Abdominal pain is a common clinical symptom that is often caused by organic or functional diseases of abdominal organs but may also result from conditions outside the abdominal cavity or systemic diseases. Based on the type of nerves involved in pain perception, abdominal pain can be classified into visceral pain, somatic pain, and referred pain.
Visceral pain is primarily transmitted by the sympathetic and parasympathetic nerves. It is sensitive to mechanical stretching, ischemia, inflammation, and chemical stimuli but not to cutting, pricking, or electrical burns, and its location is often imprecise.
Somatic pain is transmitted by the somatic nerves of the parietal peritoneum and diaphragm. It is sensitive to mechanical, inflammatory, and chemical stimuli, and its location is usually clear and precise.
Referred pain, also known as radiating pain, occurs when diseases of abdominal organs cause pain or hyperalgesia in distant superficial body regions. The mechanism may involve convergence of afferent fibers from diseased visceral organs and somatic tissues at the same spinal cord segment, leading to pain perception at the same spinal nerve level.
Clinically, abdominal pain can be categorized into acute abdominal pain and chronic abdominal pain based on the onset and progression. Acute abdominal pain has a sudden onset, severe symptoms, and rapid progression. It may resolve spontaneously in mild cases but can be life-threatening in severe cases. Chronic abdominal pain has a gradual onset, may recur, and can persist when the cause is unclear. Acute and chronic abdominal pain may alternate in some cases.
Etiology
Abdominal pain can be classified based on the anatomical location and nature of the underlying disease into pain caused by abdominal diseases and pain caused by extra-abdominal or systemic diseases.
Abdominal Diseases
Acute Inflammation
Examples include acute cholecystitis, biliary stones, acute cholangitis, acute pancreatitis, acute gastroenteritis, acute appendicitis, acute peritonitis, inflammatory bowel disease, acute hemorrhagic necrotizing enteritis, acute mesenteric lymphadenitis, acute diverticulitis, and acute pyelonephritis.
Chronic Inflammation
Examples include chronic gastritis, chronic cholecystitis and biliary infections, chronic viral hepatitis, chronic pancreatitis, chronic appendicitis, tuberculous peritonitis, inflammatory bowel disease, and abdominal lymphadenitis.
Ulcers or Perforations
Examples include peptic ulcers, small intestinal and colonic ulcers, and perforations of the stomach, intestines, or gallbladder.
Organ Obstruction, Torsion, or Ischemia
Examples include acute gastric volvulus, intestinal obstruction, intussusception, omental torsion, intestinal adhesions, duodenal obstruction syndrome, mesenteric vascular embolism, biliary ascariasis, urinary tract stones, ischemic bowel disease, internal hernia, and inguinal hernia.
Organ Enlargement, Rupture, or Hemorrhage
Examples include hepatic congestion, hepatitis, liver abscess, liver cancer, liver rupture, splenic abscess, splenic tumors, rupture of the liver or spleen, and rupture of an abdominal aortic aneurysm.
Tumors
Examples include gastric cancer, primary duodenal cancer, small intestinal tumors, lymphoma, colorectal cancer, liver cancer, gallbladder cancer, cholangiocarcinoma, peritoneal tumors, retroperitoneal tumors, adrenal tumors, and renal tumors.
Functional Disorders
Examples include functional abdominal pain, functional dyspepsia, irritable bowel syndrome, and functional constipation.
Abdominal Wall Diseases
Examples include abdominal wall trauma, abscesses, and herpes zoster.
Extra-Abdominal or Systemic Diseases
Thoracic Diseases
Examples include acute myocardial infarction, acute pericarditis, acute right heart failure, intercostal neuralgia, diaphragmatic pleuritis, reflux esophagitis, esophageal hiatal hernia, lobar pneumonia, pulmonary infarction, and thoracic spinal tuberculosis or tumors.
Pelvic Diseases
Examples include bladder cancer, chronic cystitis, prostate cancer, endometritis, acute salpingitis, ovarian cyst torsion, uterine torsion during pregnancy, ectopic pregnancy, ovarian rupture, and acute or chronic pelvic inflammatory disease.
Metabolic Disorders
Abdominal pain is a major and prominent symptom of porphyria. It may also occur in diabetic ketoacidosis and adrenal insufficiency.
Rheumatic or Immune Diseases
Examples include abdominal purpura, abdominal rheumatic fever, systemic lupus erythematosus, and polyarteritis nodosa.
Hematologic Diseases
Examples include acute hemolysis, acute leukemia, sickle cell anemia, and myelodysplastic syndromes.
Neurogenic Diseases
Examples include abdominal epilepsy, spinal or peripheral nerve lesions or tumors, and intervertebral disc herniation.
Physical or Chemical Factors
Examples include lead poisoning, thallium poisoning, and drug intoxication.
Clinical Manifestations
Location of Abdominal Pain
The location of abdominal pain often corresponds to the site of the affected organ. However, it is important to consider the presence of radiating or referred pain. Diffuse or poorly localized abdominal pain is commonly seen in conditions such as acute diffuse peritonitis, mechanical intestinal obstruction, acute hemorrhagic necrotizing enteritis, porphyria, lead poisoning, and abdominal allergic purpura.
Severity and Nature of Abdominal Pain
The severity of abdominal pain can, to some extent, reflect the extent of the underlying condition. Chronic gastritis or gastric and duodenal ulcers often present as persistent, dull pain in the upper abdomen. Gallstones or urinary stones are frequently associated with severe, colicky pain. Acute pancreatitis typically manifests as persistent, dull or knife-like pain in the upper abdomen, which may worsen intermittently. Gastric or duodenal perforation often presents as sudden, severe, knife-like or burning pain in the upper abdomen. Persistent, widespread, and severe abdominal pain with abdominal muscle rigidity or board-like stiffness suggests acute diffuse peritonitis. Colicky pain is usually caused by spasm, distension, or obstruction of hollow organs and often occurs intermittently, with pain-free intervals, as seen in small intestinal obstruction or biliary or ureteral stones with obstruction. Migratory pain to the right lower abdomen is a common clinical feature of acute appendicitis. Intermittent, drilling-like pain beneath the xiphoid process is a typical manifestation of biliary ascariasis.
Triggering and Relieving Factors
Acute gastroenteritis is often associated with a history of consuming contaminated food. Cholecystitis or gallstones may be related to the intake of fatty foods. Acute pancreatitis is frequently linked to excessive alcohol consumption or overeating. Some cases of mechanical intestinal obstruction are associated with prior abdominal surgery. Severe abdominal pain following external abdominal trauma, accompanied by shock, is often caused by rupture of the liver or spleen. Pain that is relieved by eating or taking acid-suppressing medications may suggest peptic ulcer disease. Abdominal pain relieved by antispasmodic medications is often due to smooth muscle spasm. Upper abdominal pain relieved by vomiting is often associated with gastric or duodenal conditions.
Timing of Onset
Periodic or rhythmic upper abdominal pain is commonly seen in gastric or duodenal ulcers. Postprandial pain may be related to dyspepsia or diseases of the biliary or pancreatic systems. Abdominal pain caused by endometriosis is often associated with the menstrual cycle, while pain due to follicular rupture typically occurs mid-cycle.
Relationship with Body Position
Burning pain in patients with gastroesophageal reflux disease is more pronounced in the supine or forward-leaning position and alleviated in the upright position. Pain in patients with pancreatic disease is more severe in the supine position and relieved in the forward-leaning or prone position. Pain in patients with gastric mucosal prolapse may be alleviated in the left lateral position. Symptoms such as abdominal pain and vomiting in patients with duodenal obstruction syndrome may improve in the knee-chest or prone position.
Accompanying Symptoms
Abdominal Pain with Fever and Chills
This is commonly seen in acute cholecystitis, acute obstructive suppurative cholangitis, liver abscess, and intra-abdominal abscesses. It may also occur in extra-abdominal infectious diseases.
Abdominal Pain with Jaundice
This is often associated with hepatobiliary or pancreatic diseases and may also occur in acute hemolytic anemia.
Abdominal Pain with Shock
When accompanied by anemia, it may indicate rupture of an abdominal organ, such as the liver, spleen, or ectopic pregnancy. In the absence of anemia, it may occur in cases of gastrointestinal perforation, strangulated intestinal obstruction, intestinal volvulus, or acute hemorrhagic necrotizing pancreatitis.
Abdominal Pain with Emesis
This suggests diseases of the esophagus, stomach, or intestines. Large volumes of vomitus may indicate gastrointestinal obstruction.
Abdominal Pain with Acid Reflux and Belching
This is seen in conditions such as peptic ulcers, gastritis, or dyspepsia.
Abdominal Pain with Diarrhea
This suggests intestinal inflammation, ulcers, or tumors.
Abdominal Pain with Bloody Stool
This is seen in intussusception, ischemic bowel disease, ulcerative colitis, bacterial dysentery, or intestinal tumors.
Abdominal Pain with Hematuria
This may indicate urinary system diseases, such as stones.
Auxiliary Examinations
Laboratory Tests
Complete Blood Count
An elevated total white blood cell count and neutrophil percentage suggest inflammation. Eosinophilia should prompt consideration of abdominal allergic purpura, parasitic infections, or eosinophilic gastroenteritis.
Urinalysis and Other Urinary Tests
Bacteriuria and pyuria indicate urinary tract infection. Hematuria suggests urinary tract stones, tumors, or trauma. Hemoglobinuria indicates acute hemolysis. Positive urine glucose and ketones suggest diabetic ketoacidosis. Bilirubinuria is indicative of obstructive jaundice. In suspected cases of porphyria, urinary porphyrin levels should be tested. Urinary lead levels should be measured in suspected lead poisoning. A urine pregnancy test is recommended when ectopic pregnancy is suspected.
Stool Analysis and Occult Blood Test
Macroscopic stool examination, occult blood testing, microscopic cellular examination, bacterial culture, and fat droplet analysis can aid in clinical diagnosis.
Blood Biochemistry
Serum amylase levels exceeding three times the upper limit of normal suggest acute pancreatitis. Abnormal liver and kidney function tests, blood glucose, and electrolyte levels can also help identify the cause of abdominal pain.
Tumor Markers
Elevated tumor markers such as serum alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) raise the suspicion of malignancy.
Diagnostic Paracentesis
In cases of unclear abdominal pain accompanied by ascites, abdominal paracentesis should be performed.
Imaging Studies
X-Ray
Chest and abdominal X-rays are important imaging modalities for patients with acute abdominal pain. Free air under the diaphragm and air-fluid levels are helpful in diagnosing gastrointestinal perforation or intestinal obstruction. Barium swallow or barium enema studies can detect peptic ulcers and gastrointestinal tumors.
Ultrasound
Ultrasound is useful for diagnosing conditions such as biliary stones, bile duct dilation, hepatosplenomegaly, abdominal tumors, abdominal cysts, and ascites. In ectopic pregnancy, an extrauterine gestational sac or pelvic fluid may be observed.
CT and MRI
CT and MRI have high diagnostic value for inflammatory conditions, abscesses, vascular diseases, tumors, and trauma involving solid abdominal organs.
Endoscopy
Gastroscopy and colonoscopy provide direct visualization of gastrointestinal lesions. Endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasound (EUS) are helpful in diagnosing biliary and pancreatic diseases. Cystoscopy can be used to diagnose bladder inflammation, stones, or tumors. Laparoscopy has high diagnostic value for abdominal inflammation, tumors, or adhesions.
Other Examinations
Electrocardiography (ECG) aids in differentiating upper abdominal pain caused by angina or myocardial infarction. Electroencephalography (EEG) is useful for diagnosing abdominal epilepsy. Angiography can help identify visceral vascular conditions such as superior mesenteric vein thrombosis.
Surgical Exploration
In cases of acute abdominal pain with an unclear cause, where conservative treatment fails and the patient's condition deteriorates, surgical exploration may be considered to save the patient’s life.
Diagnosis and Differential Diagnosis
Abdominal pain is a common clinical symptom. Its etiology, characteristics, location, severity, accompanying symptoms, and medical history vary widely. A thorough history-taking and understanding of the nature of the pain, combined with auxiliary examinations, are essential for making a preliminary diagnosis of the underlying cause.
Treatment
Management of abdominal pain should focus on addressing the underlying cause. A prompt assessment of the patient’s overall condition is necessary to determine the severity and urgency of the situation, followed by the initiation of appropriate symptomatic treatment. For cases where the etiology remains unclear, close observation and symptomatic treatment should be provided while further investigations are conducted to establish a definitive diagnosis.
Respiratory and Circulatory Support
Measures include airway management, oxygen supplementation, intravenous fluid administration to restore effective blood volume, and correction of water, electrolyte, and acid-base imbalances.
Gastrointestinal Decompression
This is suitable for patients with gastrointestinal obstruction or acute pancreatitis.
Analgesics
Analgesics can alleviate abdominal pain, reduce agitation, and relax the abdominal muscles, which may help detect positive abdominal signs. Previously, it was believed that analgesics should not be administered to patients with acute abdomen before a definitive diagnosis is made, as this might mask symptoms, alter physical signs, and delay diagnosis and treatment. However, current evidence does not support the notion that analgesic use obscures abdominal signs or increases mortality or disability rates. With advances in imaging techniques providing valuable objective evidence for the diagnosis of acute abdomen, the judicious use of analgesics is unlikely to delay clinical diagnosis or influence surgical decisions.
Enemas and Laxatives
These should be used cautiously, only after ruling out conditions such as intestinal necrosis or perforation.
Antibiotics
Antibiotic therapy is indicated when an infectious focus is identified.
Surgical Exploration
If abdominal pain persists, abdominal signs do not improve, and the patient’s overall condition worsens despite close observation and active treatment, surgical exploration should be considered. This is particularly important in cases of life-threatening intra-abdominal hemorrhage, perforation, intestinal obstruction, or severe peritonitis.