Stomach pain is one of the most common reasons people visit a doctor, and its meaning ranges from completely harmless to life-threatening depending on where it is, how it feels, and what other symptoms come with it. The abdomen houses dozens of organs, and pain in a specific region often points toward the organ sitting there. But the nervous system makes things tricky: internal organs share nerve pathways, so pain from a diseased gallbladder can feel identical to pain from a stomach ulcer, and a heart attack can masquerade as indigestion. Understanding how location and accompanying symptoms narrow the possibilities gives you a practical framework for deciding what to watch, what to mention at your next appointment, and what warrants an emergency room visit.
Why Abdominal Pain Is Hard to Pin Down
Pain signals from your skin and muscles travel along dedicated nerve fibers, which is why you can point to a paper cut with precision. Pain from internal organs works differently. The gut, liver, kidneys, and other abdominal organs send signals through a shared network of nerves that converge on the same segments of the spinal cord. The result is a dull, poorly localized ache that can be difficult to describe. Somatic and visceral pain signals travel via different pathways to reach the spinal cord, and those same nerve bundles also carry signals controlling blood flow and gut motility, which is why abdominal pain often comes with nausea, sweating, or changes in bowel habits that seem unrelated to the pain itself.1PubMed Central. Visceral versus somatic pain: an educational review of anatomy and clinical implications
This overlap explains a frustrating clinical reality: you feel pain “in your stomach,” but the source could be the stomach, the pancreas, the gallbladder, the abdominal wall muscles, or even the heart. Location helps narrow the field, but it rarely gives a definitive answer on its own. What it does is create a short list of likely suspects, and the character of the pain, its timing, and the symptoms that accompany it whittle that list down further.
Upper Abdominal Pain
The upper abdomen is divided into the right upper quadrant, the left upper quadrant, and the epigastric region (the area just below the breastbone). Each zone has its own set of usual culprits.
Right Upper Quadrant
This is gallbladder territory. The classic gallbladder attack produces a sharp, squeezing pain under the right rib cage that often radiates to the right shoulder blade, comes on after a fatty meal, and lasts anywhere from thirty minutes to several hours. Gallstone-related acute cholecystitis is the leading consideration when evaluating right upper quadrant pain, but the differential extends well beyond the gallbladder to include liver problems, pancreatitis, peptic ulcer disease, ascending cholangitis, and even musculoskeletal causes.2PubMed. ACR Appropriateness Criteria® Right Upper Quadrant Pain: 2022 Update Pain that comes with fever and yellowing skin suggests a bile duct obstruction or liver infection, which needs urgent attention.
Epigastric Region
Pain in the center of the upper abdomen, just below the sternum, is one of the most common complaints in gastroenterology. Acid reflux, gastritis, and ulcers are frequent causes. Ulcer pain has some useful distinguishing features: a duodenal ulcer tends to hurt several hours after eating and often wakes people at night, while a gastric ulcer causes pain immediately after eating and worsens with food.3Digestive Diseases. Chronic Abdominal Pain: Gastroenterologist Approach Hunger provokes duodenal ulcer pain and eating relieves it, which is the opposite pattern from a gastric ulcer. Epigastric pain that radiates straight through to the back raises concern for the pancreas, especially if it comes with vomiting and is severe enough to make you curl forward for relief.
Left Upper Quadrant
Left upper quadrant pain is less common in everyday practice but can indicate problems with the spleen, the tail of the pancreas, or the splenic flexure of the colon. Imaging plays an important role in evaluating this region, because the differential diagnosis includes conditions as varied as a splenic infarct, a kidney stone lodged in the left ureter, and gastric ulceration.4Radiologic Clinics of North America. Imaging of Left Upper Quadrant Pain A pulled muscle or rib injury can also produce left upper quadrant pain that worsens with deep breathing or movement, mimicking something more serious.
Lower Abdominal Pain
The lower abdomen holds the appendix, the large intestine, the bladder, and in women the uterus and ovaries. As with the upper abdomen, dividing it into right, left, and central zones helps organize the possibilities.
Right Lower Quadrant
Appendicitis is the first thing most people and most doctors think of when pain settles in the right lower quadrant. The textbook presentation starts as a vague ache around the belly button that migrates over several hours to the lower right, where it becomes sharp and worsens with movement. But right lower quadrant pain remains one of the most challenging clinical scenarios because the signs and symptoms are frequently nonspecific, and there are numerous important differential considerations beyond appendicitis, including ovarian cysts, inflammatory bowel disease (particularly Crohn’s disease), right-sided colonic diverticulitis, and kidney stones passing into the bladder.5PubMed. Imaging of acute right lower quadrant abdominal pain: differential diagnoses beyond appendicitis In women of reproductive age, a ruptured ovarian cyst or ovarian torsion can produce sudden right-sided pain that mimics appendicitis almost perfectly.
Atypical appendicitis presentations are especially common in children, older adults, and pregnant women, which leads to delays in diagnosis in those groups.6PubMed Central. Typical and Atypical Presentations of Appendicitis and Their Implications for Diagnosis and Treatment: A Literature Review In pregnancy, the appendix gets pushed upward by the growing uterus, so appendicitis pain can show up in the right flank or even the right upper quadrant instead of the expected lower right.
Left Lower Quadrant
In adults, especially those over fifty, left lower quadrant pain is diverticulitis territory. Diverticular disease tends to produce moderate-to-severe pain lasting at least a full day in the left lower abdomen, and that prolonged left-sided pattern is one of its most characteristic features.7Journal of Clinical Gastroenterology. Moderate to Severe and Prolonged Left Lower-abdominal Pain is the Best Symptom Characterizing Symptomatic Uncomplicated Diverticular Disease of the Colon Diverticulitis typically involves fever, rebound tenderness, and elevated white blood cell counts, while a less well-known condition called primary epiploic appendagitis produces localized left-sided pain without those systemic signs. One study found that patients with diverticulitis had fever and rebound tenderness far more often than those with epiploic appendagitis, and their tenderness was more diffuse across the left side of the abdomen.8PubMed Central. Differential diagnosis of left-sided abdominal pain: primary epiploic appendagitis vs colonic diverticulitis Epiploic appendagitis, while painful, is self-limiting and rarely requires anything beyond anti-inflammatory medication.
Central and Lower Pelvic Pain
Pain deep in the pelvis, especially in women, opens a wide differential that includes gynecological conditions alongside gastrointestinal and urological ones. Ectopic pregnancy, ovarian torsion, endometriosis, and fibroid-related complications can all produce acute pelvic pain.9PubMed Central. Ruptured Ectopic Pregnancy, Ovarian Torsion, Dermoid Cyst, Leiomyomata, and Endometriosis: A Case Report of a Pelvic Quintet Any woman of reproductive age with sudden lower abdominal pain should have an ectopic pregnancy considered until proven otherwise, because a ruptured ectopic can cause life-threatening internal bleeding within hours. Bladder infections produce a burning central lower pain that worsens with urination, while kidney stones typically cause one-sided flank pain that radiates into the groin.
Red Flags That Warrant Emergency Care
Most abdominal pain is not dangerous. But a handful of signs suggest something serious enough to justify going to the emergency room rather than waiting for a scheduled appointment. Here are the ones that matter most:
- Rigid abdomen: If your belly is hard and board-like and any pressure causes severe pain, that suggests peritonitis, which means the lining of the abdominal cavity is inflamed, often from a perforation.
- Signs of shock: A systolic blood pressure below 100 mmHg or a rapid heart rate relative to blood pressure strongly raises the likelihood of a serious cause. One systematic review found that a low blood pressure and an elevated shock index were significant red flags for appendicitis and other surgical emergencies.10PubMed Central. Signs and symptoms of serious illness in adults with acute abdominal pain presenting to ambulatory care: a systematic review
- Bloody or black stools: Dark, tarry stool or bright red blood suggests bleeding somewhere in the digestive tract. Upper gastrointestinal bleeding can be severe enough to require emergency blood transfusion regardless of lab values when hemodynamic instability is present.11PubMed. Emergency medicine updates: Upper gastrointestinal bleeding
- Pain out of proportion: Severe pain with a relatively soft, non-tender abdomen on exam is a hallmark of mesenteric ischemia, a condition where blood flow to the intestines is compromised. Arterial embolic disease can present with sudden, severe pain, while other forms may start with vague symptoms including generalized pain, weight loss, and diarrhea. Normal lab values do not rule it out.12PubMed. High risk and low prevalence diseases: Mesenteric ischemia
- Fever with severe pain: The combination suggests infection, whether from appendicitis, diverticulitis, cholangitis, or an abscess.
- Pain during pregnancy: Abdominal pain during pregnancy can arise from obstetric causes or from the same conditions that affect anyone, but the altered anatomy and physiology of pregnancy make diagnosis more difficult.13PubMed Central. Management of acute abdomen in pregnancy: current perspectives Any significant abdominal pain in pregnancy should be evaluated promptly.
When Pain Is Not Coming From Where You Think
Referred pain is one of the most common reasons abdominal pain gets misinterpreted. A heart attack can produce epigastric burning that feels like heartburn. Pneumonia in the lower lobes of the lungs can cause upper abdominal pain. A kidney stone lodged in the ureter can produce pain that wraps from the flank to the groin and feels like a bowel problem.
The abdominal wall itself is another underappreciated source of pain. Anterior cutaneous nerve entrapment syndrome occurs when a small nerve running through the abdominal wall muscles gets trapped, producing chronic localized pain that is frequently mistaken for an internal organ problem. Patients sometimes undergo extensive gastroenterological workups before the diagnosis is made. One useful clinical clue: the pain gets worse, not better, when the person tenses their abdominal muscles, a finding called Carnett’s sign.14PubMed Central. Anterior cutaneous nerve entrapment syndrome with pain present only during Carnett’s sign testing: a case report With visceral (organ-based) pain, tensing the muscles usually provides some relief or at least no worsening. If your doctor hasn’t checked for Carnett’s sign during a workup for chronic abdominal pain, it is worth asking about.
Chronic and Functional Abdominal Pain
Not all abdominal pain has a structural cause. Irritable bowel syndrome and other functional gastrointestinal disorders produce real, sometimes debilitating pain without the kind of visible damage that shows up on scans or scopes. A key feature of these conditions is visceral hypersensitivity, meaning the gut’s nerves fire pain signals in response to stimuli that would not normally be painful, like the normal stretch of a meal moving through the intestines.15PubMed Central. Gut pain & visceral hypersensitivity
In IBS specifically, visceral hypersensitivity plays a central role in generating symptoms, and the process involves both the peripheral nerves in the gut and the brain’s processing of those signals.16PubMed Central. The Role of Visceral Hypersensitivity in Irritable Bowel Syndrome: Pharmacological Targets and Novel Treatments Brain imaging studies have found that people with IBS who are hypersensitive to gut stimulation show altered connectivity in brain networks associated with body awareness and salience, meaning their brains are essentially turning up the volume on normal gut signals.17PubMed Central. Brain functional connectivity is associated with visceral sensitivity in women with Irritable Bowel Syndrome This is not imaginary pain. It is pain generated by a nervous system that has become oversensitive. Treatment increasingly targets these gut-brain pathways rather than focusing on the gut alone.
There is also growing evidence that the gut microbiome modulates visceral pain. Disruptions in the gut microbial environment have been associated with chronic visceral pain conditions, and signaling molecules produced by gut bacteria can influence both peripheral and central pain sensitization.18PubMed. Pain regulation by gut microbiota: molecular mechanisms and therapeutic potential This is still an active research area, but it helps explain why dietary changes, probiotics, and antibiotics sometimes improve functional abdominal pain in ways that are hard to account for through traditional models.
Abdominal Pain at Different Ages
Age changes both the likely causes and the reliability of symptoms in ways that catch people off guard.
Children
In pediatric emergency departments, acute abdominal pain is one of the most common complaints, and the leading causes vary significantly by age group. Infants under two years old are at risk for intussusception, where one part of the intestine telescopes into another. School-age children develop appendicitis at increasing rates, while adolescents begin to share the adult differential, including ovarian pathology in girls.19PubMed Central. Etiology of non-traumatic acute abdomen in pediatric emergency departments One condition that parents rarely hear about is mesenteric adenitis, where lymph nodes in the abdomen become swollen and painful, usually following a viral infection. It is a common cause of nonsurgical abdominal pain in children and can mimic appendicitis convincingly.20PubMed Central. Clinical Characteristics, Outcomes, and Interobserver Agreement of Point-of-Care Ultrasound Detected Mesenteric Adenitis in Nonsurgical Pediatric Abdominal Pain: A Retrospective Cohort Study The good news is that mesenteric adenitis resolves on its own.
Older Adults
The elderly pose a different diagnostic challenge. Abdominal pain is one of the most frequent reasons older people visit the emergency department, and the stakes are higher because the deadliest causes of abdominal pain, including mesenteric ischemia, abdominal aortic aneurysm, and appendicitis, become more common with age.21PubMed Central. Abdominal emergencies in the geriatric patient Making matters worse, older adults often have blunted pain perception, lower fevers, and less dramatic lab abnormalities than younger people with the same conditions. A perforated ulcer that would cause excruciating pain and a sky-high white blood cell count in a thirty-year-old might produce only mild discomfort and borderline labs in an eighty-year-old. Clinicians know this, but family members advocating for an older adult in the ER should know it too.
How Doctors Figure Out What Is Going On
The clinical exam remains the starting point. Your doctor’s overall impression, based on history, symptoms, and a physical exam, is itself a powerful diagnostic tool. One systematic review found that the treating physician’s clinical impression had remarkably high diagnostic accuracy for conditions like bowel obstruction, diverticulitis, and appendicitis.10PubMed Central. Signs and symptoms of serious illness in adults with acute abdominal pain presenting to ambulatory care: a systematic review This does not mean imaging is unnecessary; it means the exam guides what imaging to order and how urgently.
When imaging is needed, the choice between ultrasound and CT scan depends on the situation. CT scans are more sensitive overall for detecting urgent conditions. In one large study, CT detected about 89% of urgent diagnoses compared to 70% for ultrasound. However, a strategy of starting with ultrasound and adding CT only when the ultrasound was negative or inconclusive missed just 6% of urgent cases while cutting the number of CT scans nearly in half.22BMJ. Imaging strategies for detection of urgent conditions in patients with acute abdominal pain: diagnostic accuracy study This ultrasound-first approach is commonly used in Europe and is gaining traction elsewhere because it reduces radiation exposure without meaningfully sacrificing accuracy. For specific conditions like appendicitis and diverticulitis, CT’s sensitivity advantage over ultrasound is more pronounced.23PubMed Central. A comparison of the Accuracy of Ultrasound and Computed Tomography in common diagnoses causing acute abdominal pain
Online Symptom Checkers and Self-Diagnosis
Given how variable abdominal pain is, you might be tempted to type your symptoms into an online tool and see what comes up. The evidence on these tools is sobering. A systematic review of digital symptom checkers found that the accuracy of their primary diagnosis was low, ranging from about 19% to 38% across studies. Triage accuracy, meaning the tool’s ability to tell you whether to seek urgent care, was better but still inconsistent, ranging from roughly 49% to 90%.24PubMed Central. The diagnostic and triage accuracy of digital and online symptom checker tools: a systematic review An observational study in an emergency department found that one well-known symptom checker app matched physician sensitivity for including the correct diagnosis somewhere in its top five suggestions, but physicians rated its triage decisions as too risky in a significant minority of cases.25JMIR mHealth and uHealth. Evaluation of Diagnostic and Triage Accuracy and Usability of a Symptom Checker in an Emergency Department: Observational Study
The practical takeaway is that symptom checkers can be a reasonable starting point for generating possibilities, but they should not be the endpoint. With abdominal pain in particular, the same symptom cluster can map to benign and dangerous conditions, and telling the difference often requires physical examination and sometimes imaging. If a symptom checker tells you everything is fine but you have any of the red flags mentioned earlier, go to the emergency room anyway.