Left-sided stomach pain has several possible causes, ranging from trapped gas to conditions involving your colon, kidney, spleen, or reproductive organs. The left side of your abdomen houses a distinct set of organs, and where exactly you feel the pain, whether it’s upper or lower, sharp or dull, helps narrow down what’s going on.
What’s on Your Left Side
Your left upper abdomen contains your stomach, spleen, the tail of your pancreas, your left kidney, and a sharp bend in your colon called the splenic flexure. Your left lower abdomen holds the descending and sigmoid colon, part of your small intestine, and part of your bladder. In women, the left fallopian tube and left ovary also sit in the lower left. Pain in either zone points to different conditions.
Gas and Constipation
The most common reason for left-sided abdominal pain is also the least worrying: trapped gas or backed-up stool. Your colon makes a sharp turn near your spleen before heading downward along your left side, and gas can get stuck at that bend. This is sometimes called splenic flexure syndrome. It causes bloating, fullness, nausea, and a sharp pain in the upper left abdomen that can feel alarming even though it’s harmless.
You’re more likely to get gas trapped there if you eat or drink quickly, chew gum (which causes you to swallow extra air), or eat foods with carbohydrates your small intestine can’t fully digest. Beans, cruciferous vegetables, carbonated drinks, and dairy products in people with lactose intolerance are common triggers. Some people are also born with an unusually tight curve in that section of the colon, making them more prone to it.
Constipation tends to cause pain on the left side because stool collects in the descending and sigmoid colon before a bowel movement. The pain is typically crampy, comes and goes, and improves after passing gas or having a bowel movement.
Diverticulitis
If your left lower abdomen hurts and the pain is steady, worsening, and accompanied by fever, diverticulitis is a likely suspect. Small pouches called diverticula can form along the wall of your colon, especially in the sigmoid colon on the lower left. Most people who develop these pouches never have problems, but roughly one in four will eventually have symptoms, and up to 5% will develop an episode of acute diverticulitis, where one or more pouches become inflamed or infected.
The pain typically settles in the lower left abdomen, stays constant rather than coming in waves, and worsens over hours to days. You may also have a fever, nausea, or a change in bowel habits. Diverticulitis is increasingly common in Western countries and becomes more prevalent with age. A CT scan of the abdomen and pelvis is the standard way to confirm it, with a sensitivity above 95% for detecting the condition and showing whether any complications like an abscess have formed.
Kidney Stones
A stone in your left kidney or left ureter (the tube connecting your kidney to your bladder) can cause intense pain on the left side of your back, flank, or lower abdomen. The pain often radiates from your side toward your groin. It’s sometimes described as colicky, meaning it comes in severe waves, then eases, then surges again. Many people say it’s the worst pain they’ve ever felt.
Along with the pain, you may notice blood in your urine (which can look pink, red, or brown), pain when urinating, a frequent urgent need to pee, or cloudy, foul-smelling urine. The combination of flank-to-groin pain with urinary changes is a strong signal that a kidney stone is involved rather than a digestive issue.
Spleen Problems
Your spleen sits in the upper left abdomen, tucked under your ribs. When it becomes enlarged, a condition called splenomegaly, it can cause pain or a sense of fullness in the left upper belly that sometimes spreads to the left shoulder. You might feel full after eating only a small amount because the swollen spleen presses on your stomach.
An enlarged spleen often produces no obvious symptoms at first. Other signs include frequent infections, easy bruising or bleeding, and fatigue from low red blood cell counts. Infections, liver disease, and certain blood disorders are common underlying causes. Pain in the left upper abdomen that gets worse when you take a deep breath warrants prompt medical attention, because a severely enlarged spleen can rupture.
Gynecological Causes
In women, left lower abdominal pain can originate from the left ovary or fallopian tube. An ovarian cyst that grows large, twists, or ruptures causes sudden, sharp pain on the affected side. The pain may be accompanied by bloating or a dull ache that builds over time.
An ectopic pregnancy, where a fertilized egg implants in the left fallopian tube instead of the uterus, is a more serious possibility. The first warning signs are typically light vaginal bleeding and pelvic pain. If the tube begins to rupture, you may feel severe abdominal pain, shoulder pain, or a sudden urge to have a bowel movement. A positive pregnancy test combined with one-sided pelvic pain and vaginal bleeding requires emergency care.
Upper Left vs. Lower Left Pain
Paying attention to where the pain sits can help you and your doctor zero in on the cause more quickly.
- Upper left, under the ribs: Splenic flexure gas, gastritis, an enlarged spleen, pancreatitis, or a left kidney stone.
- Lower left, near the hip bone: Diverticulitis, constipation, a kidney stone moving toward the bladder, or (in women) an ovarian cyst or ectopic pregnancy.
- Pain that moves or radiates: Kidney stones often start in the back or flank and travel toward the groin. Splenic issues can refer pain to the left shoulder. Ectopic pregnancy pain can radiate to the shoulder if internal bleeding irritates the diaphragm.
When Left-Sided Pain Is an Emergency
Most left-sided abdominal pain resolves on its own or with simple treatment. But certain combinations of symptoms signal something that needs immediate attention:
- Vomiting blood or black/bloody stool
- Blood in your urine
- A swollen, rigid, tender abdomen
- High fever with abdominal pain
- Chest pain, shortness of breath, or dizziness alongside abdominal pain
- Severe pelvic pain with vaginal bleeding (especially with a positive pregnancy test)
- Persistent nausea or vomiting that won’t stop
These can indicate a ruptured organ, internal bleeding, a serious infection, or a bowel obstruction. Pain that started mild but has become progressively worse over hours, or pain so severe you can’t stand up straight or find a comfortable position, also warrants urgent evaluation.