HYPERKALEMIA
When confronted with a laboratory report of an unexpected elevated potassium level, the first thing to do is repeat the test in most cases. The increased potassium may be due to hemolyzed blood or excessively tight tourniquet used to draw the blood. If these causes can be ruled out one can recall most of the causes by thinking of the physiologic mechanisms of excretion and regulation.
HYPERKALEMIA
Excretion
Acute renal failure causes retention of potassium. This may be caused by drugs, heavy metals, transfusion, shock, dehydration, glomerulonephritis, or obstructive uropathy.
Regulation
The exchange of potassium and hydrogen ion for sodium in the distal tubule is regulated by the hormone aldosterone. Consequently, in Addison disease this mechanism is partially shut down causing the retention of potassium. Various diuretics such as triamterene and the spirinolactones may do the same thing. Metabolic acidosis especially diabetic acidosis may be associated with hyperkalemia because the potassium moves out of the cell in exchange for hydrogen ion to buffer the acidosis.
Approach to the Diagnosis
Most helpful in the diagnosis will be laboratory tests to rule out renal failure and Addison disease. Thus a CBC, urinalysis, chemistry panel, renal function tests, plasma cortisol, 24-hour urine aldosterone level, and serial electrolytes may be necessary. As a precaution, it may be wise to hold all but critical drugs until the diagnosis is certain.
Other Useful Tests
- Corticotropin stimulation test (Addison disease)
- Cystoscopy and retrograde pyelography (obstructive uropathy)
- CT scan of abdomen (renal disease, neoplasm)
- Renal biopsy (renal disease)
- Nephrology consult
- Endocrinology consult
- Plasma renin level (Addison disease)
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
Other Book Chapters Related to Hyperkalemia
Read excerpts from these other book chapters related to Hyperkalemia:
Medical Books Excerpts
- Hyperkalemia
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
- [ read ]
Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2008 Williams & Wilkins.
More About Causes of Hyperkalemia
» Next page: Hyperkalemia (A Pocket Manual of Differential Diagnosis)
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