Normal cytology of the oral cavity, esophagus and crop of psittacines can include moderate numbers of Gram-positive bacteria
and few to rare Gram-negative bacteria. Candida spp are not commonly present in large numbers except when an infection is present. However, moderate numbers of non-budding
yeasts are indicative of a dietary source rather than an active infection. The presence of fungal hyphae indicates a severe
fungal infection with possible tissue invasion.
Crop washes are performed by infusing a small amount of saline into the esophagus/ingluvies using a soft plastic or rubber
feeding tube, gently massaging the crop and its contents, and aspirating the fluid. The sample may be concentrated by centrifuging
the collected material and examining smears of the "pellet."
Cloacal/fecal cytology is often used as a routine part of the physical exam of avian patients. A saline-moistened cotton-tipped
swab of appropriate size is gently inserted into the cloaca to obtain a sample. For fecal cytology, fresh is best.
Normal cloacal cytology usually reveals a low to moderate number of squamous cells with varying degrees of keratinization
and centrally or eccentrically located vesicular nucleus as well as gram-positive bacteria, an occasional gram-negative or
Candida-like yeast and urate crystals The normal fecal bacterial flora of psittacines consists predominately of Lactobacillus spp, Bacillus sp, as well as Staphylococcus and Streptococcus spp. Abnormal samples may contain large numbers of Gram-negative bacteria, many Candida-like yeasts organisms (especially budding ones) and protozoa or parasitic ova. Protozoal organisms, such as Trichomonas sp. or Giardia sp. can be identified using stains specific for those organisms.
Cytology of the respiratory tract
- Infraorbital sinus aspirate/flush: Sinusitis of the nasal and infraorbital sinuses is a condition that often affects psittacine birds. Several methods (with
or without anesthesia) may be used to obtain aspirate from the infraorbital sinuses; however, a thorough knowledge of the
anatomy of the sinus and surrounding structures is necessary in order to perform these procedures correctly. The first involves
restraining the birds head and body and inserting a 20-25 gauge needle (with syringe) at the commissure of the mouth and directed
vertically to a point midway between the eye and nares passing under the zygomatic bone. The sinus may be aspirated, or a
small amount of sterile saline may be infused into the sinus and then aspirated. The second method involves approaching the
sinus at a perpendicular angle and entering the sinus directly. A third method requires entering the sinus from a rostral
direction by inserting the needle just caudal to the commissure of the mouth. The needle is directed ventral to the zygomatic
arch, ending in the sinus under the eye. Normal cytology of the infraorbital sinus is poorly cellular with little background
- Tracheal wash: In order to properly perform a tracheal wash, the patient should be anesthetized or appropriately restrained; 1-2 ml/kg of
sterile saline is infused into the trachea as close to the syrinx as possible and then quickly aspirated. Tracheal aspirations
are indicated in patients with clinical signs of a tracheobronchitis (e.g. persistent cough), radiographic evidence of respiratory
disease, other evidence of tracheobronchial disease or a lesion involving the syrinx. Normal tracheal cytology is similar
to that of the sinuses.
Air-sac wash: Lower respiratory tract diseases may be diagnosed with the aid of air-sac washes. A small amount of saline (1-3 ml depending
upon the size of the patient) may be infused into the appropriate abdominal air sac based upon radiographic evaluation. The
caudal abdominal air sac is approached through an aseptically prepared area caudal to the last rib. A small-gauge needle with
syringe attached inserted into the air sac, sterile saline is infused and then aspirated. The air-sac wash is accomplished
easily with the aid of endoscopy.
Indications for abdominocentesis include ascites, peritonitis, hemoperitoneum or other coelomic cavity fluid accumulation.
Abdominocentesis is performed by aseptically preparing a small area on ventral midline caudal to the point of the sternum.
A small-gauge needle or butterfly catheter is inserted on ventral midline and directed toward the right side of the coelomic
cavity thereby avoiding trauma to the ventriculus and other organs. Any fluid present is aspirated into a sterile syringe.
Lavage of the coelomic cavity is performed similarly. Normal abdominal fluid is poorly cellular with an occasional mesothelial
cell or macrophage.