Urinary tract infection and kidney pain: Does UTI cause kidney pain?

 Key takeaways

• Urinary tract infections can affect any part of the urinary tract, including the kidneys. When they affect the kidneys, they can cause kidney pain. 
• A kidney infection is called pyelonephritis. In addition to kidney pain, other common symptoms of kidney infections include fever and nausea or vomiting. 
• Other causes of kidney pain besides kidney infections include kidney stones, ruptured abdominal aortic aneurysms, spinal muscle strains, and kidney tumors.

The kidneys are bean-shaped organs located below the rib cage, one on each side of the spine. These organs are important parts of the urinary tract. 

Other organs that make up the urinary tract are the ureters, bladder, and urethra. Any part of the urinary tract can get infected, including the kidneys.

This article explains kidney pain, its symptoms, and possible causes of pain in the kidney area. 

 How UTI affects the kidney

A urinary tract infection (UTI) that reaches the kidneys is called pyelonephritis. It occurs when microorganisms, typically bacteria from the intestines, find their way to the kidneys, causing infection.

Escherichia coli, a microorganism and gram-negative bacteria, is the commonest cause of acute pyelonephritis. When the microorganism gets into the urethra, where urine comes out, it can ascend to the bladder and kidneys, causing pyelonephritis.

If pyelonephritis is left untreated, it can cause complications like kidney abscess (pus) formation, blood clots in the kidney (thrombosis), and kidney tissue death (necrosis). In rare cases, it can even cause complete kidney failure.

 Can UTIs cause kidney pain?

Pyelonephritis can cause kidney pain by causing the kidney tissue to become inflamed and swollen, which stretches the covering of the kidney called the renal capsule. This can lead to a steady and dull aching pain in the kidneys.

 What kidney pain feels like

Kidney pain is a mild and steady pain that's usually felt in the lower back or side (flank) and may also radiate to the center of the abdomen. The area around the kidneys might be tender to the touch, and a doctor's tapping in this region can also elicit pain.

 Symptoms of UTIs when the kidneys are affected

The three main symptoms of acute pyelonephritis include:

• Fever
• Flank pain (kidney pain)
• Nausea or vomiting 

Other symptoms that may be seen are:

• Dysuria, i.e., pain while urinating
• Haematuria, i.e.,  blood in the urine
• Cystitis, i.e.,  inflammation of the bladder
• Failure to thrive and feeding difficulties in children under two years old.
• Altered mental status and deterioration in older people.
• Damage to other organs around the kidneys. 

 Other possible causes of kidney pain

Infection of the kidneys isn't the only cause of kidney pain. Other causes include the following:

 1. Kidney stones

Kidney stones are hard objects made from chemicals such as calcium, oxalate, and xanthine in the urine. Usually, various wastes are dissolved in urine; however, when there is too much waste in too little liquid, crystals begin to form. If these crystals aren't passed out in the urine, they get larger and eventually form stones.

These stones may prevent urine from passing, causing it to remain in the urinary tract, including the kidneys. This can cause severe pain on either side of the lower back and a steady stomach ache. 

Fever, nausea and vomiting, blood in the urine, bad-smelling urine, or cloudy urine may also accompany the kidney pain caused by kidney stones.

Drinking too little water, obesity, too little exercise, too much exercise, eating lots of sugary or salty foods, and infections can increase your risk of developing kidney stones. 

 2. Blockage of blood flow to the kidneys

If the renal arteries that supply the left and right kidneys are blocked, there will be reduced or no blood flow to the kidneys. This blockage may be caused by a blood clot that has moved from another part of the body to the renal arteries or by a blood clot forming within the renal arteries. 

If the blockage isn't complete, it usually doesn't cause any symptoms. However, if the renal arteries are completely blocked, it may cause a steady aching pain in the lower back or the abdomen.

Other symptoms associated with a complete blockage of blood flow to the kidneys are fever and nausea or vomiting.

 3. Ruptured abdominal aortic aneurysm

The aorta is an artery that supplies blood to the abdomen, pelvis, and legs. An abdominal aortic aneurysm occurs if the aorta gets bigger and becomes very large. Aneurysms can develop slowly over the years without symptoms. 

However, if it gets larger very quickly or ruptures, symptoms like abdominal or back pain may develop, which may be mistaken for kidney pain. Other symptoms that can occur are nausea and vomiting, dizziness, passing out, and shock.

 4. Spinal muscle injury

The lumbar spine is prone to strain because it carries one's weight and is involved in moving and bending. When the lumbar muscle is strained or sprained, it causes inflammation of the soft tissues, which causes pain in the lower back. Lumbar muscle strain and sprain are the most common causes of low back pain.

Other symptoms accompanying lower back pain due to a lumbar spine strain or sprain include stiffness in the lower back area, muscle spasms, and abnormal posture due to pain or stiffness. 

 5. Kidney tumors

Kidney tumors are abnormal growths in the kidneys. They may be cancerous or noncancerous. The causes of kidney masses are unknown. However, smoking, high blood pressure, obesity, and exposure to chlorinated chemicals can increase one's risk of developing kidney tumors.

Most kidney tumors don't show symptoms in the initial stage. However, symptoms like flank pain, haematuria, loss of appetite, weight loss, and fever may develop.

 When to see a doctor for kidney pain or suspected UTI

You should see a doctor if you have a steady, dull, aching pain in your back that isn't going away. If it's accompanied by fever, nausea and vomiting, difficulty urinating, and blood in your urine, you should see a doctor immediately. 

Kidney pain has different causes, like infection, kidney stones, blocked renal arteries, spinal injuries, etc. A doctor will take your medical history, do some physical examinations, and run some investigations, which may include imaging, to determine the cause of your kidney pain.