Parasite eggs in urine cytology: Fact or artifact?

Abstract

Urine sediment cytology should be done for three main reasons: initial evaluation in symptomatic patients, pursuit of patients with tumoral pathology, and risk population screening. Nevertheless, in the course of microscopic observation it is possible to observe several elements or structures that initially seem unrelated to what we are looking for. Schistosomiasis is an endemic disease affecting humans and animals in tropical countries and the Middle and Far East, but infrequent in the developed countries. Typical eggs from Schistosoma are nonoperculate, embryonated when passed in feces and with transparent shell. The eggs are elongate and large in S. mansoni (114–175 3 40– 70 lm in size), with a prominent lateral spine, and in S. haematobium (112–170 3 40–70 lm) and S. intercalatum (140–240 3 50–85 lm) with a terminal spine. In the cases of S. japonicum (70–100 3 55–65 lm) and S. mekongi (51–78 3 39.66 lm) the eggs are round with a small inconspicuous spine. The presence of miracidium inside the eggs could be a method of differentiation of cytological artefacts in certain clinical settings. Eggs of S. haematobium may also be found in biopsies of the urinary bladder and rectum, and occasionally they may found in feces. Here, we show some structures observed in urinary sediment that because of their morphology, were initially mistaken for parasitic eggs (Schistosoma spp.). The images correspond to voided urine sediment from a 70year-old man presenting hematuria as the only symptom. Biochemical analysis was within normal limits, except for high level of uric acid. Presence of eosinophils in urine and/or eosinophilia was not appreciated. The patient does not report a travel to an area where schistosomiasis is endemic. Figure C-1 shows, against a clear background, and surrounding a small group of urothelial cells, several oval structures (true acid uric crystals) with a spine-like appearance at the ends (thick arrows). The similar unstained and transparent crystals are also observed (thin arrows). In Figure C-2, corresponding to the same sample, three acid uric crystals showed as structures of granular appearance are observed, being the two at the margins with oval shape, 80 3 25 microns in size, and with two spine-like projections at the ends. Figure C-3 shows a true egg of S. haematobium found in human feces (the miracidium can be observed inside of the structure). Because there are few publications relating the presence of S. haematobium eggs in urine sediment, we think that it is easy to mistake or ignore or to fall in the temptation of believing or not. Although schistosomiasis of the urinary bladder is an unusual parasitic infection in our environment, because of the increase in immigration and travel to exotic countries it may be wise to include this disease in asymptomatic hematuria differential diagnosis. The majority of crystals found in urine, except a few such as cystine, tyrosine, and leucine, are of limited clinical value. In many cases, crystals found in urine sediment are not present in the freshly voided specimen, although pH changes and refrigeration are promoters of crystals formation. Uric acid crystals present a variety of shapes such as oval with more or less eroded ends (‘‘lemon-like’’ shape), polygonal, in needles and/or rosettes, etc. Coloration may oscillate between brown-yellow or uncolored, and under polarized light the color variation is quite typical. Nevertheless, because of unusual morphology it may cause false interpretations as it is shown here in inexperienced hands. CF Anatomia Patologica y Citologia, Instituto de Piedras BlancasAsturias, Spain Faculty of Pharmacy, Departament of Parasitology, Universidad de Valencia, Spain Infectious Diseases, Medical Faculty, Ondokuz Mayis University, Samsun, Turkey *Correspondence to: Rafael Martinez-Giron, M.D., Ph.D., Marques de San Esteban, 22-2 B, Gijon 33206, Spain. E-mail: rmartinezgiron@hotmail.com Received 16 January 2008; Accepted 19 July 2008 DOI 10.1002/dc.20940 Published online 30 October 2008 in Wiley InterScience (www. interscience.wiley.com).