PATHOMA12 - Kidney and Urinary Tract Pathology Flashcards
What is the most common congenital renal anomaly?
Horseshoe kidney - Conjoined kidneys usually connected at the lower pole
In horseshoe kidney where is it located?
Kidney is abnormally located in the lower abdomen
What happens in horseshoe kidney?
The kidney gets caught on the inferior mesenteric artery root during its ascent from the pelvis to the abdomen
What is renal agenesis?
Absent kidney formation; may be unilateral or bilateral
What does unilateral renal agenesis lead to?
hypertrophy of the existing kidney; hyperfiltration increases risk of renal failure later in life.
What does bilateral agenesis lead to?
oligohydramnios with lung hypoplasia, flat face with low set ears, and developmental defects of the extremities (Potter sequence) incompatible with life
What is dysplastic kidney?
Non-inherited, congenital malformation of the renal parenchyma characterized by cysts and abnormal tissue (e.g., cartilage)
Is dysplastic kidney unilateral or bilateral?
Usually unilateral; when bilateral, must be distinguished from inherited polycystic kidney disease
What is polycystic kidney disease?
Inherited defect leading to bilateral enlarged kidneys with cysts in the renal cortex and medulla
How does the autosomal recessive form of polycystic kidney disease present?
in infants as worsening renal failure and hypertension; newborns may present with Potter sequence
What is the autosomal recessive form of polycystic kidney disease associated with?
congenital hepatic fibrosis (leads to portal hypertension) and hepatic cysts
How does the autosomal dominant form of polycystic kidney disease present?
in young adults as hypertension (due to increased renin), hematuria, and worsening renal failure
What is the autosomal dominant form of polycystic kidney disease due to?
A mutation in the APKD1 or APKD2 gene; cysts develop over time.
What is the autosomal dominant form of polycystic kidney disease associated with?
berry aneurysm, hepatic cysts, and mitral valve prolapse
What is medullary cystic kidney disease?
Inherited (autosomal dominant) defect leading to cysts in the medullary collecting ducts
What does parenchymal fibrosis result in?
shrunken kidneys and worsening renal failure
What is acute renal failure?
Acute, severe decrease in renal function (develops within days)
What is the hallmark of acute renal failure?
Azotemia, (increased BUN and creatinine) often with oliguria
What is acute renal failure divided into?
Its divided into prerenal, postrenal, and intrarenal azotemia and is based on etiology
What is prerenal azotemia?
Due to decreased blood flow to kidneys (e.g., cardiac failure)
Prerenal azotemia is a common cause of what?
ARF (acute renal failure)
What does decreased blood flow result in?
decreased GFR, azotemia, and oliguria.
In prerenal azotemia what happens to the ability to absorb fluid?
reabsorption of fluid and BUN ensues (serum BUN:Cr ratio > 15) tubular function remains intact (fractional excretion of sodium [FENa] < 1% and urine osmolality [osm] > 500 mOsm/kg)
What is postrenal azotemia due to?
obstruction of urinary tract downstream from the kidney (e.g., ureters)
In postrenal azotemia what does the decreased outflow result in?
decreased GFR, azotemia, and oliguria
In postrenal azotemia, what happens during the early stage of obstruction?
There is increased tubular pressure which forces BUN into the blood (serum BUN;Cr ratio > 15); tubular function remains intact (FENa < 1% and urine osm > 500 mOsm/kg).
In postrenal azotemia, what happens with long-standing obstruction?
tubular damage ensues, resulting in decreased reabsorption of BUN (serum BUN:Cr ratio < 15), decreased reabsorption of sodium (FENa > 2%), and inability to concentrate urine (urine osm < 500 mOsm/kg)
What is acute tubular necrosis?
It is injury and necrosis of tubular epithelial cells
What is the most common cause of acute renal failure?
Acute tubular necrosis (intrarenal azotemia)
In acute tubular necrosis, what happens?
Necrotic cells plug tubules; obstruction decreases GFR
In acute tubular necrosis, what is seen in the urine?
Brown, granular casts are seen in the urine
In acute tubular necrosis what does dysfunctional tubular epithelium result in?
decreased reabsorption of BUN (serum BUN:Cr ratio < 15), decreased reabsorption of sodium (FENa > 2%), and inability to concentrate urine (urine osm < 500 mOsm/kg).
What is the etiology for acute tubular necrosis?
may be ischemic or nephrotoxic,
What happens with ischemia and acute tubular necrosis?
Decreased blood supply results in necrosis of tubules.
With ischemia causing acute tubular necrosis, what is it often preceded by?
prerenal azotemia
With ischemia causing acute tubular necrosis, what parts of the nephron are particularly susceptible to ischemic damage?
proximal tubule and medullary segment of the thick ascending limb
What is another cause, aside from ischemia that results in acute tubular necrosis?
its nephrotoxic and toxic agents result in necrosis of tubules
In nephrotoxic damage leading to acute tubular necrosis, what parts of the nephron are particularly susceptible to damage?
Proximal tubule
What is the most common cause of nephrotoxic damage leading to acute tubular necrosis?
aminoglycosides
In nephrotoxic damage leading to acute tubular necrosis, what are the causes?
They include aminoglycosides, heavy metals, myoglobinuria, ethylene glycol, radiocontrast dye, and urate
What is an example of heavy metals leading to acute tubular necrosis?
lead
What causes myoglobinuria leading to acute tubular necrosis?
and example is from crush injury to muscle
What is ethylene glycol leading to acute tubular necrosis associated with?
oxalate crystals in urine
What is an example of urate leading to acute tubular necrosis?
tumor lysis syndrome
In nephrotoxicity leading to acute tubular necrosis what are used prior to initiation of chemotherapy?
Hydration and allopurinol
Why is hydration and allopurinol used prior to initiation of chemotherapy?
to decrease risk of urate-induced ATN.
What are the clinical features for acute tubular necrosis?
1) Oliguria with brown, granular casts 2) Elevated BUN and creatinine 3) Hyperkalemia (due to decreased renal excretion) with metabolic acidosis
Why is there hyperkalemia in acute tubular necrosis?
its due to decreased renal excretion
Is acute tubular necrosis reversible?
Yes, but often requires supportive dialysis since electrolyte imbalances can be fatal
In acute tubular necrosis, for how long can oliguria persist?
for 2 -3 weeks before recovery
In acute tubular necrosis, why is that oliguria can persist for 2-3 weeks?
tubular cells (stable cells) take time to reenter the cell cycle and regenerate
What is acute interstitial nephritis?
Drug-induced hypersensitivity involving the interstitium and tubules
What does acute interstitial nephritis result in?
acute renal failure (intrarenal azotemia)
What are the causes of acute interstitial nephritis?
They include NSAIDs, penicillin, and diuretics
What does acute interstitial nephritis present as?
oliguria, fever, and rash days to weeks after starting a drug; eosinophils may be seen in urine.
How does acute interstitial nephritis resolve?
with cessation of drug
What may acute interstitial nephritis progress to?
renal papillary necrosis
What is renal papillary necrosis?
Necrosis of renal papillae
What does renal papillary necrosis present with?
gross hematuria and flank pain
What are the causes for renal papillary necrosis?
- Chronic analgesic abuse (e.g., long-term phenacetin or aspirin use) 2. Diabetes mellitus 3. Sickle cell trait or disease 4. Severe acute pyelonephritis
What is nephrotic syndrome?
Glomerular disorders characterized by proteinuria (> 3.5 g/day)
What does nephrotic syndrome result in?
- Hypoalbuminemia 2. Hypogammaglobulinemia 3. Hypercoagulable state 4. Hvperlipidemia and hypercholesterolemia
In nephrotic syndrome, what is involved with hypoalbuminemia being the cause?
pitting edema
In nephrotic syndrome caused y hypogammaglobulinemia, what is there an increased risk of?
infection
In nephrotic syndrome caused by a hypercoagulable state, what is that state due to?
loss of antithrombin III
With hyperlipidemia and hypercholesterolemia causing nephrotic syndrome, what may result?
This may result in fatty casts in urine
What is the most common cause of nephrotic syndrome in children?
Minimal change disease (MCD)
What is the etiology for MCD?
For minimal change disease, it is usually idiopathic and may be associated with Hodgkin lymphoma
How does MCD appear on H&E stain?
Normal glomeruli on H&E stain, lipid may be seen in proximal tubule cells
In MCD, what is seen on electron microscopy?
effacement of foot processes
In MCD what is seen on immunofluorescence and why?
negative immunofluorescence (IF) because there are no immune complex deposits
In MCD, what happens in terms of proteinuria?
There is selective proteinuria where there is loss of albumin, but not immunoglobulin
What is the treatment for MCD?
It has an excellent response to steroids
How is the damage in MCD mediated?
damage is mediated by cytokines from T cells
What is the most common cause of nephrotic syndrome in Hispanics and African Americans?
Focal segmental glomerulosclerosis (FSGS)
What is the etiology for focal segmental glomerulosclerosis?
It is usually idiopathic, maybe associated with HIV, heroin use, and sickle cell disease
What is focal segmental glomerulosclerosis?
Focal (some glomeruli) and segmental (involving only part of the glomerulus) sclerosis on H&E stain
What is seen on electron microscopy in FSGS?
In focal segmental glomerulosclerosis, there is effacement of foot processes on EM
For focal segmental glomerulosclerosis, what is seen on IF?
Negative immunofluorescence due to no immune complex deposits
How does FSGS respond to steroids and what may it progress to?
Poor response to steroids and may progress to chronic renal failure
What is the most common cause of nephrotic syndrome in Caucasian adults?
Membranous nephropathy
What is the etiology for membranous nephropathy?
It is usually idiopathic, it may be associated with hepatitis B or C, solid tumors, SLE, or drugs (e.g., NSAIDs and penicillamine)
For membranous nephropathy, what is seen on H&E stain?
Thick glomerular basement membrane
What is the appearance of membranous nephropathy on electron microscopy?
subepithelial deposits with spike and dome appearance on EM
For membranous nephropathy, what is its appearance on EM due to?
immune complex deposition
How does membranous nephropathy respond to steroids and what might it progress to?
Poor response to steroids; progresses to chronic renal failure
What is membranoproliferative glomerulonephritis?
Thick glomerular basement membrane on H&E stain, often with tram-track appearance
What is membranoproliferative glomerulonephritis due to?
immune complex deposition (granular IF)
What is membranoproliferative glomerulonephritis divided into?
two types based on location of deposits
What is membranoproliferative glomerulonephritis - Type I?
subendothelial associated with HBV and HCV
What is membranoproliferative glomerulonephritis - Type II?
(dense deposit disease) intramembranous; associated with C3 nephritic factor (autoantibody that stabilizes C3 convertase, leading to overactivation of complement, inflammation, and low levels of circulating C3)
How does membranoproliferative glomerulonephritis respond to steroids and what might it progress to?
Poor response to steroids; progresses to chronic renal failure
How is diabetes mellitus related to nephrotic syndrome?
high serum glucose leads to nonenzymatic glycosylation of the vascular basement membrane resulting in hyaline arteriolosclerosis.
With diabetes mellitus leading to nephrotic syndrome what happens to the glomerular filtration pressure?
There is high glomerular filtration pressure
With diabetes mellitus leading to nephrotic syndrome why is there high glomerular filtration pressure?
glomerular efferent arteriole is more affected than the afferent arteriole