Renal cyst and potassium

Case: 62 years old male presented to ED with flank pain and accelerated hypertension (HTN). He informed that his primary care doctor recently found him to have late-onset HTN. In the last few months, he has continued to have potassium issues in his lab work for no reason. The only positive finding so far, is a simple renal cyst on abdominal ultrasound, regarded as an incidental finding by the radiologist. If a simple cyst of the kidney becomes symptomatic, it tends to cause? - Select one

A) hyperkalemia

B) hypokalemia

Answer: B

The finding of a renal cyst on ultrasound is usually benign and an incidental finding. But, if it enlarges in size, it may become a cause of late-onset hypertension. The reason is persistent pain, discomfort, and possible excess renin secretion. This should be treated as secondary HTN, which many times presents as an acute rise in blood pressure in a normotensive person. 

These patients tend to have persistent hypokalemia, which remains unexplained due to any other cause.

#nephrology

#electrolytes

References:

1. Ferrari P. The challenge of renal cystic disease and its association with hypertension, age and abnormal potassium handling. J Hypertens. 2007 Jul;25(7):1347-9. doi: 10.1097/HJH.0b013e32814db544. PMID: 17563553.

2. Gamakaranage CS, Rodrigo C, Jayasinghe S, Rajapakse S. Hypokalemic paralysis associated with cystic disease of the kidney: case report. BMC Nephrol. 2011 Apr 18;12:16. doi: 10.1186/1471-2369-12-16. PMID: 21501478; PMCID: PMC3095547.