Urine cytology
Introduction
Cytological examination of urine sediment is indicated in the investigation of suspected neoplasia. Air dried smears made of concentrated sediment should be prepared as soon as possible after collection or add 1-2 drops of formalin to either urine or to the sediment after centrifugation.
Definitive diagnosis of neoplasia is often not achieved by examination of the urine sediment and direct sampling may be more rewarding. An increased yield of epithelial cells from a suspected mass in the bladder or urethra can be obtained via traumatic catheterisation.
Traumatic catheterisation
This is most useful with masses in the urethra or bladder trigone. A urinary catheter is introduced to the level of the mass (determined by imaging or palpation), the bladder emptied and suction applied using a 10ml syringe. The catheter is withdrawn 4-6cm and the vacuum is released. The tip of the catheter often contains tissue fragments which can be fixed for histology. Alternatively, air-dried smears are made from the material collected at the tip of the catheter and submitted for cytological examination. Material collected by this method may only be representative of the most superficial layers of epithelial cells and may not represent the underlying pathology.
Direct FNA
Ultrasound guided trans-abdominal FNAs (using a 22-23g needle) are suitable for investigation of bladder masses. Tumour implantation along the needle tract following FNA has been reported (Nyland 2002) but appears to be a rare complication. However, there is some concern that when tumour implantation does occur by this method the seeded foci are less amenable to therapy. Ultrasound gel can obscure cellular detail and should be removed from the site of needle insertion.