Kidney infection vs urine infection

A kidney infection is much more serious than a urine infection. Most patients with kidney infections require hospitalization, while only a small proportion of patients with urine infections need to be hospitalized. In the last 15 years, I have personally treated thousands of hospitalized patients with both kidney infections and urine infections. I am writing this article based on my personal experience as well as a review of relevant medical journals.

In this article, I will describe the anatomic details that separate kidney infections and urine infections. I will then compare and contrast the two so that you can distinguish between them.

Kidney infections are a complex topic. This article may help you distinguish a kidney infection from a urine infection, but it is not possible to describe everything you need to know about kidney infections in one article.

I have written a separate detailed article on kidney infection symptoms. You can read it if you need more detailed information.

How are kidney infections and urine infections defined based on anatomy?

A diagram showing the areas where kidney infections and urine infections are found.
A diagram showing where kidney infections and urine infections are located

As you can see in the picture, your urinary system contains two kidneys, two tubes coming down from both kidneys into your urinary bladder, and one tube going out from your urinary bladder. Urine is made in the kidneys, and it comes down to the urinary bladder for storage through the two tubes called the ureters. When you urinate, urine leaves your bladder through the tube called the urethra.

Any infection that is limited to the urinary bladder and the urethra is simply a urine infection. It is also known by several other names. Here are some of them:

  1. Uncomplicated urinary tract infection
  2. Urinary infection
  3. Simple urinary tract infection
  4. UTI
  5. Bladder infection
  6. Cystitis

Any infection that goes above the urinary bladder is considered a kidney infection. It is also known as pyelonephritis.

Comparing and contrasting a kidney infection vs a urine infection

Here is a table comparing and contrasting the signs and symptoms of a kidney infection vs a urine infection:

Kidney infectionUrine infection
FeverMore likely to have high fevers and chillsLow grade fever or no fever
Pain or burning with urinationMaybe presentUsually present
Frequent urinationMaybe presentUsually present
Feel like the urge to urinate never goes awayMaybe presentUsually present
Dark colored urineMaybe presentMaybe present
Foul smelling urineMaybe presentMaybe present
Body achesMore likelyLess likely
Fast heart rateMore likelyLess likely
Nausea and vomitingMore likelyLess likely
Back pain or flank painPresentAbsent
Dizziness and lightheadednessMore likelyLess likely
Low blood pressureMore likelyLess likely
Confusion and disorientationMay happen to otherwise healthy adults when they have a severe kidney infection.Only happens in elderly and sick people with UTI.
Pain with vibration of the affected kidney (Read “kidney infection symptoms” to learn how to test for pain with vibration of the kidney)PresentAbsent
(Table comparing and contrasting symptoms of a kidney infection vs a urine infection)

When you review this table carefully, you can see the general pattern. Symptoms of kidney infections are usually more severe and more serious than symptoms of urine infections. High fevers and chills along with severe body aches and sharp back or flank pain are very specific symptoms of a kidney infection rather than just a simple urine infection.

There are times when it may be difficult to distinguish between a simple urinary tract infection and a kidney infection. It is mostly true in people who are already suffering from other medical illness, people who have problems with their immune system, people who have issues with mobility, or people who have underlying dementia living in a nursing home. In these people, a simple urine infection may cause more severe symptoms, and that makes it difficult to distinguish between the two based on symptoms alone.

This next table compares findings of diagnostic tests with a kidney infection vs a urine infection:

Diagnostic testKidney infectionUrine infection
WBCs in the urineUsually presentUsually present
Bacteria in the urineUsually presentUsually present
WBC casts in the urineMaybe presentDoes not appear
WBCs in the bloodUsually elevatedLess likely to be elevated
Inflammatory markersUsually elevatedLess likely to be elevated
CT scan of the abdomenShows inflammation around the affected kidneyUsually not done, likely to be normal when done
(Table comparing diagnostic tests with a kidney infection vs a urine infection)

White blood cells or WBCs are the cells of the immune system in our body. They are normally floating in the blood, but are not present in the urine. Whenever you have any infection in your body, the number of WBCs in the blood goes up. With a kidney infection, the number of WBCs in the blood may be very high.

Whenever you have an infection in your urine, WBCs squeeze out of your blood and go to your urine to try and fight the infection. With a simple urine infection, the WBCs in the urine are all single and scattered. In addition to single WBCs, special clusters of WBCs may appear in a kidney infection.

Inside your kidneys, there are microscopic tubes where urine is collected. The WBCs squeeze into these tubes to fight kidney infections. When they sit there for a while, they stick to one another and form a cast that looks similar to the tube. When you see these WBC casts in the urine, you can be fairly certain that they came from the kidneys.

Treatment of kidney infections vs urine infections

The treatment of a kidney infection is complicated and may need hospitalization. The treatment of a simple UTI is usually straightforward. Antibiotics are prescribed for the urine infection based on the local sensitivity pattern of common bacteria in your particular community. You simply need to take the prescribed antibiotics and drink plenty of fluids. Call your doctors if your symptoms don’t improve or get worse.

In conclusion, kidney infections are more severe and more serious than simple urine infections. You should be able to distinguish between the symptoms of kidney infections and urine infections in most cases. There are also diagnostic tests that can help make the distinction.