Pain on the left side of your abdomen can come from dozens of different structures, from your colon and kidney to your stomach, spleen, and abdominal wall muscles. The most common cause in adults over 40 is diverticulitis, but the location of the pain (upper versus lower) and how it started (sudden versus gradual) narrow the possibilities considerably.
Your left abdomen is divided into two zones. The upper left holds your stomach, spleen, tail of the pancreas, left kidney, and part of the colon. The lower left holds the descending and sigmoid colon, part of the small intestine, and in women, the left ovary and fallopian tube. Pain in each zone points to different problems.
Lower Left Abdominal Pain
Diverticulitis
Diverticulitis is the single most likely diagnosis when pain is isolated to the lower left abdomen, especially if you’re over 40. Small pouches that form in the colon wall become inflamed or infected, producing a steady, aching pain that can last for days. You may also notice bloating, fever, loss of appetite, or changes in bowel habits. Tenderness limited to the lower left quadrant is the most specific physical finding for diverticulitis, making it roughly 10 times more likely than other diagnoses when that pattern is present.
Diverticular disease is uncommon before age 40 (affecting fewer than 10% of people) but becomes extremely prevalent with age, reaching about 80% in people older than 85. Most people with diverticula never develop symptoms, so having them doesn’t guarantee pain. When symptoms do appear, a CT scan with contrast is the preferred way to confirm the diagnosis and check for complications like a perforation or abscess.
Constipation and Gas
The descending colon runs down the entire left side of your abdomen, so trapped stool or gas frequently causes left-sided cramping. This pain tends to come and go, shifts location slightly, and improves after a bowel movement or passing gas. It’s one of the most common and least dangerous explanations for left-sided discomfort.
Irritable Bowel Syndrome
IBS can produce recurring crampy pain anywhere in the abdomen, but the lower left is a frequent site because the sigmoid colon (the S-shaped segment just before the rectum) is prone to spasm. The hallmark of IBS is that pain improves or worsens with bowel movements and accompanies changes in stool consistency or frequency. There’s no structural damage visible on imaging, which distinguishes it from diverticulitis or inflammatory bowel disease.
Kidney Stones
A stone moving through the left kidney or ureter causes intense, wave-like pain that typically starts in the flank (the area between your ribs and hip on the back side) and radiates forward and downward toward the groin. The pain comes in waves as the ureter squeezes to push the stone along. Blood in the urine, nausea, and an urgent need to urinate are common alongside the pain. Kidney stone pain rarely stays in one spot. It shifts as the stone moves.
Ovarian Cysts and Gynecological Causes
In women, the left ovary sits in the lower left pelvis. A cyst on the left ovary can cause a dull ache or sudden sharp pain if it ruptures or twists. A ruptured cyst can cause severe pain and internal bleeding. Sudden, intense pelvic pain with lightheadedness, rapid breathing, or cold and clammy skin is an emergency regardless of the cause.
An ectopic pregnancy on the left side (where a fertilized egg implants in the left fallopian tube instead of the uterus) also produces sharp lower left pain, often with vaginal bleeding and dizziness. This is a life-threatening condition that requires immediate treatment.
Upper Left Abdominal Pain
Splenic Flexure Syndrome
One of the more underrecognized causes of upper left pain is splenic flexure syndrome. Your colon makes a sharp turn just below the spleen, and gas can get stuck at that bend. The result is bloating, pressure, and pain in the upper left abdomen that can feel alarmingly intense for something so benign. Think of water rushing toward a sharp bend in a river: too much volume overwhelms the curve. Some people are born with an unusually tight bend that makes them more prone to this. The pain typically resolves once the gas moves through.
Enlarged Spleen
The spleen sits just under your left rib cage. When it enlarges (from infections, liver disease, blood disorders, or other causes), it produces a full or aching feeling in the upper left abdomen that can radiate to the left shoulder or back. Pain that worsens when you breathe in is particularly concerning because it can signal that part of the spleen’s tissue has lost blood supply. A severely enlarged spleen can outgrow its own blood supply, causing tissue to die, which is a surgical emergency.
Gastritis and Stomach Ulcers
Your stomach sits in the upper left portion of your abdomen. Inflammation of the stomach lining (gastritis) or an ulcer produces a burning or gnawing pain just below the left rib cage or in the upper center of the abdomen. Eating may make the pain better or worse depending on the specific cause. Warning signs of a bleeding ulcer include vomiting blood, vomit that looks like coffee grounds, or black, tarry stools.
Pancreatitis
The tail of the pancreas extends into the upper left abdomen. Inflammation of the pancreas causes a deep, boring pain that often radiates straight through to the back. It typically worsens after eating, especially fatty meals, and may improve when you lean forward. Pancreatitis pain is usually severe enough that it’s hard to ignore, and it’s often accompanied by nausea and vomiting.
Abdominal Wall Pain
Not all left-sided pain comes from internal organs. Strained muscles, nerve entrapment, or inflammation in the abdominal wall itself can mimic deeper problems. This is more common than many people realize and often leads to unnecessary imaging and specialist visits. The key difference is that abdominal wall pain gets worse when you tense your muscles (like sitting up from a lying position) while pain from internal organs tends to feel the same or even improve with that movement. Doctors use a simple physical exam maneuver to test this: they press on the sore spot, then ask you to lift your head and shoulders off the table. If the pain stays the same or gets worse, the problem is likely in the wall rather than inside.
When Left-Sided Pain Is an Emergency
Most left-sided abdominal pain turns out to be something manageable, but certain patterns require immediate attention. Sudden, severe pain that radiates to your back, groin, or legs could signal a ruptured abdominal aortic aneurysm, particularly in older adults with a history of high blood pressure or smoking. Feeling faint or lightheaded alongside abdominal pain suggests internal bleeding, whether from a ruptured cyst, ectopic pregnancy, or vascular emergency.
Other combinations that warrant urgent evaluation: pain with a high fever and rigid abdomen (suggesting infection or perforation), pain with bloody or black stools (suggesting a bleeding ulcer or other gastrointestinal bleed), and pain that started mild but is steadily getting worse over hours. Abdominal pain that is escalating rather than stable is a consistent red flag across nearly every serious cause.
How Doctors Narrow the Diagnosis
Your doctor will start by asking where exactly the pain is, when it started, what makes it better or worse, and what other symptoms you have. The physical exam, including pressing on the abdomen to locate tenderness, provides surprisingly strong diagnostic clues. Isolated lower left tenderness in a middle-aged or older adult, for instance, points strongly toward diverticulitis without any imaging at all.
When imaging is needed, CT with contrast is the most informative test for both upper and lower left abdominal pain. It picks up diverticulitis, splenic problems, kidney stones, abscesses, and many other causes in a single scan. Ultrasound is a reasonable first step when spleen enlargement is suspected or in pregnant women, but it misses many conditions that CT catches. One study found ultrasound detected only 18% of splenic infarcts that were visible on CT. Blood work and a urine sample round out the initial evaluation, helping to identify infection, inflammation, or urinary tract involvement.