Kidney infection often comes with a mix of urinary, whole-body, and sometimes stomach symptoms. These can appear suddenly or build up slowly, depending on how bad the infection is and the person’s overall health. Because kidney infections are more serious than simple urinary tract infections (UTIs), spotting symptoms early is very important. Early treatment helps stop kidney damage or sepsis.
1. Fever and Chills
A main symptom of kidney infection is a high fever, usually above 38.5°C (101.3°F), with chills and shaking. The body raises its temperature to fight the bacteria. Unlike bladder infections, kidney infections cause a stronger whole-body reaction, so fever is a key sign.
Chills may come in waves and be strong enough to make the teeth chatter. Anyone with these signs, plus pain or urinary problems, should see a doctor quickly.
2. Flank or Lower Back Pain
Pain on one or both sides of the lower back or just below the ribs is a classic kidney infection sign. The pain can be sharp, throbbing, or dull and last a long time. It usually stays on the side of the infected kidney.
Sometimes, the pain spreads to the lower belly or groin. It often gets worse with movement and can make walking or lying down uncomfortable. Unlike muscle back pain, this pain gets worse with infection and comes with other body symptoms.
3. Painful or Frequent Urination
Since kidney infections often start as urinary tract infections, urinary symptoms are common:
- Dysuria: Burning or stinging when peeing
- Urgency: Feeling the need to pee all the time, passing only small amounts
- Frequency: Needing to pee more often, including waking at night (nocturia)
These symptoms also occur in bladder infections, but if they come with fever or back pain, the infection may have reached the kidneys.
4. Cloudy or Foul-Smelling Urine
Kidney infections often change urine’s look and smell. It may be:
- Cloudy because of white blood cells, bacteria, or pus
- Smelly due to bacteria and infection by-products
- Dark or bloody if the infection irritates the urinary tract lining
These changes are warning signs, especially with fever and pain.
5. Nausea and Vomiting
The infection can cause stomach upset, especially in more severe cases. Nausea and vomiting happen because of chemicals released by the infection, fever, and bacterial toxins in the blood.
These symptoms are worrying since they can cause dehydration and hurt kidney function. Hospitals often give fluids and medicine to stop vomiting.
6. Fatigue and Malaise
People with kidney infection often feel very tired, weak, and generally unwell. This is the body’s normal response to infection and can last even after other symptoms fade.
Fatigue may be stronger in older adults or those with diabetes, kidney problems, or weak immune systems. Sometimes, tiredness comes before more obvious signs like fever or pain.
7. Confusion in Older Adults
Older people may not show typical symptoms. Instead, they may become confused, disoriented, or act strangely. These signs might be mistaken for dementia or stroke. This sudden confusion, called delirium, is a medical emergency. It usually results from infection-related inflammation or dehydration.
Caregivers and doctors must watch for these changes and check for kidney infections if confusion happens.
8. Pelvic or Abdominal Discomfort
Some people, especially women, may feel a dull ache or pressure in the lower belly or pelvic area. This can feel like menstrual cramps or stomach upset but usually comes with urinary pain or fever.
Men may feel discomfort between the anus and scrotum if the infection involves the prostate. These symptoms help tell apart different conditions.
9. Shivering and Sweating
Shivering and heavy sweating, especially at night, are common. The body swings between feeling cold and hot as it tries to control fever.
Sweating can cause fluid loss and upset body salts, so drinking fluids and watching for worsening infection is important.
10. Urine Retention or Difficulty Passing Urine
Less often, some patients find it hard to pee or cannot pee at all if swelling or inflammation blocks urine flow.
This happens more in men with enlarged prostates or those with kidney stones or urinary problems. Immediate medical help is needed to avoid more damage.
Final Notes on Symptom Recognition
Knowing the symptoms of kidney infection early can improve treatment and recovery. Many signs overlap with other urinary problems like cystitis or prostatitis, so proper medical checks are key. Anyone with high fever, side pain, or lasting urinary discomfort should get medical help fast.
Quick action stops infection from reaching the blood, where it can cause life-threatening sepsis or permanent kidney injury. Spotting symptoms early can save lives, especially in the elderly, babies, or people with weak immunity.
