Pain on the left side of your abdomen can come from several different organs and structures, and the location, whether upper or lower, narrows the list considerably. The most common causes range from trapped gas and muscle strain to conditions like diverticulitis and kidney stones. Where exactly the pain sits, how it started, and what makes it worse are the best clues to what’s behind it.
Organs on the Left Side of Your Abdomen
Your left upper abdomen houses the stomach, spleen, the main body of the pancreas, the left portion of the kidney, the adrenal gland, and a sharp bend in the colon called the splenic flexure. Lower down, you’ll find the sigmoid colon, and in women, the left ovary and fallopian tube. Pain can originate from any of these structures, which is why doctors typically divide left-sided pain into upper and lower categories before working through the possibilities.
Upper Left Abdominal Pain
Trapped Gas at the Splenic Flexure
One of the most common and least serious causes of sharp upper left pain is splenic flexure syndrome. Your colon makes a tight turn near the spleen, and gas traveling through the large intestine can get stuck at this bend. When too much gas builds up, it stretches the colon wall and produces sharp pain in the upper left abdomen, along with bloating, fullness, and sometimes nausea. The pain can be severe enough to mimic something more dangerous, which often leads to a frustrating diagnostic process. Splenic flexure syndrome isn’t harmful, but the discomfort can significantly affect daily life until it’s managed, usually through dietary changes that reduce gas production.
Pancreatitis
The pancreas sits behind the stomach, and when it becomes inflamed, the main symptom is pain in the upper left or middle abdomen. Pancreatitis pain typically worsens within minutes of eating or drinking, especially fatty foods. It becomes constant and more severe over several days, and lying flat on your back tends to make it worse. A hallmark feature is that the pain radiates to the back or below the left shoulder blade. Acute pancreatitis can also cause nausea, fever, and a rapid pulse, and it often requires emergency care.
Enlarged Spleen
The spleen normally sits quietly under your left ribcage, and many people with an enlarged spleen have no symptoms at all. When symptoms do appear, they include pain or a sense of fullness in the upper left abdomen that can spread to the left shoulder. Viral infections like mononucleosis are a common trigger, but bacterial infections, liver disease, certain blood cancers, and autoimmune conditions like lupus can also cause the spleen to swell. An enlarged spleen is soft and vulnerable to rupture, particularly from trauma like a car accident, which can cause life-threatening internal bleeding.
Gastritis and Stomach Ulcers
Since the stomach itself sits in the upper left abdomen, inflammation of the stomach lining (gastritis) or ulcers can produce a burning or gnawing pain in this area. The pain often worsens after eating or on an empty stomach, depending on the cause. Overuse of anti-inflammatory painkillers and infection with a specific type of bacteria are the two most frequent culprits.
Lower Left Abdominal Pain
Diverticulitis
Diverticulitis is one of the most common causes of pain in the lower left abdomen, particularly in people over 50. Small pouches called diverticula form along the colon wall over time, and when one or more of these pouches become inflamed or infected, the result is sudden, intense pain in the lower left side. The pain can also start mild and gradually worsen over several days, fluctuating in intensity. Along with the pain, you may notice fever, nausea, tenderness when the area is pressed, and sudden changes in bowel habits like diarrhea or constipation.
A CT scan is the standard imaging test for suspected diverticulitis, with a sensitivity greater than 95% for detecting the condition. It also reveals whether complications like an abscess have formed, which influences how aggressively the problem needs to be treated.
Ovarian Cysts and Torsion
In women, a cyst on the left ovary can produce pain below the bellybutton on the left side. Most ovarian cysts are fluid-filled sacs that cause no symptoms and resolve on their own. Larger cysts, however, can create a dull ache or sharp pain that comes and goes. The bigger concern is ovarian torsion: when a large cyst shifts the ovary out of position and the ovary twists on itself, cutting off its blood supply. Torsion causes sudden, severe pelvic pain with nausea and vomiting and requires immediate medical attention.
Kidney Stones
A stone in the left kidney or ureter often starts as serious, sharp pain in the side and back below the ribs. As the stone moves through the urinary tract, the pain can shift, spreading to the lower abdomen and groin. The pain’s location and intensity change as the stone travels, which is a distinguishing feature. Fever and chills suggest an infection has developed alongside the stone.
Muscle and Rib-Related Causes
Not all left-sided pain originates from internal organs. Costochondritis, an inflammation of the cartilage connecting the ribs to the breastbone, causes pain in the upper and middle rib area that worsens when lying down, coughing, or taking deep breaths. It can mimic heart-related pain, which makes it particularly alarming. Muscle strains from exercise, heavy lifting, or even prolonged coughing can also produce localized pain on the left side of the abdomen that worsens with movement.
How to Tell What’s Serious
Certain features of abdominal pain signal that something needs urgent evaluation. Pain so severe it interrupts your ability to function, pain paired with vomiting to the point where you can’t keep liquids down, and pain combined with a complete inability to have a bowel movement are all reasons to seek emergency care. Fever alongside abdominal pain raises the possibility of infection, whether from diverticulitis, pancreatitis, or an infected kidney stone.
If you’ve had abdominal surgery in the past, new pain in the same area deserves attention because of the risk of adhesions or bowel obstruction. Similarly, if the pain resembles something you’ve experienced before but feels different this time, more severe, or accompanied by new symptoms, that change matters. Sudden, severe pain that comes on without warning is particularly concerning, as it can indicate ovarian torsion, a ruptured cyst, or a splenic rupture.
What to Expect During Diagnosis
For lower left pain, a CT scan is typically the first imaging test ordered, largely because diverticulitis is so common in that area and CT detects it reliably. For upper left pain, the approach depends on the suspected cause. Ultrasound is often used to evaluate the spleen and kidneys, while blood tests can flag pancreatic inflammation or infection. MRI is sometimes used as an alternative to CT for diverticulitis, with sensitivity between 86% and 94%, and avoids radiation exposure.
Many causes of left-sided abdominal pain share overlapping symptoms, so diagnosis can take time, especially when the pain is intermittent or mild. Keeping track of when the pain occurs, what makes it better or worse, and any other symptoms helps your provider narrow the possibilities faster.