Pain in your right lower side most commonly comes from your appendix, a buildup of gas or stool, or, in women, an ovarian issue. The cause ranges from completely harmless to a surgical emergency, so the pattern of your pain, how fast it came on, and what other symptoms you have are the key details that separate one from another.
Appendicitis: The Most Concerning Cause
Appendicitis is the first thing most people worry about with right lower side pain, and for good reason. The lifetime risk is about 9% for men and 7% for women, with the highest rates between ages 15 and 30. It follows a fairly predictable pattern: pain starts around your belly button as a vague, dull ache that may come and go for several hours. Nausea and vomiting often develop during this early phase. Then, over the next several hours, the pain migrates down and to the right, settling into a spot roughly two inches inward from the bony point of your hip. At that stage, the pain becomes sharper, more focused, and steadily worse.
A few features distinguish appendicitis from less serious causes. The pain doesn’t let up. It gets worse when you walk, cough, or go over a bump in the car. You lose your appetite entirely. You may develop a low fever. Pressing on the lower right area and then quickly releasing often causes a sharp spike of pain (called rebound tenderness), which suggests the lining of your abdominal wall is inflamed. If you notice this progression over 12 to 24 hours, that warrants an emergency room visit.
Gas and Constipation
Trapped gas is by far the most common and least dangerous explanation. Gas pain can show up anywhere in your abdomen, including the lower right side, and sometimes feels surprisingly sharp. The key differences: gas tends to move around, you can often feel it shifting through your intestines, and the discomfort usually resolves quickly once you pass gas or have a bowel movement. It doesn’t steadily worsen over hours the way appendicitis does.
Constipation can cause similar cramping in the lower right side because a portion of your large intestine (the cecum) sits in that area. If you haven’t had a regular bowel movement in a few days and the pain is more of a dull pressure that eases after passing stool, constipation is the likely culprit. Interestingly, appendicitis itself can sometimes cause an inability to pass gas, so if bloating is paired with escalating pain, fever, and nausea, don’t assume it’s just digestive trouble.
Kidney Stones
A stone moving through your right ureter (the tube connecting your kidney to your bladder) can produce intense pain in your lower right side, flank, or back. This pain tends to come in waves, building to an agonizing peak and then easing before surging again. It often radiates from your back around to your groin or inner thigh.
The giveaway symptoms are urinary: blood in your urine (even a faint pink tinge counts), a burning sensation when you pee, or feeling like you constantly need to go but producing very little. Nausea and vomiting are common. Kidney stone pain can rival or exceed appendicitis in intensity, but the wave-like pattern and urinary symptoms usually point in the right direction.
Ovarian Causes in Women
For women, the right ovary sits in the lower right pelvis, and several conditions can cause pain there. A ruptured or enlarged ovarian cyst typically causes a sudden, sharp pain on one side that may gradually improve over hours to days. Mid-cycle ovulation pain (sometimes called mittelschmerz) can produce a similar one-sided twinge that resolves within a day or two.
Ovarian torsion is more serious. It happens when the ovary twists on its blood supply, causing sudden, severe lower abdominal pain on one side along with nausea, vomiting, and sometimes fever or dizziness. The onset is abrupt, not the slow migration you see with appendicitis. Torsion is a surgical emergency because the ovary can lose blood flow permanently.
An ectopic pregnancy, where a fertilized egg implants in the right fallopian tube instead of the uterus, also causes sharp lower right pain. It can be accompanied by vaginal bleeding and dizziness. Any woman of reproductive age with sudden right-sided pelvic pain should consider a pregnancy test as an early step.
Crohn’s Disease and Chronic Causes
If your right lower side pain keeps coming back over weeks or months, Crohn’s disease is one possibility worth knowing about. Crohn’s most commonly affects the very end of the small intestine (the ileum), which connects to the large intestine in your lower right abdomen. This means flare-ups often produce cramping right-sided pain along with diarrhea, fatigue, and unintended weight loss. Unlike appendicitis, Crohn’s develops gradually, and the symptoms tend to cycle between better and worse periods.
Mesenteric Adenitis in Children and Teens
In kids and teenagers, swollen lymph nodes inside the abdomen can closely mimic appendicitis. This condition, called mesenteric adenitis, usually follows a viral infection and causes pain in the lower right side along with fever and general belly tenderness. The critical difference is that the pain tends to be more spread out rather than pinpointed to one spot, and it clears up on its own as the underlying infection resolves. Still, because it looks so much like appendicitis, doctors often run imaging tests to tell them apart.
How Doctors Figure Out the Cause
When you go to the ER or urgent care with right lower side pain, the physical exam comes first. A provider will press on specific areas of your abdomen, check for rebound tenderness, and ask about the timeline and character of your pain. Blood work typically follows to look for signs of infection or inflammation.
For imaging, a CT scan is the most reliable tool for evaluating right lower quadrant pain, with a sensitivity of about 88% for detecting appendicitis. Ultrasound is often used first in children, pregnant women, and younger patients to avoid radiation exposure, though its sensitivity is lower at around 73%. In women, a pelvic ultrasound can simultaneously check for ovarian issues. A urinalysis helps rule out kidney stones quickly.
When to Go to the Emergency Room
Not every episode of right-sided pain needs an ER trip, but certain combinations of symptoms do. Head in right away if your pain started near your belly button and has migrated to the lower right over several hours, if your abdomen is swollen and tender to the touch, if you have a high fever alongside the pain, if you’re vomiting blood or see blood in your stool, or if you notice blood in your urine along with severe flank pain. Dizziness, persistent vomiting, or pain so intense you can’t stand up straight also warrant emergency evaluation.
If your pain is mild, comes and goes, improves with passing gas or having a bowel movement, and you have no fever or other symptoms, it’s reasonable to monitor it for a day. But pain that steadily worsens over 6 to 12 hours without letting up is the pattern that most often signals something that needs medical attention.