A Systematic Approach to the Urinary Sediment
The examination of the urinary sediment has been compared to a liquid biopsy of the kidney and urinary tract. Although it clearly does not reach the anatomical resolution and precision of a tissue biopsy, it oftentimes allows correct identification of the principal site and extent of injury.
Moreover it excels with a couple of distinct advantages: It is fast, cheap and noninvasive. You can repeat it as often as you like. For focal processes it may be more sensitive and less prone to sampling error than a tissue biopsy.
To get the most out of the sediment examination it is important to approach it in a systematic fashion. I recommend the following steps:
- Get an idea of the clinical scenario and formulate specific questions.
- Be aware of the results of the urine dipstick (pH, density, hemoglobin, albuminuria) and take a look at the macroscopic appearance of the urine and sediment.
- Assess the sediment findings within the framework of the three principal pathoanatomical compartments (Table).
- Correlate your findings with the clinical information and formulate a conclusion.
In my opinion, best results of urinary sediment examination are obtained with intimate knowledge of the clinical situation. So I strive to look at sediments of patients I treat by myself. Outsourcing of the urinary sediment examination is of course possible, but grasping the “Gestalt” of a sediment from a written report, I find exceedingly difficult.