Miscellaneous Flashcards
What is Fabry disease?
X-linked (disease mainly in males), little/no functional alpha-galactosidase A enzyme actvity causing glycolipid accumulation (globotriaosylceramide ie. G3b) -> disease
What are the clinical manifestations of Fabry’s?
- Corneal opacities
- Infiltrative cardiac disease, concentric LVH, aortic and mitral valve abN, conduction abN, CAD
- Cerebrovascular/stroke
- Acroparesthesias (neuropathic, limb pain)
- Telangiectasis and angiokeratomas, thickening of the lips and bulbous nose
- Heat/cold/exercise intolerance, hypo or hyperhidrosis
- GI sx
- Renal disease
What are the specific renal manifestations of Fabry’s and renal pathologic findings?
- Renal manifestations:
- Earliest: Distal tubules affected → decreased urinary concentrating ability -> polyuria
- Proximal tubules affected → Fanconi
- Mild-moderate proteinuria
- +/- microscopic hematuria (early adulthood)
- Gradual decline in GFR to ESRD in 4 th and 5 th decade (in affected males, less common in women)
- Renal sinus and parapelvic cysts
- Renal biopsy:
- LM: vacuolization of podocytes + distal tubular epithelial cells (AKA glycolipid accummulation), renal arteries/arterioles show smooth muscle cell Gb3 accummulation and degenerative changes, IFTA
- EM: Gb3 deposits within lysosomes as lamellated membrane structures called myeloid or zebra bodies
How do you diagnose Fabry’s?
- In all males: leukocyte alpha-galactosidase A (alpha-Gal A) activity
- <3% - diagnostic -> procedwith genetic
- 3-35% - genetic test
- >35% - cannot establish dx
- In females: genetic mutational analysis of the GLA gene as the initial diagnostic assay is required
- alpha-Gal A activity level is unreliable in heterozygotes
What are the mechanisms of increased Cr without affecting GFR?
What drugs can do this?
- Mechanisms
- Decreased creatinine secretion
- Septra, Cimetidine, Salicylates, Dronedarone
- Interference with assay
- Flucytosine, Cefoxitin
- Increased production of creatinine
- Fenofibrates
- Decreased creatinine secretion
5 NON-renal/PD related causes of elevated urea?
GI bleeding
High protein intake
Hyperthyroidism
Steroids
Loss of residual renal function
cysts required for PKD in those with FHx
- Age 15-39: 3 uni or bilat (1.5 each)
- Age 40-59: 2 bilat
- Age >60: >=4 bilat
Intracranial aneurysms in ADPKD incidence?
Who to screen?
- ~10%
- Screen those with:
- FHx intracranial aneurysm
- High risk occupation (eg. bus drivers)
- Before major surgery
- Require anticoagulation
- Symptoms
- Screen with MRA
How can someone have ADPKD without family history?
- De novo mutation (5%)
- Undiagnosed family (died or living without detection)
- Misdiagnosed family
- Paternity issue
Frequency of PKD1 and PKD2 and differences
PKD1 about 80%, PKD2 15%
PKD1 earlier age onset of HTN and renal disease/failure (FHx ESKD age <55 highly predictive)
PKD2 later age onset of HTN and renal disease (FHx no ESKD age >70 highly predictive)
Extra-renal manifestations of ADPKD?
- Polycystic liver disease
- Intracranial aneurysms
- Cardiac disease - valvular lesions, MV prolapse
- Pancreatic cysts, seminal vesicles and ovarian cysts
- Hernias, GI diverticuli
ADPKD vs. simple cysts?
- +FHx with cyst # criteria
- No FHx and >10 cysts in each kidney
- Extrarenal cysts
- Impaired GFR
- HTN
- Impaired urinary concentrating ability
What is medullary sponge kidney?
Congenital disorder characterized by malformation of the terminal collecting ducts in the pericalyceal region of the renal pyramids -> develop medullary “cysts” that are often diffuse but do not involve the cortex.
Can be autosomal dominant but not always, can be variable.
Clinical manifestations of medullary sponge kidney?
- Cystic kidney disease
- Recurrent stones (calcium oxalate, calcium phosphate)
- Due to stasis in ectatic collecing ducts and “cysts”
- ?Impaired calcium reabsorption in the damaged collecting tubules
- dRTA -> hypocitraturia
- Decreased concentrating ability - polyuria
- Hematuria - gross or microscopic
- UTIs
- dRTA
- Decreased bone mineral density
What do you see on 24 hr urine studies for medually sponge kidney?
Low urine citrate and high urine calcium excretion rate
fHow is medullary sponge kidney diagnosed?
- IV pyelography or CT urography shows pooling of radiocontrast leading to calyceal “brush”-like appearance, with either nephrocalcinosis or stones
Management of medullary sponge kidney
- Non-pharm general stone management
- Pharm: K citrate, thiazides
- Monitor kidney function annually in those with kidney stones
3 urinary or structural abnormalities of medullary sponge kidney?
Cystic kidney disease (involving medulla only)
Nephrocalcinosis, recurrent kidney stones (ca oxalate, ca phosphate)
dRTA
24 hr urine: low citrate and high urine calcium excretion rate
What is cystinuria and how do cystine stones form?
- Cystinuria is an autosomal disorder (dominant or recessive; incomplete penetrance) that causes a tubular defect in dibasic amino acid transport, resulting in increased cystine excretion.
- Impaired renal cystine transport -> decreased proximal tubular reabsorption of filtered cystine -> increased urinary cystine excretion and cystine stones.
- Cystine is poorly soluble -> stones
What do cystine stones look like under microscopy?
Hexagonal
How do you investigate and diagnose cystinuria?
- Cyanide nitroprusside screen (purple=positive)
- If positive screen, 24-hour urinary excretion of cystine (also check for other stones calcium, oxalate, phosphate, citrate, magnesium, uric acid)
- Normal excretion = 30mg/day (0.13 mmol/day)
- Cystinuria = >400 mg/day (1.7 mcol/day)
Management of cystine stones?
-
High fluid intake to maintain urine cystine concentration < 1mmol/L (<250 mg/L) at pH 7
- Need 24-hr urine cystine excretion information to determine how much volume of urine. Eg. if cystine excretion 3.1 mmol/day, need urine volume >3L/day.
- Low Na diet (reduce urine cystine excretion)
-
Urine alkalinization (increase solubility of cystine) - target urine pH >7
- Higher alkali diet (fruits, vegetables)
- Potassium citrate
- ?Low animal protein intake (little evidence but reducing animal protein intake may help by increasing urine pH)
- Thiol-containing drug if conservative measures fail (tiopronin, penicillamine)
Meds that can cause kidney stones?
- Calcium stones (hypercalciuria)
- Loop diuretics (calciuric)
- Calcium supplements
- Vitamin D
- Uric acid stones (hyperuricosuria/proximal)
- Salicylates
- Probenacid
- Acetazolamide
- Meds that precipitate into stones
- Acyclovir (rapid infusion)
- Indinavir
- Methotrexate
- Triamterene
Loin pain hematuria syndrome - what is it and how does it happen?
Benign condition, presents in young and middle-aged women with loin pain and microscopic glomerular hematuria
Thought to be due to rupture of GBM leading to bleeding into renal tubules -> tubular obstruction -> renal parenchyma edema -> renal capsule stretch and pain