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Critical Care |

A Case of Extreme Hypokalemia Whose Histologic Findings on Autopsy Resemble Distal Renal Tubular Acidosis

Takuya Ogami*, MD; Akihiko Sotomatsu, MD; Sandra Moody, MD; Makito Yaegashi, MD
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Kameda Medical Center, Kamogawa, Japan


Chest. 2012;142(4_MeetingAbstracts):320A. doi:10.1378/chest.1389515
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Abstract

SESSION TYPE: Critical Care Global Case Report Posters

PRESENTED ON: Tuesday, October 23, 2012 at 01:30 PM - 02:30 PM

INTRODUCTION: Distal (Type 1) renal tubular acidosis (RTA) is characterized by a normal anion gap (hyperchloremic) metabolic acidosis with hypokalemia, while furosemide use results in a hypochloremic metabolic alkalosis. We treated a patient with severe hypokalemia, which was clinically compatible with these disorders, though the histologic findings were slightly different on autopsy.

CASE PRESENTATION: The patient was a 58-year-old woman with an 11-year history of furosemide use and hypokalemia who presented to an outside hospital with a 2-week history of weakness, dysphagia, and dyspnea. After admission, her consciousness and respiratory status deteriorated, and arterial blood gas showed a pH of 6.964, PaCO2 105 mmHg, PaO2 113 mmHg, and HCO3 23.9 mEq/L on 10 litter/minute of oxygen. The serum potassium was 1.0 mEq/L. She was intubated and mechanically ventilated. Ventricular tachycardia was treated with vasopressors, defibrillation, and lidocaine. She became hypotensive and was transferred to our hospital. Her lowest serum potassium was 0.6 mEq/L, which was repleted aggressively . Her hypotension, hypoxemia and oliguric renal failure became progressively worse, though we gave antibiotics for suspected septic shock. The mode of mechanical ventilation was changed to airway pressure release ventilation from assist/control mode. Her respiratory status continued to deteriorate and blood pressure did not respond to vasopressors. She died on day 2. In the differential diagnosis of hypokalemia, hyperaldosteronism was ruled out (plasma renin activity [PRA] 12 ng/mL/h, plasma aldosterone concentration [PAC] 114 pg/mL, PAC/PRA ratio 9.5) as well as Cushing disease (serum cortisol 85 mcg/dL, ACTH 9.9 pg/mL with normal adrenals on autopsy suggesting a stress-mediated cortisol secretion). Urinalysis was consistent with distal RTA: pH 6.0, specific gravity 1.011, sodium 65.6 mEq/L, potassium 26.8 mEq/L, chloride 67.3 mEq/L, and anion gap of 25.1. The autopsy showed distal renal tubule atrophy, vacuolization, destroyed brush border of the proximal renal tubule, and calcification in both the proximal and distal renal tubules of the outer medulla. These findings could not be explained by circulatory impairment. Additionally, it showed destroyed epithelial cells in the collecting duct, glomerulonephritis that resembles focal glomerulosclerosis, mild hyperplasia of the juxtaglomerular apparatus, and tubulo-interstitial nephritis without fibrosis.

DISCUSSION: The differential diagnoses of hypokalemia include type 1 RTA and chronic furosemide use. The main histologic abnormalities in distal RTA were plugging of the inner medullary collecting and Bellini ducts with deposits of calcium phosphate in the form of apatite, epithelial cell injury and marked loss, and marked interstitial fibrosis surrounding the dilated ducts. In our patient, the histology revealed calcification in both distal and proximal tubules, but not in collecting and Bellini ducts in the medulla . These were similar, but slightly different from RTA. Additionally, the findings were not consistent with nephrocalcinosis associated with long-term furosemide use. In patients with furosemide-induced nephrocalcinois, the histologic findings include focal tubulo-interstitial fibrosis and atrophy and calcifications in the outer medullary tubulo-interstitium. The histologic findings of distal RTA are not established, since the best available data are based on a case series of five cases. Although the patient’s clinical course resembled that of distal RTA, the histologic findings were slightly different.

CONCLUSIONS: In our patient with extreme hypokalemia, histologic findings were different from that of distal RTA with calcification in the renal tubules without fibrosis. Further studies are needed to elucidate the clinical meaning of this difference.

1) Evan AP, Lingeman J, Coe F, et al. Renal histopathology of stone-forming patients with distal renal tubular acidosis. Kidney Int. Apr 2007;71(8):795-801.

2) Kim YG, Kim B, Kim MK, et al. Medullary nephrocalcinosis associated with long-term furosemide abuse in adults. Nephrol Dial Transplant. 2001;16:2303-2309.

DISCLOSURE: The following authors have nothing to disclose: Takuya Ogami, Akihiko Sotomatsu, Sandra Moody, Makito Yaegashi

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Kameda Medical Center, Kamogawa, Japan

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