Chronic pyelonephritis is a serious, progressive condition affecting the kidneys. It is characterized by long-term inflammation and subsequent scarring of the renal tissue. The condition develops over time, often resulting from persistent or recurring issues within the urinary tract. This disease leads to a gradual loss of kidney function and requires sustained medical attention.
Differentiating Chronic from Acute Pyelonephritis
Chronic pyelonephritis fundamentally differs from the acute form in its progression and long-term effects on kidney structure. Acute pyelonephritis is a sudden bacterial infection, typically presenting with dramatic symptoms and treatable with antibiotics, often without permanent damage. The chronic form, however, is defined by permanent structural damage to the kidney tissue, known as renal parenchyma.
This enduring damage manifests as scarring, atrophy, and a deformity of the renal calyces, the cup-like structures that collect urine. The chronic process results from repeated episodes of infection or inflammation, or from the continuous effects of an underlying structural problem. Unlike the abrupt onset of acute infection, chronic pyelonephritis often progresses silently over many years, slowly diminishing the kidney’s ability to function.
Underlying Causes and Risk Factors
The development of chronic pyelonephritis is almost always linked to major anatomical or functional abnormalities within the urinary system. The most commonly identified underlying cause is vesicoureteral reflux (VUR), particularly in children. VUR is a condition where a faulty valve mechanism allows urine to flow backward from the bladder toward the kidneys.
This backflow of urine, especially if infected, exposes the kidney to high pressure and bacteria, triggering inflammation and scarring of the renal tissue over time. The severity of the resulting chronic pyelonephritis often correlates with the grade of VUR. Structural obstructions elsewhere in the urinary tract also pose a significant risk, as they cause urine stasis, creating a breeding ground for bacteria.
Other obstructive uropathies, such as kidney stones, tumors, or strictures, can impair the normal flow of urine and predispose the patient to recurrent infections. These persistent infections or the high pressure from obstruction contribute to progressive parenchymal damage. Factors like diabetes mellitus and neurogenic bladder dysfunction also increase the risk by promoting urine retention and ascending infection.
Recognizing the Signs and Symptoms
The clinical presentation of chronic pyelonephritis is often subtle and insidious, contrasting sharply with the dramatic, sudden onset of acute infection. Since the damage is progressive, symptoms are frequently non-specific and related to the gradual decline in kidney function. Patients may experience persistent, dull flank or abdominal pain, which is less intense than the pain associated with an acute kidney infection.
Systemic signs include persistent low-grade fever, general malaise, fatigue, and unintentional weight loss. In children, this can manifest as a failure to thrive. As the condition advances and kidney function is lost, patients may develop complications like hypertension or anemia due to the kidney’s impaired regulatory capabilities.
Diagnosis and Long-Term Management
The diagnosis of chronic pyelonephritis relies heavily on identifying the characteristic signs of structural damage. Imaging studies are crucial for this definitive diagnosis, particularly to visualize renal scarring and atrophy. Static renal scintigraphy, often performed using a DMSA scan, is considered the most sensitive method for detecting parenchymal scarring.
Other imaging modalities like ultrasound or computed tomography (CT) scans help visualize the kidney’s irregular shape, loss of cortical thickness, and the blunting or deformity of the calyces. Supporting laboratory work involves blood tests to assess kidney function, checking for elevated levels of waste products like creatinine and blood urea nitrogen (BUN). Urinalysis can also reveal signs of inflammation and infection, such as white blood cells or protein in the urine.
The long-term management strategy focuses on controlling the disease’s progression and treating underlying causes. A central component of this management is the rigorous control of blood pressure, as hypertension accelerates kidney damage. Maintaining blood pressure within a normal range helps slow the loss of renal function.
In cases where VUR or an obstruction is present, surgical correction may be necessary to normalize urine flow and prevent further damage. Long-term, low-dose antibiotic prophylaxis may be prescribed if recurrent urinary tract infections are a persistent issue. Chronic pyelonephritis can still progress to end-stage renal disease (ESRD), requiring consistent monitoring of kidney function. Patients who reach ESRD may require a kidney transplant or long-term dialysis.