What could cause a painful lump on the left side of back beside spine?

There are several potential causes for a painful lump on the left side of the back beside the spine. Here are some possible causes:

1. Kidney Infection: A kidney infection, also known as pyelonephritis, can cause pain and tenderness in the back, particularly on the affected side. The pain is often accompanied by other symptoms such as fever, chills, and frequent urination.

2. Kidney Stone: A kidney stone can also cause back pain, which can be felt in the lower back on the affected side. Severe pain may occur if the stone obstructs the flow of urine, leading to pressure buildup in the kidney.

3. Muscle Strain or Spasm: Back muscles can sometimes become strained or go into spasms due to overuse, poor posture, or trauma. This can lead to painful knots or lumps in the affected area.

4. Herniated Disc: A herniated disc occurs when the soft inner material of a spinal disc protrudes through a tear in the outer layer. This can put pressure on the surrounding nerves and cause back pain, which may be felt on one side or both sides of the spine.

5. Spinal Tumor: In rare cases, a painful lump on the left side of the back beside the spine could be due to a spinal tumor. However, tumors that cause back pain typically manifest with other symptoms such as progressive weakness, numbness, or changes in bowel or bladder function.

6. Bone Infection or Tumor: Although less common, infections or tumors of the bone itself, such as osteomyelitis or bone metastases, can also cause localized back pain.

It's important to consult a healthcare professional for an accurate diagnosis and appropriate treatment. The doctor will likely recommend appropriate imaging tests, such as an X-ray, MRI, or CT scan, to determine the underlying cause of the lump and provide the most suitable treatment options. Self-diagnosis and treatment of back pain are not recommended as some underlying causes can be serious and require prompt medical attention.