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Serous Effusion Cytology

Cellular Pathology

Principle of Examination

There are 3 body cavities which under normal conditions contain a small amount of fluid

  • Peritoneal (ascites)
  • Pleural
  • Pericardial

Accumulation of fluid in these serous cavities is a reflection of local or systemic disease and examination of the cells in the fluid can be of great value in establishing the underlying disease process.

Serous fluids may be either transudates or exudates.

  • Transudates appear due to an infiltration of blood serum across an intact vascular wall. Conditions that produce transudates are:
  • Cirrhosis
  • Heart conditions
  • Liver conditions


Exudates appear due to an active accumulation of fluid within the body cavities, associated with damaged capillary walls.

There are two main causes of exudates:

  • Inflammatory processes
  • Malignant cell infiltration

Specimen Requirements

When sending a serous effusion (including peritoneal, ascites, pleural and pericardial samples) to Cytology:

  • To ensure best results, we request that as much fresh specimen be sent to the laboratory as possible, within 24hrs of collection.  Fresh or unfixed specimens must be received on the same day as collection.
  • Use a 120ml or 150ml container – specimen containers are available from pathology stores on 01392 402906. We regret that we are unable to accept specimens in drainage bags or leaking containers.
  • Best practice recommends 50 – 75ml of fluid is sent to the laboratory for optimal cytodiagnosis
  • Send a separate specimen and request to Microbiology if a microbiological investigation is required.

The request should state:

  • Three patient identifiers
  • Specimen type i.e. ‘pleural fluid’, ‘pericardial fluid’, ‘ascitic/peritoneal fluid’
  • Date and time of sample collection
  • Requesting clinician
  • Patient location – inpatient/outpatient and ward
  • All relevant clinical information – including if there is a history of relevant foreign travel

Specimen Delivery and Labelling

All Trust specimens must be requested on Epic and be labelled with an Epic label. GPOCS requests must be labelled with a GPOCS label. All other samples must have a request form.

HIGH RISK SPECIMENS: Requests must indicate if a specimen is high risk.  Please indicate details of the risk, eg: TB, blood-borne virus, etc.

URGENT SPECIMENS: Please label urgent specimens clearly; an explanation as to why the specimen is urgent is helpful.  On receipt, laboratory staff will notify the pathologist who will report the specimen as soon as possible.

Turnaround Time

The Laboratory aims to comply with The Royal College of Pathologists Key Performance Indicator (KPI 6.4) for Cellular Pathology reporting turnaround times with 90% of all cases reported within 10 calendar days.



Specimen Labelling Procedure
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