Pain under the left rib cage can come from several different organs and structures packed into that area, including the spleen, stomach, pancreas, left kidney, colon, and the lower portion of the left lung. The cause ranges from something as simple as trapped gas to conditions that need prompt medical attention. Where exactly the pain sits, what makes it worse, and what other symptoms come with it are the best clues to narrowing down the source.
Trapped Gas in the Colon
One of the most common and least serious causes is gas getting stuck at a sharp bend in your large intestine called the splenic flexure. This bend sits high up on the left side, right under your ribs. Gas normally passes through without trouble, but when too much builds up, it can overwhelm this curve, much like water backing up at a sharp bend in a river. The result is a crampy, bloated feeling under the left rib cage that can be surprisingly intense.
Some people are born with an unusually tight curve in this part of the colon, making them more prone to the problem. Carbonated drinks, high-fiber foods, and eating too quickly (which causes you to swallow air) all make it worse. Cutting back on these triggers, following a low-FODMAP diet, and giving the gas time to pass typically resolves the pain without any treatment.
Stomach Ulcers and Gastritis
Your stomach sits partly behind the left rib cage, and inflammation of its lining (gastritis) or an open sore in that lining (a peptic ulcer) can produce a burning, gnawing pain in the upper abdomen that you may feel radiating under the ribs. A stomach ulcer feels like a localized acid burn, often between the breastbone and belly button, slightly to the left. Many people also feel uncomfortably full soon after eating or long after a meal has ended.
The two most common triggers are a bacterial infection called H. pylori and overuse of anti-inflammatory painkillers like ibuprofen or aspirin. Smoking, alcohol, and acidic or spicy foods don’t cause ulcers on their own, but they irritate an existing wound and make the pain worse. If you recognize this pattern, especially if it’s been going on for weeks, a doctor can confirm it with an upper endoscopy and start treatment that usually clears the problem.
Worth noting: some people have chronic indigestion with the same burning and fullness but no visible damage to the stomach lining. This is called functional dyspepsia, and while it’s not dangerous, it can be frustrating to manage because acid-reducing medications don’t always help.
Costochondritis
Costochondritis is inflammation of the cartilage connecting your ribs to your breastbone. It most commonly affects the upper ribs on the left side, and the pain tends to be sharp, aching, or feel like pressure. It can radiate into your arms and shoulders, which is one reason it’s frequently mistaken for a heart attack.
The key difference is that costochondritis pain gets worse with specific physical triggers: taking a deep breath, coughing, sneezing, or any twisting movement of the chest wall. Pressing on the area where the rib meets the breastbone usually reproduces the pain. It often affects more than one rib at a time. The condition is usually self-limiting, meaning it resolves on its own over days to weeks, though the discomfort can be significant while it lasts.
Enlarged Spleen
Your spleen is tucked directly under your left rib cage, next to your stomach. When it swells, it creates a feeling of fullness or dull pressure in the left upper belly that can spread to the left shoulder. Because the enlarged spleen presses against the stomach, you may feel full after eating only a small amount of food.
A wide range of conditions can cause the spleen to enlarge:
- Viral infections like mononucleosis (one of the most common causes in younger adults)
- Liver disease including cirrhosis, which increases pressure in the veins feeding the spleen
- Blood disorders where red blood cells are destroyed faster than normal
- Blood cancers such as leukemia or lymphoma
- Autoimmune conditions like lupus
- Parasitic infections such as malaria
An enlarged spleen is typically discovered during a physical exam or imaging. Because a swollen spleen is more vulnerable to rupture, especially from a blow to the abdomen, identifying the underlying cause matters.
Pancreatitis
The pancreas sits behind the stomach, and when it becomes inflamed, the pain is distinctive. It’s typically a constant, severe, dull ache in the upper-middle abdomen that radiates straight through to the back. It almost always gets worse after eating. People often describe it as relentless, unlike the cramping that comes and goes with gas or digestive upset.
Acute pancreatitis comes on suddenly and is most often caused by gallstones or heavy alcohol use. Chronic pancreatitis develops gradually, usually from years of repeated inflammation. The back-radiating quality and the intensity of the pain are the hallmarks that distinguish it from other causes of left rib cage pain. This is a condition that typically requires medical evaluation, as severe cases can lead to complications.
Pericarditis
The heart sits behind the left rib cage, surrounded by a thin protective sac called the pericardium. When that sac becomes inflamed, the result is a sharp, stabbing chest pain that worsens when you cough, swallow, take a deep breath, or lie flat. The pain often improves when you lean forward. It can spread to your back, neck, or left shoulder.
Pericarditis is most often triggered by a viral infection, though it can also follow heart surgery, a heart attack, or an autoimmune condition. Because its symptoms overlap with a heart attack, any sharp left-sided chest pain with breathing difficulty warrants prompt medical attention.
Rib Injuries
A fractured or bruised rib on the left side produces pain that’s sharply localized and worsens with breathing, laughing, or pressing on the spot. You don’t need a major injury to fracture a rib. Severe coughing, a fall, or even a forceful twist during sports can do it. Standard chest X-rays miss a significant number of rib fractures. In one study of patients with no fractures visible on X-ray, ultrasound detected fractures in nearly 70% of them. CT scans are considered the most accurate tool, though minor fractures found on CT don’t always change how the injury is managed, since most rib fractures heal on their own over four to six weeks with pain control and gradual return to activity.
Kidney Problems
The left kidney sits toward the back, partially protected by the lower ribs. Kidney stones or a kidney infection can produce pain that wraps from the left flank around toward the front, settling under or behind the ribs. Kidney stone pain tends to come in intense waves and may be accompanied by blood in the urine, nausea, or pain that radiates down toward the groin. A kidney infection usually brings fever, chills, and pain when urinating along with the flank discomfort.
Signs That Need Immediate Attention
Most causes of pain under the left rib cage are not emergencies, but certain combinations of symptoms signal something more serious. Seek medical care if your pain comes with shortness of breath or a tight, squeezing sensation in the chest, which could indicate a cardiac event. Blood in your vomit or stool, high fever, dizziness or confusion, difficulty breathing, or yellowing of your skin and eyes are all red flags that call for prompt evaluation. Severe pain that’s getting steadily worse rather than coming and going also warrants a visit, as does left-sided pain during pregnancy, which can sometimes signal complications.