Pain in the left side of your abdomen can come from dozens of different structures, from your large intestine and stomach to your kidney, spleen, and (in women) the left ovary. The cause depends heavily on where exactly the pain sits, whether it’s upper or lower, and what other symptoms come with it. Here’s a breakdown of the most common reasons, organized by location.
Lower Left Abdomen: The Most Common Culprits
Diverticulitis
This is one of the most frequent causes of pain in the lower left abdomen, especially in adults over 40. Small pouches called diverticula form along the wall of the large intestine, particularly in the sigmoid colon, which sits in your lower left side. When one or more of these pouches becomes inflamed or infected, the result is a steady, often worsening pain in that area. You may also notice fever, nausea, tenderness when you press on your belly, and sudden changes in bowel habits like diarrhea or constipation.
Diverticulitis is no longer just a condition of older adults. A UCLA Health analysis of 5.2 million hospitalizations for diverticulitis between 2005 and 2020 found that about 16% of cases occurred in patients younger than 50. More concerning, the proportion of younger patients admitted with complicated diverticulitis (involving abscesses or perforations) rose from 18.5% to 28.2% over that period, a 52% relative increase.
Irritable Bowel Syndrome
IBS frequently causes cramping and pain on the left side because the descending and sigmoid colon run along that area. The pain is typically tied to bowel movements: it gets worse before you go and often improves afterward. Bloating, gas, and alternating constipation and diarrhea are hallmarks. Unlike diverticulitis or inflammatory bowel disease, IBS doesn’t damage your intestinal tissue or raise your risk of colorectal cancer. It’s a functional disorder, meaning the gut looks normal on imaging but doesn’t work the way it should.
Ovarian Cysts (Women)
A cyst on the left ovary can produce a dull ache or sharp pain below the bellybutton on the left side. Most ovarian cysts are small, cause no symptoms, and resolve on their own within a few menstrual cycles. Larger cysts are more likely to cause fullness, pressure, or bloating in the abdomen.
Two complications make ovarian cysts more urgent. Ovarian torsion happens when a large cyst causes the ovary to twist on itself, cutting off its blood supply. This triggers sudden, severe pelvic pain along with nausea and vomiting. A ruptured cyst can cause intense pain and internal bleeding. Either situation needs immediate medical attention, particularly if the pain comes on suddenly and is accompanied by fever, vomiting, cold or clammy skin, rapid breathing, or lightheadedness.
Upper Left Abdomen: Spleen, Stomach, and Pancreas
Enlarged Spleen
Your spleen sits just under your rib cage on the left side, tucked next to your stomach. When it becomes enlarged (a condition called splenomegaly), you may feel pain or fullness in the upper left abdomen that sometimes spreads to your left shoulder. Infections, liver disease, and certain blood disorders can all cause the spleen to swell. Pain that worsens when you take a deep breath is a notable sign worth getting checked promptly.
Gastritis and Peptic Ulcers
The stomach sits in the upper left portion of the abdomen. Inflammation of the stomach lining (gastritis) or an open sore in the stomach or upper small intestine (peptic ulcer) can both produce a burning or gnawing pain in this region. The pain often gets worse on an empty stomach or after eating acidic or spicy foods. Nausea, a feeling of fullness, and occasionally dark stools (a sign of bleeding) can accompany it.
Pancreatitis
The pancreas stretches across the upper abdomen, and inflammation here typically causes pain in the upper left or center of the belly that may radiate to the back. Pancreatitis pain tends to be severe and constant rather than crampy, and it often worsens after eating. Gallstones and heavy alcohol use are the two leading triggers. Nausea, vomiting, and a rapid pulse are common alongside the pain.
Kidney Stones on the Left Side
A stone in the left kidney or ureter can cause pain anywhere from the left flank (the side of your back below the ribs) down into the lower abdomen, groin, or even the testicle or labia. The pain pattern depends on where the stone is lodged. Stones stuck high in the ureter tend to radiate to the flank and lower back. Stones farther down radiate forward into the lower belly and groin.
Kidney stone pain is notorious for its severity. It comes in waves (colicky pain), often builds abruptly, and can be accompanied by nausea, vomiting, and blood in the urine. About 85% of people with kidney stones will have at least microscopic blood in their urine, but 15% won’t, so the absence of blood doesn’t rule stones out. If a stone sits near the bladder, it can mimic a urinary tract infection, causing frequent urination, urgency, and burning with urination.
Less Obvious Causes: Heart and Blood Vessels
Upper left abdominal pain isn’t always about the digestive system. Heart conditions, including angina, heart attack, and inflammation of the sac around the heart (pericarditis), can produce pain that feels like it’s in the upper left abdomen rather than the chest. This is more likely if the pain comes on with exertion, is accompanied by shortness of breath, or radiates to the jaw, arm, or back. Vascular problems like aortic dissection or reduced blood flow to the intestines (mesenteric ischemia) also present in this area, though both are rare and tend to cause sudden, severe symptoms.
How the Pain Feels Matters
The character of your pain gives important clues about its source. Sharp, sudden pain that makes it hard to sit still points toward something acute like a kidney stone, ovarian torsion, or a ruptured cyst. Steady, worsening pain with fever and tenderness suggests an inflammatory or infectious process like diverticulitis. A dull ache that comes and goes with meals or bowel movements is more consistent with gastritis, IBS, or constipation. Pain that starts around the belly button and migrates to a specific spot tends to be more concerning than vague, shifting discomfort.
Location also narrows things down. Lower left pain in someone over 40 with fever immediately raises suspicion for diverticulitis. Upper left pain that spreads to the shoulder suggests the spleen. Flank pain radiating to the groin with bloody urine is classic for a kidney stone.
How Doctors Figure Out the Cause
When you describe left-sided abdominal pain, expect questions about exactly where it hurts, when it started, whether it’s constant or comes in waves, what makes it better or worse, and whether you have fever, nausea, changes in urination, or changes in bowel habits. These details help narrow a broad list of possibilities quickly.
CT scans are the recommended first imaging test for left lower quadrant pain. CT has a sensitivity of over 95% for detecting diverticulitis and can reveal abscesses, perforations, kidney stones, and ovarian problems in a single scan. For upper left pain, CT is also valuable because it can image the pancreas, spleen, kidneys, intestines, and blood vessels all at once. Ultrasound is often used first in women of childbearing age to evaluate for ovarian cysts or ectopic pregnancy, and blood and urine tests help identify infection, inflammation, or bleeding.
When Left-Sided Pain Is an Emergency
Most left-sided abdominal pain turns out to be something manageable, but certain combinations of symptoms signal a more dangerous situation. Severe pain that keeps you from sitting still or finding a comfortable position warrants immediate medical attention. The same goes for abdominal pain paired with fever, persistent vomiting, a bloated or rigid abdomen, reduced urine output, or signs of shock like cold and clammy skin, rapid breathing, and lightheadedness. Severe pain following an accident or injury also needs emergency evaluation. These patterns can indicate peritonitis (infection of the abdominal lining), a perforated organ, or internal bleeding, all of which require urgent treatment.