Left-side stomach pain spans a wide range of causes, from trapped gas and constipation to conditions that need surgery within hours. What matters most is where exactly the pain sits, how it behaves, and what other symptoms come with it. The left side of your abdomen houses parts of the stomach, pancreas tail, spleen, left kidney, descending colon, and, in women, the left ovary and fallopian tube. Sorting through the possibilities starts with narrowing down whether the pain is in the upper left, lower left, or wrapping around from the flank.
Why the Exact Location Matters
Your abdomen is roughly divided into quadrants, and doctors rely heavily on which quadrant hurts to guide their thinking. The left upper quadrant sits beneath the lower ribs and contains the spleen, the tail of the pancreas, part of the stomach, and the upper curve of the colon (the splenic flexure). The left lower quadrant, below the navel line, houses the descending and sigmoid colon, the left ureter, and in women, the left ovary. The left flank, running along your side between the ribs and hip, overlies the left kidney. Pain that stays put in one of these zones points toward different organs than pain that moves or radiates.
That said, abdominal pain is famously misleading. The gut shares nerve pathways that make pinpointing the source harder than it sounds, and some conditions produce “referred” pain that shows up far from the actual problem. Still, location is the single best starting clue you have before any tests are done.
Lower Left Abdominal Pain
If you’re an adult with pain focused in the lower left part of your belly, the most likely culprit is diverticulitis. Diverticula are small pouches that form in the wall of the colon, most often in the sigmoid colon on the left. When one of those pouches becomes inflamed or infected, you get a steady, aching pain in the lower left that often worsens over a day or two. It frequently comes with a low-grade fever, bloating, and changes in bowel habits. Diverticulitis is the single most common cause of left lower quadrant pain in adults.1PubMed. ACR Appropriateness Criteria Left Lower Quadrant Pain-Suspected Diverticulitis
A surprisingly common and often overlooked cause of left-sided abdominal pain is plain constipation. In one emergency department study, roughly a quarter of patients who came in with acute abdominal pain turned out to have functional constipation, and the pain was frequently rated as moderate to severe. The location of the pain on physical exam alone was not enough to distinguish constipation from other diagnoses.2Pediatric Emergency Care. Acute Abdominal Pain: Recognition and Management of Constipation in the Emergency Department This matters because stool tends to accumulate in the descending and sigmoid colon on the left side, making left-sided cramping one of constipation’s most recognizable patterns. Many people don’t realize they’re backed up until a doctor presses on the area and the diagnosis becomes obvious.
Ulcerative colitis is another condition that often announces itself on the left side. The inflammation in ulcerative colitis typically starts in the rectum and extends upward into the sigmoid and descending colon. When the disease is limited to that segment, the pain, cramping, and bloody diarrhea concentrate on the left.3PubMed Central. Drug therapy for ulcerative colitis If you’re having repeated bouts of left-sided cramping with bloody or mucus-streaked stools, inflammatory bowel disease belongs on the list of things to investigate.
Infections can mimic these patterns too. Cytomegalovirus colitis, for example, can produce thickening and inflammation of the descending and sigmoid colon that looks a lot like ulcerative colitis on imaging.4PubMed Central. Cytomegalovirus infection in the setting of occult ulcerative colitis: case report and review of the literature Infectious colitis from bacteria like Salmonella or Campylobacter can also hit the left colon and cause pain in the same spot, though it usually comes on faster and with more prominent diarrhea and fever.
Upper Left Abdominal Pain
Pain beneath the left ribcage shifts the conversation toward different organs. The spleen sits tucked against the ribs on the left, and when it’s enlarged or injured, it produces a deep, sometimes sharp pain under the lower ribs that can radiate to the left shoulder. Splenic problems include enlargement from infections like mononucleosis, splenic infarction from a blood clot, and, rarely, traumatic rupture. Splenic rupture is a surgical emergency and usually follows a blow to the left side, though spontaneous rupture can occur in a severely enlarged spleen.
The tail of the pancreas curls to the left, so pancreatitis occasionally presents as left-sided pain rather than the classic central upper-abdominal pain that bores through to the back. In rare cases, left flank pain can be the only symptom of acute pancreatitis, particularly when the inflammation is isolated to the pancreatic tail and fluid tracks into the left side of the abdomen.5PubMed. Left flank pain as the sole manifestation of acute pancreatitis: a report of a case with an initial misdiagnosis Because this is unusual, it can lead to an initial misdiagnosis. If you have upper left pain with nausea, vomiting, and a history of heavy alcohol use or gallstones, pancreatitis should be considered even if the pain isn’t in the textbook location.
Gastritis and stomach ulcers also produce upper left pain, often described as a burning or gnawing sensation that may improve or worsen with food. The stomach sits mostly in the upper left quadrant, and inflammation of its lining from NSAIDs, alcohol, or Helicobacter pylori infection can create persistent discomfort in that area. The pain tends to be more of a dull ache than the sharp, sudden onset you’d expect from something like a kidney stone.
Kidney Stones and Left Flank Pain
Kidney stones deserve their own discussion because the pain they produce is distinctive and often dramatic. A stone forming in the left kidney or traveling down the left ureter causes pain that typically starts in the left flank, just below the ribs in the back, and radiates forward and downward toward the groin. The pain comes in waves, can be excruciating, and is often accompanied by nausea. You might also notice blood in your urine, though not always.
Even a small stone can cause significant symptoms. In one documented case, a stone measuring just 2 millimeters at the junction where the ureter meets the bladder caused moderate swelling of the kidney, fluid around the kidney, and acute left-sided abdominal and flank pain severe enough to bring the patient to the emergency department.6PubMed Central. A Patient with an Unusual Cause of Acute Left Flank and Lower Abdominal Pain The lesson is that stone size doesn’t always predict pain severity. A tiny stone lodged in the wrong spot can be agonizing.
Urinary tract infections can also cause left-sided discomfort, especially when the infection climbs to the left kidney (pyelonephritis). That usually shows up as flank pain combined with fever, chills, and painful urination, and it needs prompt antibiotic treatment.
Gynecologic Causes in Women
If you’re a woman experiencing sudden, severe left-sided lower abdominal pain, reproductive organs enter the picture. The left ovary can develop cysts that rupture or twist (ovarian torsion), both of which cause sharp, one-sided pelvic pain that can be intense. Ruptured cysts often produce a burst of pain followed by some relief, while torsion pain tends to be unrelenting and may come with nausea and vomiting.
Ectopic pregnancy is a more dangerous possibility. When a fertilized egg implants outside the uterus, it sometimes lands on the left ovary or in the left fallopian tube. As the pregnancy grows, it can rupture, causing internal bleeding and severe pain. In one reported case, a ruptured ovarian ectopic pregnancy presented with an acute abdomen and required emergency surgery that revealed significant blood in the abdominal cavity.7BMJ Case Reports. Ruptured ovarian ectopic pregnancy presenting with an acute abdomen In another case, a left ovarian ectopic pregnancy was caught before rupture, presenting with lower abdominal pain, vaginal spotting, nausea, and fatigue, and was managed with laparoscopic surgery.8PubMed Central. Laparoscopic management of unruptured left ovarian ectopic pregnancy: a rare case report
The key point for any woman of reproductive age with sudden left-sided lower abdominal pain: a pregnancy test is one of the first things the emergency department will order, and for good reason. Ectopic pregnancy can be life-threatening if it ruptures, and the early symptoms are easy to mistake for a cyst or gastrointestinal problem.
When the Problem Is the Abdominal Wall
Not all left-sided abdominal pain comes from the organs inside. The abdominal wall itself has muscles, fascia, and nerves that can be the source. Muscle strains from exercise, coughing, or lifting heavy objects produce a pain that worsens when you tense your abdominal muscles, like when you sit up or twist.
A less well-known cause is abdominal cutaneous nerve entrapment syndrome. Small nerves that run through the abdominal wall can become compressed as they pass through a fibrous ring in the muscle, leading to chronic, localized pain that often puzzles both patients and doctors. Family physicians frequently see patients with abdominal pain that resists a clear diagnosis, and nerve entrapment is one of those conditions that gets missed because it doesn’t show up on imaging.9The Journal of the American Board of Family Practice. Microanatomy of the Structures Contributing to Abdominal Cutaneous Nerve Entrapment Syndrome A clue to this diagnosis is pain that gets worse or is reproduced when the doctor has you tense your abdominal muscles (Carnett’s sign). If the pain increases with muscle contraction, it’s likely in the wall rather than inside the abdomen.
Herpes zoster (shingles) can also cause left-sided abdominal pain before the telltale rash appears. The pain follows a band-like pattern along one nerve and can be burning, sharp, or aching. If you’re over 50 and develop unexplained one-sided abdominal pain that doesn’t match any internal organ pattern, it’s worth watching for a rash over the next few days.
When Left-Side Pain Needs Emergency Attention
Most left-sided stomach pain turns out to be something manageable: gas, constipation, a mild stomach bug, or muscle soreness. But certain patterns warrant a trip to the emergency department rather than a wait-and-see approach.
- Sudden, severe pain: Pain that comes on abruptly and is immediately intense suggests something has ruptured, twisted, or perforated. Ruptured ectopic pregnancy, splenic rupture, a perforated ulcer, and ovarian torsion all present this way.
- Pain with fever and chills: Infection is likely, and conditions like diverticulitis with abscess, pyelonephritis, or perforated bowel may need antibiotics or surgery.
- Pain with fainting or lightheadedness: This can signal internal bleeding, particularly from a ruptured ectopic pregnancy or splenic injury.
- Pain with bloody stool or vomiting blood: Internal bleeding somewhere in the gastrointestinal tract needs prompt evaluation.
- Pain that steadily worsens over hours: Pain that escalates without letting up, especially with a rigid or tender abdomen, suggests peritonitis or another condition that may need surgery.
- Pain with inability to pass gas or stool: This may indicate a bowel obstruction, which can become dangerous if the blood supply to the trapped bowel is compromised.
None of these features guarantee you need surgery, but all of them justify being evaluated promptly rather than toughing it out at home.
What to Expect During a Medical Workup
When you show up with left-sided abdominal pain, the evaluation typically starts with your history and a physical exam. Where exactly does it hurt? When did it start? Is it constant or intermittent? Does anything make it better or worse? What other symptoms do you have? Blood work usually follows, checking for signs of infection, inflammation, anemia, and organ function.
Imaging often comes next, and the choice between ultrasound and CT matters. A large study of patients with acute abdominal pain found that CT was more sensitive than ultrasound, detecting urgent diagnoses about 89% of the time compared with 70% for ultrasound. However, a strategy that starts with ultrasound and adds CT only when the ultrasound is negative or inconclusive caught the most problems overall, missing only about 6% of urgent cases while cutting the number of patients needing CT nearly in half.10BMJ. Imaging strategies for detection of urgent conditions in patients with acute abdominal pain: diagnostic accuracy study This is why many emergency departments start with ultrasound for certain presentations (especially in younger women, where gynecologic causes are likely) and reserve CT for when the picture is still unclear.
For lower left quadrant pain in an older adult where diverticulitis is suspected, CT is usually the first-line imaging choice because it can show the inflamed diverticulum, any abscess, and whether there’s a perforation. For kidney stone symptoms, a CT without contrast is the gold standard because stones light up clearly on the scan.
How Age Changes the Picture
The likely causes of left-sided abdominal pain shift depending on your age. In younger adults, constipation, menstrual-related pain, ovarian cysts, and irritable bowel syndrome top the list. In middle-aged and older adults, diverticulitis becomes much more common because diverticula develop over decades of life.
Older adults pose a particular diagnostic challenge because they often present with vague or muted symptoms. Conditions that cause obvious pain and fever in a 30-year-old may produce only mild discomfort and no fever in a 75-year-old. The medical literature recognizes that common conditions frequently show up in atypical ways in geriatric patients, falling into patterns of vague symptoms, altered symptoms, or even absent symptoms entirely.11Journal of the American Medical Directors Association. Atypical Presentations of Common Conditions in Geriatric Patients A perforated bowel that would cause a younger person to writhe in pain might produce only mild tenderness in an older adult taking anti-inflammatory medications. The practical takeaway: if you’re caring for an older family member who has even mild abdominal complaints with subtle changes in behavior, appetite, or mental sharpness, don’t assume it’s minor just because they’re not in obvious distress.
Chronic mesenteric ischemia, a condition where blood flow to the intestines is gradually reduced, tends to affect older adults with atherosclerosis. The hallmark is pain after eating, often described as a crampy ache that comes on within an hour of a meal and leads to weight loss because people start eating less to avoid the pain.12PubMed Central. Chronic mesenteric ischemia: diagnosis and treatment It’s an uncommon diagnosis, but one worth knowing about if an older person develops predictable post-meal abdominal pain and unintentional weight loss.
Children and Adolescents
In children, left-sided abdominal pain is often functional, meaning no structural problem is found. Constipation is one of the most frequent diagnoses, and it’s just as commonly underrecognized in children as in adults. Functional abdominal pain disorders, essentially the pediatric version of irritable bowel syndrome, can also produce recurring left-sided discomfort.
Rarely, congenital anatomical abnormalities can cause chronic or episodic pain that goes undiagnosed for years. Paraduodenal hernias, the most common type of congenital internal hernia, are a striking example. In one reported case, a child first presented at age 8 with vague symptoms of nausea, vomiting after meals, and chronic abdominal pain. Over six years of repeated evaluations, the symptoms always resolved on their own, and the diagnosis was missed until the hernia caused a life-threatening bowel obstruction.13Pediatrics. Congenital Left Paraduodenal Hernia Causing Chronic Abdominal Pain and Abdominal Catastrophe Cases like this are uncommon, but they underscore the importance of pursuing a diagnosis when a child has recurring abdominal pain that keeps bringing them back to the clinic, especially if the symptoms follow meals.
Rare Complications You Might Not Expect
Some causes of left-sided abdominal pain are so unusual that they catch both patients and doctors off guard. Splenic rupture after colonoscopy is one example. While bowel perforation and bleeding are known risks of colonoscopy, injury to the spleen is rare and easy to miss. In one case, a patient was diagnosed with splenic rupture 18 hours after a routine colonoscopy and required emergency removal of the spleen. Most patients with this complication develop symptoms within 24 hours of the procedure, though delayed presentations days later have been described.14PubMed Central. Splenic rupture after colonoscopy If you develop new left upper quadrant pain or left shoulder pain in the days following a colonoscopy, it’s worth calling your doctor rather than assuming the discomfort is normal post-procedure cramping.
Another unusual scenario involves the spleen and infectious diseases. Splenic infarction, where part of the spleen loses its blood supply, can occur in the setting of blood disorders, heart conditions that produce blood clots, or tropical infections. The pain is typically sudden, sharp, and localized under the left ribs, sometimes with a friction rub that a doctor can hear with a stethoscope. Because spleen-related pain isn’t something most people think about, it can go unrecognized until imaging is done.
Left-sided pain can even come from above the diaphragm. Heart attacks, particularly in the inferior or lateral wall of the heart, sometimes present with upper abdominal pain rather than chest pain. This is more common in older adults and in women. If upper left abdominal pain comes with shortness of breath, sweating, jaw pain, or a sense of impending doom, treat it as a possible cardiac event until proven otherwise.