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Chronic Pyelonephritis: Causes, Diagnosis and Treatment

Definition of Chronic Pyelonephritis

Chronic pyelonephritis is a chronic relapsing inflammatory destruction of the renal parenchyma (chronic destructive tubulointerstitial nephritis), usually caused by recurrent febrile urinary tract infections in combination with predisposing factors such as vesicoureteral reflux, intrarenal reflux, urinary obstruction, or neurogenic lower urinary tract dysfunction. Although the term is frequently used in clinical practice, no uniform, precise definition exists.

Epidemiology of Chronic Pyelonephritis

Chronic pyelonephritis accounts for up to 20% of cases of end-stage kidney disease in children, although this proportion is declining.

Pathology of Chronic Pyelonephritis

• Small kidney with an irregular surface and cicatricial retractions
• Loss of corticomedullary demarcation in areas of scarring; in reflux nephropathy, initial scars are often located at the renal poles
• Distortion of the pyelocalyceal system by scarring
• Nonspecific histologic findings in affected areas, including lymphocytic infiltrates, fibrosis, and atrophic tubules with hyaline casts

Etiology of Chronic Pyelonephritis

Recurrent Acute Pyelonephritis

Recurrent episodes of acute pyelonephritis cause renal parenchymal scarring in childhood. New renal scars rarely develop after age five but may occur until puberty. In children, a higher frequency of febrile urinary tract infections is associated with more extensive scarring. See also the section on acute pyelonephritis and renal scarring.

Vesicoureteral Reflux

Because VUR causes recurrent urinary tract infections, it is an important risk factor for chronic pyelonephritis (reflux nephropathy). The severity of chronic pyelonephritis correlates with the severity of vesicoureteral reflux. Reflux nephropathy is a common cause of end-stage kidney disease in children.

Neurogenic Lower Urinary Tract Dysfunction

High storage pressures, detrusor-sphincter dyssynergia, residual urine, and recurrent infections can lead to progressive damage to the upper urinary tract. High detrusor pressures during the storage or voiding phase are important risk factors.

Other Risk Factors

Other risk factors include urinary obstruction, nephrolithiasis, chronic catheterization, bladder-emptying disorders, obstructive uropathies, diabetes mellitus, and, rarely, anatomic abnormalities associated with recurrent infections.

Pathophysiology of Chronic Pyelonephritis

Ask-Upmark Kidney

In the Ask-Upmark kidney, scarring caused by chronic pyelonephritis leads to renin release, secondary hyperaldosteronism, and arterial hypertension. Hypertension is an additional vascular risk factor for progressive kidney damage.

Kidney Failure

Bilateral involvement and extensive scarring may lead to chronic kidney disease.

Signs and Symptoms of Chronic Pyelonephritis

• Chronic pyelonephritis is generally asymptomatic in the absence of acute infection
• Relevant history includes febrile urinary tract infections in early childhood, vesicoureteral reflux, and neurogenic lower urinary tract dysfunction
• With progressive bilateral disease, arterial hypertension, anemia, and symptoms of uremia may develop

Diagnosis of Chronic Pyelonephritis

• Urinalysis: leukocyturia and proteinuria; a positive urine culture indicates a urinary tract infection
• Laboratory tests: elevated creatinine and cystatin C, depending on kidney function
• Renal ultrasound: small kidney, cortical thinning, focal parenchymal scars, or asymmetry in kidney size
• CT or MR urography: used to assess upper urinary tract anatomy when ultrasound findings are abnormal
• Urography: intravenous urography has been replaced by CT or MR urography and is no longer a routine diagnostic test
• Voiding cystourethrography: used to confirm or exclude VUR when indicated by the history, age, clinical findings, or imaging
• Renal scintigraphy: static DMSA renal scintigraphy is the most sensitive method for detecting renal parenchymal scarring (Maringhini et al., 2024)
• Urodynamics: indicated when neurogenic lower urinary tract dysfunction or clinically significant bladder-emptying dysfunction is suspected

Treatment of Chronic Pyelonephritis

The cornerstones of treatment are prompt antibiotic treatment of febrile urinary tract infections and treatment or correction of the risk factors listed above (VUR and neurogenic lower urinary tract dysfunction) and complications (arterial hypertension and chronic kidney disease).

Vesicoureteral Reflux

See the section on vesicoureteral reflux.

Neurogenic Lower Urinary Tract Dysfunction

See the section on neurogenic lower urinary tract dysfunction.

Nephrectomy

Nephrectomy is indicated for unilateral disease with a nonfunctioning kidney to control symptoms such as recurrent urinary tract infections or arterial hypertension.

References

Dalla-Palma und Pozzi-Mucelli 2000 DALLA-PALMA, L. ; POZZI-MUCELLI, F.: [The imaging of chronic renal infections].
In: Radiologe
40 (2000), Nr. 6, S. 537–46

  Deutsche Version: Chronische Pyelonephritis

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