Michael Laposata

All articles by Michael Laposata

Decreased Urine Specific Gravity

Differential Diagnosis Loss of renal tubular concentrating ability Overhydration Continue Reading Diabetes insipidus Unsatisfactory collection of specimen producing low specific gravity Suggested Additional Lab Testing Serum or plasma BUN and/or creatinine as initial assessment for renal disease Repeat urinalysis to assess whether unsatisfactory collection (most likely dilution with water) produced the low specific gravity Tests…

Decreased Serum Aldosterone

Differential Diagnosis Primary hypoaldosteronism Secondary hypoaldosteronism Continue Reading Suggested Additional Lab Testing Primary hypoaldosteronism Serum potassium usually elevated Low serum sodium Normal or elevated plasma renin Secondary hypoaldosteronism In most cases, elevated serum potassium and low or low-normal serum sodium Low renin production with certain causes of secondary hypoaldosteronism but normal or elevated with other…

BUN and/or Creatinine Increased: Prerenal Cause

Differential Diagnosis Renal artery stenosis Atherosclerotic renal vascular disease Continue Reading Hypovolemia Thromboembolic renal vascular disease HUS or TTP Sickle cell disease-associated nephropathy Suggested Additional Lab Testing Studies that would permit a diagnosis of HUS, TTP, or sickle cell disease are valuable. Tests that identify a predisposition to thrombosis may also be informative.

Casts in the Urine

Differential Diagnosis Hyaline casts as indicative of: Glomerulonephritis PyelonephritisContinue Reading Chronic renal disease Congestive heart failure Strenuous exercise Red blood cell casts as indicative of: Glomerulonephritis Strenuous exercise White blood cell casts as indicative of pyelonephritis Epithelial cell casts as indicative of renal tubular damage Granular casts as indicative of: Stasis of urine flow UTI…

BUN and/or Creatinine Increased: Postrenal Cause

Differential Diagnosis Obstruction originating within the urinary tract: Congenital anomalies Urinary calculiContinue Reading Benign prostatic hyperplasia (BPH) Infection Tumors Blood clots or sloughed cells Functional abnormalities of urinary tract. Obstruction originating outside the urinary tract : Tumor or mass adjacent to the urinary tract Pregnancy Uterine prolapse Suggested Additional Lab Testing Tests to assess predisposition…

BUN and/or Creatinine Increased: Intrarenal Cause

Differential Diagnosis Congenital kidney anomalies Diseases of the kidney associated with a cystic mass Continue Reading Diseases of the kidney associated with a solid mass Diseases without a mass primarily manifested as glomerular defects Diseases without a mass in which there is primarily tubular or interstitial (tubulointerstitial) disease Suggested Additional Lab Testing For diseases associated…

Bilirubinuria

Differential Diagnosis Hepatitis Cirrhosis Continue Reading Biliary obstruction Suggested Additional Lab Testing Tests for hepatitis (serologic or DNA-based) may be important if hepatitis is suspected as a cause for the bilirubinuria. Alkaline phosphatase or 5´-nucleotidase is useful as a marker of biliary obstruction, especially when the value for either parameter is significantly more abnormal than…

An Elevated Value for Human Chorionic Gonadotropin (hCG)

Differential Diagnosis Confirmation of intrauterine pregnancy Ectopic pregnancy Continue Reading Abortion Gestational trophoblastic disease Nongestational malignancies Suggested Additional Lab Testing Human chorionic gonadotropin (hCG) tests can be performed using serum or urine. Urine test is qualitative (yes/no). Serum test can be qualitative or quantitative. Serial quantitative measurements of hCG may be useful, especially in suspected…

An Elevated Value of Troponin I, Troponin T, CK-MB, and/or Myoglobin

Differential Diagnosis Troponin I or T is now widely used over other markers for acute MI in the absence of other markers. Any elevation can indicate myocyte damage; interpret results with defined institutional cutoffs for myocardial infarction. Continue Reading Suggested Additional Lab Testing Appropriate follow-up testing with troponin level. Test as appropriate to rule out…

Altered Urinary pH

Differential Diagnosis Respiratory or metabolic acidosis Respiratory or metabolic alkalosis Defect in renal tubular secretion and reabsorption Continue Reading Don't Miss – Dangerous Situations Severe acidosis or alkalosis could result in a lethal outcome in the short term and should be addressed immediately. Commonly Encountered Situations There are many causes of acidosis and alkalosis with…

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