The lower back left side organs are mainly the left kidney, part of the large intestine (the descending colon) and, higher up, the spleen and the tail of the pancreas. Most of the lower back itself is made up of the spine, discs, muscles and nerves, so pain here has many possible causes. See a doctor if it is severe, persistent or comes with other symptoms.
Key takeaways
- Most lower back pain comes from muscles, joints, discs or nerves, not from organs.
- The left kidney, descending colon, spleen and part of the pancreas lie close to the left side of the back.
- Pain with fever, blood in urine, numbness or loss of bladder control needs urgent medical attention.
- This guide is general information and cannot diagnose a cause.
What is in the lower left back?
When people say lower back, they usually mean the area between the bottom of the ribs and the top of the buttocks. The structures most directly there are the lumbar spine, discs, ligaments, nerves and layers of muscle. These are far more common sources of back pain than any organ.
Deeper inside the body, some organs sit close to the back on the left side. Where you feel pain does not always match where the problem is, because organs can send pain signals that appear in a different place, a process known as referred pain.
The organs near the left side of the back
| Organ | Where it sits | Why it may be relevant |
|---|---|---|
| Left kidney | High in the back, under the lower ribs, either side of the spine | Kidney stones or infections can cause flank or back pain |
| Descending colon | Runs down the left side of the abdomen towards the pelvis | Bowel problems may cause left-sided discomfort |
| Spleen | Upper left abdomen behind the ribs | Usually causes upper left pain, sometimes felt in the back |
| Tail of the pancreas | Deep in the upper abdomen, near the spleen | Pancreatic pain can radiate to the back |
| Left ureter | Tube from kidney to bladder | A stone passing along it can cause severe pain |
Kidney
The kidneys sit higher than many people expect, protected by the lower ribs. Kidney pain is typically felt in the flank, below the ribs on one side, rather than in the very low back. A kidney infection may bring fever, chills, nausea and a need to pass urine often. A kidney stone can cause sudden, severe pain that comes in waves.
Descending colon
The large intestine runs down the left side of the abdomen. Constipation, trapped wind, inflammation or infection in this part of the bowel may cause cramping or aching that some people feel through to the back.
Spleen and pancreas
These sit higher up, but the pain may be felt toward the left side of the back. For more detail on what lies behind the left side of the back, see our guides to organs behind the left side of your back and the organ on the upper left side of the back.
Common non-organ causes of lower left back pain
- Muscle strain from lifting, twisting or sudden movement
- Poor posture or long periods of sitting
- Slipped or bulging disc pressing on a nerve
- Sciatica, with pain travelling down the buttock or leg
- Sacroiliac joint irritation
- Arthritis or age-related wear in the spine
Muscular pain is often worse with certain movements and eases with rest or gentle activity. Organ-related pain is more likely to be constant, unrelated to movement, or to come with other symptoms.
When to get medical help urgently
Call 999 or go to A&E, or use the equivalent emergency service where you live, if you have back pain together with any of these:
- Numbness around your genitals or buttocks (saddle area)
- New difficulty controlling your bladder or bowels
- Weakness or numbness in both legs
- Severe pain following an injury or fall
- Chest pain, shortness of breath or sweating
- High temperature with shaking and severe pain
See a doctor soon if you notice blood in your urine, burning when passing urine, unexplained weight loss, pain at night that does not ease, or pain that lasts more than a few weeks. In the UK you can use NHS 111 for advice if you are unsure how urgent it is.
What you can do for ordinary back pain
Self-care steps
- Keep moving gently; staying active usually helps recovery more than bed rest.
- Use heat or a covered cold pack on the sore area for short periods.
- Take over-the-counter pain relief if it is suitable for you, following the label and checking with a pharmacist if you have other conditions or take other medicines.
- Avoid heavy lifting and long periods of sitting until it settles.
- Return to normal activity gradually.
The NHS website has detailed pages on back pain, kidney infections and kidney stones that explain symptoms and treatment.
How a doctor works out the cause
A doctor will ask when the pain began, what makes it better or worse, and whether you have urinary, bowel or other symptoms. They may examine your back and abdomen and test your urine. Depending on the findings, you may need blood tests or imaging such as an ultrasound or scan. Being specific about your symptoms helps, so jot down the details before your appointment.
Useful details to note
- Exactly where the pain is and whether it moves
- How long it has lasted and whether it is constant or comes in waves
- Any fever, nausea, changes in urine or bowel habits
- Recent injuries, lifting or changes in activity
- Any medicines you take
Frequently asked questions
What organ is in the lower left back?
The left kidney sits high in the back, and the descending colon runs down the left side nearby. The spleen and tail of the pancreas lie higher up.
Is lower left back pain usually a kidney problem?
Not usually. Most cases are caused by muscles, joints or discs. Kidney pain tends to be felt higher, under the ribs, and often comes with other symptoms.
Can constipation cause left-sided back pain?
It can cause discomfort in the left abdomen that some people feel in the back, though a musculoskeletal cause is still more common.
When is back pain an emergency?
Seek urgent care for saddle numbness, loss of bladder or bowel control, leg weakness, severe pain after injury, or pain with chest symptoms or high fever.
Should I see a GP for lower back pain?
Yes if it is severe, getting worse, lasts more than a few weeks, or comes with symptoms such as fever or urinary changes.
Conclusion
The lower back, left side organs include the left kidney and descending colon, with the spleen and pancreas tail higher up, but muscles and the spine are the most common sources of pain. Learn the warning signs, try gentle self-care for mild pain, and speak to a doctor or pharmacist whenever you are worried or the pain does not settle.
Key takeaways about lower back left side organs
Here is a short summary of lower back left side organs so you can find the main points quickly.
- The lower back left side organs are mainly the left kidney, part of the large intestine (the descending colon) and, higher up, the spleen and the tail of the pancreas.
- When people say lower back, they usually mean the area between the bottom of the ribs and the top of the buttocks.
- Deeper inside the body, some organs sit close to the back on the left side.
- The kidneys sit higher than many people expect, protected by the lower ribs.
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For general background, you can look up lower back left side organs on Wikipedia.
