15
Urinary Tract
Aspirates, Washings, Brushings, and cell Blocks
of Ureters and Renal Pelvis
If lesions in this region are suspected, urine aspirates, washings,
and brushings can be obtained by retrograde catheterization.15
These specimens contain larger numbers of superficial and
often multinucleated urothelial cells with greater variation in
their appearance than bladder urine and must be interpreted
conservatively. Cell blocks may be prepared when tissue frag-
ments are present.
Sample Preparation
Sm ears of Fresh and Fixed Specim ens
Direct smears may be prepared after centrifugation of 50 mL
of urine for 10 minutes at 1200 rpm. Albuminized or charged
slides are recommended for better attachment of cells in direct
smears.
Filtration and Cytocentrifugation-Based Preparations
Specimens may be processed using a filtration or a cytocentrifu-
gation protocol. The slides are then stained by the Papanicolaou
method.
Cell Blocks
Cell blocks may be prepared when visible tissue fragments are
present. Cytopreparatory techniques for urine specimens are
described in detail in Chapter 31.
Urothelium and Specialized Lining
Histology
Urinary tract cytology is almost exclusively concerned with eval-
uation of the urothelium that lines the urinary bladder and other
excretory passages—namely, the renal pelves, ureters, and por-
tions of the urethra. The epithelium is adaptable to the chang-
ing volume and permits the storage and discharge of the urine.
This transitional cell epithelium is highly specialized and
uniform but does include epithelial buds, subepithelial often
centrally cystic nests (the nests of Brunn), and areas of squa-
mous metaplasia or squamous variance. The transitional epithe-
lial cells have unique ultrastructural features including surface
folds believed to provide additional plasma membrane during
bladder expansion and robust junctional complexes that pro-
vide a watertight seal. The predominant transitional cell epithe-
lium or urothelium in the calices is two or three cells thick, in
the ureters is four or five, and in the empty bladder is lined by
six to eight layers of transitional cells. Three cell types are recog-
nizable by light microscopy. These are the large, often binucle-
ated or multinucleated superficial cells covering the cells that
form the lower portions of the epithelium-like umbrellas. The
underlying intermediate pyramidal cells are smaller and some-
what elongated. A layer of even smaller cuboidal cells with little
cytoplasm is located adjacent to the basement membrane. The
three cell types can be distinguished by flow cytometry and by
different patterns of lectin binding. These cells can also be well
defined by morphologic examination of urine specimens. The
superficial cells are characterized by a shape maintained by a
rigid surface membrane (Fig. 15.2). They have an acidophilic
cytoplasm. Many are binucleated and some (approximately 3%)
are multinucleated (Fig. 15.3). The nuclei are large and are likely
to undergo reactive change. The intermediate and basal cells are
similar and have well-developed desmosomal connections and
a plasma membrane that is folded in the empty bladder. It is
capable of unfolding when the bladder becomes dilated. The
arrangement of these cells is regular, with their long axis perpen-
dicular to the basal membrane. Their cytoplasm contains glyco-
gen, often resulting in a clear appearance during processing. The
superficial cells also contain glycogen and sometimes mucus.
The prostatic segment of the male urethra is lined by transiti-
onal epithelium, but the short membranous and long cavernous
portions of the urethra are lined by stratified or pseudostratified
columnar epithelium. The epithelium near the meatus is squa-
mous. Many recesses, namely the lacunae of Morgagni, commu-
nicate with deeper branching tubules and the glands of Littré.
The epithelium of the female urethra near the bladder is also
transitional and in the remaining parts usually squamous, often
with interspersed areas of pseudostratified columnar epithelium.
Invaginations lined by mucus-producing cells similar to those
found in the glands of Littré may be present.
Fig. 15.2 Normal urothelial cells. The large cells are from the superficial
and the small cells from the basal layers (Papanicolaou x MP).
Fig. 15.3 Superficial cells, with a multinucleated cell in an umbrella
configuration (Papanicolaou x MP).
411
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