The lower left side of your abdomen contains part of your colon (specifically the descending and sigmoid colon), the left ureter, the lower portion of your left kidney, and, in women, the left ovary and fallopian tube. In men, the left spermatic cord runs through this area. When you feel pain here, one of these structures is almost always involved, and the specific cause ranges from very common and harmless to something that needs prompt attention.
Key Organs and Structures
The most prominent organ in the lower left quadrant is the sigmoid colon, the S-shaped section of your large intestine that connects to your rectum. Because it sits directly in this region, the sigmoid colon is responsible for the majority of pain that people feel here. Behind and slightly to the side lies the left ureter, a narrow muscular tube that carries urine from the left kidney down to the bladder. The lower tip of the left kidney also extends into this zone.
In women, the left ovary and left fallopian tube occupy the lower part of this quadrant, close to where the pelvic area begins. In men, the spermatic cord passes through the inguinal canal in this region. Blood vessels, lymph nodes, and muscles of the abdominal wall round out the anatomy.
Diverticulitis: The Most Common Cause
If you’re over 40 and feeling a steady, aching pain in the lower left side, diverticulitis is the first condition doctors consider. It happens when small pouches that form in the wall of the colon (diverticula) become inflamed or infected. The pain is typically constant rather than crampy, and it often comes with fever, bloating, and changes in bowel habits like constipation or diarrhea. Some people also notice nausea or pain when urinating, because the inflamed colon sits close to the bladder.
Diverticulitis has traditionally been thought of as an older person’s condition, but that’s changing. A UCLA analysis of 5.2 million U.S. hospital admissions between 2005 and 2020 found that about 16% of diverticulitis cases occurred in patients younger than 50. More concerning, the proportion of younger patients with complicated diverticulitis (involving abscesses or perforations) rose by 52% over that period. So while age increases risk, this is no longer a diagnosis reserved for seniors.
A CT scan of the abdomen and pelvis is the standard way to confirm diverticulitis. It has about 98% diagnostic accuracy and can also reveal complications or an alternative diagnosis. Ultrasound is sometimes used in other countries but is less reliable, especially in people with higher body weight or when the inflammation is deep in the pelvis.
Bowel Conditions: IBS and IBD
Irritable bowel syndrome (IBS) is a common cause of recurring left-sided abdominal pain, especially in younger adults. The hallmarks are chronic abdominal pain that improves after a bowel movement, alternating constipation and diarrhea, bloating, and gassiness. IBS does not damage the intestine and doesn’t raise your risk of colon cancer. It’s diagnosed based on a pattern of symptoms lasting at least 12 weeks over the past year, not by imaging, because nothing abnormal shows up on scans or colonoscopy.
Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, is a separate and more serious condition. Unlike IBS, IBD causes visible inflammation and can permanently damage the intestines. It also carries an increased risk of colon cancer. The key distinguishing symptoms are bleeding, unexplained weight loss, anemia, and fever. If you have abdominal pain along with any of those, the cause is more likely to be inflammatory rather than functional.
Kidney Stones in the Left Ureter
When a kidney stone drops from the left kidney into the left ureter, the pain is hard to miss. It typically starts as severe, wave-like pain in the back or side below the ribs, then radiates into the lower abdomen and sometimes toward the groin. Unlike diverticulitis pain, which is constant and dull, stone pain comes in intense surges that make it nearly impossible to sit still. Nausea, vomiting, and bloody or discolored urine are common. You may also feel a persistent urge to urinate but only pass small amounts.
The character of the pain is one of the most useful clues. People with kidney stones tend to pace or shift positions constantly, while people with conditions involving the lining of the abdomen (like a perforated diverticulum) tend to lie very still because movement makes their pain worse.
Reproductive Causes in Women
Because the left ovary and fallopian tube sit in this quadrant, several gynecological conditions can cause lower left pain. Ovarian cysts are fluid-filled sacs that form on the ovary, and most resolve on their own. But when a cyst ruptures or twists (ovarian torsion), the pain can be sudden and severe. Endometriosis, where tissue similar to the uterine lining grows outside the uterus, can cause chronic pelvic pain that worsens during menstrual periods.
An ectopic pregnancy, where a fertilized egg implants in the fallopian tube instead of the uterus, causes sharp, one-sided lower abdominal pain and is a medical emergency. Tenderness during a pelvic exam, particularly with movement of the cervix, raises the likelihood of ectopic pregnancy or infection of the fallopian tubes.
Other Possible Causes
Constipation is probably the most underappreciated source of lower left pain. Stool accumulates in the sigmoid colon before reaching the rectum, and when it backs up, the distension can produce significant discomfort in exactly this spot. A muscle strain in the abdominal wall can also mimic internal pain, particularly after exercise or heavy lifting. In men, testicular problems like torsion or infection can refer pain upward into the lower abdomen.
Inguinal hernias, where tissue pushes through a weak spot in the groin area, are another possibility. They’re more common in men and may cause a visible bulge along with a dull ache that worsens with coughing, bending, or lifting.
Warning Signs That Need Urgent Attention
Most lower left abdominal pain turns out to be something manageable, but certain symptoms change the picture. Severe pain that won’t let up, vomiting blood, blood in your urine or stool, fever with chills, yellow discoloration of the skin or eyes, an inability to pass gas or have a bowel movement, and shortness of breath all warrant immediate evaluation. Pain that has been mild but has gradually worsened over days or weeks, or pain that keeps returning, also deserves a medical workup even if it doesn’t feel like an emergency in the moment.