Type 4 Hyperkalemic Renal Tubular Acidosis After Coronary Artery Bypass Grafting.

SUMMARY Type 4 renal tubular acidosis is a rare condition that can result in a life threatening hyperkalemia. It is caused by an impaired response to aldosterone, or more commonly, an aldosterone deficiency. Known factors that can contribute to the development of hypoaldosteronism include adrenal insufficiency, diabetic nephropathy, and certain medications – including angiotensin-converting enzyme inhibitors and heparin. Many patients with significant coronary artery disease are exposed to multiple - if not all - of these risk factors, putting this population at a potentially increased risk for development of hypoaldosteronism and severe hyperkalemia. Here, we present a case of a patient with diabetic nephropathy and chronic lisinopril use who required systemic heparinization for a non-ST-elevation myocardial infarction. This was followed by coronary artery bypass grafting and the development of severe hyperkalemia requiring renal replacement therapy, and our patient was subsequently found to have hyporeninemic-hypoaldosteronism. We review the pathophysiology, risk factors, diagnosis, and management of Type 4 hyperkalemic renal tubular acidosis.