Lesa-Marie McKinley, MBBS, Joy-Ann Tabanor, MBBS and Hyun Bae, MD
Department of Medicine, Englewood Hospital and Medical Center, Englewood NJ
Introduction:Hypokalemia is an electrolyte abnormality commonly attributed to gastrointestinal losses, insufficient oral intake or urinary losses from diuretic therapy. We report a case of hypokalemia that highlights how imaging studies can be useful to support the diagnosis of an unusual cause.
Case Presentation: A 59 y.o. female presented with fatigue, dizziness, muscle weakness, loss of appetite and vomiting for three weeks and diarrhea for one day. Physical exam was unremarkable. Laboratory studies showed mild leukocytosis, hypokalemia and acute kidney injury (AKI) with concomitant high and normal anion gap metabolic acidosis. The initial impression was that her electrolyte derangements and AKI were due to vomiting, diarrhea and dehydration, however, a renal ultrasound was performed that demonstrated bilateral increased echogenicity and acoustic shadowing consistent with advanced medullary nephrocalcinosis (Figure 1). CT scan of the abdomen and pelvis (Figure 2) showed similar findings, but no nephrolithiasis. Nephrology consult was obtained and the impression was that although urine studies were inconclusive, the laboratory and imaging studies suggested distal renal tubular acidosis (dRTA) as the primary cause of hypokalemia. Investigations to identify other possible causes of nephrocalcinosis were negative. She was treated with intravenous fluids, bicarbonate and potassium supplementation. Her acidosis and AKI had significantly improved.
Discussion: Nephrocalcinosis may be both a cause and consequence of dRTA. This makes identifying the true inciting event difficult. Nevertheless, demonstrating this finding on renal imaging supported our suspicion of dRTA as the cause for our patient’s hypokalemia. dRTA is commonly associated with hypokalemia due to renal potassium wasting. There may also by hypocitraturia, which is thought to contribute to nephrocalcinosis by facilitating the precipitation of calcium crystals. Correction of the acidosis by treating with bicarbonate or alkalizing potassium salts decreases these complications.
Conclusions: This case highlights that imaging studies are useful in the investigation of patients with metabolic acidosis and hypokalemia, especially in the setting of inconclusive urinary studies.
References
- J Gen Intern Medicine 2016 Oct; 31(10):1261. doi: 10.1007/s11606-016-3697-z. Epub 2016 Apr 18.Bilateral Nephrocalcinosis in Primary Distal Renal Tubular Acidosis.
- Wrong O. Nephrocalcinosis. In: Oxford Textbook of Clinical Nephrology, Davison AM, Cameron JS, Grünfeld J, et al (Eds), Oxford University Press, Oxford 2005. p.1375.
