An otherwise healthy 6-year-old boy presented to the emergency department after falling out of bed and sustaining a testicular injury. The examination and evaluation, including urinalysis (revealing hematuria) and ultrasound, were suggestive of minor injury but were otherwise unremarkable. The patient was started on amoxicillin and had orders for a repeat urinalysis in a week. The microscopy review of the urine sample a week later demonstrated numerous crystals and moderate hematuria (Fig. 1). 

Amoxicillin crystals in urine.

Two images from a microscopy examination of the patient's urine demonstrating the fine, needle-like singular and clustered crystals, as well as moderate hematuria. Although difficult to distinguish from tyrosine crystals, amoxicillin crystals may appear slightly more blunted and have branching near the crystal base (arrowheads). The diagnosis is best made according to the clinical presentation and medical history. Definitive identification of amoxicillin crystals may be achieved with infrared spectroscopy (2).


  1. What kind of fairly common urine crystals do these appear to be?
  2. Does the patent's history suggest another explanation for the crystals?

Read the article here for the answers.