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Flashcards in Renal Pathology part 5 Deck (65)
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Acute Pyelonephritis

-suppurative inflammation of the kidney caused by bacterial and sometimes viral (e.g., polyomavirus) infection, which can reach the kidney by hematogenous spread or, more commonly, through the ureters in association with vesicoureteral reflux


Acute Pyelonephritis hallmarks

-patchy interstitial suppurative inflammation, intratubular aggregates of neutrophils, neutrophilic tubulitis and tubular necrosis
-suppuration may occur as discrete focal abscesses or large wedge-like areas and can involve one or both kidneys


complications of acute pyelonephritis

-papillary necrosis is seen mainly in diabetes, sickle cell disease, and in those with urinary tract obstruction
-pylonephrosis is seen when there is total or almost complete obstruction, particularly when it is high in the urinary tract
-perinephric abscess is an extension of suppurative inflammation through the renal capsule into the perinephric tissue


After acute phase of pyelonephritis,

healing occurs
-neutrophilic infiltration is replaced by one that is predominantly composed of macrophages, plasma cells, and lymphocytes
-inflammatory foci are eventually replaced by irregular scars that can be seen on the cortical surface as fibrous depressions.
-such scars are characterized microscopically by tubular atrophy, interstitial fibrosis, and a lymphocytic infiltrate in a characteristic patchy, jigsaw pattern with intervening preserved parenchyma


Pyelonephritic scar is

almost always associated with inflammation, fibrosis, and deformation of the underlying calyx and pelvis, reflecting the role of ascending infection and vesicoureteral reflux in the pathogenesis of disease


Acute pyelonephritis can be associated with

-urinary tract obstruction
-instrumentation of the urinary tract
-vesicouteral reflux
-gender and age
-preexisting renal lesions, causing intrarenal scarring and obstruction
-diabetes mellitus
-immunosuppression and immunodeficiency


Acute pyelonephritis usually presents with

-a sudden onset of pain at the costovertebral angle and systemic evidence of infection, such as fever and malaise
-there are often indications of bladder and urethral irritation, such as dysuria, frequency, and urgency
-urine contains many leukocytes (pyuria) derived from the inflammatory infiltrate, but pyuria does not differentiate upper from lower UTI


Indicates renal involvement in UTI

-the finding of leukocyte casts, typically rich in neutrophils (pus casts)
-casts are formed only in tubules


Diagnosis of UTI infection is established by

-quantitative urine culture


Uncomplicated acute pyelonephritis follows

a benign coures, and symptoms disappear within a few days after the institution of appropriate antibiotic therapy
-bacteria may persist in the urine though or there may be recurrence of infection with new serologic types of E. coli or other organisms.


In the presence of unrelieved urinary obstructor, diabetes, or immunodeficiency, acute pyelonephritis may

be more serious leading to repeated septicemic episodes
-superimposition of papillary necrosis may lead to acute renal failure


An emerging viral pathogen causing pyelonephritis in kidney allografts is

-latent infection with polyomavirus is widespread in general population, and immunosuppression of the allograft recipient can lead to reactivation of latent infection and the development of nephropathy resulting in allograft failure in up to 5% of kidney transplant recipients


Polyomavirus nephropahty

-characterized by infection of tubular epithelial cell nuclei, leading to nuclear enlargement and intranuclear inclusions visible by light microscopy (viral cytopathic effect)


Chronic pyelonephritis

-a disorder in which chronic tubulointerstitial inflammation and scarring involve the calyces and pelvis
-only chronic pyelonephritis and analgesic nephropathy affect the calyces
-important cause of kidney destruction in children with severe lower urinary tract abnormalities
-2 forms: reflux nephropathy and chronic obstructive pyelonephritis


Reflux Nephropathy

-occurs early in childhood as a result of superimposition of a urinary infection on congenital vesicoureteral reflux and internal reflux
-may be unilateral or bilateral; thus, the continuous renal damage may cause scarring and atrophy of one kidney or involve both, leading to renal insufficiency
-vesicoureteral reflux occasionally cause renal damage in the absence of infection (sterile reflux), but only when obstruction is severe.


Chronic obstructive pyelonephritis

-recurrent infections superimposed on diffuse or localized obstructive lesions lead to repeated bouts of renal inflammation and scarring, resulting in chronic pyelonephritis
-the effects of obstruction contribute to the parenchymal atrophy; indeed, it is sometimes difficult to differentiate the effects of bacterial infection from those of obstruction alone
-can be bilateral, as with posterior urethral valves, resulting in renal insufficiency unless the anomaly is corrected, or unilateral, as occurs with calculi and unilateral obstructive anomalies of the ureter


Chronic Pyelonephritis and Reflux Nephropathy Morphology

-kidneys usually irregularly scarred; if bilateral, the involvement is asymmetric
-coarse, discrete, corticomedullary scars overlying dilated, blunted, or deformed calyces, and flattening of the papillae
-dilated tubules with flattened epithelium may be filled with casts resembling thyroid colloid
-varying degrees of fibrosis
-Arcuate and interlobular vessels demonstrate obliterative intimal sclerosis in the scarred areas


Xanthogranulomatous pyelonephritis

-relatively rare form of chronic pyelonephritis characterized by accumulation of foamy macrophages intermingled with plasma cells, lymphocytes, polymorphonuclear leukocytes, and occasional giant cells


Chronic obstructive pyelonephritis may have

a silent onset or present with manifestations of acute recurrent pyelonephritis, such as back pain, fever, pyuria, and bacteria
-receive medical attention relatively late in their disease course because of the gradual onset of renal insufficiency and hypertension


Reflux nephropathy is often

discovered in children when the cause of hypertension is investigated
-radiographic studies show asymmetrically contracted kidneys with characteristic coarse scars and blunting and deformity of the calyces system


Loss of tubular function in reflux nephropathy gives rise to

polyuria and nocturia


Tubulointerstitial Nephritis Induced by drugs and toxins

-can trigger an immunology reaction, exemplified by the acute hypersensitivity nephritis induced by drugs such as methicillin; cause acute tubular injury; and cause subclinical but cumulative injury to tubules that takes years to result in chronic renal insufficiency


Acute Drug-Induced Interstitial Nephritis

-most frequently occurs with synthetic penicillins, other synthetic antibiotics, diuretics, NSAIDs, and miscellaneous drugs


Drug-induced acute interstitial nephritis begins

about 15 days after drug exposure and is characterized by fever, eosinophils, a rash in about 25% of patients, and renal abnormalities (hematuria, mild proteinuria, and leukocyturia)
-rising serum creatinine or acute kidney injury with oliguria develops in about 50% of cases, particularly in older patients


Acute Drug-Induced Interstitial Nephritis histologic exam

-interstitium shows variable but frequently pronounced edema and infiltration by mononuclear cells, principally lymphocytes and macrophages
-eosinophils and neutrophils may be present, often in clusters and large numbers, and smaller numbers of plasma cells and mast cells are sometimes also present


With methicillin and thiazides,

interstitial nonnecrotizing granulomas may be seen


Acute Drug-Induced Interstitial Nephritis Morphology

-Inflammation may be more prominent int he medulla her the inciting agent is often concentrated
-tubulitis is common
-variable degrees of tubular necrosis and regeneration are present
-glomeruli are normal except in some cases caused by NSAIDs, when minimal-change disease and the nephrotic syndrome develop concurrently


In analgesic nephropathy

-papillae can show various stages of necrosis, calcification, fragmentation, and sloughing


It is important to recognize drug-induced acute interstitial nephritis because

-withdrawal of the offending drug is followed by recovery, although it may take several months, and irreversible damage can occur


Acute Drug-Induced Interstitial Nephritis Clinical Features

-on occasion, necrotic papillae are excreted and may cause gross hematuria or renal colic due to ureteric obstruction