Pain in the lower left side of your abdomen usually comes from the digestive tract, most commonly trapped gas, constipation, or diverticulitis. This area of your body houses the descending colon, the S-shaped sigmoid colon, parts of the small intestine, and the left ureter. In women, the left ovary and fallopian tube sit here too. The cause can range from completely harmless to something that needs prompt medical attention, and the specific quality of the pain, how it started, and what other symptoms you have are the best clues to tell the difference.
Trapped Gas and Constipation
The most common reason for lower left abdominal pain is also the least serious: gas trapped in the descending or sigmoid colon. The left side of the colon has a natural bend where gas can pool, creating sharp or crampy pain that shifts around and comes in waves. You might feel bloated, hear rumbling, or notice the pain gets worse after eating. The key giveaway is that the pain tends to improve after passing gas or having a bowel movement.
Constipation works similarly. Stool building up in the sigmoid colon creates pressure and cramping on the lower left side. If you haven’t had a regular bowel movement in a few days and the pain feels dull or achy rather than sharp, constipation is a likely culprit. Gentle movement can help with both issues. Lying on your back and pulling your knees to your chest, doing a seated forward bend, or squatting can help release trapped gas. Lying twists, where you lower bent knees to each side while keeping your back flat, also stretch the lower abdomen and encourage things to move along.
Diverticulitis
Diverticulitis is the most important diagnosis to consider when pain in the lower left abdomen is persistent, worsening, or accompanied by fever. It happens when small pouches that form in the wall of the colon become inflamed or infected. Left lower abdominal pain is the most common symptom, showing up in about 70% of patients. You may also have nausea, bloating, constipation, or a change in bowel habits alongside the pain.
Diverticulitis has traditionally been thought of as a condition affecting older adults, with roughly 60% of people over 60 having these pouches in their colon. But it’s increasingly common in younger people. Hospital admissions for diverticulitis in patients under 45 increased by more than 70% between 1998 and 2005, and the percentage of cases in people under 50 has risen nearly fivefold in recent years, reaching as high as 18% to 34% in some studies. If your lower left pain is steady rather than crampy, gets worse over a day or two, and comes with a low-grade fever, diverticulitis is worth considering regardless of your age.
IBS and Inflammatory Bowel Disease
Irritable bowel syndrome (IBS) frequently causes pain on the lower left side because the sigmoid colon is one of the most sensitive segments of the gut. IBS pain tends to be chronic, recurring over weeks or months, and often comes with constipation alternating with diarrhea, gassiness, bloating, and mucus in the stool. A hallmark feature is that the pain improves after a bowel movement. IBS doesn’t cause visible inflammation or damage to the intestines. There’s no bleeding, no fever, and no weight loss.
Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, can cause similar cramping and diarrhea but is a fundamentally different condition. IBD causes actual inflammation and damage to the intestinal wall that shows up on imaging and colonoscopy. If your lower left pain comes with blood in your stool, unexplained weight loss, anemia, or fever, those are red flags that point toward IBD rather than IBS. IBD also carries an increased risk of colon cancer over time, while IBS does not.
Kidney and Ureteral Stones
The left ureter, the tube that carries urine from the kidney to the bladder, runs through the lower left abdomen. A stone passing through the lower portion of the ureter can cause sudden, severe pain in this area. The pain is typically sharp and comes in intense waves as the ureter contracts to push the stone along. You may also notice blood in your urine, nausea, vomiting, or an urgent need to urinate frequently.
Ureteral stones are most common in men between 20 and 50. When a stone sits low in the ureter, the pain can radiate into the groin or, in men, the testicle, because both areas share the same nerve pathways. This type of pain is hard to get comfortable with. Unlike gas pain, changing positions doesn’t help, and it often drives people to the emergency room purely because of its intensity.
Gynecological Causes in Women
Women have additional structures in the lower left abdomen that can be a source of pain. The most common gynecological causes are ovarian cysts, pelvic inflammatory disease (PID), and ovarian torsion.
A ruptured ovarian cyst causes sudden, sharp pain on one side of the lower abdomen. It typically happens mid-cycle and resolves on its own within hours to a day or two. PID, an infection of the reproductive organs usually caused by sexually transmitted bacteria, produces a duller, more constant pelvic pain that may come with abnormal vaginal discharge or bleeding, pain during sex, and fever.
Ovarian torsion, where the ovary twists on itself and cuts off its blood supply, is less common but more urgent. It causes severe, sudden, one-sided pain with nausea and vomiting. Cysts or tumors larger than 5 cm increase the risk. This is a surgical emergency.
In pregnant women, lower left pain raises concern for ectopic pregnancy, where a fertilized egg implants in the left fallopian tube instead of the uterus. This typically causes pain between 6 and 10 weeks of pregnancy, often alongside vaginal bleeding. A ruptured ectopic pregnancy is life-threatening and requires immediate emergency care.
Inguinal Hernia
An inguinal hernia occurs when tissue pushes through a weak spot in the abdominal wall near the groin. The hallmark sign is a visible bulge on one side of the pubic bone that becomes more obvious when you stand up, cough, or strain. The pain or pressure tends to worsen when bending over, coughing, or lifting something heavy, and it often eases when you lie down. Inguinal hernias are far more common in men but can occur in women as well. They don’t resolve on their own and typically require surgical repair if they cause symptoms.
When the Pain Needs Urgent Attention
Most lower left abdominal pain turns out to be gas, constipation, or a mild flare of a chronic condition. But certain features signal something more serious. Pain that comes on suddenly and is severe from the start raises concern for a vascular emergency, a ruptured cyst, or ovarian torsion. A rigid abdomen that feels board-like when you press on it suggests the lining of the abdominal cavity is inflamed. Pain that wakes you from sleep is considered serious until proven otherwise.
Blood in your stool alongside significant abdominal pain raises suspicion for compromised blood flow to the intestines. Fainting, lightheadedness, or a rapid pulse with abdominal pain can indicate internal bleeding. And a sudden urge to have a bowel movement during intense abdominal pain has been described as a warning sign for serious conditions like a ruptured aneurysm in older adults or ruptured ectopic pregnancy in younger women.
How Doctors Figure Out the Cause
Your doctor will start with your symptoms and a physical exam, but imaging is often needed to pin down a diagnosis. Ultrasound is typically the first choice because it’s quick, widely available, and doesn’t involve radiation. It’s particularly useful for gynecological causes and is the standard first-line tool for evaluating pelvic pain in women.
CT scans are more accurate for several key conditions. For diverticulitis, CT catches 81% of cases compared to 61% for ultrasound. For appendicitis (which can occasionally cause left-sided pain), CT sensitivity is 94% versus 76% for ultrasound. Many guidelines recommend starting with ultrasound and moving to a CT scan if the results are negative or unclear. The tradeoff is radiation exposure, which is why ultrasound remains the preferred starting point, especially in younger patients and women of childbearing age. MRI is sometimes used as a second-line option when ultrasound or CT results need further clarification.