William Van Bonn; Eric D. Jensen
U.S. Navy Marine Mammal Program, SPA WARSYSCEN San Diego, San Diego,
Effective diagnosis of suspected or confirmed disease in dolphins often
presents many challenges to the clinician. Diagnostic imaging techniques including endoscopy,
sonography, radiology, computed tomography (CT), magnetic resonance imaging (MRI) and
thermography each have inherent indications and limitations. To address many of the limitations
of these diagnostic techniques for the evaluation of thoracic disease, fine needle aspiration
biopsy (FNAB) of intra and extra-thoracic structures in the dolphin has been investigated. This
paper reports our clinical experience illustrated by findings in three cases.
Imaging techniques often effectively localize pathology but do not give
etiologic diagnoses. Respiratory endoscopy of dolphins is still within the developmental stage.
Our experience has shown that collection of materials from airways via lavage or brush is often
limited by the animals' physiologic status, risk associated with out-of-water time and general
tolerance of the procedure. Furthermore, directing lavage or brush techniques to areas with
lesions may be difficult. Lesions may also be located in lung regions not accessible via an
airway approach. Percutaneous biopsy techniques have been described in marine mammals (Sweeney,
1990) however it appears they are only rarely employed in practice.
Fine needle aspiration biopsy (FNAB) techniques are easy, low-risk and
provide aseptically collected samples directly from imaged lesions for cytological,
microbiologic and chemical analyses. Results of these analyses often lead to valuable
information for clinical decision making. FNAB is indicated for the further characterization of
accessible lesions when other techniques do not provide a definitive diagnosis or carry too high
a risk/benefit ratio.
The technique of FNAB is routinely used in other animal species and the
methods of specimen collection, processing and interpretation are widely reported (Cowell and
Tyler, 1989; Mills, 1989; Rakich and Latimer, 1989). Minimal risk is associated with needle
aspiration biopsy techniques when a body cavity is not entered. Reported complications from
percutaneous FNAB of lung lesions in other species include, pneumothorax, minor hemoptysis,
hemothorax, subcutaneous emphysema and air embolism. All are infrequent, generally minor and
usually require no treatment (Rakich and Latimer, 1989). We anticipate that the unique anatomy
of the dolphin skin, pleura and lung parenchyma will result in lower complication rates in these
species. Specifically, we expect that the prominent elastic and connective tissue elements, the
thick pleura and highly specialized skin elements will effectively lower risk of pneumothorax,
iatrogenic hemorrhage or subcutaneous emphysema. Complications due to iatrogenic trauma are
avoided by knowledge of the sonographic intrathoracic anatomy.
The technique of thoracic FNAB in dolphins follows that described for
other species with few modifications. If the thoracic cavity is not entered with the needle, the
site is prepared as for a routine injection. If the needle will enter the thoracic cavity the
site must be prepared as for surgery and aseptic technique is used. Longer needles than are
routinely used for other animal species are usually required due to the thick skin of the
dolphin. We use spinal needles with stylets for FNAB. The stylet is useful to avoid plugs of
blubber that may be cut as the needle is advanced through the skin. A stab incision in the skin
at the site of needle entry with a No. 11 scalpel blade is also helpful in reducing blubber
plugs. A 20-cc syringe is generally sufficient to create necessary negative pressure during
aspiration and allows for ease of handling by the operator.
Lesions outside the thoracic cavity and of sufficient size can be aspirated
blindly. The clinician triangulates the insertion of the needle so that the tip will be within
the desired area when advanced to the appropriate depth. Redirection of the needle is difficult
due to the thickness of the skin so a route is chosen that is expected to produce a useful
sample with careful advance and withdrawal only. Intrathoracic lesions require ultrasound
guidance and the procedure is best performed by two operators. One maintains sonographic
visualization of the lesion and the anatomy along the needle course while the other advances the
needle and performs the aspiration. Ultrasound guidance localizes the lesion in three
dimensions. Needle guides that attach to the ultrasound transducer have not been very helpful in
our experience. Sites along the caudal border of the ribs are avoided to prevent trauma to the
intercostal vessels and nerves. The needle tip is advanced to the level of the intercostal
muscles and the triangulation confirmed. The needle is then advanced into the region of interest
immediately after a breath. In most cases, sufficient samples can be collected between breaths
so that the needle does not remain in the thoracic cavity during a breath. However, we have had
on several occasions a needle within lung parenchyma during a breath without recognized
The experience of our first case presented, in spite of a non-productive
aspirate, increased our confidence in the safety and value of the technique. A 14-year-old
female Atlantic bottlenose dolphin (Tursiops truncatus) presented with signs suggestive
of a respiratory tract infection. Radiographs demonstrated several foci of increased mixed
interstitial pattern deep within the left lung. Transcutaneous sonography demonstrated a
subpleural lesion in the caudal ventral left lung measuring approximately 4 x 2 x 2 cm. FNAB was
performed due to the location of the lesion and the animal's temperament. An 18 gauge x 3
½" spinal needle was advanced into the lesion under ultrasound guidance after aseptic
preparation of the skin. The sonographic appearance of the lesion changed markedly as the needle
entered. The borders became much less distinct and the lesion much harder to visualize. The
procedure was aborted over concern that the change in appearance was due to rupture of an
abscess or bulla. The animal remained stable throughout the procedure and after. Five days later
sonography of the area showed no evidence of complications and the lesion was not seen on the
sonograms. Seven days later the lesion was again evident on sonography but no signs of
complication from the procedure ever developed and the animal continued to improve clinically.
The dolphin has since recovered completely and no lesions are evident on radiography or
A second case illustrates the indication for aspiration of a lesion that did
not appear to be accessible via airway approach. A 14-year-old male dolphin developed a firm,
progressive swelling of the left dorso-lateral thorax that was not adequately characterized with
plain radiography or sonography. The swelling appeared to be adjacent to and possibly associated
with the dorsal aspect of a rib and had a mixed echogenic pattern suggesting a fluid filled
center. The only contributing history was the recent observation of the animal passing a
tapeworm segment. The skin overlying the swelling was aseptically prepared and an 18 gauge x 3
½" spinal needle was inserted into the center of the lesion under ultrasound guided
triangulation. A large volume of serosanginous clear fluid was collected. Cytological assessment
of the fluid was consistent with an organizing hematoma and ruled out a parasitic cyst or
abscess, which would have required more aggressive therapy. The lesion resolved without further
intervention and the animal remains clinically normal to date.
Another case illustrates the value of FNAB in an animal that was deemed too
compromised for bronchoalveolar lavage (BAL) and the value of the technique in determining an
etiological diagnosis. An 18-year-old male dolphin had progressive refractory lung disease
documented with sonography and radiography, but no etiological diagnosis. A lung lesion was
localized with ultrasound and the overlying skin prepared aseptically. An 18 gauge x 3 ½
"needle was directed with ultrasound guided triangulation to the center of the lesion.
Initial aspiration was non-productive. A syringe pre-loaded with 10 cc of sterile
non-bacteriostatic saline was attached to the needle and ~ 5cc was infused. Immediate aspiration
produced a return that when analyzed by cytocentrifugation revealed cryptococcal organisms. This
animal ultimately died from cryptococcal pneumonia. Necropsy results did not reveal any evidence
of immunosuppression or underlying disease and earlier FNAB with definitive diagnosis may have
led to successful treatment.
The technique of FNAB has proven valuable in the clinical care of dolphins
and holds promise for additional applications. Our experience has shown the technique to be
rapid, safe and produce valuable information for case management decisions. We have not
experienced complications as a result of FNAB in any of the procedures conducted to date. There
are several lymph nodes that should be accessible to FNAB techniques in dolphins, specifically,
the superficial cervical lymph node complex and the marginal lymph node of the lung. These
structures are reliably imaged with diagnostic ultrasound and are expected to yield aspirates
that reflect disease processes in the anatomy that drains to them. Our initial work toward
obtaining FNAB of these nodes has been hampered by difficulty stabilizing the nodes within
surrounding tissues. There are also some large cardiovascular structures near the marginal
nodes, namely the heart and internal thoracic vessels that increase the risk of complications
but with continued development we hope to further adapt FNAB to lymph node aspiration.
T. Romano lab for time critical in-house cytocentrifugation of FNAB
samples. W. G. Miller for photomicrographs.
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