“What am I looking at? ” Phagocytosis and particle internalization by cells in the urine is not common, but of clinical interest when it occurs.
Phagocytosis/particle internalization can be observed in urine microscopy by the usual culprits: professional phagocytes like neutrophils and macrophages , but also by cells that we
usually don’t think performs phagocytosis – that’s why the term “particle internalization” is used here.
Professional phagocytes like macrophages (Fig1) and neutrophils (Fig 2) are not
a surprise but are still pretty neat to see in the urine sediment and can be confusing if you don’t expect them. In Fig 2, neutrophils are taking on a fungus particle much bigger than themselves!
What’s less expected, however, is non-professional phagocytes like renal
tubular epithelial cells (Fig. 3) doing the same job.
Frequently, it is not an easy task to properly identify the phagocytic/particle
internalization process, because the literature has infrequent examples,
usually as case reports. Also, the identification of these “particles within other particle”
usually requires proper microscopic resources like polarized light microscopy (Figures 3-5) and
stains like Sternhemer-Malbin stain (Figure 2) or May-Grunwald-Giemsa stain (Figure 6).
However, independently of the availability of microscopic resources or stains, we need to be able
to see that there is something unusual on the slide. As we are seeing here, virtually any particle (Figures 1-8) can be
phagocytosed/internalized by both professional or non-professional phagocytes, from crystals,
to microrganisms, from lipid droplets to cells [5,6].
There is a lack of published work on phagocytosis/particle internalization in the urinalysis
subject, this is surely an opportunity for professionals interested on this field to develop works and
clarify these very interesting findings.
1- Tesser Poloni JA, Perazella MA, Neild GH. Macrophages at work: phagocytosis of
urinary fungi. Clin Kidney J. 2013 Apr;6(2):233-4. doi: 10.1093/ckj/sfs184. Epub 2013
Feb 3. PMID: 26019856; PMCID: PMC4432439.
2- Poloni JAT, Rotta LN. Urine Sediment Findings and the Immune Response to
Pathologies in Fungal Urinary Tract Infections Caused by Candida spp. J Fungi (Basel).
2020 Oct 23;6(4):245. doi: 10.3390/jof6040245. PMID: 33114117; PMCID:
3- Poloni JAT, Garcia CD, Rotta LN, Urban CF. Neutrophils phagocytosing fungal hyphae in
urinary sediment. J Bras Nefrol. 2021 Jul-Sep;43(3):431-433. doi: 10.1590/2175-8239-
JBN-2019-0245. PMID: 33350430; PMCID: PMC8428652.
4- Poloni JA, Garcia CD, Rotta LN, Perazella MA. Calcium oxalate crystalluria points to
primary hyperoxaluria type 1. Kidney Int. 2016 Jan;89(1):250. doi:
10.1016/j.kint.2015.11.001. PMID: 26759051.
5- Koene RA, Bogman MJ. Sperm body in the urinary sediment. Nephrol Dial Transplant.
1993;8(11):1296. PMID: 8302476.
6- Oki R, Kono M, Kubo K, Tojo A, Yamamoto K. Urinary phagocytic macrophages in
hemophagocytic lymphohistiocytosis. Kidney Int. 2016 Oct;90(4):908. doi:
10.1016/j.kint.2016.07.023. PMID: 27633873.
Post by José Antonio Tesser Poloni
Edited by Anna Gaddy
Great content! This is exactly the sort of thing I was looking for. Thanks for your help
Una felicitación a todos los colaboradores de este sitio, conozco un poco del trabajo del Dr Poloni y son magníficas sus fotografías, también soy un apasionado del tema, les escribo desde México. Éxito