SAN DIEGO -- Nephrolithiasis caused by abuse of an over-the-counter drug used to treat excess mucus may mimic kidney disorders, a researcher said here.
In a poster presentation at the annual meeting of the Society of Hospital Medicine, Neil Shah, MD, of Tulane University in New Orleans, and colleagues presented a case they called "Not Quite the Rolling Stones."
"A 42-year-old woman came to our clinic with left flank pain that had been present for a year but had been worsening for the past 3 days," Shah said.
Action Points
- Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
- Explain that nephrolithiasis caused by over-the-counter drug medication abuse (guaifenesin-pseudoephedrine or Mucinex D) may mimic kidney disorders.
- Nephrolithiasis caused by beta-hydroxybutyric acid causes kidney stones that are radiolucent and seen only on CT.
She had the typical findings associated with renal tubular acidosis, including tachycardia, a positive urine anion gap, and urinary pH of 6.5.
"Renal tubular acidosis is the accumulation of acid in the body due to the failure of the kidneys to appropriately acidify the urine and is typically diagnosed by the presence of a non-anion gap metabolic acidosis along with a positive urinary anion gap," he explained.
The various types of renal tubular acidosis (RTA) are classified according to the site of the injury.
Type 1 RTA, distal injury, is most often caused by a loss of renal perfusion, hypercalcemia, hydronephrosis, autoimmunity, and toxic damage.
There were no signs of autoimmune disease, with normal antinuclear antibodies and other markers, so the hospitalist team arranged for abdominal x-rays. However, no stones were visible.
They then obtained an abdominal CT scan, which showed multiple bilateral calculi. Further findings included hydronephrosis and a left proximal hydroureter.
Because the ingestion of certain substances and toxins can lead to atypical stones that are not composed of the usual substances such as calcium oxalate, they questioned the patient and learned that as a legal way of getting high, she had been ingesting 3 to 4 grams daily of guaifenesin-pseudoephedrine (Mucinex D) for 2 years.
The metabolite of these compounds that led to stone deposition was beta-hydroxybutyric acid, which appears only on CT. "Unlike more common calcium-containing radio-opaque stones, stones containing this component are radiolucent on plain films," Shah said.
The patient was treated with potassium bicarbonate following reversal of the obstruction with stents and was instructed to avoid taking the guaifenesin-pseudoephedrine medication.
"There is a lot of over-the-counter medicine abuse going on now," Shah told 鶹ý. In the acute setting, clinicians need to learn exactly what patients are taking, including herbal supplements and cold remedies, he advised.
"She wasn't trying to hide the fact that she was taking the medication -- we just weren't asking the right questions," he said.
Disclosures
The authors had no disclosures.
Primary Source
Society of Hospital Medicine
Source Reference: Shah N, et al "Not Quite the Rolling Stones" SHM 2012; Abstract 380.