25 Important Causes of Stomach Pain – Understanding Abdominal Pain

Stomach pain, also known as abdominal pain, is caused by a variety of conditions most of whom are innocent or benign. However, sometimes, abdominal pain may be due to a severe disorder needing immediate intervention.

The abdomen is the part of the body between the thorax (chest) and the pelvis. Other common names used to describe the abdomen are belly, stomach, and tummy.

25 Important Causes of Stomach Pain - Understanding Abdominal PainThe abdominal cavity contains many vital organs such as the stomach, the liver, the gallbladder, the pancreas, the spleen, the kidneys, and the small and large intestine.

Abdominal pain is a common medical symptom. Although most abdominal pain resolves spontaneously without specific treatment, as many as 10 percent of patients in the emergency department setting and a lesser percentage in the outpatient setting have a severe or life-threatening cause or require surgery (1).

In the 1983 edition of Harrison’s Principles and Practice of Internal Medicine, a textbook I heavily relied upon during medical school, William Silen wrote:

The correct interpretation of acute abdominal pain is one of the most challenging demands made of any physician. Since proper therapy often requires urgent action, the luxury of the leisurely approach suitable for the study of other conditions is frequently denied.

The location of the pain is a useful starting point that should guide further workup. Hence, pain may be classified as upper abdominal pain and lower abdominal pain. Upper abdominal pain is further divided into right upper quadrant (RUQ) pain, epigastric pain, and left upper quadrant (LUQ) pain.

For practical purposes, lower abdominal pain may be regarded as one group although it may also be divided into right and left lower quadrant pain.

Abdominal pain can also be diffuse and not distinctly positioned in a particular part of the abdomen.

25 Important Causes of Stomach Pain - Understanding Abdominal Pain
Abdominal pain may be classified into upper and lower abdominal pain. Upper abdominal pain is further divided into right upper quadrant (RUG) pain, epigastric pain, and left upper quadrant pain (LUQ). Lower abdominal pain is divided into right left quadrant (RLQ) and left lower quadrant (LLQ) abdominal pain.

Acute vs. Chronic Abdominal Pain

Determining whether the pain is acute or chronic is of crucial importance when evaluating patients with abdominal pain.

However, there is no strict time period that will define abdominal pain as acute. The most important question is whether the symptoms are a part of an accelerating process or a long-standing disorder. However, keep in mind that patients with chronic abdominal pain may experience an acute worsening of a chronic problem.

Apparently, a pain that has remained unchanged for years will be classified as chronic. On the other hand, a pain that has been present for days but is getting worse all the time is classified as acute.

The term ‘acute abdomen’  was defined to describe a rapid onset of severe abdominal pain that may represent a serious and sometimes life-threatening condition. Hence, the condition needs an urgent and specific diagnosis and sometimes immediate surgical intervention.

Examples of underlying causes of ‘acute abdomen’ are acute appendicitis, acute cholecystitis, acute pancreatitis, acute diverticulitis, biliary colic, and kidney stones.

Associated symptoms that suggest that early surgical intervention is needed include protracted vomiting, fainting (syncope), and evidence of gastrointestinal tract blood loss.

Special populations may also be at risk for certain conditions causing abdominal pain, For example, women are at risk for genitourinary tract disease, and older adults may show atypical symptoms of a disease.

Right Upper Quadrant (RUQ) Abdominal Pain

Right upper quadrant pain is typically caused by disorders of the liver, gallbladder and the biliary tree. The pain is located below the ribcage, in the upper-right region of the abdomen. It may radiate upwards to the right side of the chest, to the epigastrium, to the right side of the back, and to the left lower quadrant.

1. Gallstones

Abdominal pain caused by gallstones is called biliary colic.

Bile is a liquid that helps to digest fats. It is produced by the liver and stored in the gallbladder. When we eat, bile passes from the gallbladder through the bile ducts into the small intestine, where it mixes with partially digested food.

Biliary colic is a steady or intermittent ache usually located in the right upper quadrant of the abdomen. Sometimes the pain spreads backward to the right shoulder blade.

Biliary colic is usually caused by gallstones blocking the normal flow of bile from the gallbladder.  A tumor can also block bile flow and cause biliary colic. The worst pain of biliary colic usually lasts for 30 minutes to an hour but may continue at a lower intensity for several more hours. The pain stops when the gallstone breaks free of the bile duct and passes into the intestine.

The standard imaging test used to detect gallstones is an ultrasound.

A removal of the gallbladder (cholecystectomy) by laparoscopic surgery (keyhole surgery) is a standard treatment for patients with gallstones and biliary colic.

Being female and middle-aged is a risk factor for developing gallstones.

25 Important Causes of Stomach Pain - Understanding Abdominal Pain
Biliary colic is a steady or intermittent ache usually located in the right upper quadrant of the abdomen. It is generally caused by gallstones blocking the normal flow of bile from the gallbladder.

2. Acute Cholecystitis

Acute cholecystitis is an inflammation of the gallbladder. In most cases, gallstones blocking the transport of bile from the gallbladder are the underlying cause of cholecystitis.

Usually, patients with acute cholecystitis experience steady, severe upper right quadrant or epigastric pain. Nausea and vomiting are sometimes present. Usually, there is associated fever and elevated leucocyte (white blood cells) count in the blood suggesting inflammation.

Palpation of the abdomen usually reveals tenderness in the right upper quadrant of the abdomen. Murphy’s sign is typically present (2).

Murphy’s sign is elicited by firmly placing a hand on the right upper quadrant of the abdomen and asking the patient to breathe deeply. If cholecystitis is present, the patient will experience pain and catch his/her breath as the gallbladder descends and contacts the palpating hand. A similar maneuver in the left upper quadrant should not cause discomfort.

History, physical examination, blood tests, and imaging tests such as abdominal ultrasound or computerized tomography (CT) usually reveal the diagnosis. HIDA scan is sometimes performed as well (3).

Hospitalization is usually necessary. Treatment is based on fasting, pain medication, antibiotics if an infection is present, and cholecystectomy.

3. Acute Cholangitis

Acute cholangitis occurs when gallstones become impacted in the biliary ducts resulting in blockage of bile flow and dilatation of the ducts leading to a bacterial superinfection (4).

Acute cholangitis is characterized by fever, jaundice, and abdominal pain, known as Charcot’s triad (5).

Jaundice is a term used to describe yellowing of the skin and the whites of the eyes. It is caused by the build-up of a substance called bilirubin in the blood and tissues of the body.

Bilirubin is excreted in the bile. Blockage of bile flow in cholangitis cause accumulation of bilirubin in the body, leading to jaundice.

Cholangitis is a serious medical condition.  Treatment includes fasting, and intravenous fluids need to be administered. The infection is treated with broad-spectrum antibiotics.

ERCP (Endoscopic Retrograde Cholangio-Pancreatography) is used to examine the bile ducts, and the same technique may be used to remove the stones causing the blockage (6).

Sometimes, a tumor blocking blood flow through the bile ducts is the underlying cause of acute cholangitis.

4. Sphincter of Oddi Dysfunction

A sphincter is a muscle that can open and close. The sphincter of Oddi is a muscular valve that controls the flow of bile and pancreatic juice through ducts from the liver and pancreas into the first part of the small intestine (duodenum).

When it’s working properly, the sphincter of Oddi opens to allow bile and pancreatic juice to flow through and then closes again. When sphincter of Oddi dysfunction is present, the sphincter muscle does not open when it should. This prevents the bile and pancreatic juice from flowing through, causing bouts of severe pain in the right upper quadrant of the abdomen. Nausea, vomiting, fever, chills, and diarrhea may sometimes be present as well.

Sphincter of Oddi dysfunction is relatively uncommon. People who have had their gallbladders removed are most likely to develop sphincter of Oddi dysfunction.

If symptoms are severe and sphincter of Oddi dysfunction has been documented, surgically cutting the sphincter during an ERCP may be done. This procedure is called sphincterotomy. It’s effective and relieves symptoms of SOD about 70% of the time (7).

5. Hepatitis

Hepatitis is inflammation of the liver, usually caused by a viral infection. There are several types of viral hepatitis.

Hepatitis A is a caused by the hepatitis A virus. The virus is primarily spread when a person ingests food or water that is contaminated with the feces of an infected person. The disease is closely associated with unsafe water or food, inadequate sanitation, and poor personal hygiene (7).

Typical symptoms of hepatitis A include right upper quadrant abdominal pain, fatigue, nausea, vomiting, clay colored stools, dark urine, joint pain, and jaundice.

Hepatitis B is a viral infection that causes inflammation of the liver. The virus is transmitted through contact with the blood or other body fluids of an infected person. It spreads through contact with blood, semen, or other bodily fluids.

Symptoms of hepatitis B include right upper quadrant abdominal pain, dark urine, fever, joint pain, fatigue, nausea, vomiting, and jaundice. The disease may lead to scarring of the liver, and there is an increased risk of liver cancer and liver failure.

An estimated 257 million people are living with hepatitis B virus infection (defined as Hepatitis B surface antigen positive)(8). Most of these individuals have no symptoms.

A vaccine is available for both hepatitis A and B. The hepatitis B vaccine has been used since 1982. The vaccine is 95% effective in preventing infection and the development of chronic disease and liver cancer due to hepatitis B (8).

Hepatitis C is a caused by the hepatitis C virus. The virus can cause both acute and chronic hepatitis, ranging in severity from a mild illness lasting a few weeks to a serious, lifelong illness (9).

The hepatitis C virus is a blood-borne virus, and the most common modes of infection are through exposure to small quantities of blood. This may happen through injection drug use, unsafe injection practices, unsafe healthcare, and the transfusion of unscreened blood and blood products.

Globally, an estimated 71 million people have chronic hepatitis C infection. A significant number of those who are chronically infected will develop cirrhosis or liver cancer (9).

Approximately 80% of people with hepatitis C have no symptoms. Those who are acutely symptomatic may exhibit right upper quadrant abdominal pain, fever, fatigue, decreased appetite, nausea, vomiting, dark urine, gray colored feces, joint pain, and jaundice.

Medical treatment for hepatitis C is available but remains limited. However, the disease does not always require treatment as the immune response in some people will clear the infection, and some people with chronic infection do not develop liver damage.

6. Budd-Chiari Syndrome

Budd-Chiari syndrome is a very rare condition affecting 1 in a million adults (10). It is caused by obstruction of venous blood flow from the liver.

Symptoms include upper right quadrant abdominal pain, jaundice, enlarged liver (hepatomegaly), and ankle edema.

7. Perihepatitis

Perihepatitis, also known as Fitz-Hugh-Curtiss syndrome is an inflammation of the membranous coating of the liver (11).

It is primarily a disease of women and often associated with pelvic inflammatory disease (PID). PID is an inflammation of a woman’s reproductive organs.

Perihepatitis typically presents with right upper quadrant abdominal pain. The pain may radiate to the right shoulder area and sometimes gets worse with movement, breathing, coughing, and sneezing.

Epigastric pain

Epigastric pain is located in the central portion of the upper abdomen, below the sternum and above the umbilicus. It is often associated with disorders of the stomach and pancreas.

8. Peptic Ulcer Disease 

Epigastric pain is the most common symptom of ulcers in the lining of the lower esophagus, the stomach, and the first part of the small intestine. An ulcer in the stomach is known as gastric ulcer whereas an ulcer of the first section of the small intestine is called a duodenal ulcer. Together these disorders are known as peptic ulcer disease (PUD).

The epigastric pain of PUD is characterized by a gnawing or burning sensation and occurs after meals, classically, shortly after meals with gastric ulcer and 2-3 hours afterward with duodenal ulcer (12).

Infection of the lining of the stomach from a bacteria called H pylori is a common underlying cause of peptic ulcer disease. Hence, testing for H pylori infection is essential (13).

A gastroscopy usually reveals the diagnosis.

Treatment of peptic ulcer disease includes antibiotic medication to kill H pylori when it is present.

Drugs that inhibit stomach acid production, like proton pump inhibitors (PPI’s), are given to promote healing.  Examples of PPI’s are omeprazole (Prilosec), lansoprazole (Prevacid), rabeprazole (Aciphex), esomeprazole (Nexium) and pantoprazole (Protonix).

Histamine (H-2) blockers also reduce the amount of stomach acid released and may reduce ulcer pain and promote healing. Examples are Tagamet (cimetidine), Zantac (ranitidine), Pepcid (famotidine), and Axid (nizatidine).

Antacids can provide rapid pain relief by neutralizing existing stomach acid. However, they are not considered useful enough to promote healing.

9. Gastroesophageal Reflux Disease (GERD)

Gastroesophageal reflux disease (GERD) is a common cause of epigastric pain.

It is a chronic digestive disease that occurs when stomach acid or, occasionally, stomach content, flows back (reflux) into the esophagus. The reflux irritates and may damage the lining of the esophagus causing the disease.

Most healthy people experience acid reflux and heartburn once in a while. However, when these symptoms occur at least twice each week or interfere with daily life, GERD should be suspected.

The pain associated with GERD may be described as squeezing or burning. It may radiate up to the chest, and sometimes to the back, neck, jaw or arms. It is usually relieved by antacids.

Most people can manage the symptoms of GERD with lifestyle changes and over-the-counter medications. However, some patients may need prescription drugs, or even surgery, to reduce symptoms. PPI’s, H-2 blockers and antacids are the most frequently used drugs.

25 Important Causes of Stomach Pain - Understanding Abdominal Pain
Gastroscopy is a commonly used diagnostic tool when evaluating patients with epigastrial pain. It may detect GERD, gastritis, and peptic ulcer disease.

10. Gastritis

Gastritis is an inflammatory process affecting the lining of the stomach.

Gastritis, similar to stomach ulcer is sometimes caused by an underlying infection with H pylori. 

The symptoms of gastritis include a gnawing or burning ache or pain in the epigastrium. Sometimes there is nausea and vomiting.

Common over the counter pain relievers, such as aspirin, ibuprofen (Advil, Motrin IB, others), and naproxen (Aleve, Anaprox) can cause gastritis. Stress and excessive alcohol consumption are also common underlying causes.

If left untreated, gastritis may cause stomach ulcers and stomach bleedings.

Medical treatment is essentially same as that of peptic ulcer disease and GERD.

11. Pancreatitis

Pancreatitis is an inflammation of the pancreas. It can be both acute and chronic.

The main symptoms of acute pancreatitis are abdominal pain, nausea, vomiting, and sometimes diarrhea. The pain is characteristically dull, boring, and steady; usually sudden in onset and gradually becoming more severe until reaching a constant ache; most often located in the upper abdomen and may radiate directly through to the back (14).

Gallstones and binge alcohol consumption are the most common underlying causes of acute pancreatitis. Very high levels of triglycerides in blood may also promote pancreatitis (15).

Serum levels of amylase and lipase are typically elevated in acute pancreatitis.

12. Acute Coronary Syndrome (ACS)

Patients with acute coronary syndrome (ACS) usually experience pressure, fullness or tightness in the chest (16). Sometimes there is searing pain that may radiate to the back, neck, jaw, shoulders, and arms, particularly the left arm.

Some patients with ACS experience epigastric pain. There may even be a feeling of indigestion or fullness and gas (17).

The term acute coronary syndrome covers a range of conditions associated with a sudden reduction in blood flow to the heart muscle. It includes conditions such as ST-segment elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI) (18).

ACS and acute heart attack are one and the same and should always be treated as an emergency.

13. Functional Dyspepsia (FD)

Functional dyspepsia (FD) is a chronic disorder involving sensation and movement (peristalsis) in the upper digestive tract. It is characterized by postprandial fullness, early satiation, and epigastric pain (19).

The disorder is defined as functional because there are no observable or measurable structural abnormalities found to explain the symptoms. Hence, it is sometimes called non-ulcer dyspepsia.

Dyspepsia is a common term used to characterize abdominal pain centered in the epigastrium, sometimes combined with other gastrointestinal complaints (20).

Left Upper Quadrant (LUQ) Abdominal Pain

14. Disorders of the Spleen

Left upper quadrant pain is sometimes related to diseases of the spleen.

Enlargement of the spleen (splenomegaly) may cause pain or discomfort in the upper left upper quadrant of the abdomen, sometimes radiating to the left shoulder (21).

Splenic infarction may cause severe left upper quadrant pain (22).

Lower Abdominal Pain

Lower abdominal pain and/or pelvic pain in women is frequently caused by disorders of the internal female reproductive organs. Examples are endometriosis, pelvic inflammatory disease (PID), ectopic pregnancy, ovarian torsion, and ruptured ovarian cysts. These disorders are not covered here.

15. Kidney Stones (Urolithiasis)

Kidney stones can be both small and large. Some stones stay in the kidney and do not cause any problems.

Most kidney stones are made of calcium (80%). Uric acid stones are less common (5-10%)(23).

Sometimes, the kidney stone can travel down the ureter, the tube between the kidney and the bladder. If the stone reaches the bladder, it can be passed out of the body in urine.

25 Important Causes of Stomach Pain - Understanding Abdominal Pain
A kidney stone can travel down the ureter, the tube between the kidney and the bladder. If the stone reaches the bladder, it can be passed out of the body in urine. If the stone becomes lodged in the ureter, it may cause severe pain.

If the stone becomes lodged in the ureter, it blocks the urine flow from that kidney and causes pain that may be very serious and intense. It is usually a sharp, cramping pain in the back and side, often radiating to the lower abdomen and groin. The pain often starts suddenly and comes in waves. It may be associated with nausea and vomiting.

There may also be an intense feeling of a need to urinate. The urine may be dark or red due to blood (hematuria).

16. Pyelonephritis

Pyelonephritis is a urinary tract infection that begins in the urethra or bladder and travels up to one or both kidneys.

The symptoms of pyelonephritis include fever, chills, pain in the back or side (flank) of the abdomen or the groin. There may be frequent urination, nausea, and vomiting.

The infection is usually caused by bacteria. Hence, antibiotics are the first line of treatment.

17. Cystitis

Cystitis is an inflammation of the of the urinary bladder. Most often, the inflammation is caused by a bacterial infection. The term urinary tract infection (UTI) is often used to describe the condition.

Cystitis may cause pain in the lower mid-portion of the abdomen (suprapubic pain). There may also be a persistent urge to urinate, a burning sensation while urinating, blood in the urine (hematuria), and a cloudy and strong smelling urine.

The usual treatment for bacterial cystitis is antibiotics.

18. Acute Appendicitis

Acute appendicitis is an acute inflammation of the appendix.

Acute appendicitis typically presents with pain around the umbilicus, usually radiating to the right lower quadrant of the abdomen. The pain may increase with coughing, walking or jolting movements. Nausea and vomiting may be present, and there is usually lack of appetite.

There is usually tenderness on palpation of the lower left quadrant of the abdomen. The pain may get worse if the pressure is suddenly released.

If the appendix ruptures, the infection may spread throughout the abdomen causing peritonitis which may be life threatening. A pocket of pus, called abscess, may also form at the site of the appendix.

Acute appendicitis is usually treated by removing the appendix by open appendectomy or a less-invasive laparoscopic appendectomy (keyhole surgery) (24).

19. Diverticulitis

Diverticulitis is defined as an inflammation of one or more diverticula, which are small pouches created by the herniation of the mucosa into the wall of the colon.

Diverticulitis is often considered a disease of the elderly, but as many as 20% of patients with diverticulitis are younger than 50 years. In its chronic form, patients may have recurrent bouts of low-grade or overt diverticulitis (25).

The symptoms of diverticulitis include left lower quadrant pain, nausea, vomiting, fever, abdominal tenderness, constipation, or less commonly, diarrhea.

Treatment usually includes antibiotics. Surgery is rarely needed unless complications are present.

Diffuse Abdominal Pain

Abdominal pain may often be diffuse and not located in a particular part of the abdomen. An extensive list of conditions may cause diffuse abdominal pain, and only a few of them will be covered here.

20. Inflammatory Bowel Disease (IBD)

Inflammatory bowel disease (IBD) is an idiopathic disease caused by an abnormal immune response to intestinal microflora.

The two major types of inflammatory bowel disease are ulcerative colitis (UC), which is limited to the colon, and Crohn’s disease (CD), which can affect any segment of the gastrointestinal tract.

There is a genetic predisposition for IBD, and patients with this condition are more prone to the development of intestinal cancer (26).

The symptoms include abdominal pain and cramping, irregular bowel habits, a passage of mucus with blood, weight loss, joint pain (arthralgia), sweats, and fatigue.

Pain is commonly located in the right lower quadrant in Crohn’s Disease and around the umbilicus (periumbilical) or in the left lower quadrant in ulcerative colitis.

21. Intestinal Obstruction

Intestinal obstruction is a blockage that keeps food or liquid from passing through the small or large intestine.

There may be several underlying causes including fibrous bands of tissue (adhesions) in the abdomen that form after surgery, inflammatory bowel disease (IBD), diverticulitis, twisting of the colon (volvulus), impacted feces, hernias, and cancer.

The symptoms include crampy abdominal pain that comes and goes in waves, loss of appetite, swelling of the abdomen, vomiting, and inability to have a bowel movement or pass gas.

Treatment of intestinal obstruction depends on the underlying cause.

22. Gastroenteritis

Viral gastroenteritis, sometimes called stomach flu, is an intestinal infection marked by watery diarrhea, abdominal cramps, nausea or vomiting, and sometimes fever (27).

Symptoms range from mild to severe and usually last only a day or two.

Bacterial gastroenteritis is usually caused by an infection with foodborne bacteria. Typical examples include Campylobacter and Salmonella.

Because most infectious diarrheas are self-limited, medical care is primarily supportive. Drinking fluid (oral hydration) is important. When oral rehydration is unsuccessful, intravenous fluids may have to be administered. Antibiotics are administered for some cases of bacterial gastroenteritis (28).

23. Mesenteric Ischemia

Acute mesenteric ischemia is caused by inadequate blood flow through the mesenteric vessels, resulting in insufficient blood flow to the bowel wall. It is a potentially life-threatening condition.

The condition is characterized by severe abdominal pain, sometimes associated with bloody diarrhea.

Chronic mesenteric ischemia occurs more gradually and is caused by narrowing in one or more of the arteries supplying blood to the intestines (visceral arteries). Abdominal pain usually develops 1-2 hours after eating.

Acute mesenteric ischemia must be treated immediately to prevent tissue death. Surgery may be necessary to remove parts of the intestine.

24. Cancer

Several gastrointestinal cancers may be associated with abdominal discomfort and abdominal pain. Examples are gastric cancer (cancer of the stomach), pancreatic cancer and colorectal cancer.

25. Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder. It describes a group of symptoms that affect the large intestine without a known cause.

IBS is a common disorder and occurs more often in women than in men. It has been estimated that as many as 1 in 5 American adults has signs and symptoms of irritable bowel syndrome (29).

Symptoms of IBS include cramping, abdominal pain, bloating, gas, diarrhea, and constipation.

The diagnosis of IBS is largely based on a complete medical history and physical examination. Before the diagnosis is made, other more serious underlying causes of the patient’s symptoms should be excluded.

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