12. Kidney and Urinary Tract Pathology Flashcards
What are a few congenital disorders of the kidneys?
horseshoe kidney, renal agenesis, dysplastic kidney, polycystic kidney disease, medullary cystic kidney disease
describe a horseshoe kidney. how did it occur?
conjoined kidneys, connected at the lower pole. kidney unit got caught on the inferior mesenteric artery root during ascent from pelvis to abdomen
what is the most common congenital renal abnormality?
horseshoe kidney
what does agenesis mean?
“without production”
what is renal agenesis?
kidneys did not form. may be uni- or bi-lateral
what does unilateral renal agenesis lead to?
hypertrophy of the existing kidney
–> hyperfiltration which increases risk of renal failure later in life
what does bilateral renal agenesis lead to?
Potter sequence.
oligohydramnios with lung hypoplasia, flat face with low set ears, dev defects of the extremities. incompatible with life
what is Potter sequence?
lung hypoplasia, flat face with low set ears, dev defects of the extremities. due to oligohydramnios.
how should I think of the Potter sequence mechanistically?
think that due to oligohydramnios, there is not room in the uterus –> flat face and mis-formed extremities. the lung hypoplasia is because there is not room for the lungs to stretch and expand.
memory: Potter because the Pot was too small?
what is oligohydramnios? what causes it?
not enough amniotic fluid –> fetal abnormalities. many causes: bilateral renal agenesis is one.
how does bilateral renal agenesis cause oligohydramnios?
the amniotic fluid is formed from fetal filtrate (urine). if the fetus cannot make urine, there will be little amniotic fluid.
what is dysplastic kidney?
noninherited, congenital malformation of renal parenchyma characterized by cysts and abnl tissue. (one ex: cartilage growing where it should not be)
dysplastic kidney: inherited? uni or bilateral?
non-inherited. usually unilateral. if bilateral, must be distinguished from inherited polycystic kidney disease
what is polycystic kidney disease (PKD)?
inherited defect, leading to bilateral enlarged kidneys with cysts in the cortex and medulla.
what does polycystic kidney disease look like grossly?
kidney with lots of dark shiny bubbles on the surface
PKD: autosomal recessive form generally presents in what population? how does it present?
infants. presents as worsening renal failure, hypertension. may present as Potter sequence because so severe it’s as though they have oligohydramnios
PKD: auto dominant form generally presents in what population? how does it present?
young adults (ADults). presents as HTN (due to incr renin), hematuria, progressive renal failure
auto recessive form of PKD: associated with what?
congenital hepatic fibrosis and hepatic cysts.
auto dom form of PKD: why does it present as it does?
presents as HTN, hematuria, progressive renal failure: think about cysts in liver/brain/kidney.
Mutation of APKD1 or APKD2 gene. cysts develop over time.
what gene is responsible for the auto dom form of PKD?
mutation in the APKD1 or APKD2 genes (adult polycystic kidney disease genes). cysts develop over time.
auto dom PKD: what is it associated with?
berry aneurysm, hepatic cysts, mitral valve prolapse.
auto dom PKD: generally, what is the cause of death?
berry aneurysm rupture
what is medullary cystic kidney disease?
inherited defect leading to cysts in the medullary collecting ducts.
medullary cystic kidney disease: what type of inheritance?
AD
medullary cystic kidney disease: presentation? Why?
presents as worsening renal failure, due to shrunken kidneys from parenchymal fibrosis
what is the most obvious difference between dysplastic kidney and polycystic kidney disease?
dysplastic kidney = usually unilateral (but might be BIL on USMLE)
polycystic kidney disease = bilateral. presents with HTN, worsening renal failure.
Define Acute Renal Failure.
What are the hallmarks?
acute, severe decrease in renal function (occurs over days)
Azotemia (incr BUN, incr Creatinine), often Oliguria
Divided into Pre-renal, Post-renal, Intra-renal types.
Pre-renal Azotemia
what is a common cause?
Serum BUN:Cr ratio = ?
FENa = ?
Urine osm = ?
Decr blood flow to kidneys (cardiac failure is common cause)
Serum BUN:Cr ratio > 15 (high)
FENa < 1% (tubular function = intact)
Urine osm > 500 (tubules can concentrate urine)
NORMAL values are….?
Serum BUN:Cr ratio
FENa
Urine osm
Normal Values:
Serum BUN:Cr ratio = 15
FENa < 1% (tubular function intact)
Urine osm > 500 (tubules can concentrate urine)
Pre-renal Azotemia
why is Serum BUN:Cr ratio high?
low blood flow to kidney due to pre-renal obstruction or overall low volume.
RAAS activated -> aldosterone -> **more Na, water, BUN resorbed. **
Cr is filtered and excreted as usual.
Serum BUN:Cr ratio therefore increases.
Postrenal Azotemia, Early stage
Serum BUN:Cr ratio = ?
FENa = ?
Urine Osm = ?
Serum BUN:Cr ratio > 15
FENa < 1%
Urine Osm > 500
Postrenal Azotemia, Later stage
Serum BUN:Cr ratio = ?
FENa = ?
Urine Osm = ?
Serum BUN:Cr ratio < 15
FENa > 2%
Urine Osm < 500
All due to tubular damage
Acute Tubular Necrosis: clinical findings?
- Brown granular casts in urine
- Elevated BUN and creatinine (decr GFR)
- Hyperkalemia
- Metabolic acidosis with anion gap
Acute Tubular Necrosis: 2 etiologies?
Ischemia
Toxicity
Acute Tubular Necrosis due to toxicity: what are most common causes?
Aminoglycosides (gentamycin, tobramycin, amikacin)
Heavy metals/lead
Myoglobinuria (crush injury)
Ethylene glycol ingestion (kid, accidental)
Radiocontrast dye
Urate due to tumor lysis syndrome
If a patient is on chemo for leukemia, what do we give to avoid Tumor Lysis Syndrome/Acute Tubular Necrosis?
- Hydration
- Allopurinol to decr synthesis of urate.
- Rasburicase (synthetic urate oxidase) to metabolize uric acid –> Allantoin (more soluble)
Ethylene glycol ingestion: high-yield association?
kids (accidental ingestion)
Oxalate crystals in urine
Acute Tubular Necrosis
why does it take 2-3 weeks to recover from?
Tubular cells can regenerate, but they are Stable cells and need time to re-enter the cell cycle.
Acute Interstitial Nephritis: cause?
drug-induced hypersensitivity
NSAIDs, penicillin, diuretics
Acute Interstitial Nephritis: presentation?
a few days/weeks after starting a new drug, oliguria, fever, rash
Eosinophils in urine
Renal Papillary Necrosis
Presentation? Cause?
(a form of intra-renal azotemia)
Presents with gross hematuria, flank pain
Causes: chronic analgesic abuse, diabetes, sickle cell, severe acute pyelonephritis
6 causes of nephrotic syndrome?
6 causes, grouped in pairs:
minimal change and FSGS
Membranous nephropathy and membranoproliferative glomerulonephritis
diabetes mellitus and amyloidosis
Nephrotic syndrome: basic principles?
proteinuria
hypoalbuminemia -> pitting edema
hypogammaglobilinemia -> incr risk of infection
hyperlipidemia and hyperchol (due to ‘thin’ blood; liver puts out lipids and chol) -> fatty casts
minimal change disease: where is the damage?
what cancer is it associated with?
effacement of foot processes
associated with Hodgkin lymphoma (huge production of cytokines by Reed-Sternberg cells)
minimal change disease: what proteins are lost?
treatment?
albumin but NOT immunoglobulin
responds to steroids
Focal Segmental Glomerulosclerosis: associations?
where is the damage?
treatment?
associations: HIV, heroin use, sickle cell
effacement of foot processes
no response to steroids -> progresses to renal failure
most common cause of death with SLE?
renal failure
usually due to diffuse progressive glomerulonephritis - or membranous nephropathy
membranous nephropathy
where is the damage?
associations?
appearance on IF?
damage = subepithelial deposits of immune complexes
associated with Hep B, Hep C, SLE, solid tumors, NSAIDs
appearance = granular IF, spike and dome
membranoproliferative glomerulonephritis
associations
damage
appearance
Tram-track appearance! granular IF
associations:
Type I: HBV and HCV
Type II: autoantibody to C3 convertase -> overactivation of complement cascade
Diabetes nephrosis
damage?
appearance?
treatment?
high glucose -> NEG of vascular basement membrane -> hyaline arteriolosclerosis of efferent vessel
high GFR, hyperfiltration, albumin in urine
Kimmelstiel-Wilson nodules
treatment: ACE inhibitors to counteract the efferent blockage effect
systemic amyloidosis
damage?
appearance?
amyloid deposits in mesangium
apple-green birefringemce under polarized light w/ Congo red stain
