Dioscorea quinqueloba induces acute kidney injury

To the Editor:

Dioscorea quinqueloba is a medicinal herb that is widely used in Asia to treat cardiovascular disease and various medical conditions. Acute kidney injury associated with the use of herbal medicine is common throughout the world, but acute kidney injury caused by Dioscorea quinqueloba has not been reported. We report two cases of acute kidney injury that occurred after ingestion of Dioscorea quinqueloba.

Case report 1. A 68-years-old man was referred to our hospital for generalized edema, vomiting and diarrhea from a local hospital. He had a history of hypertension, hyperlipidemia and diabetes mellitus. Seven days previously, he had taken approximately 3 ounces of uncooked powder of the yam Dioscorea quinqueloba as a dietary supplement after he heard that it is good for diabetes mellitus. He was oliguric at admission. Physical examination showed dry tongue and pitting edema of lower extremities. Pulse was 60 beats/min and blood pressure 130/70 mmHg. Serum creatinine level was 406.6 μmol/L, sodium 133 mmol/L, potassium 4.7 mmol/L, chloride 105 mmol/L, creatinine kinase 66 U/L (normal range, 35–172) and blood urea nitrogen 21.2 mmol/L. Arterial blood gas analysis revealed a pH 7.436, pCO₂ 28.7 mmHg, pO₂ 88.1 mmHg, HCO₃⁻ 18.9 mmol/L and 97.7% O₂ saturation. Urine sodium and creatinine were 50 mmol/L and 2846 μmol/L, respectively. The fractional excretion of sodium into urine (FE_Na) was 3.5%. Urine osmolality was 199 mmol/kg. The urine analysis was clear. He was admitted with a diagnosis of intrinsic acute renal failure. The powder from Dioscorea quinqueloba was thought to be the nephrotoxic agent. He was hydrated and the powder stopped. Six days later edema was improved. Serum creatinine slowly decreased from 521.6 (peak) to 106.1 μmol/L, over 7 weeks. Kidney ultrasound examination revealed only increased cortical echogenicity, but renal biopsy was not performed. He was discharged without any complications, and followed up regularly.

Case report 2: A 58-years-old man, the younger brother of case-1 patient, was also referred to our hospital with pitting edema of the lower extremities, vomiting, diarrhea and polydipsia. He had taken 3 ounces of uncooked powder of Dioscorea quinqueloba as a health tonic 7 days earlier. The urine volume was not decreased, but his serum creatinine was 512.7 μmol/L. Pulse rate was 72 beats/min, blood pressure of 110/70 mmHg. Blood urea nitrogen was 18.1 mmol/L. The FE_Na was also increased to 6.4%, and urine osmolality 250 mmol/kg. Arterial blood gas analysis revealed a pH 7.456, pCO₂ 32.5 mmHg, pO₂ 94.3 mmHg, HCO₃⁻ 22.6 mmol/L and 97.6% O₂ saturation. Urine analysis showed protein 3 +, 1–4 red blood cells/high power fields. As in the case of his brother, he was diagnosed as intrinsic acute renal failure due to toxicity from Dioscorea quinqueloba. We treated him with hydration. Renal function recovered and creatinine improved to 114.9 μmol/L about 10 days later and urinary abnormalities normalised. He was discharged without complications rather earlier than his brother.

Although the pathogenesis by which Dioscorea quinqueloba induces acute renal failure remained unknown, several factors are thought to be important. First, Dioscorea species contain dioscorine and dioscine, which have convulsive, local anesthetic and antidiuretic effects.¹ In normal use, yams are detoxified before eating by placing them in running water for a few days, soaking in salt water and boiling for several hours. Incorrectly prepared yam can lead to convulsions, hepatic and renal failure.² Therefore, we assume that the raw powder may have caused acute kidney injury in our patients. Many traditional remedies frequently cause gastro-intestinal complications including vomiting or diarrhea in up to half of the patients,³ so concomitant volume depletion can induce renal ischemia. In both cases, such concurrent volume depletion state may have aggravated acute kidney injury.

These are the first cases of acute kidney injury associated with ingestion of Dioscorea quinqueloba. We emphasize that this yam should be correctly prepared for traditional medicine, otherwise it may cause a life-threatening acute kidney injury.