Renal Pathology Flashcards
Most common congenital renal anomaly in which there is conjoined kidneys usually connected at the lower pole due to restricted ascension by inferior mesenteric artery
Horseshoe kidneys
Unilateral renal agenesis leads to _______ of existing kidney. _______ increases the risk of renal failure later in life
Hypertrophy; hyperfiltration
Bilateral renal agenesis is incompatible with life and is associated with oligohydramnios. What are the consequences of oligohydramnios?
Lung hypoplasia, flat face with low set ears, and developmental defects of extremities (Potter sequence)
Noninherited, congenital malformation of renal parenchyma characterized by cysts and abnormal tissue (e.g., cartilage)
Dysplastic kidney
[Important to note that this is NOT an inherited disorder!]
T/F: dysplastic kidney is most commonly unilateral
True
NOTE — when it is bilateral, it must be distinguished from inherited polycystic kidney disease
Inherited renal defect resulting in bilateral enlarged kidneys with cysts in renal cortex and medulla
Polycystic kidney disease
The _____ ______ inheritance pattern of PKD presents in infancy with worsening renal failure and HTN. Newborns may present with Potter sequence. This condition is associated with congenital _______ fibrosis and _______ cysts
Autosomal recessive; hepatic; hepatic
The ______ ______ inheritance pattern of PKD presents in young adults with HTN, hematuria, and worsening renal failure (with increased plasma renin). It is caused by a mutation in the ____ or ______ gene and cysts develop over time
Autosomal dominant; APKD1; APKD2
3 associations with autosomal dominant PKD
Berry aneurysm
Hepatic cysts
Mitral valve prolapse
Medullary cystic kidney disease is a ______ _______ inherited defect leading to cysts in medullary collecting ducts. ________ fibrosis results in shrunked kidneys and worsening renal failure
Autosomal dominant; parenchymal
Acute renal failure is defined as acute, severe decrease in renal function. The hallmark is ________, often with oliguria. It is divided into prerenal, postrenal, and intrarenal based on etiology
Azotemia
increase in nitrogenous waste products in the blood — measured as BUN/Cr
Cause of prerenal azotemia
Decreased blood flow to kidneys
Decreased blood flow to the kidney leads to prerenal azotemia which manifests as azotemia and oliguria. How does this alter the GFR, BUN:Cr, FeNa, and urine osmolality?
Decreased GFR
Increased BUN:Cr (>15-20 — due to increase in reabsorption of fluid and BUN)
FENa <1% and Urine osmolality >500 (kidneys retain ability to concentrate the urine)
What causes postrenal azotemia?
Obstruction of urinary tract downstream from kidney
How does postrenal azotemia alter the GFR, BUN:Cr, FeNa, and urine osmolality in the EARLY stages?
GFR Decreases
Serum BUN:CR increases (>15) — due to increased tubular pressure
FeNA <1%, urine osmolality >500 — kidneys retain ability to concentrate the urine
How does postrenal azotemia alter the BUN:Cr, FeNa, and urine osmolality in the LATE stages in the case of longstanding obstruction and tubular damage?
BUN:Cr decreases (<15) due to decreased reabsorption
FENa >2% due to decreased reabsorption
Urine osmolality <500 — inability to concentrate urine!
Most common cause of acute renal failure
Acute tubular necrosis — causes injury and necrosis of tubular epithelial cells
How does ATN cause acute renal failure?
Necrotic tubular epithelial cells plug the tubules — obstruction decreases GFR
Brown granular casts are seen in the urine
How does acute tubular necrosis alter the GFR, BUN:Cr, FeNa, and urine osmolality in the EARLY stages?
Decreased GFR
Decreased reabsorption of BUN —> BUN:Cr <15
Decreased reabsorption of sodium —> FENa >2%
Inability to concentrate urine —> urine osmolality <500
2 major etiologies of acute tubular necrosis
Ischemic (often preceded by prerenal azotemia; proximal tubule and medullary segment of thick ascending limb are particularly susceptible)
Nephrotoxic (toxic agents result in necrosis of tubules; proximal tubule is particularly susceptible)
Causes of nephrotoxic ATN
Amingoglycosides Heavy metals (e.g., lead) Myoglobinuria (e.g., crush injury) Ethylene glycol (present with oxalate crystals) Radiocontrast dye Urate (e.g., tumor lysis syndrome)
Clinical features of ATN include oliguria with brown granular casts, elevated BUN and creatinine, and what electrolyte/acid-base disturbance?
Hyperkalemia with high anion gap metabolic acidosis
[decreased renal excretion of potassium and organic acids]
T/F: ATN is reversible, but often requires supportive dialysis since electrolyte imbalances can be fatal
True
Oliguria can persist for 2-3 weeks before recovery because tubular cells (stable cells) take time to reenter cell cycle and regenerate)
Drug-induced HSR of interstitium and tubules, resulting in intrarenal acute renal failure
Acute interstitial nephritis
Causes of acute interstitial nephritis
NSAIDs
PCN
Diuretics
Clinical presentation of acute interstitial nephritis includes oliguria, fever, and rash days to weeks after starting the offending drug. ______ may be seen in the urine. Symptoms resolve with cessation of drug, however they may also progress to ______ ______ ______
Eosinophils; renal papillary necrosis
Clinical features of renal papillary necrosis
Gross hematuria
Flank pain
Causes of renal papillary necrosis
Chronic analgesic abuse (e.g., long term phenacetin or ASA use)
Diabetes mellitus
Sickle cell trait or disease
Severe acute pyelonephritis
Which one is characterized by proteinuria >3.5g/day — nephritic syndrome or nephrotic syndrome?
Nephrotic syndrome
Nephrotic syndromes are characterized as glomerular disorders with proteinuria >3.5g/day. What are the other features of nephrotic syndromes?
Hypoalbuminemia
Hypogammaglobulinemia (increased risk of infection)
Hypercoagulable state (loss of antithrombin III)
Hyperlipidemia and hypercholesterolemia
Most common cause of nephrotic syndrome in children
Minimal change disease
Minimal change disease is usually idiopathic, but may be associated with _____ lymphoma
Hodgkin
Minimal change disease findings on H and E stain, EM, and IF
H and E = Normal glomeruli, lipid may be seen in PCT cells
EM = effacement of foot processes
IF = negative — no immune complex deposits
Minimal change disease exhibits selective proteinuria, so there is loss of ______, but not immunoglobulin
Albumin
Tx for minimal change disease
Excellent response to steroids (damage is mediated by cytokines from T cells)
Most common cause of nephrotic syndrome in hispanics and african americans; usually idiopathic but may be associated with HIV, heroin use, and sickle cell disease
FSGS
FSGS findings on H and E, EM, and IF
H and E = focal and segmental sclerosis
EM = effacement of foot processes
IF = negative — no immune complex deposition
T/F: FSGS has an excellent response to steroids
False — it has a poor response to steroids; often progresses to chronic renal failure
Most common cause of nephrotic syndrome in Caucasian adults. Usually idiopathic but may be associated with hepatitis B or C, solid tumors, SLE, or drugs (e.g., NSAIDs and penicillamine)
Membranous nephropathy
Membranous nephropathy findings on H and E, EM, and IF
H and E = thick glomerular basement membrane
EM = subepithelial deposits with ‘spike and dome’ appearance
IF = granular due to immune complex deposition
Membranoproliferative glomerulonephritis findings on H and E and IF
H and E = thick capillary membranes with ‘tram-track’ appearance
IF = granular due to immune complex deposition
Membranoproliferative glomerulonephritis is divided into 2 types based on location of the deposits. What are the 2 types and their disease associations?
Type I = subendothelial — associated with HBV and HCV
Type II = intramembranous — associated with C3 nephritic factor (stabilizes C3 convertase, potentiates complement activation and inflammatory damage)
Which is more often associated with tram-track appearance on H and E — Type I or Type II membranoproliferative glomerulonephritis?
Type I