Pyonephrosis is a kidney infection in which microbes--bacterial or fungal--infect a kidney, traveling up from the urethra or into the kidney through the blood. Pus forms, blocking urine from exiting the kidney and, if left unchecked, causes the loss of kidney function. Doctors diagnose pyonephrosis based on the symptoms, imaging tests such as ultrasound or CT scans, urinalysis, and blood tests. Initial treatment consists of IV antibiotics, but surgical evacuation of the pus is also necessary to remove the blockage. In some cases, when a blockage is initially caused by something other than infection (e.g., kidney stones and tumors), additional treatment is needed to ensure pyonephrosis does not recur.
If pyonephrosis is treated quickly, the infected kidney usually recovers within 24 to 28 hours. In severe cases, permanent kidney damage or complete kidney failure is possible. In these circumstances, it may be necessary to remove part or all of the affected kidney.
Medications for the Treatment of Pyonephrosis
Once pyonephrosis is diagnosed, a patient must receive IV antibiotics (e.g., gentamicin or ampicillin) before any procedures are done. In many people, the infection reaches the blood (sepsis), which manifests with symptoms such as high fever, elevated heart rate, low blood pressure, rapid heart beat, rapid breathing, and altered mental status. These patients also require vigorous rehydration with IV fluids and mineral salts, and may also need pressors, such as dopamine, to maintain adequate blood pressure.
Once urinalysis and bacterial culture results come back, a physician may need to make changes to the initially prescribed antibiotics. Additionally, imaging tests may reveal signs that the infection is due to fungal infection (which shows up as clumps of fungus) or tuberculosis (which appear as tubercules, the small, rounded masses of bacteria characteristic of tuberculosis). In these cases, antifungal medications or multiple antibiotics will be used.
Then, once the pus is drained from the infected kidney, cultures will also be done on the pus. This can uncover pathogens not present in urine cultures. Medications such as antibiotics or antifungals may also be infused directly into the kidney at the time of drainage.
Surgical Treatment of Pyonephrosis
Pyonephrosis, once diagnosed, requires surgery almost immediately in order to decompress the kidney, drain the pus, and definitively diagnose and medicate the source of infection. There are three surgical options:
- Retrograde decompression with a ureteral stent: If a patient is generally healthy and doesn’t show signs of sepsis, a surgeon may insert a ureteral stent to drain the pus and accumulated urine. With the patient under general anesthesia, the surgeon inserts a cytoscope into the bladder through the urethra and uses it to locate the ureter and affected kidney. He then places a guide wireinto the ureter, confirms placement with an x-ray or fluoroscopy (continuous x-ray images), then inserts a stent over the guide wire and past the obstruction. The stent is left in place for anywhere from a few days up to 12 weeks, until the obstruction causing the pyonephrosis is cleared. Complications, such as pain and infection, are common the longer the stent remains in place; it should be monitored and removed as soon as it is no longer necessary. This approach avoids the need for incision and keeps the drainage catheter internal. However, medication cannot be infused directly into the kidney with a ureteral stent, and treatment of any obstruction must be delayed until the pyonephrosis is resolved. In some cases, such obstructions may make retrograde decompression impractical.
- Nephrostomy: The most common treatment for pyonephrosis is drainage by placement of a nephrostomy tube. This procedure is usually done under local anesthetic, and involves a small incision in the skin, though the back, and into the affected kidney. A surgeon uses CT or ultrasound is to guide a tube into the interior of the kidney; this is the nephrostomy. The tube is left in place until the pus and urine drain and the infection resolves. Antibiotics, antifungals, and other drugs can be infused directly into the kidney through the nephrostomy tube if more aggressive drug therapy is needed. If the blockage is caused directly by the pus accumulation or by aggregation of fungal or tubercular cells, antimicrobial therapy should resolve the blockage. If the obstruction is caused by kidney stones, damage to the ureter, or other sources, additional treatment may be needed to deal with it.
- Nephrectomy: If the infection does not resolve with drainage by stent or nephrostomy, or if treatment was delayed resulting in serious kidney damage, part or all of the affected kidney may need to be removed. This surgery, known as a nephrectomy (radical or partial), can be done laparascopically--laparoscopic removal has been shown to be safe and effective if an infection is limited to the kidney. In some cases, a surgeon may need to do an open procedure, in which a large incision is made in the abdomen.
Regardless of the surgical method, cultures should be done on the fluid drained from the infected kidney. This provides a definitive diagnosis of pyonephrosis and also allows doctors to identify which organism caused the infection and which drugs will most effectively eradicate the infection.
Prognosis for Pyonephrosis
Prompt drainage of the infected kidney usually results in full recovery with few complications. If treatment is delayed, a partial or full nephrectomy may be necessary. Even in these cases, most people who have only one kidney live full, healthy lives.
References:
Dyer, R.B., Chen, M.Y., Zagoria, R.J., Regan, J.D., Hood, C.G., Kavanaugh, P.V. (2002). Complications of Ureteral Stent Placement. RadioGraphics. 22: 1005-1022.
Harrison, G.S. (1983). The Management of Pyonephrosis. Annals of the Royal College of Surgeons of England. 65: 126–127.
Yoder, I.C., Pfister, R.C., Lindfors, K.K., and Newhouse, J.H. (1983). Pyonephrosis: imaging and intervention. AJR: American Journal of Roentgenology. 141:735-40.
