Renal Emergencies



Renal Emergencies


Jennifer Thull-Freedman



Introduction



  • Most common cause of acute renal failure in children is prerenal


  • Common to find varying degrees of functional/transient proteinuria or hematuria


Proteinuria


Common Causes of Isolated Proteinuria



  • Functional/transient proteinuria



    • Caused by fever, exercise, dehydration, seizures, exposure to cold, congestive heart failure


    • Urine dip usually < 2+ proteinuria (< 100 mg/dL)


  • Benign postural (orthostatic) proteinuria



    • Usually occurs after 7 years of age


    • Urine protein: creatinine ratio in a first morning void is normal


  • Glomerulopathy



    • Nephrotic syndrome (see below)


  • Tubular



    • Overload proteinuria


    • Tubular dysfunction (reflux nephropathy, ischemic injury, cystinosis)


  • Benign persistent proteinuria


Laboratory Evaluation



  • Dipstick:



    • False positive with concentrated urine, pH > 8, gross hematuria or pyuria


    • False negative with very dilute, acidic urine (pH < 4.5)


  • Urine protein: creatinine ratio (mg/mg)



    • < 0.5 if < 2 years age or < 0.2 for older children considered normal



    • > 1 suspicious for nephrotic range proteinuria


    • > 2 suggestive of nephrotic range proteinuria


  • Consider 12-24 hour collection if urine protein:creatine ratio is abnormal


  • Additional evaluation to consider: electrolytes, urea, creatinine, albumin, cholesterol, C3, C4, ANA, CBC, VBG


Nephrotic Syndrome



  • Clinical syndrome of proteinuria due to loss of glomerular membrane selectivity


  • Characterized by proteinuria, hypoproteinemia, edema, hyperlipidemia


  • Secondary disturbances: hypocalcemia (due to hypoalbuminemia), hyperkalemia (due to prerenal azotemia), hyponatremia, hypercoagulability, hypogammaglobulinemia


Epidemiology



  • Primary acquired form (idiopathic minimal-change nephrosis) most common from 18 months to 6 years of age; 80% of cases


  • Secondary acquired form most common > 6 years; causes include infection, drugs, systemic disease (HUS, HSP, SLE, sickle cell, etc.)


Diagnosis



  • Hypoalbuminemia < 3.0 g/dL


  • Urine protein 100-300 mg/dL or > 40 mg/m2/hour in 24-hour period


Treatment for New-Onset Disease



  • Prednisone 2 mg/kg/day for 4-6 weeks, then taper



    • Anticipate response in 7-10 days


  • Furosemide may be considered (1-2 mg/kg/day)


  • Albumin infusion if needed to emergently increase oncotic pressure



    • Indications: symptomatic hypovolemia, peritonitis, clinically significant edema



    • 1 g/kg of 25% solution over 4 hours with furosemide midway through transfusion


    • Watch for pulmonary edema


  • Optimize dietary protein


Complications



  • Infection: peritonitis, cellulitis, sepsis, meningitis


  • Thrombosis and thromboembolism: caution with femoral venous access


  • Other: ascites, pleural effusion, intravascular hypovolemia (shock, prerenal acute renal failure)


Hematuria



  • > 5-10 RBCs per high-power field from a centrifuged voided urine sample


  • Confirm with microscopy: RBCs, hemoglobin, myoglobin give positive dipstick


  • False positive dipstick can result from drugs (ascorbic acid, sulfonamides, iron sorbitol, metronidazole, nitrofurantoin); beets, dyes, drugs; urate crystals may discolor urine


  • False negative microscopy may occur in setting of low specific gravity causing cell lysis

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Jun 22, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Renal Emergencies

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