Abdominal pain can be characterized by the region it affects.
Abdominal pain (or stomach ache) is a common symptom associated with transient disorders or serious disease. Diagnosing the cause of abdominal pain can be difficult, because many diseases can cause this symptom. Most frequently the cause is benign and/or self-limiting, but more serious causes may require urgent intervention.
- GI tract
- Inflammatory: gastroenteritis, appendicitis, gastritis, esophagitis, diverticulitis, Crohn's disease, ulcerative colitis, microscopic colitis
- Obstruction: hernia, intussusception, volvulus, post-surgical adhesions, tumours, superior mesenteric artery syndrome, severe constipation, hemorrhoids
- Vascular: embolism, thrombosis, hemorrhage, sickle cell disease, abdominal angina, blood vessel compression (such as celiac artery compression syndrome), Postural orthostatic tachycardia syndrome
- digestive: peptic ulcer, lactose intolerance, coeliac disease, food allergies
- GI tract
- Renal and urological
- Gynaecological or obstetric
- Abdominal wall
- Referred pain
- Metabolic disturbance
- Blood vessels
- Immune system
- irritable bowel syndrome (affecting up to 20% of the population, IBS is the most common cause of recurrent, intermittent abdominal pain)
Acute abdominal pain
Acute abdomen can be defined as severe, persistent abdominal pain of sudden onset that is likely to require surgical intervention to treat its cause. The pain may frequently be associated with nausea and vomiting, abdominal distention, fever and signs of shock. One of the most common conditions associated with acute abdominal pain is acute appendicitis.
Selected causes of acute abdomen
- Traumatic : blunt or perforating trauma to the stomach, bowel, spleen, liver, or kidney
- Inflammatory :
- Infections such as appendicitis, cholecystitis, pancreatitis, pyelonephritis, pelvic inflammatory disease, hepatitis, mesenteric adenitis, or a subdiaphragmatic abscess
- Perforation of a peptic ulcer, a diverticulum, or the caecum
- Complications of inflammatory bowel disease such as Crohn's disease or ulcerative colitis
- Mechanical :
- Vascular : occlusive intestinal ischemia, usually caused by thromboembolism of the superior mesenteric artery
- Upper middle abdominal pain
- Upper right abdominal pain
- Upper left abdominal pain
- Spleen pain (splenomegaly)
- Colon pain (below the area of spleen - bowel obstruction, functional disorders, gas accumulation, spasm, inflammation, colon cancer)
- Middle abdominal pain (pain in the area around belly button)
- Appendicitis (starts here)
- Small intestine pain (inflammation, intestinal spasm, functional disorders)
- Lower abdominal pain 
- Lower right abdominal pain
- Lower left abdominal pain
- Sigmoid colon (polyp), sigmoid volvulus, obstruction or gas accumulation)
- Pelvic pain
- Right lumbago and back pain
- liver pain (hepatomegaly)
- right kidney pain (its location below the area of liver pain)
- Left lumbago and back pain
- less in spleen pain
- left kidney pain
- Low back pain
When a physician assesses a patient to determine the etiology and subsequent treatment for abdominal pain the patient's history of the presenting complaint and physical examination should derive a diagnosis in over 90% of cases.
It is important also for a physician to remember that abdominal pain can be caused by problems outside the abdomen, especially heart attacks and pneumonias which can occasionally present as abdominal pain.
Investigations that would aid diagnosis include
- Blood tests including full blood count, electrolytes, urea, creatinine, liver function tests, pregnancy test, amylase and lipase.
- Imaging including erect chest X-ray and plain films of the abdomen
- An electrocardiograph to rule out a heart attack which can occasionally present as abdominal pain
If diagnosis remains unclear after history, examination and basic investigations as above then more advanced investigations may reveal a diagnosis. These as such would include
- Computed Tomography of the abdomen/pelvis
- Abdominal or pelvic ultrasound
- Endoscopy and colonoscopy (not used for diagnosing acute pain)
- Boyle, J. T.; Hamel-Lambert, J. (2001). "Biopsychosocial issues in functional abdominal pain". Pediatr Ann 30 (1): 32–40. PMID 11195732..