Abstract: PUB176
A Case of Medullary Sponge Kidney Presented With Persistent Hypokalemia
Session Information
Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders
- 1002 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Clinical
Authors
- Song, Rui, Abington Memorial Hospital, Abington, Pennsylvania, United States
- Lakhani, Sunita, Abington Memorial Hospital, Abington, Pennsylvania, United States
- Hassan, Syeda, Abington Memorial Hospital, Abington, Pennsylvania, United States
- Kyriakos, Raja N., Abington Memorial Hospital, Abington, Pennsylvania, United States
- Freitas, Lawrence, Abington Memorial Hospital, Abington, Pennsylvania, United States
Introduction
Medullary sponge kidney (MSK) is a rare and benign congenital abnormality of renal tubules characterized by cystic dilation of the renal medullary collecting ducts. We present a case who was found to have MSK during hypokalemia workup.
Case Description
A 33-year-old female with well-controlled HIV on Biktarvy (HIV-1 RNA < 20 copies/ml) presented with palpitations and tingling in the arms and legs for one day. She was found to have a serum potassium of 2.8mmol/L, magnesium of 1.6mEq/L, normal anion gap metabolic acidosis (NAGMA), creatinine of 0.8mg/dL, calcium of 9mg/dL and phosphorus of 3mg/dL. She is normotensive. She denies diuretic/laxative use, eating disorder, hypothyroidism, polyuria or diarrhea. She had chronic persistent hypokalemia (2.7-3.3mmol/L) and one episode of pyelonephritis 7 years ago. Family history includes ESRD of her grandmother. Her urine tests showed a urine potassium of 22 mmol/L, urine sodium of 64 mmol/L, urine anion gap of 13, urine PH of 7.5 with no proteinuria or hematuria. The urine drug screen was negative. Nephrology was consulted and further workup showed normal serum cortisol level, TSH and aldosterone/renin ratio, vitamin D deficiency (25-OH vitamin D 16.4ng/mL) with secondary hyperparathyroidism (PTH 252 pg/mL). A urine diuretic screening test was sent. Renal ultrasound (US) showed bilateral diffuse echogenic renal medullary pyramids, no hydronephrosis, mass or stone. The cause of the hypokalemia was thought to be MSK complicated by incomplete distal renal tubular acidosis (RTA). Potassium citrate was started but she was lost to follow-up.
Discussion
Incomplete distal RTA is common in MSK and is often asymptomatic. The patient was detected with mild hypokalemia, NAGMA and a urine pH of 7 since 7 years ago when having pyelonephritis, indicating distal RTA. Her distal RTA could be multifactorial. Vitamin D deficiency might be a factor but her normal serum calcium level does not support it. Her HIV and Biktarvy (has Tenofovir) usage are unlikely the main contributors as her hypokalemia happened much earlier than the HIV history. Her kidneys from the CT scan 7 years ago did not show calcification or increased density of the pyramids but now she has a typical US finding of MSK. This case highlights that hypokalemia and distal RTA might be the first sign of MSK while structural changes were not prominent in the imaging.