Severe stomach pain has dozens of possible causes, ranging from a passing stomach bug to a surgical emergency. The most common diagnoses in adults who seek care for acute abdominal pain are gastroenteritis (about 11% of cases) and nonspecific abdominal pain (about 10%), followed by gallstones, kidney stones, diverticulitis, and appendicitis, each accounting for roughly 4% of cases. Where the pain is, how it started, and what it feels like can narrow the possibilities significantly.
Appendicitis
Appendicitis follows a distinctive pattern. Pain typically begins around the belly button, hovering or coming and going for several hours. It then intensifies, often with nausea and vomiting. Several hours later, the pain shifts to the lower right side of the abdomen and becomes sharper and more constant. Moving, coughing, sneezing, or taking a deep breath makes it worse. Fever, loss of appetite, and an inability to pass gas often follow.
The timeline matters here. The appendix can rupture within 36 hours of the first symptoms, so pain that follows this belly-button-to-lower-right pattern deserves urgent evaluation. A CT scan is the primary imaging tool, with sensitivity and specificity both around 90% to 91%.
Gallstones and Gallbladder Problems
Gallstone pain centers in the upper right abdomen or the upper middle area, often radiating to the right shoulder blade. It tends to strike after eating, especially fatty or heavy meals. The pain can range from several minutes to a few hours, then resolve completely before returning days or weeks later. A high-fat, high-cholesterol, low-fiber diet increases the risk of developing gallstones over time.
When a gallstone blocks a duct and doesn’t pass, the gallbladder can become inflamed. At that point, pain becomes more persistent and is often accompanied by fever. Ultrasound is the first imaging test used, since it’s widely available, avoids radiation, and can also reveal other causes of upper-right-quadrant pain.
Kidney Stones
Kidney stones produce some of the most intense pain people experience. The pain starts when a stone gets stuck in one of the tubes connecting the kidney to the bladder, blocking urine flow and causing the kidney to swell. You’ll feel serious, sharp pain in your side and back below the ribs. It often spreads down to the lower abdomen and groin, coming in waves that vary in intensity.
Other telltale signs include pink, red, or brown urine and a burning sensation while urinating. CT scans are the preferred imaging method. Ultrasound can detect a blockage but is poor at visualizing the stones themselves.
Pancreatitis
Acute pancreatitis causes upper abdominal pain that radiates straight through to the back or shoulders. It often starts mild, then worsens after eating and can become so severe that you can’t sit still or find a comfortable position. Nausea, fever, and a rapid pulse often accompany it. The abdomen may feel tender to the touch.
Gallstones and heavy alcohol use are the two most common triggers. Pancreatitis pain is distinctive because of its boring, relentless quality and the way it drives through to the back, unlike most other causes of upper abdominal pain.
Diverticulitis
Diverticulitis is the inflammation or infection of small pouches that form in the walls of the colon, most commonly on the left side. The hallmark is steady, aching pain in the lower left abdomen, often accompanied by fever, nausea, and changes in bowel habits. It’s more common in adults over 40.
CT scans detect diverticulitis with greater than 95% sensitivity and can also reveal complications like abscesses, making it the standard imaging choice for lower-left-quadrant pain.
Bowel Obstruction
When the intestine becomes partially or fully blocked, food and gas can’t pass through normally. The result is crampy abdominal pain that comes in waves, a swollen belly, vomiting, constipation, and an inability to pass gas. Previous abdominal surgery is one of the biggest risk factors, since scar tissue (adhesions) can kink or compress the bowel years later.
The wave-like quality of the pain is a key distinguishing feature. It builds, peaks, then fades, reflecting the intestine contracting against the blockage. Vomiting often becomes more prominent as the obstruction persists.
Ovarian Torsion and Ectopic Pregnancy
In women and people with ovaries, two reproductive emergencies can cause sudden, severe abdominal pain. Ovarian torsion occurs when an ovary twists on its supporting tissue, cutting off its blood supply. The pain is sudden, moderate to severe, and located in the lower belly, usually on one side. It can come with nausea and vomiting.
Ectopic pregnancy, where a fertilized egg implants outside the uterus (usually in a fallopian tube), produces sharp lower abdominal or pelvic pain, often on one side, sometimes with vaginal bleeding. If the tube ruptures, the pain becomes severe and may be accompanied by dizziness or fainting from internal bleeding. Pelvic ultrasound is the primary imaging tool for both conditions.
Peptic Ulcers and Gastritis
Ulcers in the stomach or the first part of the small intestine cause a burning or gnawing pain in the upper middle abdomen. The pain often worsens on an empty stomach and improves temporarily with eating or antacids, though stomach ulcers can sometimes feel worse after meals. If an ulcer perforates (eats through the wall), the pain becomes sudden, knife-like, and spreads across the entire abdomen as the abdominal lining becomes irritated.
Vascular Emergencies
Rarely, severe abdominal pain signals a problem with major blood vessels. A ruptured abdominal aortic aneurysm causes sudden, very bad, long-lasting belly or back pain that may feel like ripping or tearing. This is a life-threatening emergency most common in older adults, especially men with a history of smoking or high blood pressure. Mesenteric ischemia, where blood flow to the intestines is reduced, causes pain that is often out of proportion to what a physical exam reveals.
Pain Location as a Guide
Where you feel the pain is one of the most useful clues:
- Upper right: gallstones, gallbladder inflammation, kidney infection, or occasionally pneumonia
- Upper middle: ulcers, pancreatitis, gallbladder problems, or in some cases heart-related pain
- Upper left: pancreatitis, ulcers, kidney stones, or spleen-related issues
- Lower right: appendicitis, ovarian problems, kidney stones
- Lower left: diverticulitis, ovarian problems, kidney stones
- Around the belly button: early appendicitis, ulcers, or vascular problems
- Lower center: bladder infection, appendicitis, pelvic inflammatory disease
When Severe Pain Needs Emergency Care
Certain patterns signal that you should get to an emergency room rather than waiting for an office visit. Pain so severe it interrupts your ability to function, pain with vomiting that won’t stop or an inability to keep liquids down, inability to have a bowel movement combined with severe pain, and pain that is unlike anything you’ve experienced before all warrant an ER visit. If you’ve had prior abdominal surgery, that raises the concern for a bowel obstruction.
Pain that starts suddenly and is immediately severe is more concerning than pain that builds gradually over days. Fever with abdominal pain suggests infection or inflammation that may need urgent treatment. And abdominal pain accompanied by lightheadedness, a racing heart, or fainting could indicate internal bleeding.