Pyonephrosis (patient information)

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What are the symptoms?

What are the causes?

Who is at highest risk?


When to seek urgent medical care?

Treatment options

Where to find medical care for Polynephrosis?


What to expect (Outlook/Prognosis)?

Possible complications

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Harsh Vardhan Chawla, M.B.B.S.[2]


Pyonephrosis (Greek pyon "pus" + nephros "kidney") is an infection of obstructed renal collecting system leading to accumulation of pus in the renal collecting system. Pus collects in the renal pelvis and eventually causes destruction of the renal parenchyma. Pyonephrosis is sometimes a complication of renal stones, which can be a source of persisting infection. It may also occur spontaneously.

It needs an early diagnosis and immediate intervention as it may progress to urosepsis. Treatment may require drainage, best performed by nephrostomy.

What are the symptoms of pyonephrosis?

Patients with pyonephrosis present with the following symptoms:

What causes pyonephrosis?

  • Pyonephrosis is commonly caused by bacteria like Escherichia coli, Enterococcus species among others.
  • Accumulation of pus as a result of an ongoing upper urinary tract infection (acute pyelonephritis) combined with inability to drain due to obstruction of the renal collecting system results in pyonephrosis.

Who is at highest risk?

Factors that increase the risk of pyonephrosis are:

  • Obstruction of the urinary tract: This includes conditions that reduces the flow of urine and the ability to empty the bladder (urinary retention) such as enlarged prostate in elderly men, kidney stones, ureteral strictures, tumors.
  • Immunocompromised conditions: This includes medical conditions that weaken the body's defence mechanisms, such as diabetes mellitus and AIDS. Certain medications, such as steroids, anti-cancer drugs also compromise the immunity.
  • Damaged nerves supplying the bladder: Lack of bladder control due to brain, spinal cord or nerve problems which can lead to urinary retention or leakage.
  • Pregnancy: The hormonal and mechanical changes in the urinary tract promotes stasis of urine and a tendency of the urine to go back up the ureters. Coupled with difficulty in maintaining hygiene due to distended abdomen and already shorter urethra in females, increases the risk of pyonephrosis.


The initial workup of a patient with pyonephrosis includes:

The following imaging tests may be used to help in the diagnosis:

  • Renal ultrasonography
  • Computed tomography (CT) of the abdomen and pelvis with contrast - is considered the optimal imaging modality for diagnosis of pyonephrosis
  • Excretory urography
  • Diffusion-weighted (DW) magnetic resonance imaging (MRI)

When to seek urgent medical care?

Please seek immediate medical attention if the following symptoms develop alongside the other symptoms of urinary tract infection (burning sensation or pain while urinating, frequent and intense urge to urinate):

These may be signs of a possible kidney infection which may require emergent care.

Also contact your healthcare provider immediately if symptoms re-appear shortly after treatment with antibiotics for a diagnosed urinary tract infection.

Treatment options

  • Treatment of pyonephrosis involves intravenous antibiotics and immediate decompression and drainage of pus.
  • Drainage of the pus can be done through either retrograde catheterization (placing a catheter in the ureter) or nephrostomy tube placement.
  • If the infection spreads to bloodstream, patients may require fluids and medicines intravenously to maintain adequate blood pressure.
  • The management of stones or other causes of obstruction is done later, after the acute condition is resolved.

What to expect (Outlook/Prognosis)?

Upon early treatment, the prognosis of pyonephrosis is good. There is significant improvement in the condition within 24-48 hours after drainage of the pus.

Possible complications

Long-term complications of pyonephrosis are rare if prompt medical care is received.

If not diagnosed and treated promptly, pyonephrosis can lead to septic shock causing rapid deterioration of patient's condition.

Structural changes like scarring, fistulas, and abscesses may occur if the treatment of the cause of obstruction is delayed.