Cytology

Diagnostic cytology is a very simple and valuable diagnostic tool. For details of individual collection techniques, we are pleased to supply protocols, on request, or discuss them by telephone.

Fluid samples should, in general, be submitted in sequestrene (EDTA) for a nucleated cell count, and fixed with cytospin fixation fluid for specific cytological processing. Sampling 'kits' and/or fixatives are available on request.

Peritoneal fluid analysis is particularly useful as a diagnostic aid in cases of colic, weight loss and other suspected abdominal disease. It may be of particular value in helping to make the decision for surgical intervention. With the horse restrained in the standing position, a 19 gauge, 1.5 or 2.0 inch needle is carefully advanced through the skin at the lowest part of the abdomen and then through the linea alba. If fluid is not immediately forthcoming, the needle may be rotated or the tap may be repeated at other sites. Ultrasound echographic examination may be useful to locate a pool of peritoneal fluid for collection. A turbid and homogeneously blood stained sample may indicate abdominal vascular embarrassment. A white, turbid fluid may suggest peritonitis. A brown, foul smelling fluid may indicate intestinal rupture or an intestinal tap. Total nucleated cell counts >10 x 10⁹/l suggest the presence of a peritonitis or an intestinal or peritoneal lesion which may warrant surgical investigation. Cytological examinations may suggest acute or chronic infection, inflammation or neoplasia.

Pleural fluid analysis may help with the diagnosis of pleuritis. Ultrasound echographic examination is recommended to confirm the presence of pleural effusion prior to tap. A 7.5 cm. blunt teat cannula is inserted, with a 35 ml. syringe attached to prevent aspiration of air into the pleura, through a small skin incision, between the 6th or 7th intercostal space, 15 cm. dorsal to the olecranon. Pleural fluid is collected by suction. Total nucleated cell counts >10 x 10⁹/l suggest the presence of a pleuritis. Cytological examinations may reveal neoplasia, e.g. lymphosarcoma.

Synovial fluid analysis is useful in the diagnosis of arthritis and in particular, in 'joint-ill' in foals. Total nucleated cell counts >0.5 x 10⁹/l suggest an inflammatory lesion. Septic arthritis usually produces cell counts >10 x 10⁹/l, with toxic cytopathological changes.

Tracheal washes or aspirations may be collected either via a suitable endoscope or by the trans-tracheal route, depending on equipment available and the importance of bacterial culture results. A long, fibre-optic endoscope is passed through the pharynx, larynx and into the trachea. A long polyethylene tube is passed down the instrument channel and accumulated secretions may be aspirated directly. Alternatively, 50 ml. sterile saline may be injected quickly and then aspirated while withdrawing the tube. If a suitable endoscope is not available, a sterile polyethylene tube may be passed down a trochar inserted surgically between two tracheal rings at the mid lower third of the cervical trachea. We are also pleased to examine broncho-alveolar lavage samples. Cytological examinations of tracheal wash or BAL samples may help in the characterisation of acute and chronic inflammatory responses, allergic and obstructive pulmonary disease. The demonstration of large numbers of eosinophils appears to be a valuable diagnostic aid in lungworm (Dictyocaulus arnfieldi) infestation.

Endometrial smears are simple and quick to perform and provide a much more accurate and direct test for the diagnosis of acute endometritis in mares, pre-coitus than swab examinations alone. When used in conjunction with endometrial swabs for bacteriological examinations, results are infinitely more meaningful and valuable. The presence of endometrial epithelial cells is used as a test of smear quality and the presence or absence of polymorphonuclear leucocytes is used as the diagnostic test for acute endometritis. Smears should only be taken during oestrus, with an extended sterile large tipped swab, via a sterile speculum and should be immediately rolled onto gelatine-coated slides and fixed with 'cytofix' prior to transport to the laboratory for staining. Smear 'kits' are available on request. Excellent results have been obtained by rolling smears onto 'Testsimplet' (Boehringer Mannheim UK Ltd.) pre-stained slides, then after three minutes at room temperature, washing off the background blue colour, drying and cover slipping.

Semen samples should be collected into an artificial vagina to allow a meaningful interpretation. We may be able to help with the collection of samples, if requested, on a referral basis. Please contact us for more details before sending samples. In addition to a full case history, we require details of methods of collection, the colour, consistency, volume and motility of the ejaculate. Please send an undiluted sample in a sterile container for density estimations and bacteriological examinations, and a sample diluted immediately 1:1 with formol citrate solution (available on request) for live:dead and morphology examinations.