nelson essential Flashcards
What is needed for normal renal function?
- intact flomerular filtration - regulated by pressure, arterial tone, renin played a part in it
- intact tubular function: includes the proximal tubule, loop of hence and distal tubule
to result in urine formation
What does the proximal tubule do?
isosmotic reabsorption
- reabsorbs 2/3 of filtered volume, sodium and chloride
- almost completely reabsorbes glucose, amino acids, potassium and phosphate
- reabsorb 75% of bicarbonate - where it exceeds the threshold, it gets spilled into the urine
- also secretes organic acids, penicillins, other drugs
which part of the kidney makes calcitriol
proximal tubule cells make calcitriol (aka 1,25 OH2) in response to PTH and intracellular Ca/PO4 concentrations
what happens in the loop of Henle
reabsorb NaCl (25%) of what is filtered in the glomerulus active chloride transport makes the gradient needed to concentrate urine
What does the distal tubule do
includes
- distal convoluted tubule : active sodium absorption, helps to dilute urine
- collecting ducts -
- primary site of ADH response
- aldosterone regulates Na/K and Na/H exchange
- active H ion secretion to acidify the urine
What is the urinary anion gap?
measures the renal ammonia production - the gap between measured anions and cations are largely of NH4
normal urinary gap is 1meq/kg body weight
cause of decreased urinary anion gap
problems with renal acid excretion or ammonia production
true or false - preterm newborns are less capable to concentrate urine than term newborns?
true
their maximum urinary concentrating capacity is only 400 mosm/L (vs 600-800 mosm/L for full-term newborn) , which is less than in older children and adults
why are infants less capable to excrete a water load than adults
because lower GCF (although they can dilute urine similar to adults )
when does GFR reach adult levels
age 1-2
GCF in newborn is 40 ml/min/1.73m2
in adult 100-120 ml/min/1.73 m2
neonate can absorb Na efficiently ASAP, but takes 2 years for bicarb
Differential of flank mass in neonate
- multicystic dysplasia
- urinary tract obstruction (hydronephrosis)
- polycystic disease
- tumor
Differential of hematuria in a neonate
- acute tubular/cortical necrosis
- Urinary tract malformation
- trauma
- renal vein thrombosis
Differential of anuria/oliguria in a neonate
- renal agenesis
- obstruction
- acute tubular necrosis
- vascular thrombosis
creatinine affected by which
mucle mass, age (plasma creatinine )
BUN affected by which
hydration, nutrition, catabolism, tissue breakdown
cause of false positive nitrite test
prolonged contact (ie uncircumsied) gross hematuria
measure of proteinuria
protein/creatinine ratio - very good approximation of 24 hour protein clearance
2.0 in children
nephrotic proteinuria
urine protein/creatinine >2.0 or 24 hour protein 40 mg/m2/hour
(normal is <4 mg/m2/hour)
Definition of nephrotic syndrome
- heavy proteinuria (mainly albumin)
- hypoptroteinemia (albumin 250 mg/dL) (- elevated cholesterol/TG
- edema
**renal blood flow and GFR not usually diminished, rather get change in oncotic pressure and fluid shifts
Causes of primary nephrotic syndrome
- Minimal change disease - most common, in >80% of children 35% of these kids progress to renal failure
- Membranoproliferative glomerulonephritis - low complement with signs of glomerular renal disease , 5-15%, usually persistent, high likelihood of renal failure
- membranous nephropathy - <5%, in teens, with systemic infections/meds
teenager with nephrotic syndrome, has hep B, what type of nephrotic syndrome most likely?
membranous nephropathy
occurs in teens/kids with systemic infection - i.e. hepatitis B, syphilis, malaria, todo or on gold/penicillamine
What is congenital nephrotic syndrome
presents in first 2 months of type
2 common type - #1: Finnish type, autosomal recessive, mutation in nephron
#2: heterogeneous group of abnormalities
prenatal onset - elevated levels of maternal alpha-fetoprotein
Treatment of familial congenital nephrotic syndrome: early nephrectomy, dialysis and transplantation
Name some secondary causes of nephrotic syndrome in kids
SLE HSP/Wegener/other vasculitides chronic infections allergic reactions diagetes amyloidosis malignancies CHF, pericarditis renal vein thrombosis
Clinical presentation of nephrotic syndrome
sudden onset pitting edema/ascites - most common
can get anorexia, malaise, abdo pain
BP can be elevated in up to 25%
diarrhea (intestinal edema) and resp distress (pulmonary edema/pleural effusion) can occur
Typical minimal change disease - clinical characteristics
no hematuria (can occasionally have microscopic hematuria in MCNS) normal BP normal complement (if low suggests other cause than minimal change, also if low should do renal biopsy)
Differential of proteinuria
- transient proteinuria - after vigrous exercise, fever, dehydration, seizures, adrenergic agonist therapy; usually mil (urine protein/cr <1), glomerular in origin, always resolves in few days.
- postural (orthostatic proteinuria) - normal protein exertion when laying down but significant when upright
(can also have tubular or glomerular proteinuria)
Treatment of nephrotic syndrome
> 80% of children with nephrotic syndrome who are t work to relieve the edema, cautious admin of 25% albumin with loop diuretic can help
HTN treat with beta blockers/Ca channel blockers, ACEi for persistent
Complications of nephrotic syndrome
- infections - bacteremia and peritonitis - Strep pneumo, E. coli, Klebsiella -since have urinary loss of immunoglobulins and complement
- hyper coagulable state - since lose antithrombin/plasminogen - risk of thromboembolism - sometimes may need blood thinner
- increased atherosclerotic vascular disease from hyperlipidemia
can also get SEs of steroids, hypovolemia (from diarrhea/diuretic)
Prognosis of nephrotic syndrome
most go to remission , 80% with MCNS can have relapse (heavy proteinuria >3 days) can have transient proteinuria with infection, not considered relapse
FSGS - can progress to kidney failure
Microscopic hematuria -
> 3-5 RBC/HPF on fresh urine, often benign
can have isolated asymptomatic microscopic hematuria in 4% of healthy children
usually it is transient
Ddx of hematuria
- factitius - non pathologic: ie urate cystals, ingested foods, medications, dyes (ie will be negative on urinalysis); pathologic (i.e. hemoglobinuria from hemolytic anemia, myoglobin from rhabdo)
- glomerular - immunological (ie GN - PSGN, IgA, membranoproliferative GN, systemic disease ), structural (Alport, Bm disease), toxin (ie HUS)
- Tubulointerstitial/parenchymal
- lower urinary tract (UTI, trauma/kidney stone, hypercalciuria)
Features of acute post streptococcal glomerulonephritis
hematuria - gross or microscopic proteinuria hypertension edema oliguria renal insufficiency age: 2-12 year old more in boys usually 5-21 days (mean 10 days) after strep pharyngitis infection and 4-6 weeks after impetigo
acute post infections GN
same as post strep GN but with other infections - can happen regardless of whether the kid gets antibiotics
treatment priorities in GN
take care of BP! can cause heart failure, seizures, encephalopathy
treatment is supportive, involves sodium restriction, diuretics and BP meds as needed
treating strep doesn’t prevent PSGN - should still treat with antibiics if active strep infection
occasionally use steroids/other immunosuppression
ACEi - might help (but use with caution)
Presentation of IgA nephropathy
can vary, acute GN, asymptomatic microscopic hematuria, recurrent gross hematuria CONCURRENT with URTI
What is rapidly progressive GN?
typical feutres of acute GN but renal insufficiency progresses more quickly and severely
renal biopsy shows crescents
can be idiopathic or secondary to knob types of GN
What is Alport syndrome
X linked
mutation in type IV collagen - leads to abnormal glomerular basement membrane - asymptomatic microscopic or gross hematuria
Males: progressive renal failure and sensorineural hearing loss in teens/young adults
Females: more benign, but have usually at least microscopic hematuria
prognosis: all have end stage renal disease - men in 30s, women later
What is benign familial hematuria
autosomal dominant
often have hematuria in 1st degree relatives
usually the renal disease is not progressive, have good prognosis
Painless gross hematuria
sickle cell, Wilms, strenuous exercise
What is nutcracker syndrome?
can be a cause of hematuria (with or without pain) - from the compression of the renal vein between other “stuff”
hematuria with low complement C3
PSGN
membranoproliferative GN
lupus nephritis
true or false - all gross hematuria should be investigated
true
prognosis of post streptococcal GN
usually resolves - within 5-10 days
can have microscopic hematuria for months/years- most recover
IgA nephropathy more likely to progress
findings associated with poor prognosis in glomerulonephritis
- persistent/heavy proteinuria
- hypertension
- decreased kidney function
- severe glomerula lesions
management plan for isolated asymptomatic microscopic hematuria/familial hematuria
usually good prognosis
do yearly urinalysis to rule out proteinuria
and also do BP yearly (rule out progressive forms of renal disease)
What are the findings in hemolytic anemic syndrome?
- microangiopathic hemolytic anemia
- thrombocytopenia
- renal injury
age group of most patients with HUS?
usually <5 year old, can happen in older kids
What are the prodromal infections most common in HUS?
- Typical HUS (with diarrhea prodrome): hemorrhagic enterocolitis from verotoxin and then leads to HUS in 5-15% of kids - most common is E. Coli (most commonly E. coli O156: H7, although other strains can also cause ) which can contaminate meat, fruit, veggies or water with verotoxin; Shigella can also cause verotoxin
- Atypical HUS:
- without a diarrhea prodrome
- can occur at any age , usually MORE SEVERE than with diarrheal illness prodrome
- infection: Strep pneumo, HIV, genetic and acquired defects in complement regulation, meds, malignancy, SLE and pregnancy
Causes of atypical HUS (i.e. not with diarrhea)
infection - strep pneumo, HIV complement defects (genetic and acquired) medications malignancy SLE pregnancy
How does HUS present
- initially have bloody diarrhea
- 7-10 days later have weakness, lethargy and oliguria/anuria
- irritable, pallor petechiae
- dehydration often present, but can have volume overload
- Hypertension from volume overload or kidney injury
- CNS involvement - in 25% of cases ; including seizures
- Other organs: pancreatitis, cardiac dysfunction, colonic perforation
Lab findings in HUS
- Evidence of microangiopathic hemolytic anemia: anemia, thrombocytopenia, shistocytes, helmet cells, burr cells on peripheral blood smear, increased LDH, decreased haptoglobin, increased indirect bill, increased AST, elevated reticulocyte count
- evidence of renal injury : elevated creatinine; presence of hematuria, proteinuria, pyuria, casts on urinalysis
- Other - leukocytosis, positive stool culture for E. coli O157: H7; positive stool test for shiga-toxin; elevated amylase/lipase
What is TTP?
rare combination of Fever, microangiopathic hemolytic anemia, thrombocytopenia, abnormal renal function and CNS changes - clinically similar to HUS, but usually in older teens/adults
get more CNS manifestations (from microvascular thrombi) in the CNS, can also have significant renal disease; can have recurrent episodes
What is the mutation in TTP?
most cases are caused by ADAMTS-13 deficiency - responsible for cleaving high molecular weight mol timers of VWF (vs these will be normal in HUS)
Coombs test in HUS?
negative
stool is negative but you think a kid has HUS?
totally possible, E coli might be gone by the time HUS is diagnosed
Treatment of HUS
- volume repletion
- control hypertension
- manage complications of renal insufficiency - including dialysis
Should you transfuse platelets in HUS?
no, because they may only add to the thrombotic microangiopathy
should only do if active hemorrhage or in anticipation of a procedure
Antibiotics for diarrheal illness and antidiarrheal agents- what do they do to the risk of HUS?
they might increase the risk of HUS
what intervention in the diarrheal phase of HUS might reduce the severity of renal insufficiency?
early hydration
most kids survive the acute phase and recover normal renal function
Proteinuria
Proteinuria : - protein/creatinine ratio >0.2 - 24 hour protein excretion : 4 mg/m2/hour Nephrotic range: - protein/creatnine ratio: >2 - 40 mg/m2/hour
