Introduction
Pyonephrosis occurs as a result of obstruction of the urinary tract. It can be caused due to a variety of reasons which in turn causes distension of the kidneys and subsequently leads to renal failure. Purulent exudate such as inflammatory cells, infectious organisms, and necrotic tissues gets accumulated in the urinary tract and forms abscesses. Rapid diagnosis is essential to fend off the development of sepsis and renal failure.
What Is Pyonephrosis?
Pyonephrosis is a term used to describe the collection of pus in the renal pelvis. It is derived from the Greek word "pyon" - pus and "nephros" - kidney. It is the suppurative infection of the upper respiratory tract. Pyonephrosis mostly develops in patients with hydronephrosis, in which the urine gets accumulated in the urinary tract and associated calculi or other obstructions.
What Is the Difference Between Pyonephrosis and Pyelonephritis?
Pyonephrosis is a condition in which there is a collection of pus in the renal pelvis due to obstruction of the urinary tract. At the same time, pyelonephritis is a bacterial infection of the upper respiratory tract causing inflammation of the kidneys. Pyelonephritis can turn anytime into pyonephrosis if it obstructs the urinary tract.
What Are the Causes of Pyonephrosis?
It is caused mainly due to the obstruction of the urinary tract. The possible reasons for such obstruction include:
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Urolithiasis (Renal Calculi) - Renal stones are the main cause of pyonephrosis as it obstructs the urinary tract causing infection. Studies report that 70% of pyonephrosis occurs due to renal stones.
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Intrinsic Causes - This includes:
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Fungal Balls - Caused due to fungal infections.
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Tumors - Tumors in the urinary tract.
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Blood Clots - Formed due to an injury or surgical procedures.
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Extrinsic Causes - This includes:
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Lymph Nodes - Any lymph nodes obstructing the urinary tracts.
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Prostatic Cancer - Cancer of the prostate can also cause obstruction.
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What Are the Organisms Involved in the Etiology of Pyonephrosis?
Studies report that the most common organisms involved in the pathogenesis of pyonephrosis involve;
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Escherichia coli.
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Klebsiella enterococcus.
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Proteus organisms.
What Is the Pathogenesis of Pyonephrosis?
The obstruction of the urinary tract by the above said causative factors will lead to the accumulation of purulent exudates such as inflammatory cells, waste products, and infectious organisms. These accumulated substances are walled off by the infection, which protects the infected foci from the body's immune response and antibiotics. If not recognized, this will further progress to urosepsis [bacterial infection of the urinary tract], causing deterioration of the renal tissues. If left untreated, this, in turn, will develop into an early-stage renal disease.
What Are the Clinical Signs of Pyonephrosis?
The clinical presentation of this condition involves:
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Asymptomatic - 15% of patients affected will remain asymptomatic for a long duration.
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Pain - The majority of patients develop flank pain in the abdomen, back, and while urinating.
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Urosepsis - Infection of the urinary tract, mostly seen in immunocompromised patients.
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Associated Symptoms - Pain will be associated with fever and chills.
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Hematuria - Blood in the urine (hematuria) is seen in a few patients.
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Gastrointestinal Discomfort - Reported in a few patients with a high fever.
How Is Pyonephrosis Diagnosed?
The steps in diagnosis involve:
1. History
A thorough history of the symptoms associated with the disease should be collected from the patient. Any previous history of renal calculi, surgery, or infection will also give clues in the diagnosis of the disease condition.
2. Ultrasound of Kidney
Kidney ultrasound show dilation and focal areas of decreased echogenicity due to the presence of pus in the renal parenchyma.
3. Computerized Tomography (CT) Scan.
CT scan findings typically show hydronephrosis (high-density fluid in the renal parenchyma), thickening of the renal pelvis, and perirenal inflammation.
4. Magnetic Resonance Imaging (MRI) Scan.
MRI scan may demonstrate renal pelvic thickening and fluid collection in the kidneys.
5. Cyto Bacteriological Examination of Urine
Cytopathalogical examination of urine will show the presence of infected cells, inflammatory cells, and dead cells.
Why Are Antibiotics Not So Effective in the Treatment of Pyonephrosis?
Pyonephrosis usually does not respond well to antibiotics because of the obstruction in the urinary tract. Due to this obstruction, there will be reduced blood flow and edema in the infected area that hinders the entry of antibiotics.
How Is Pyonephrosis Managed?
Treatment of this condition requires interventional surgery to eliminate the infection from the urinary system. The different modalities of management include
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Percutaneous Nephrostomy - This is a procedure in which a small flexible catheter is inserted into the kidney through the skin in the back or flank treason to drain the urine. It is an effective and minimally invasive procedure to remove the retained urine and drain the pus from the kidney.
It is reported to be the first line of treatment in the management of pyonephrosis.
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Ureteral Stent - This is a thin tube that is placed inside the ureter, with one end of the tube placed inside the kidney and the other end in the bladder. This helps in draining the accumulated urine from the kidney, thereby relieving infection.
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Radical Nephrectomy - Radical nephrectomy is indicated in patients with tumors obstructing the urinary tract. In this procedure, the entire kidney and a portion of the tube connecting it to the bladder are removed. It is found to be effective in patients where one kidney has lost most of its function and the other kidney is functioning normally.
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Antibiotics - Antibiotics can be given along with interventional therapies to reduce the aggressiveness of the infection and to limit the hematogenous spread of infection.
Conclusion
Pyonephrosis is the pus in the renal pelvis. Caused due to the majority of factors that obstruct the urinary tract. This obstruction slowly affects the renal parenchyma leading to sepsis and renal failure. Early diagnosis and treatment of the condition are important. The first and foremost aim is to eliminate the etiological factors obstructing the urinary tract. The prognosis of this condition is good if addressed earlier.
