Renal Pathology Part 7 Flashcards Preview

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Flashcards in Renal Pathology Part 7 Deck (51)
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Urinary Tract Obstruction (Obstructive Uropathy)

-obstructive lesions of the urinary tract increase susceptibility to infection and to stone formation, and unrelieved obstruction almost always leads to permanent renal atrophy, termed hydronephrosis or obstructive uropathy
-obstruction may be sudden or insidious, partial or complete, unilateral or bilateral; it may occur at any level of the urinary tract from the urethra to the renal pelvis


Common causes of urinary tract obstruction

-Congenital anomalies: posterior urethral valves and urethral strictures, meatal stenosis, bladder neck obstruction; ureteropelvic junction narrowing or obstruction; severe vesicoureteral reflux
-Urinary calculi
-Tumors: carcinoma of the prostate, bladder tumors, contiguous malignant disease (retroperitoneal lymphoma), carcinoma of the cervix or uterus
-inflammation: prostatis, ureteritis, urethritis, retroperitoneal fibrosis
-sloughed papillae or blood clots
-uterine prolapse and systole
-functional disorders: neurogenic (spinal cord damage or diabetic nephropathy) and other functional abnormalities of the ureter or bladder (often termed dysfunctional obstruction)



-dilation of the renal pelvis and calyces associated with progressive atrophy of the kidney due to obstruction to the outflow of urine
-even with complete obstruction, glomerular filtration persists fro some time because the filtrate subsequently diffuse back into the renal interstitium and peritoneal spaces, from where it ultimately returns to the lymphatic and venous systems


When urinary obstruction is sudden and complete, it leads to

-mild dilation of the pelvis and calyces and sometimes to atrophy of the renal parenchyma


When urinary obstruction is subtotal or intermittent,

-progressive dilation ensues, giving rise to hydronephrosis


Depending on the level of the urinary block,

-the dilation may affect the bladder first, or the ureter and then the kidney
-kidney may be slightly to massively enlarged, depending on the degree and the duration of the obstruction


Urinary obstruction morphology

-earliest features are those of simple dilation of the pelvis and calyces, but in addition there is often significant interstitial inflammation, even in the absence of infection


In chronic cases of urinary obstruction, there is

cortical tubular atrophy with marked diffuse interstitial fibrosis
-progressive blunting of the apices of the pyramids occurs, and these eventually become cupped


Acute urinary obstruction may provoke

-pain attributed to distention of the collecting system or renal capsule
-most of the early symptoms are produced by the underlying cause of the hydronephrosis
-calculi lodged in the ureters may give rise to renal colic, and prostatic enlargement may give rise to bladder symptoms


Unilateral complete or partial hydronephrosis may

-remain silent for long periods, since the unaffected kidney can maintain adequate renal function


In early stages of urinary obstruction,

-relief of obstruction leads to reversion to normal function


In bilateral partial obstruction,

-the earliest manifestation is inability to concentrate urine, reflected by polyuria and nocturne
-some patients develop distal tubular acidosis, renal salt wasting, secondary renal calculi, and chronic tubulointerstitial nephritis with scarring and atrophy of the papilla and medulla
-hypertension common


Complete bilateral obstruction of rapid onset result in

-oliguria or anuria and is incompatible with survival unless the obstruction is relieved


After relief of complete urinary tract obstruction,

-postobstructive diuresis occurs
-this can often be massive, with the kidney excreting large amounts of urine that is rich in sodium chloride



-affects 5-10% of Americans in their lifetime and the stones may form anywhere in the urinary tract
-men affected more than women, peak age at onset is between 20 and 30 years
-familial and hereditary predisposition to stone formation


4 main types of calculi

-calcium stones (about 70%) composed largely of calcium oxalate or calcium oxalate mixed with calcium phosphate
-another 15% of triple stones or struvite stones, composed of magnesium ammonium phosphate
-5-10% are uric acid stones
-1-2% are made up of cysteine


Calcium oxalate stones

-associated in about 5% of patients with hypercalcemia and hypercalciuria, such as occurs with hyperparathyroidism, diffuse bone disease, sarcoidosis, and other hypercalcemic states
-about 55% have hypercalciuria without hypercalcemia
-caused by several factors, including hyper absorption of calcium from intestine, an intrinsic impairment in renal tubular reabsorption of calcium, or idiopathic fasting hypercalciuria with normal parathyroid function


Magnesium ammonium phosphate stones

-formed largely after infections by urea-splitting bacteria (proteus and some staphylococci) that convert urea to ammonia
-resultant alkaline urine causes precipitation of magnesium ammonium phosphate salts
-form some of the largest stones, as the amount of urea excreted is large
-staghorn calculi occupying large portions of renal pelvis are frequently consequence of infection


Uric acid stones

-common individuals with hyperuricemia, such as patients with gout, and diseases involving rapid cell turnover, such as the leukemias
-more than half of patients have neither hyperuricemia nor increased urinary excretion of uric acid


Cysteine stones

-caused by genetic defects in the renal reabsorption of amino acids, including cysteine, leading to cystinuria
-form at low urinary pH


Urolithiasis Morphology

-stones are unilateral in about 80% of patients
-favored sites for formation are within renal calyces and pelves and int he bladder
-if formed in renal pelvis tend to be small
-may have smooth contours or may take the form of an irregular, jagged mass of spicules
-often many stones are found within one kidney
-on ocasión, progressive secretion of salts leads to development of branching structures known as stag horn calculi, which create a cast of the pelvic and calyceal system


Urolithiasis Clinical Features

-may be asymptomatic, produce severe renal colic and abdominal pain, or may cause significant renal damage
-larger stones often manifest themselves by hematuria
-stones also predispose to superimposed infection, both by their obstructive nature and by trauma they produce


Renal Papillary Adenoma

-small, discrete adenomas arising from renal tubular epithelium
-most frequently papillary
-present invariably within the cortex and appear grossly as pale yellow-gray, discrete, well-circumscribed nodules
-complex, branching, papillomatous structures with numerous complex fronds; or as tubules, glands, cords, or sheets of cells
-cuboidal to polygonal in shape
-do not differ from low-grade papillary renal cell carcinoma histologically



-benign neoplasm consisting of vessels, smooth muscle, and fat originating from perivascular epithelioid cells
-present in 25-50% of patients with tuberous sclerosis (loss of function mutations in TSC1 or TSC2)


Tuberous sclerosis characterized by

-lesions of the cerebral cortex that produce epilepsy and mental retardation, a variety of skin abnormalities, and unusual benign tumors at other sites, such as the heart
-susceptibility to spontaneous hemorrhage



-epithelial neoplasm composed of large eosinophilic cells having small, round, benign-appearing nuclei that have large nucleoli
-thought to arise form intercalated cells of CDs
-eosinophilic cells have numerous mitochondria
-tumors are tan or mahogany brown,r relatively homogeneous and usually well encapsulated with a central scar in 1/3 of cases
-may achieve a large size


Renal Cell Carcinoma

-represent about 3% of all newly diagnosed cancers in U.S. and accounts for 85% of renal cancers in adults
-occur most often in older individuals in their 60s and 70s and 2:1 male preponderance


Renal Cell carcinoma risk factors

-unopposed estrogen therapy
-exposure to asbestos, petroleum products, and heavy metals
-ESRD, chronic kidney disease, acquired cystic disease and tuberous sclerosis


Von Hippel-Lindaue (VHL) Syndrome

-half to 2/3s of individuals with VHL develop renal cysts and bilateral, often multiple, renal cell carcinomas
-studies implicate VHL gene in development of both familial and sporadic clear cell carcinomas


Hereditary leiomyomatosis and renal cell cancer sydnrome

-autosomal dominant disease
-caused by mutations of the FH gene, which expresses fumarate hydratase
-characterized by cutaneous and uterine leiomyomata and an aggressive type of papillary carcinoma with increased propensity for metastatic spread