Pyonephrosis refers to an extensive purulent lesion caused by infection of the renal parenchyma or the formation of a pus-filled cavity resulting from pyogenic infection in the setting of hydronephrosis due to urinary tract obstruction. It commonly arises secondary to conditions such as upper urinary tract calculi, renal tuberculosis, pyelonephritis, hydronephrosis, or uncontrolled diabetes when complicated by a pyogenic infection.
The clinical manifestations are predominantly systemic signs of infection. During acute episodes, patients may experience chills, high fever, lumbar pain, and the presence of a palpable mass. In cases of chronic pyonephrosis, symptoms may include weight loss, anemia, and recurrent urinary tract infections. In cases where the urinary tract obstruction is incomplete, pus may drain into the bladder through the ureter, leading to bladder irritative symptoms. Cystoscopy may reveal purulent drainage from the affected ureteral orifice. Ultrasonography typically demonstrates pyonephrosis, while CT imaging can further aid in diagnosis. Excretory urography or radionuclide renography often reveals reduced or absent renal function on the affected side. For right-sided pyonephrosis, differentiation from suppurative cholecystitis is necessary.
Treatment primarily involves anti-infective therapy. Nutritional support and correction of water-electrolyte imbalances are important considerations. When indicated, retrograde catheterization or nephropyelostomy for drainage of the pus provides relief. Definitive treatment addresses the underlying causative condition once the infection is controlled. If the affected kidney has lost its function and the contralateral kidney is normal, nephrectomy of the diseased kidney may be performed.