Pain in the lower left abdomen most commonly comes from the sigmoid colon, the S-shaped section of the large intestine that sits in that area. Diverticulitis, an inflammation of small pouches in the colon wall, is the single most frequent diagnosis. But several other structures live in or near the lower left quadrant, including the left ureter, left ovary, and portions of the small intestine, and problems with any of them can produce pain in the same spot.
Diverticulitis
Small bulging pouches called diverticula form along weak spots in the colon wall, and they tend to develop in the lower portion of the colon, right where it curves through the left side of the abdomen. When one or more of those pouches becomes inflamed or infected, the result is diverticulitis. The hallmark is a steady, aching pain in the lower left abdomen, often accompanied by fever, nausea, and a change in bowel habits.
Diverticulitis has historically been considered a condition of people over 65, but rates among younger adults are climbing fast. The incidence among people aged 18 to 44 rose from 0.15 to 0.25 per 1,000 within just seven years, and acute cases among those aged 40 to 49 increased by 132% between 1980 and 2007. Younger patients, particularly men who smoke or drink regularly, actually tend to develop more serious complications at the time of diagnosis, including abscesses and perforations. About 15% of people with diverticulitis develop complications such as a pus-filled abscess, a blockage in the colon, an abnormal connection (fistula) between the bowel and another organ, or a tear in the colon wall that leaks waste into the abdominal cavity.
Mild cases are typically treated at home with antibiotics and a temporary liquid or low-fiber diet. Complicated cases, especially those involving perforation, often require hospitalization or surgery.
Irritable Bowel Syndrome
IBS is one of the most common reasons for recurring lower abdominal pain, and many people feel it most prominently on the left side because the descending and sigmoid colon sit there. The pain tends to come and go rather than stay constant, and it’s closely linked to bowel movements. You might notice the pain eases after going to the bathroom, or that it flares when your stool consistency changes.
A diagnosis generally requires recurrent abdominal pain at least one day per week for the past three months, connected to at least two of the following: the pain relates to defecation, it comes with a change in how often you go, or it comes with a change in stool appearance. Symptoms also need to have started at least six months before diagnosis. Unlike diverticulitis or colitis, IBS doesn’t cause visible damage to the intestinal lining, which is why imaging and lab work often come back normal. Treatment focuses on dietary changes, stress management, and sometimes medications to manage specific symptoms like cramping or diarrhea.
Left-Sided Ulcerative Colitis
Ulcerative colitis is an inflammatory bowel disease that starts in the rectum and can extend upward. When inflammation reaches through the sigmoid and descending colon, it’s classified as left-sided colitis, and it produces pain concentrated in the lower left abdomen. The key symptoms are bloody diarrhea, belly cramps, and tenesmus, a persistent urge to have a bowel movement even when the bowel is empty.
A milder form called proctosigmoiditis involves only the rectum and sigmoid colon. In the most limited version, ulcerative proctitis, inflammation stays in the rectum alone, and rectal bleeding or urgency may be the only noticeable sign. Diagnosis requires a colonoscopy, during which a doctor views the colon lining with a small camera and takes tissue samples for biopsy. Treatment depends on how far the inflammation extends and how severe it is.
Kidney Stones in the Left Ureter
A kidney stone that moves out of the kidney and into the ureter (the thin tube connecting the kidney to the bladder) can cause intense pain that radiates from the back or side down into the lower abdomen. If the stone is traveling through the left ureter, the pain lands squarely in the lower left quadrant. This pain is distinctive: it comes in sharp waves, often described as the worst pain a person has ever felt, and it can shift location as the stone moves.
Stones smaller than 4 millimeters (roughly a quarter of an inch) typically pass on their own within one to two weeks. Larger stones may need intervention to break them up or remove them. Blood in the urine, nausea, and a frequent urge to urinate are common accompanying symptoms.
Ovarian Cysts
For people with ovaries, a cyst on the left ovary is a common cause of lower left abdominal pain. Most ovarian cysts form during the menstrual cycle and resolve on their own without treatment. They often cause a dull ache or sense of pressure. The situation changes if a cyst ruptures: that typically produces sudden, sharp pain on one side of the lower abdomen.
Most ruptured cysts cause temporary pain that resolves as the fluid is reabsorbed. Some, however, cause significant internal bleeding that needs immediate medical attention. Severe lower abdominal pain with lightheadedness, rapid heartbeat, or heavy vaginal bleeding after a sudden onset of pain warrants emergency care.
Inguinal Hernia
An inguinal hernia occurs when tissue, usually part of the intestine, pushes through a weak spot in the abdominal wall near the groin. It shows up as a bulge on one or both sides of the pubic bone that becomes more obvious when you stand, cough, or strain. The pain is typically a burning or aching sensation at the bulge, along with pressure in the groin that worsens with bending, lifting, or coughing.
Men are 8 to 10 times more likely than women to develop inguinal hernias. Other risk factors include aging, previous hernia repair, pregnancy, chronic coughing (including from smoking), and straining during bowel movements. The concern is strangulation, where the trapped tissue loses its blood supply. Warning signs include sudden worsening pain, nausea or vomiting, fever, and a bulge that turns red, purple, or dark. A strangulated hernia requires emergency surgery.
How Doctors Identify the Cause
A CT scan is the recommended first-line imaging test for lower left quadrant pain. It has a sensitivity greater than 95% for detecting diverticulitis specifically, and it can also identify kidney stones, abscesses, hernias, and other abnormalities in a single scan. Ultrasound is sometimes used, particularly when evaluating ovarian cysts or when avoiding radiation exposure is a priority, but its sensitivity for conditions like diverticulitis is less consistent than CT.
Beyond imaging, your doctor will rely heavily on the character of the pain itself. Constant, localized pain with fever points toward diverticulitis or another infection. Crampy pain that improves after a bowel movement suggests IBS. Wave-like pain radiating from the flank hints at a kidney stone. Sudden, one-sided pain in someone with ovaries raises suspicion for a cyst. A visible bulge near the groin makes a hernia the likely answer.
When the Pain Needs Emergency Care
Most causes of lower left abdominal pain are manageable and not immediately dangerous, but certain patterns signal something that can’t wait. Get to an emergency room if you experience pain with uncontrollable vomiting or an inability to keep liquids down, severe constipation with inability to pass stool or gas (especially if you’ve had prior abdominal surgery), or pain that resembles a previous episode but is noticeably more severe or different in character.
A rigid abdomen that hurts more when you release pressure than when you press in, a high fever alongside abdominal pain, or any signs of a strangulated hernia (sudden severe pain, discolored bulge, vomiting) all require immediate evaluation. Significant rectal bleeding or blood in the urine alongside pain also moves the timeline from “schedule an appointment” to “go now.”