Congenital Kidney Disorders

Question 1

is renal hypoplasia more commonly unilateral or bilateral? how do hypoplastic kidneys appear?

Answer 1

more commonly unilateral

truly hypoplastic (not acquired) kidneys have no scars and a reduced number of renal lobes/pyramids (<6)

Question 2

where are ectopic kidneys found? How do they appear?

Answer 2

Just above the pelvic brim or sometimes within the pelvis

Usually normal or slightly small in size, there may be kinking of the ureters that cause obstruction and predisposes to bacterial infections

Question 3

Hereditary disorder characterized by multiple expanding cysts of both kidneys that ultimately destroy the renal parenchyma and cause renal failure, presenting in adulthood (40-50s)

Answer 3

autosomal dominant (adult) polycystic kidney disease - major cause of chronic kidney disease

although disease is inherited as an AD trait, both alleles have to be nonfunctional for disease development - affected patients inherit 1 mutated copy of APKD gene, and the other mutation is acquired in the somatic kidney cells

Question 4

what occurs from a mutation in polycystin-1 vs polycystin-2?

Answer 4

polycystin-1 (PKD1 gene): membrane protein expressed in tubular epithelial cells of distal nephron —> mutation accounts for 85% of AD polycystic kidney disease

polycystin-2 (PKD2 gene): membrane protein expressed throughout renal tubules, but mutation confers less severe AD polycystic kidney disease

Question 5

from where do the cysts arise in autosomal dominant polycystic kidney disease?

Answer 5

cysts arise from the tubules throughout the nephron - lined by various kind of epithelia

due to mutations in polycystin-1 or polycystin-2 membrane protein in the nephron tubules

Question 6

what protein is mutated in autosomal recessive polycystic kidney disease?

Answer 6

fibrocystin (PKHD1 gene) - localized to primary cilium of tubular cells, function unclear

highly expressed in liver also, which makes sense considering ARPKD is associated with liver cysts

Question 7

from where do cysts arise autosomal recessive polycystic kidney disease?

Answer 7

arise from distal collecting ducts - lined by cuboidal cells

almost always, liver will also have cysts associated with portal fibrosis and proliferation of portal bile ducts

Question 8

what is medullary sponge kidney?

Answer 8

multiple cystic (lined by cuboidal or transitional epithelium) dilations of the collecting (papillary) ducts in the medulla

Occurs in adults, usually discovered radiographically - renal function is normal

Question 9

nephronopthisis

Answer 9

Progressive renal disorders characterized by variable number of cysts in the medulla, usually concentrated at the cortical medullary junction

cortical tubulointerstitial damage ultimately causes renal insufficiency

Question 10

how is familial juvenile nephronopthisis inherited and how do the kidneys appear?

Answer 10

autosomal recessive mutation in nephrocystins, manifests in childhood/adolescent - most common genetic cause of ESRD in children/young adults

kidneys are small with contracted granular surfaces and cysts in the medulla (esp. at corticomedullary junction)

cortical tubulointerstitial damage is cause of eventual renal insufficiency

Question 11

what is the clinical triad of hemolytic uremic syndrome (HUS)?

Answer 11

HUS: most common cause of acute renal failure in childhood, secondary to E. coli (diarrheal) or strep. pneumonia (non-diarrheal)

1. Microangiopathic hemolytic anemia.
2. Acute renal failure.
3. Thrombocytopenia.

Question 12

what are the two types of hemolytic uremic syndrome (HUS), and which one is more severe?

Answer 12

HUS: most common cause of acute renal failure in childhood - high acute mortality but most recover completely, 2 types:

1. Diarrhea (D+): secondary to E. coli O157-H7
2. No diarrhea (D-): secondary to strep. pneumonia - worse prognosis with recurrent disease and eventual ESRD

in either case, endothelial damage mediated by verotoxin

Question 13

Pt is 8yo M presenting with vomiting and 6 days of watery diarrhea with occasional streaks of blood, but no fever. Labs show elevated creatinine, low hemoglobin, low platelet count, urine 3+ for protein and hematuria. Which of the following is most likely?
a. Acute post infectious glomerulonephritis
b. Pyelonephritis.
c. Hemolytic uremic syndrome.
d. Acute renal failure, secondary to dehydration.

Answer 13

c. Hemolytic uremic syndrome.

diarrheal (D+) type most likely secondary to E. coli O157-H7