24.5
Pyélonéphrite aiguë I : Introduction
La pyélonéphrite est une infection bactérienne qui affecte principalement le parenchyme rénal et le système collecteur, incluant le bassinet, les tubu…
La pyélonéphrite est une infection bactérienne qui affecte le bassinet du rein, les tubules et le tissu interstitiel d’un ou des deux reins.
Il peut être classé comme aigu, une infection grave soudaine ou chronique en raison d’infections répétées ou d’anomalies structurelles qui endommagent le rein.
La principale cause de pyélonéphrite aiguë est une infection bactérienne, généralement Escherichia coli. Cependant, d’autres bactéries, telles que Proteus, Klebsiella, Enterococcus et Pseudomonas, sont également à l’origine de la maladie.
La pyélonéphrite aiguë commence généralement par une colonisation bactérienne de l’urètre, suivie d’une migration vers la vessie, provoquant une cystite.
De la vessie, les bactéries peuvent remonter par les uretères jusqu’aux reins, notamment en cas de stase urinaire ou de reflux vésico-urétéral.
Une fois que les bactéries atteignent les reins, elles envahissent l’interstitium rénal, déclenchant la libération de cytokines et d’autres médiateurs inflammatoires par le système immunitaire.
Cette réponse entraîne un œdème rénal, une infiltration de neutrophiles et des lésions du tissu rénal, provoquant des symptômes tels qu’une forte fièvre et des frissons, une leucocytose, une bactériurie, des douleurs au flanc et au bas du dos, des mictions douloureuses, des nausées et des vomissements.
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Q1: What is acute pyelonephritis and which parts of the kidney does it affect?
Acute pyelonephritis is a sudden, severe bacterial infection affecting the renal pelvis, tubules, and interstitial tissue of one or both kidneys. It differs from chronic pyelonephritis, which develops from repeated infections or structural abnormalities that progressively damage kidney tissue. The infection typically ascends from the lower urinary tract.
Q2: How does bacteria cause acute pyelonephritis to develop?
Acute pyelonephritis typically begins with bacterial colonization of the urethra, followed by migration to the bladder, causing cystitis. From the bladder, bacteria ascend through the ureters to the kidneys, particularly when urinary stasis or vesicoureteral reflux is present. Once bacteria invade the renal interstitium, they trigger an inflammatory immune response.
Q3: Which bacteria most commonly cause acute pyelonephritis?
Escherichia coli is the primary cause of acute pyelonephritis, accounting for approximately 70-80% of cases. Other bacteria responsible for the infection include Proteus, Klebsiella, Enterococcus, and Pseudomonas. These organisms typically originate from the lower urinary tract and ascend to the kidneys.
Q4: What inflammatory changes occur in the kidney during acute pyelonephritis?
When bacteria invade the renal interstitium, the immune system releases cytokines and inflammatory mediators, triggering renal edema and neutrophil infiltration. This inflammatory response causes injury to renal tissue. If untreated, the inflammation can progress to serious complications like renal abscess formation or sepsis.
Q5: What are the typical symptoms patients experience with acute pyelonephritis?
Patients with acute pyelonephritis commonly present with high fever and chills, flank and lower back pain, painful urination, nausea, and vomiting. Laboratory findings include leukocytosis (elevated white blood cells), bacteriuria, and pyuria (pus in urine). Malaise and headache often accompany these symptoms as part of the systemic inflammatory response.
Q6: What risk factors increase susceptibility to acute pyelonephritis?
Several factors predispose individuals to acute pyelonephritis, including untreated urinary tract infections, vesicoureteral reflux, obstructive uropathy from kidney stones or tumors, immunosuppression from diabetes or HIV, pregnancy-related hormonal changes, and indwelling catheters. These conditions either promote bacterial ascension or compromise the immune system's ability to fight infection.
Q7: How does acute pyelonephritis differ from chronic pyelonephritis?
Acute pyelonephritis is a sudden, severe bacterial infection, while chronic pyelonephritis develops from repeated infections or structural abnormalities that progressively damage kidney tissue over time. Acute cases present with acute symptoms like high fever and severe flank pain, whereas chronic pyelonephritis may develop insidiously with long-term kidney damage.