Year: 2024
Type: article
Study design: Case Report
Abstract: An unusual urine sample with macroscopic fat droplets (Fig. 1A) was obtained by cystoscopy from a 59-year-old male patient with abdominal pain. Laboratory testing revealed triglycerides in the urine (55.8 mg/dL [0.63 mmol/L]) and fat layer (250.5 mg/dL [2.83 mmol/L]). Microscopic evaluation showed spherulites (diameter: 20 to 30 µm) embedded in fat droplets (Fig. 1B–D). These crystals were absent in cystoscopy gel and fluids. Kidney function analysis did not explain the lipiduria (estimated glomerular filtration rate: 56 mL/min/1.73 m2, albumin/creatinine ratio: 7.1 mg/g [0.8 mg/mmol]). Spherulites observed in the top layer of fatty urine. (A), Urine sample with fat droplets on top layer. The urinary sediment did not show pathological abnormalities. The fat layer contained spherulites visualized by (B) Oil-Red-O staining with polarized light, (C) bright-field, and (D) polarized light. What is the likely composition of these crystals observed in urine? Which conditions are associated with lipiduria? What is the clinical significance of the crystals in urine? The answers are below. The spherulites resemble triglyceride crystals, previously reported in synovial fluid (1, 2) and the food industry (3). Triglycerides in urine are pathological and may occur in nephrotic syndrome (4). However, proteinuria was absent in our patient. The presumed mechanism for his fatty urine was lymphatic injury from radiofrequency ablation of a renal tumor (5). The spherulites were confined to the top urine layer, emphasizing the importance of examining the entire sample. Their clinical significance is uncertain, though visually striking. The corresponding author takes full responsibility that all authors on this publication have met the following required criteria of eligibility for authorship: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; (c) final approval of the published article; and (d) agreement to be accountable for all aspects of the article thus ensuring that questions related to the accuracy or integrity of any part of the article are appropriately investigated and resolved. Nobody who qualifies for authorship has been omitted from the list. Jorik Amesz (Conceptualization-Equal, Investigation-Equal, Visualization-Equal, Writing—original draft-Equal, Writing—review & editing-Equal), Erika Huijser (Conceptualization-Equal, Investigation-Equal, Writing—original draft-Equal, Writing—review & editing-Equal), Rob F. M. Bevers (Conceptualization-Equal, Resources-Equal, Writing—review & editing-Equal), and Arjan Albersen (Conceptualization-Equal, Investigation-Equal, Supervision-Equal, Writing—review & editing-Equal) No authors declared any potential conflicts of interest.
Source: Clinical Chemistry
Institution: Leiden University Medical Center
Language: English
Subfield: Cardiology and Cardiovascular Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $4,868
OpenAlex ID: W4405387042