Franz Volhard Clinic Berlin, Germany Email: roland.schmitt{at}charite.de
Nephrologists in medieval times had a pretty good time of it. They examined their patients' urine by placing the liquid in a matula (glass receptacle). They then held the matula up to the light. The urine was judged in terms of its colour and turbidity. Subsequently, nephrologists have fallen onto harder times. The specialty today is held in less high esteem, although we can now actually do something for the patients. Nephrologists no longer rely on the matula. However, since the times of Thomas Addis and other pioneers, no physical examination is said to be complete without the doctor looking at the patient's urine, grossly and under the microscope [1]. Our patient's urine was revealing in that regard, even without the microscope.
Case
A 69-year-old woman was referred to our service because of vertigo. The attack was sudden and was accompanied by nausea and vomiting. She had never experienced such symptoms before. She was diagnosed as hypertensive 12 years earlier and had an elevated cholesterol level. Her gall bladder had been removed because of cholecystitis. She had also undergone several gynaecological and orthopaedic operations. Her renal function had always been normal. Specifically, she had never had stone disease or arthritis.
Her physical examination was unremarkable. Her blood pressure was well controlled, her cardiovascular and pulmonary examinations were normal, she had no abdominal findings, no signs of joint disease, no nodules or tophi, and no peripheral oedema. Her blood counts, electrolytes, enzymes, and a host of other laboratory tests were either unremarkable or consistent with her known conditions. The urine pH was 5.0, the protein, glucose, and ketones were negative. Her creatinine concentration was 70 µmol/l, the urea concentration was 6.9 mmol/l, and the uric acid level was 383 µmol/l. The latter value is at the upper limits of normal for a lady her age.
After completing her neurological examination and examining her gait and station, we made the diagnosis of probable positional vertigo. The appropriate manoeuvres were applied and her symptoms promptly resolved. Thereafter, we got to the part that Addis designated as absolutely essential, examining her urine. We placed 10 ml into a test tube and centrifuged the turbid, but otherwise unremarkable urine at 3000 r.p.m. for 10 min. To our surprise, the tube showed an apricot coloured precipitate as shown below (Figure 1).
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Can you make the diagnosis by merely a glance, as a medieval nephrologist would surely have done?
Answer to the question on the preceding page
The urinary sediment was revealing (Figure 2). In the photomicrograph under phase contrast, we observed beautiful rhomboid crystals consistent with uric acid [2]. Subsequently, we added a few drops of potassium hydroxide to the precipitate in the test tube and the apricot-coloured material disappeared immediately. Merely shifting the pH from 5 to 6 increases the solubility of uric acid in urine 1000-fold, allowing the material to go back into solution.
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Conflict of interest statement. None declared.
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