NEPHROLOGY SN Flashcards
Fill in the blank: Problems with filtration are due to problems with _________ whereas problems with secretion and reabsorption are due to problems with _______. -what is the definition of GFR? -what is used as an estimate for GFR?
Problems with filtration: glomeruli = act as sieves to filter serum, creating ultrafiltrate Problems with secretion and reabsorption: tubules = reabsorb and secrete solutes, concentrate the urine and create and respond to endocrine signals -GFR = glomerular filtration rate = amount of ultrafiltrate produced by all of the glomeruli (ml/min). Varies with age and height -Creatinine clearance = estimate for GFR since creatinine is not significantly secreted or absorbed in the renal tubules
What level of protein on a urine dipstick warrants further testing? -what further testing can you order? (2 options) -what test can be used for tracking progression of proteinuria but not for initial diagnosis?
> 2+ protein = need to do further testing -can have false positives Further testing: 1. Protein-Cr ratio: only requires one sample but not as accurate as 24-h protein collection 2. 24 hr urine for protein = GOLD STANDARD for severity of protein loss but difficult to obtain (Microalbumin/Cr = good for tracking progression of disease but is not used for initial diagnosis)
What is the criteria for proteinuria? -What is the criteria for nephrotic range proteinuria?
-Proteinuria = > 0.2 urine spot protein/Cr ratio or >4 mg/m2/h on 24 hr urine collection -nephrotic range proteinuria = > 2.0 urine spot protein/Cr ratio or > 40 mg/m2/h on 24 hour urine collection (10x more than proteinuria) = this is NEVER benign and always warrants further evaluation
What is the differential diagnosis for proteinuria? -benign causes (6) -pathologic causes (9)
Benign causes: 1. Acute illness 2. Fever 3. Pregnancy 4. Trauma 5. Exercise 6. Orthostatic proteinuria Pathologic causes: -Glomerular: 1. Nephrotic syndrome 2. Glomerulonephritis 3. Reflux nephropathy 4. Long-standing infections -Tubular: 5. Fanconi syndrome 6. Metal poisoning 7. Ischemic injury (ie. ATN) -Increased protein burden (overwhelms tubular reabsorption) 8. Rhabdomyolysis 9. Neoplasms
What is the most common cause of persistent proteinuria in school-aged children and adolescents? -clinical features? -how is diagnosis made? -treatment?
Orthostatic proteinuria -occurs in up to 60% of children with persistent proteinuria Clinical features: -usually asymptomatic and condition is discovered on routine urinalysis -patients excrete normal or minimally increased amounts of protein in the supine position; however, in the upright position, urinary protein excretion increases up to 10 fold (1 g/24 h) once patient is up and moving. -Hematuria, hypertension, hypoalbuminemia, edema and renal dysfunction MUST BE ABSENT to make this diagnosis -diagnosis: Collect first morning urine sample (must be first voided urine immediately upon rising in the morning) = absence of proteinuria (dipstick negative or trace for protein and urine Pr:Cr < 0.2) x 3 consecutive days confirms the diagnosis -no further work-up is needed and no treatment since condition is benign
What is the work-up for proteinuria? -lab tests? -imaging tests?
Initial labs: UA with microscopy, lytes, BUN, Cr, albumin, serum protein, urine protein, urine Cr to calculate Ur Pr:Cr ratio. Consider CRP, ESR, complement -always order renal U/S to rule out structural abnormality that might lead to obstruction of renal vessels -renal biopsy may or may not be indicated depending on suspected diagnosis
What is the definition of hematuria? -definition of gross hematuria vs. microscopic hematuria?
>5 RBCs/HPF on urine microscopy -gross hematuria = visible redness of urine with > 5 RBCs/HPF on microscopy -microscopic hematuria = normally colored urine with > 5 RBCs/HPF on microscopy x 2 occasions or more
What is the differential diagnosis for hematuria?
Pre-renal: (not true hematuria) 1. Hemolysis = hemoglobinuria = positive heme in urine but NO RBCs 2. Rhabdomyolysis = myoglobinuria = positive myoglobin in urine but NO RBCs ***other causes of red urine but not hematuria: rifampin, chloroquine, beets, food coloring, etc. 3. Coagulopathy Renal: 1. IgA nephropathy 2. Postinfectious glomerular nephritis 3. Alport syndrome (hereditary nephritis) 4. Thin glomerular basement membrane nephropathy 5. Membranous nephropathy 6. Focal segmental glomerulosclerosis Multisystem disease: 7. SLE nephritis 8. HSP nephritis 9. Wegener granulomatosis 10. HUS Tubulointerstitial disease: 11. Pyelonephritis 12. Interstitial nephritis 13. ATN Vascular: 14. Arterial or venous thrombosis Malignancy: 15. Wilms, rhabdomyosarcoma, angiomyolipoma = look for abdo mass and order renal U/S Post-renal: 16. Trauma (look at urethra, genital lesions) 17. Cystitis 18. Renal calculus
What information on the microscopy can give you a clue as to where the location of defect is causing hematuria?
Look at the RBC shape! -If normally shaped, think post-renal causes -if abnormally shaped RBCs, hemoglobin, RBC casts, or proteinuria, think renal parenchymal causes
You see a patient presenting with gross hematuria. There is proteinuria and RBC casts seen on urine microscopy. Which region of the kidney is most likely involved?
Glomerulus! -will usually see brown, cola or tea colored urine -will see proteinuria, RBC casts and deformed urinary RBCs (acanthocytes)
What can give false-negative results on urinalysis for a child presenting with gross hematuria? -what can give false-positive results in a child who is not having hematuria?
False negatives: presence of formalin or high urinary concentrations of vitamin C False positives: alkaline urine, contamination with hydrogen peroxide used to clean the perineum before obtaining a specimen
What are common causes of rhabdomyolysis? (9)
- Prolonged seizures 2. viral myositis 3. Crush injury 4. Severe electrolyte abnormalities (hyperNa, hypoPO4) 5. hypotension 6. extreme exercise 7. DIC 8. toxins 9. metabolic disorders
A patient presents to you with gross hematuria. On urine microscopy, you see RBCs, leukocytes, and renal tubular epithelial cell casts. Where is the most likely location of the renal abnormality?
Convoluted or collecting tubules
What is the most common cause of gross hematuria in children?
Bacterial urinary tract infection
You find microscopic hematuria on a routine UA performed for one of your patients. They are otherwise asymptomatic, physical exam is normal, and there is no personal or family history of renal disorders. What is your management plan?
- Repeat the UA and BP in one month 2. If positive, initiate further work up at that time
What is the most common cause of renal failure in neonates?
Obstruction due to outflow anomalies
What is the differential diagnosis for acute kidney injury?
Prerenal: 1. Dehydration leading to hypoperfusion 2. Cardiogenic shock 3. Sepsis 4. Hemorrhage Renal: 1. Glomerular disease: acute glomerulonephritis (postinfectious, SLE, HSP, membranoproliferative, anti-glomerular basement membrane) 2. Tubular disease: ATN, AIN, HUS, tumor lysis syndrome 3. Vascular: vasculitis, renal vein thrombosis Postrenal: 1. acute urinary obstruction = posterior urethral valves, ureterocele, tumor, urolithiasis, neurogenic bladder
What are the clinical manifestations of acute kidney injury? (5)
- Decreased urine output 2. Fluid overload (weight gain, peripheral edema, pulmonary edema) 3. Hypertension (headaches, papilledema) 4. Electrolyte abnormalities: hyperkalemia, acidosis 5. Elevated BUN and Cr = signs of uremia (pericardial rub)
What is the pediatric rifle criteria?
RIFLE = risk, injury, failure, loss, end-stage -Risk: estimated creatinine clearance (CCI) decreased by 25%, U/O 3 mo
How do you calculate FENa? -what does FENa < 1% mean? -FENa > 2%?
FENa helps you differentiate between prerenal cause of ARF from renal cause of ARF FENa calculation: 100 x (Urinary sodium x plasma creatinine) / (plasma sodium x urinary creatinine) -think “U PE, PE U!!” Gotta pee first to get a “peeewww, it stinks!” -OR just remember that U pee sodium = urine sodium is on top (numerator) and then you can figure out the rest! -Prerenal cause: patients whose urine showed an ELEVATED specific gravity (ie. concentrated), elevated urine osmolality (UOsm > 500 mOsm/kg), low urine sodium (UNa < 20 mEq/L) and FENa < 1% =if there is a prerenal cause of poor perfusion to the kidneys, the kidneys will still try to concentrate the urine in order to reserve as much fluid for the body as possible, THUS urine will be very concentrated and urine Na will be low since body is trying to conserve it to reabsorb water -Renal cause: patients whose urine showed DECREASED specific gravity (dilute urine), low urine osmolality (UOsm < 350 mOsm/kg), high urine sodium (UNa > 40 mEq/L) and FENa > 2% = kidney is not able to concentrate urine and thus losing lots of Na and fluids
What are clinical features of acute interstitial nephritis? -Cause?
AIN = immune-mediated inflammatory response affecting renal interstitium and tubules (spares glomeruli and vasculature) -clinical features: acute renal failure, fever, flank pain, rash, arthralgias from hypersensitivity reaction and inflammation
What drugs are known to be causes of AIN? (3 groups) -abnormal lab findings in patients with AIN? -treatment?
- Antibiotics (penicillin analogs, cephalosporins, sulfonamides, rifampin) 2. NSAIDs 3. Diuretics (thiazides and furosemide) -lab findings: urinary sediment (RBCs, EOSINOPHILS, WBC casts), proteinuria, FENa > 1%, electrolyte abnormalities -treatment: usually high fluid volume to dilute and wash through the offending agent
What are main concerning clnical features of chronic renal failure?
- Anemia (decreased Epo production) 2. Growth failure 3. Fluid overload 4. Bone deformities (vit D deficiency) 5. Electrolyte abnormalities 6. Hypertension
What is the most common cause of nephrotic syndrome in young children (ie. < 8 yo)? -treatment?
Minimal change disease -always assume that young children with nephrotic syndrome have minimal change disease and treat them with steroids - only get a renal biopsy if they do not respond to steroids -steroids 2 mg/kg/day x 4-6 weeks, then taper -most patients with minimal change disease will respond within the first month of treatment with normalization of urinary protein excretion
Compare and contrast peritoneal dialysis vs. hemodialysis.
Peritoneal dialysis: -slow, small volume fluid shifts -done at home every night during sleep -need initial minor surgery to place peritoneal catheter -infection risk: peritonitis -slow toxin removal -better for growth than HD -children feel better with PD since there are no acute fluid shifts and less cytokine release as a result HD: -faster large volume fluid shifts -rapid toxin removal -needs to be done 3x/wk at medical centre -need initial minor surgery to place graft -infection risk: graft infection/bacteremia
What are the clinical features of nephrotic syndrome?
Think PALE 1. Proteinuria > 40 mg/m2/hr, Pr:Cr ratio > 2 2. hypoAlbuminemia 3. hyperLipidemia (since liver is working overtime to try to replace lost proteins ) 4. Edema ***may also have hypercoagulability from loss of protein C & S (thus increasing risk of clots) and high risk of infections from loss of complement and antibodies in urine
What is the differential diagnosis for nephrotic syndrome? (4)
- Minimal change disease 2. Membranous nephropathy 3. Focal segmental glomerular sclerosis 4. Diabetic nephropathy
What is the underlying pathophysiology behind nephrotic syndrome?
Podocyte effacement, vacuolation, appearance of microvilli on electron microscopy -unclear etiology -called minimal change disease because changes to kidneys are very subtle
What is the pathophysiology of membranous nephropathy? -usually seen in which population? -gold standard for diagnosis? -treatment? -prognosis?
Membranous nephropathy = rare but seen in older children, autoimmune or infectious cause in about 33% -gold standard for diagnosis and only way to diagnosis = renal biopsy = serum IgG complex deposition leading to glomerular basement membrane damage -on pathology: see basement membrane spikes, granular C3 and IgG deposits -treatment: immunosuppression and steroids but may not change course of illness -prognosis: 1/3 remission spontaneously, 1/3 ongoing proteinuria, 1/3 ESRD
What are the 2 main glomerular disease entities?
Nephrotic syndrome vs. Nephritic syndrome
Which children with nephrotic syndrome should receive a renal biopsy?
- Children of any age who do NOT respond to initial course of steroids or have persistent relapses despite steroids 2. Children > 8 years old with nephrotic syndrome (minimal change disease less likely in older children so gotta rule out FSGS, membranous nephropathy) 3. Presence of hypertension, renal insufficiency, RBC casts = should NOT be seeing this in minimal change disease and so biopsy
In which population do you see focal segmental glomerular sclerosis? -pathophysiology? -diagnosis? -treatment? -prognosis?
Usually see FSGS in patients with HIV, hep B, IV drug users, sickle cell disease -pathophysiology: sclerosis and scarring of glomeruli -diagnosis: renal biopsy -treatment: long-term immunosuppression and plasmaphresis -prognosis: poor (high rate of ESRD in kids)
What do you see on renal biopsy of a patient with diabetic nephropathy?
Basement membrane damage from glucose end products -thick basement membrane, Kimmesteil-wilson nodules
What are clinical features seen in nephritic syndrome?
PHAROH 1. Proteinuria (but less than nephrotic range) 2. Hematuria 3. Azotemia (elevated BUN) 4. RBC casts 5. Oliguria 6. Hypertension
What is the differential for nephritic syndrome? (10)
PIGS Always Pick the Most Wealthy Hogs 1. Postinfectious glomerulonephritis 2. IgA nephropathy 3. Alport syndrome 4. Membranoproliferative GN 5. Thin basement membrane 6. Goodpasture/anti-GBM 7. Wegener’s 8. HUS 9. SLE 10. Pauci-immune microscopic polyangitis
Which glomerulonephritidies are associated with low complement levels? (3)
- Postinfectious glomerulonephritis (C3 will normalize 1-8 wks after presentation) 2. Membranoproliferative GN 3. SLE
How can you differentiate between IgA nephropathy vs. postinfectious glomerulonephritis in terms of: -clinical presentation? -duration of hematuria in each? -what about on labwork?
-IgA nephropathy = hematuria starts within 1-2 days after a viral URTI. Duration of hematuria = short (5 days) -Postinfectious GN = hematuria starts after 7-21 days after a viral URTI or impetigo skin infection (has a latency period). Duration of hematuria = long (4-6 wks) -labwork: IgA = NORMAL C3 levels whereas in postinfectious GN, have low C3 levels
How do you diagnose IgA nephropathy? -incidence in boys vs. girls -what is the benefit of ordering serum IgA levels? -treatment? -prognosis?
Renal biopsy = see IgA deposits in glomerulus with MESANGIAL inflammation/proliferation -more common in boys -no benefit in ordering serum IgA -treatment: supportive (treat hypertension and proteinuria with ACE-I, may benefit from steroids) -prognosis: 20-40% with ESRD but MOST have benign courses. Need long term follow up
What is thin basement membrane disease? -inheritance pattern? -treatment?
A cause of glomerulonephritis = presence of persistent microscopic hematuria and isolated thinning of the glomerular basement membrane -type 4 collagen mutation -familial (sporadic or AD trait) -treatment: none needed
What gene mutation causes Alport syndrome? -inheritance pattern? -what do you see on renal biopsy?
Type 4 collagen mutation (major component of basement membranes) -inheritance: 85% are X-linked, rest are autosomal recessive -renal biopsy: mesangial proliferation, glomerular sclerosis, FOAM CELLS (lipid containing interstitial cells)
What are clinical manifestations of Alport syndrome? -investigations for work-up of Alport? -treatment? -prognosis?
- Asymptomatic microscopic hematuria -some may have recurrent gross hematuria 1-2 d after URTI 2. Proteinuria in boys more commonly than in girls 3. Bilateral sensorineural hearing loss 4. Ocular abnormalities (anterior lenticonus = extrusion of the lens into the anterior chamber is pathognomonic, corneal erosions) Investigations: 1. Urinalysis of patient and all 1st degree relatives 2. Ophtho exam 3. Hearing test 4. Skin or Renal biopsy Treatment: No treatment available although ACE-I can slow progression to ESRD Prognosis: all progress to ESRD in adulthood and eventually require dialysis or renal transplant. -15% of affected boys have ESRD before age 15. -Boys have worse prognosis than girls
A patient presents to you with gross hematuria . You do a ophtho exam and see anterior lenticonus. What is your diagnosis?
Alport syndrome! -anterior lenticonus is pathognomonic
What is the cause of Anti-GBM glomerulonephritis? -what is your diagnosis if they have this AND pulmonary hemorrhage? -renal biopsy findings? -treatment?
Anti-GBM glomerulonephritis = autoimmune condition where IgG attacks type 4 collagen in glomerular basement membrane -if pulmonary involvement = Goodpasture disease -renal biopsy: see anti-GBM antibiodies -treatment: plasmapheresis and steroids
What is the triad of HUS? -criteria for diagnosis?
- Microangiopathic hemolytic anemia -need to see acute onset anemia with microangiopathic changes on peripheral blood smear (schistocytes, burr cells, helmet cells) 2. Renal failure -need to see hematuria, proteinuria or elevated Cr 3. Thrombocytopenia -may not see initially early in the illness Criteria for CONFIRMED diagnosis: 1. Lab criteria: need both ANEMIA and RENAL INJURY (thrombocytopenia is variably seen and thus not necessary for diagnosis) 2. Acute illness that began 3 weeks after onset of an episode of acute or bloody diarrhea ****Probable diagnosis = no clear history of acute or bloody diarrhea in preceding 3 weeks but meets lab criteria
What are potential causes of HUS in terms of large classifications? (4)
- Infection: verotoxin producing E coli, shiga toxin-producing shigella, neuraminidase-producing Strep pneumo, HIV 2. Genetic 3. Diseases causing microvascular injury: SLE, HELLP, antiphospholipid antibody syndrome 4. Medication induced: cyclosporine, tacrolimus, etc.
What environmental things can be the source of verotoxin producing E coli causing HUS?
- Undercooked meat 2. Unpasteurized milk or apple cider 3. Petting farms 4. Swimming in contaminated ponds/lakes/pools
How is the diagnosis of HUS made? -pathogenesis?
Based on clinical diagnosis!!! -rarely need renal biopsy since the risk of biopsy is significant during active phase of disease -pathogenesis: toxins cause direct endothelial cell damage in the glomerulus which then activates platelets and localized thrombosis = then the RBCs being filtered through the glomerulus get sheared and you get anemia
What differs in the clinical presentation between E.coli related HUS vs. strep pneumo related HUS? -which has worse prognosis? -how crucial is stool culture for the diagnosis of HUS?
-E coli HUS = usually have diarrheal prodrome -strep pneumo = usually have pneumonia and empyema when they develop HUS -Strep pneumo has much worse prognosis (mortality 20% compared to <5% seen in E Coli) -can order stool sample but it has little utility because by the time the patient presents with HUS, usually the organism has been cleared already
What electrolyte abnormality should you monitor for in a patient with HUS?
Hyperkalemia due to renal failure AND hemolysis spilling K into the serum and not being able to pee it out
What is the incidence of CNS involvement in HUS?
Majority of patients with HUS have some CNS involvement = most are mild (irritability, lethargy, nonspecific encephalopathic features) -some have seizures and strokes (due to microvascular CNS thrombosis)
What are 3 conditions on the differential diagnosis for HUS?
Conditions causing acute kidney failure with hemolytic anemia and thrombocytopenia: 1. SLE 2. Malignant hypertension 3. Bilateral renal vein thrombosis
What is the prognosis for HUS? -mortality? -percentage requiring dialysis during acute phase? -full recovery? -chronic renal insufficiency?
<5% mortality rate -50% require dialysis during acute phase of disease -70% fully recover -30% have chronic renal insufficiency (some remain dependent on dialysis)
Are antibiotics indicated in diarrheal associated HUS? -what about antibiotics in strep-pneumo associated HUS?
NO! Antibiotics can result in increased toxin release worsening the HUS so don’t use it! -if pneumonia associated HUS, then yes use antibiotics
What type of clots can be seen in nephrotic syndrome? (3)
Nephrotic syndrome is considered a hypercoagulable condition! 1. DVT with pulmonary embolism 2. Renal vein thrombosis 3. Sinus venous thrombosis (Neuro recommends CT head in any patient with nephrotic syndrome presenting with headache)
A patient with postinfectious glomerulonephritis suddenly develops blurred vision, severe headaches, and altered mental status. What do you need to rule out?
Hypertensive encephalopathy! -take BP right away