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Chronic Pyelonephritis: Causes, Diagnosis and Treatment

Definition of chronic pyelonephritis

Chronic pyelonephritis is a chronic relapsing inflammatory destruction of renal tissue (chronic tubulointerstitial nephritis) and is usually caused by relapsing ascending urinary tract infections (acute pyelonephritis). Chronic pyelonephritis is not defined precisely (Dalla-Palma and Pozzi-Mucelli, 2000).

Epidemiology of chronic pyelonephritis

The proportion of chronic pyelonephritis as a cause of end-stage renal disease in children is up to 20%, but the frequency decreases.

Pathology of Chronic Pyelonephritis

• Small kidney with a nodular surface and cicatricial retractions
• Lost demarcation of cortex and medulla in affected areas of the kidney.
• Initial renal scars are frequently found at the poles.
• Irregular pyelocalyceal system (blunt or dilated calyces)
• Histologic changes are nonspecific: infiltrates of lymphocytes, fibrosis, and atrophic tubules with hyaline casts.

Etiology of Chronic Pyelonephritis

Relapsing Acute Pyelonephritis:

Recurrent acute pyelonephritis in childhood causes renal scarring. New renal scars seldom develop after the age of five years but are possible until puberty. The frequency of febrile urinary tract infections in children correlates with the severity of the scarring and the risk of chronic pyelonephritis. See also section acute pyelonephritis.

Vesicoureteral Reflux:

Since vesicoureteral reflux (VUR) causes recurrent urinary tract infections, VUR is also a significant risk factor for chronic pyelonephritis (reflux nephropathy). The severity of chronic pyelonephritis correlates with the severity of vesicoureteral reflux, and reflux nephropathy is a common cause of end-stage renal disease in children.

However, severe vesicoureteral reflux sometimes does not lead to chronic pyelonephritis. In animal experiments, only vesicoureteral reflux with infected urine causes renal scarring, sterile reflux is not harmful. This finding was confirmed in human clinical trials and is the basis for successful antibiotic prophylaxis in vesicoureteral reflux.

Neurogenic Lower Urinary Tract Dysfunction (NLUTD):

NLUTD may lead, comparable to vesicoureteral reflux, to chronic pyelonephritis by ascending infections and intrarenal reflux. High bladder pressures in the storage phase or during micturition are important risk factors.

Other Risk Factors:

Diabetes mellitus, nephrolithiasis, chronic catheterization.

Pathophysiology of Chronic Pyelonephritis

Ask-Upmark Kidney:

The Ask-Upmark kidney is a unique form of chronic pyelonephritis with an activated renin-angiotensin-aldosterone system (RAAS). The RAAS activation leads to secondary hyperaldosteronism and severe arterial hypertension, which results in further vascular injury and progressive chronic kidney disease.

Renal Insufficiency:

Chronic pyelonephritis with bilateral involvement and severe scarring may lead to end-stage renal disease.

Signs and Symptoms of Chronic Pyelonephritis

• In general, chronic pyelonephritis is asymptomatic in the absence of acute infection.
• History: risk factors are recurrent episodes of febrile urinary tract infections in childhood, neurogenic bladder disorders, and vesicoureteral reflux.
• Complications: severe bilateral chronic pyelonephritis causes arterial hypertension, anemia, and symptoms of uremia.

Diagnostic Workup of Chronic Pyelonephritis

• Urine analysis: leukocyturia, proteinuria, decreased urine concentration after thirst trial.
• Laboratory tests: elevated creatinine concentration or cystatin C.
• Renal ultrasound: small kidneys, focally thin echogenic cortex.
• Intravenous urography: blunt and deformed calyces with a thin cortex.
• Voiding cystourethrogram: for the confirmation or exclusion of vesicourethral reflux.
• Renal scintigraphy: static DMSA renal scintigraphy is the most sensitive method for the detection of parenchymal scarring of the kidney.
• Urodynamics: if neurogenic bladder dysfunction is suspected.

Treatment of Chronic Pyelonephritis

The cornerstones of treatment in chronic pyelonephritis are the consequent antibiotic therapy of urinary tract infections and the treatment of all above mentioned risk factors (vesicoureteral reflux, neurogenic bladder dysfunction, arterial hypertension). Consider low-dose longterm antibiotic treatment with nitrofurantoin, trimethoprim or an oral cephalosporin (see section vesicoureteral reflux and neurogenic bladder disorders).

Indications for nephroureterectomy: for single-sided chronic pyelonephritis with severe organ dysfunction to control recurrent urinary tract infection or arterial hypertension. Consider laparoscopic nephroureterectomy to minimize complications.

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