Question

Now that you know how hypokalemia can cause your patient's muscle weakness, you have to figure out what is causing his hypokalemia. Dehydration from vomiting or diarrhea is a major cause of hypokalemia, but your patient has not reported being sick. This leaves two possible causes: kidney problems or a genetic mutation in ion channels.

• The kidneys are important for regulating the levels of potassium released in urine. A patient with malfunctioning kidneys may be releasing too much potassium in urine, causing the level of potassium in the blood to drop.
• Abnormal ion channels can allow large amounts of potassium to be shifted from the blood into cells under certain conditions, causing the level of potassium in the blood to drop.

A quick way to tell the difference between these two diagnoses is to calculate the transtubular potassium gradient (TTKG). The TTKG is a measurement of the amount of K⁺ kept in the collecting ducts of the kidneys. If the patient's kidneys are working properly, low blood potassium should trigger the kidney to severely reduce the amount of K⁺ being released into urine in order to attempt to raise blood K⁺ levels. However, if the hypokalemia is caused by malfunctioning kidneys, K⁺ levels in the urine will be high.

TTKG is calculated using the following equation. In patients with hypokalemia, a value greater than 7 indicates a kidney dysfunction, and a value less than 3 indicates an ion channel disorder.

TTKG= Urine K+ Blood K+ Urine Osmolarity Plasma Osmolarity

Answer 1

As the TTKG value is 1.87 which is lesser than 3 , so -

TTKG = Urine kt) Blood kt ( Urine Osmolarity Plasma Osmolarity - 4 V 14 1.869 TT KG = 1.87

2) If the TTKG value is more than 7 then there are possibilities of kidney dysfunction. But here it is 1.87 , so The answer is [no]

3) [yes]