Can A CT Tell If There is A Kidney Infection?

A CT can often identify a kidney infection or pyelonephritis.  The CT is better done with contrast given through a vein.  The contrast let’s us see the infection and any complications better.  Imaging is often not needed in uncomplicated cases.  Treatment with antibiotics is sufficient for these cases.

How does a kidney infection present?

A kidney infection is more common in young women and often presents with pain and fever in the flank.  Often, the urine looks infected with white cells and bacteria.  The infection spreads from the bladder, into the ureter and then the kidney.

Imaging of the kidneys is indicated for high risk patients.  Those are patients who may have an underlying condition like diabetes or immunocompromised states.  Patients who are suspected of having an obstructed kidney are often imaged.  An infected obstructed kidney is an emergency.

What does a kidney infection look like?

CT with contrast is best for identifying kidney infection.  This will often show wedge shaped areas in the outer part of the kidney.  Some areas may look more mass like.  There may be inflammation or stranding in the fat around the kidney.

Complications can also be imaged with CT.  An emergency would be an obstructed infected kidney which must be treated with a drain.  An abscess or pocket of pus can form in the kidney.  This will need to be treated with antibiotics and drainage.

The infection can spread from the kidney into the blood and cause sepsis.  Gas forming bacteria can infect the kidney which can have a high mortality if not treated promptly.   There can be scarring in the kidneys and infarctions.  The vein from the kidney can become occluded with clot.

Can anything look like kidney infection on CT?

The imaging appearance can sometimes mimic other conditions like kidney infarcts.  This occurs when a portion of the kidney is lacking blood flow from various causes.  This can also cause wedge shaped defects.  Drug reactions and certain inflammatory conditions can also mimic pyelonephritis or kidney infection.

Should every kidney infection be imaged?

CT is mostly indicated for imaging complicated kidney infections.  The clinical presentation of kidney infections is characteristic.   Treatment with antibiotics is sufficient.  When imaged, we are usually looking for complications.  These may require additional treatment in addition to antibiotics.  This is particularly true when the infected kidney is blocked, say from a stone in the ureter or cancer.

Kidney infections are often identified on CT.  We can diagnose many complications.  We may also see additional diagnosis which can be contributing to the patients symptoms.  Kidney infections are also often accompanied by infections of the bladder and ureters which we often see.  Combined with the clinical impression, CT will make a more confident diagnosis and identify any complications.