Pyonephrosis is a serious medical condition involving an infected and obstructed kidney. It is characterized by the accumulation of pus within the kidney’s collecting system, which results from a blockage in the urinary tract that prevents normal urine drainage. The stagnant urine creates a breeding ground for bacteria, leading to a severe infection. This condition is a urological emergency because the pressure from the pus can cause significant damage to the kidney tissue and potentially lead to a life-threatening systemic infection known as urosepsis.
Underlying Causes and Risk Factors
Pyonephrosis arises from the combination of an upper urinary tract obstruction and a concurrent kidney infection, known as pyelonephritis. The obstruction prevents the normal flow of urine, causing it to back up and distend the kidney, a condition called hydronephrosis. This stagnant urine provides an ideal environment for bacteria to multiply and form pus. The infection itself begins in the lower urinary tract and ascends to the kidneys.
The most common causes of urinary tract obstruction are kidney stones, which can become lodged along the urinary path. Other causes of blockage include tumors in the kidney or ureter, congenital abnormalities that result in a narrowing of the urinary tract, and strictures, which are areas of scarring from surgery or infection. In some cases, fungus balls can also obstruct the ureter, especially in individuals with compromised immune systems.
A history of recurrent urinary tract infections (UTIs) is a significant risk factor. Conditions that weaken the immune system, such as diabetes mellitus or AIDS, also make it more difficult for the body to fight off the initial infection. The use of immunosuppressive medications, like steroids, can have a similar effect.
Identifying Symptoms
The classic triad of symptoms for pyonephrosis includes a high fever, shaking chills, and flank pain. The flank pain is located on one side of the back, just below the ribs, and can be severe. This pain is a direct result of the kidney swelling and the pressure exerted by the accumulated pus.
Individuals with pyonephrosis may experience other symptoms. Nausea and vomiting are common, and a general feeling of illness or discomfort, known as malaise, is also reported. Some people may have symptoms of a lower urinary tract infection, such as painful or frequent urination, and the urine itself may appear cloudy or have a foul odor.
Diagnostic Process
Diagnosis begins with a medical history and a physical examination. During the physical exam, a doctor will check for fever and tenderness in the flank area, which are indicators of a kidney infection. Laboratory tests are ordered to confirm the presence of an infection and assess its severity. Blood tests can reveal a high white blood cell count.
A urinalysis and a urine culture are performed to analyze the urine for bacteria, pus, and blood. The urine culture helps identify the type of bacteria causing the infection to guide antibiotic treatment. While these tests can confirm an infection, imaging studies are necessary to visualize the obstruction and the pus within the kidney.
An ultrasound is often the initial imaging test used to detect hydronephrosis and potential blockages like kidney stones. A computed tomography (CT) scan is the most definitive imaging study for diagnosing pyonephrosis. A CT scan provides detailed cross-sectional images of the kidneys, showing the extent of the pus collection, the precise location of the obstruction, and the degree of inflammation in the surrounding tissues.
Treatment and Management
The treatment for pyonephrosis is urgent and has two primary objectives: draining the pus from the obstructed kidney and administering antibiotics to control the infection. Drainage relieves the pressure within the kidney, prevents further damage, and controls the source of the infection. Without immediate intervention, the infection can spread to the bloodstream, leading to sepsis.
Two main procedures are used to drain the pus from the kidney. The first is a percutaneous nephrostomy, a procedure where a thin tube is inserted through the skin of the back directly into the kidney, allowing pus to drain into an external collection bag. The second option is the placement of a ureteral stent, a thin, flexible tube inserted through the bladder and up into the ureter that bypasses the obstruction, allowing drainage into the bladder.
Along with the drainage procedure, patients are given broad-spectrum intravenous antibiotics to fight the infection. The choice of antibiotic may be adjusted once urine culture results are available for a more targeted approach. In severe cases where the kidney has been irreversibly damaged, a nephrectomy, or surgical removal of the kidney, may be required after the acute infection has resolved. The underlying cause of the obstruction, such as a kidney stone or tumor, must also be addressed to prevent recurrence.