From the Guidelines
Amorphous crystals in urine are generally not clinically significant and typically don't require specific treatment. These crystals appear as small, colorless, granular clumps without defined shapes and are commonly found in normal urine samples, especially when the urine has been standing for some time before analysis. Amorphous crystals are usually composed of phosphates in alkaline urine or urates in acidic urine. Their presence is often related to dietary factors, urine concentration, or pH changes. Unlike structured crystals such as calcium oxalate or struvite, amorphous crystals rarely contribute to kidney stone formation or indicate underlying pathology.
Key Points to Consider
- If amorphous crystals are consistently present in large amounts, basic management includes increasing fluid intake to 2-3 liters daily to dilute the urine and reduce crystal formation, as recommended by the American College of Physicians 1.
- For amorphous phosphates in persistently alkaline urine, addressing any urinary tract infection may be necessary, while amorphous urates in acidic urine might benefit from dietary modifications to reduce purine intake.
- Laboratory technicians should note their presence during urinalysis, but clinicians generally don't need to pursue further investigation or treatment unless accompanied by other concerning urinary findings or symptoms of urinary tract disease.
Management Approach
The management approach for amorphous crystals in urine focuses on preventive measures rather than treatment, aiming to reduce the risk of kidney stone formation and alleviate symptoms if present. Increasing fluid intake is a key recommendation, with the goal of producing at least 2 liters of urine per day, as suggested by studies 1. Additionally, dietary adjustments may be beneficial in certain cases, such as reducing purine intake for amorphous urates in acidic urine.
Clinical Decision Making
Clinical decision making for patients with amorphous crystals in their urine should prioritize a thorough assessment of overall urinary health, considering factors such as the presence of other urinary abnormalities, symptoms of urinary tract disease, and the patient's medical history. While amorphous crystals themselves are typically not a cause for concern, their presence in conjunction with other findings may warrant further investigation or management, guided by the most recent and highest quality evidence available, such as the clinical practice guidelines from the American College of Physicians 1.
From the FDA Drug Label
Crystals of ciprofloxacin have been observed rarely in the urine of human subjects but more frequently in the urine of laboratory animals, which is usually alkaline. Alkalinity of the urine should be avoided in patients receiving ciprofloxacin. Patients should be well hydrated to prevent the formation of highly concentrated urine
The presence of amorphous crystals in urine is likely related to the use of ciprofloxacin, especially if the urine is alkaline. To manage this, patients should be advised to:
- Stay well hydrated to prevent the formation of highly concentrated urine
- Avoid alkalinity of the urine The clinical significance of amorphous crystals in urine in this context is that it may be a sign of crystalluria related to ciprofloxacin, which is rare in humans but can occur, especially if the urine is not acidic 2.
From the Research
Significance of Amorphous Crystals in Urine
- Amorphous crystals in urine can be a marker of urine supersaturation with substances deriving from metabolic disorders, inherited diseases, or drugs 3.
- The presence of amorphous crystals can be associated with pathological conditions such as urolithiasis, acute uric acid nephropathy, ethylene glycol poisoning, and hypereosinophilic syndrome 4.
- Crystalluria, including amorphous crystals, can also be caused by drugs such as sulphadiazine, acyclovir, triamterene, piridoxylate, and primidone, which can crystallize within the tubular lumina and cause renal damage 4.
Appropriate Management of Amorphous Crystals in Urine
- The investigation of crystalluria, including amorphous crystals, must be done according to a protocol that includes the delivery to the laboratory of a proper urine sample, the use of a microscope equipped with polarized light, and the accurate knowledge of urine pH 3, 5.
- A comprehensive examination of the crystals, including identification, quantification, and size measurement, is necessary for diagnosis and monitoring of diseases associated with urinary stone formation or renal function impairment 3, 5.
- Fourier-Transform Infrared Spectroscopy (FTIR) or other infrared spectroscopy methods may be needed for the identification of unusual crystals, including amorphous crystals 3, 6, 5.
- The management of amorphous crystals in urine should also include the evaluation of the underlying cause of crystalluria, such as metabolic disorders, inherited diseases, or drug-induced crystalluria 4, 3, 6.
Diagnostic Tools and Techniques
- Microscopy with polarized light is a useful tool for the identification and examination of crystals in urine 4, 3, 5.
- FTIR spectroscopy is a rapid and specific tool for the identification of crystals, including amorphous crystals, and can be useful in supporting renal disease diagnosis and monitoring drug therapy 6, 5.
- Quantitative morphoconstitutional analysis of urinary calculi can provide valuable information on stone activity and underlying pathology 5.