position, movement?
• Associated symptoms: Fever, vomiting, diarrhea, constipation, jaundice, urinary complaints?
• In women: Last menstrual period, possibility of pregnancy, vaginal bleeding?

Physical Examination

Inspection (visual assessment), auscultation (listening to bowel sounds), palpation (manual examination) and percussion (assessment by tapping) are performed systematically. Assessing for guarding, rebound, rigidity, a palpable mass, and bowel sounds is critical.

Laboratory Tests

• Complete blood count (leukocytosis, anemia)
• CRP and ESR (inflammatory markers)
• Liver function tests, amylase, lipase
• Complete urinalysis (urinary tract infection, kidney stone)
• Beta-hCG (pregnancy test in women of reproductive age)

Imaging Methods

• Upright abdominal X-ray: Free air (perforation), air-fluid levels (obstruction)
• Ultrasonography: First choice for gallbladder, liver, kidney, and gynecological pathologies
• Computed tomography (CT): The gold standard in the evaluation of the acute abdomen; appendicitis, diverticulitis, pancreatitis, vascular pathologies

Red Flags: When to Go to the Emergency Room?

If any of the following are present, go to the emergency department immediately:

• Sudden-onset, severe and unbearable abdominal pain
• Abdominal rigidity, swelling and tenderness
• Blood in vomit or stool
• Abdominal pain accompanied by fever above 39°C
• Inability to pass gas or stool (suspected bowel obstruction)
• Fainting, low blood pressure and signs of shock
• Abdominal pain during pregnancy
• Epigastric pain together with chest pain (possible heart attack)
• Abdominal pain after trauma
• Progressively worsening localized pain lasting more than 6 hours

Conclusion

Abdominal pain is a common complaint with a very wide range of possible causes, requiring careful assessment. The location, character, mode of onset and accompanying symptoms of the pain provide critical clues for reaching the correct diagnosis. Although the great majority of mild and transient abdominal pains are harmless, in the presence of the alarm symptoms I noted above I recommend that you seek emergency medical care without delay.

Wishing you healthy days.
Dr. Emre Gecer

References

• Harrison's Principles of Internal Medicine, 22nd Edition — Chapter: Abdominal Pain
• Sabiston Textbook of Surgery, 21st Edition — Chapter: Acute Abdomen
• Tintinalli's Emergency Medicine, 9th Edition — Chapter: Abdominal Pain
• Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 11th Edition
• Cartwright SL, Knudson MP. Evaluation of Acute Abdominal Pain in Adults. Am Fam Physician. 2008;77(7):971-978