Pain in the lower left side of your stomach most commonly comes from the colon, specifically the descending and sigmoid colon that run down the left side of your abdomen before connecting to the rectum. But several other organs sit in this area too, including portions of the small intestine, the left ureter (the tube connecting your kidney to your bladder), and in women, the left ovary and fallopian tube. The cause of your pain depends on what the pain feels like, how long it’s lasted, and what other symptoms come with it.
Diverticulitis: The Most Common Cause
If you’re over 40 and the pain came on suddenly, diverticulitis is one of the first things to consider. This happens when small pouches that form in the colon wall become inflamed or infected. Left lower quadrant pain is the hallmark symptom, often accompanied by fever, changes in bowel habits, or nausea. The condition used to be considered a problem mainly for older adults, but the rate in people aged 40 to 49 increased by 132% between 1980 and 2007, so it’s no longer unusual in younger people either.
One important detail: clinical suspicion alone is only correct in 40 to 65% of cases. That means even experienced clinicians frequently mistake other conditions for diverticulitis, or vice versa. A CT scan of the abdomen and pelvis is the standard way to confirm the diagnosis, with about 95% accuracy. For mild, uncomplicated cases in otherwise healthy people, treatment may just involve a clear liquid diet while symptoms are at their worst, with food gradually reintroduced as things improve. Antibiotics aren’t always necessary for mild episodes, though they’re recommended when symptoms are more severe or when you have other health conditions.
Digestive Causes Beyond Diverticulitis
Irritable bowel syndrome (IBS) is a common explanation for recurring lower left pain that comes and goes over months. The pattern to look for: abdominal pain or discomfort at least three days per month for the past three months, linked to at least two of these features. The pain improves after a bowel movement. It started around the same time your stool frequency changed. Or it started when your stool began looking different (harder, looser, or more irregular than usual). IBS doesn’t cause structural damage, but the discomfort is real and can significantly affect daily life.
Constipation is another straightforward possibility. Stool tends to accumulate in the sigmoid colon on the lower left side before a bowel movement, and when things back up, you can feel cramping, pressure, or a dull ache in that exact spot. Gas trapped in the colon can produce similar sharp, fleeting pains that shift around.
Causes Specific to Women
Several gynecological conditions produce pain that localizes to the lower left abdomen. Ovarian cysts on the left ovary can cause a dull ache or sudden sharp pain, especially if a cyst ruptures or twists. Ovulation itself sometimes causes temporary one-sided pain (called mittelschmerz) around the middle of your cycle, lasting anywhere from a few minutes to a couple of days.
Endometriosis, where tissue similar to the uterine lining grows outside the uterus, can cause chronic pelvic pain that worsens with periods. Pelvic inflammatory disease, an infection of the reproductive organs usually caused by sexually transmitted bacteria, produces lower abdominal pain along with unusual discharge, fever, or pain during sex. An ectopic pregnancy, where a fertilized egg implants in the fallopian tube instead of the uterus, causes sharp, worsening pain on one side and is a medical emergency.
Kidney Stones and Urinary Causes
A stone moving through the left ureter can produce intense pain that starts in the flank (the side of your back below the ribs) and radiates downward into the lower abdomen, groin, or even the labia or testicle. This pain typically peaks within 90 to 120 minutes and comes in waves. It’s often described as the worst pain people have experienced. Blood in the urine, nausea, and an urgent need to urinate are common accompanying symptoms. If the pain is more of a constant, deep ache without those wave-like surges, a kidney stone is less likely.
Hernias and Muscle Strain
An inguinal hernia occurs when tissue pushes through a weak spot in the abdominal wall near the groin. You might notice a visible bulge, along with discomfort, heaviness, or a burning feeling in the groin area. These symptoms tend to get worse when you strain, lift, cough, or stand for long periods, and improve when you lie down. Inguinal hernias form on the right side more often than the left, but they can happen on either side.
Sometimes the pain is coming from the abdominal wall itself rather than from an internal organ. A pulled muscle or a nerve irritation in the abdominal wall can mimic deeper problems. There’s a useful clue to tell them apart: if you can point to the exact spot of pain with a single fingertip, and the pain stays the same or gets worse when you tense your stomach muscles (like doing a partial sit-up), it’s more likely a wall issue. Internal organ pain tends to be harder to pinpoint and often comes with other symptoms like fever, nausea, changes in appetite, or abnormal bowel habits.
When the Pain Needs Urgent Attention
Most lower left abdominal pain turns out to be something manageable, but certain patterns signal a potentially serious problem. Seek emergency care if you experience sudden, severe pain that came on quickly, especially with any of the following:
- Rigid or very tender abdomen that hurts more when someone presses and releases (rebound tenderness)
- Fever with worsening pain
- Blood in your stool or vomit, or dark, tarry stools
- Signs of shock such as dizziness, rapid heartbeat, or feeling faint
- Severe pain with a positive pregnancy test
One practical test from emergency medicine: if hitting a bump while riding in a car makes the pain significantly worse, that’s a sign of peritoneal irritation, which needs prompt evaluation. The same applies if walking or any jarring movement intensifies the pain considerably.
How the Cause Gets Identified
Your doctor will start with your symptoms, medical history, and a physical exam. If imaging is needed, CT scans are the most accurate tool for this area of the body. For diverticulitis, CT picks up the diagnosis about 81% of the time compared to 61% for ultrasound. Ultrasound is often used first in women of childbearing age because it’s effective for gynecological causes and avoids radiation exposure. For suspected kidney stones, CT is again the preferred option.
In cases where the pain is chronic and linked to bowel habits, your doctor may diagnose IBS based on your symptom pattern alone, since the condition doesn’t produce visible abnormalities on imaging. The diagnosis requires that symptoms have been present for at least six months, so a single episode of pain wouldn’t qualify.