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
