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Common causes include gastroenteritis and irritable bowel syndrome. In a third of cases the exact cause is unclear. About 10% of people have a more serious underlying condition such as appendicitis or diverticulitis. Determining the cause can be difficult, because many diseases can cause this symptom.

Differential diagnosis

The most frequent cause of abdominal pain is gastroenteritis (13%), irritable bowel syndrome (8%), urinary tract problems (5%), inflammation of the stomach (5%) and constipation (5%). About 30% of cases the cause is not determined. About 10% of cases have a more serious cause including gallbladder or pancreas problems (4%), diverticulitis (3%), appendicitis (2%) and cancer (1%). More common in those who are older, mesenteric ischemia and abdominal aortic aneurysms are other serious causes.

A more extensive list includes the following:

• Gastrointestinal
  • 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
  • Glands
    • Bile system
      • Inflammatory: cholecystitis, cholangitis
      • Obstruction: cholelithiasis, tumours
    • Liver
      • Inflammatory: hepatitis, liver abscess
    • Pancreatic
      • Inflammatory: pancreatitis
• Renal and urological
  • Inflammation: pyelonephritis, bladder infection
  • Obstruction: kidney stones, urolithiasis, Urinary retention, tumours
  • Vascular: left renal vein entrapment
• Gynaecological or obstetric
  • Inflammatory: pelvic inflammatory disease
  • Mechanical: ovarian torsion
  • Endocrinological: menstruation, Mittelschmerz
  • Tumors: endometriosis, fibroids, ovarian cyst, ovarian cancer
  • Pregnancy: ruptured ectopic pregnancy, threatened abortion
• Abdominal wall
  • muscle strain or trauma
  • muscular infection
  • neurogenic pain: herpes zoster, radiculitis in Lyme disease, abdominal cutaneous nerve entrapment syndrome (ACNES), tabes dorsalis
• Referred pain
  • from the thorax: pneumonia, pulmonary embolism, ischemic heart disease, pericarditis
  • from the spine: radiculitis
  • from the genitals: testicular torsion
• Metabolic disturbance
  • uremia, diabetic ketoacidosis, porphyria, C1-esterase inhibitor deficiency, adrenal insufficiency, lead poisoning, black widow spider bite, narcotic withdrawal
• Blood vessels
  • aortic dissection, abdominal aortic aneurysm
• Immune system
  • sarcoidosis
  • vasculitis
  • familial Mediterranean fever
• Idiopathic
  • 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:
  • Small bowel obstruction secondary to adhesions caused by previous surgeries, intussusception, hernias, benign or malignant neoplasms
  • Large bowel obstruction caused by colorectal cancer, inflammatory bowel disease, volvulus, fecal impaction or hernia
• Vascular: occlusive intestinal ischemia, usually caused by thromboembolism of the superior mesenteric artery

By location

Location

• Upper middle abdominal pain
  • Stomach (gastritis, stomach ulcer, stomach cancer)
  • Pancreas pain (pancreatitis or pancreatic cancer, can radiate to the left side of the waist, back, and even shoulder)
  • Duodenal ulcer, diverticulitis
  • Appendicitis (starts here, after several times moves to lower right abdomen)
• Upper right abdominal pain
  • Liver (caused by hepatomegaly due to fatty liver, hepatitis, or caused by liver cancer, abscess)
  • Gallbladder and biliary tract (gallstones, inflammation, roundworms)
  • Colon pain (below the area of liver — bowel obstruction, functional disorders, gas accumulation, spasm, inflammation, colon cancer)
• Upper left abdominal pain
  • Spleen pain (splenomegaly)
  • Pancreas
  • 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 (diarrhea, colitis and dysentery)
• Lower right abdominal pain
  • Cecum (intussusception, bowel obstruction)
  • Appendix point (Appendicitis location)
• Lower left abdominal pain
  • Sigmoid colon (polyp), sigmoid volvulus, obstruction or gas accumulation)
• Pelvic pain
  • bladder (cystitis, may be secondary to diverticulum and bladder stone, bladder cancer)
  • pain in women (uterus, ovaries, fallopian tubes)
• 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
  • kidney pain (kidney stone, kidney cancer, hydronephrosis)
  • Ureteral stone pain

Diagnostic approach

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 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 aid diagnosis include

• Blood tests including full blood count, electrolytes, urea, creatinine, liver function tests, pregnancy test, amylase and lipase.
• Urinalysis
• 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)

Management

Butylscopolamine (Buscopan) is used to treat cramping abdominal pain with some success.

Epidemiology

Abdominal pain is the reason about 3% of adults see their family physician. Rates of emergency department visits in the United States for abdominal pain increased 18% from 2006 through 2011. This was the largest increase out of 20 common conditions seen in the ED. The rate of ED use for nausea and vomiting also increased 18%.