Abstract

Interventional Radiology (IR) is a medical imaging specialty in which minimally invasive diagnostic procedures and treatments are performed under image guidance. Common imaging modalities utilized include ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and fluoroscopy. IR has widespread applications in human medicine, including but not limited to image guided vascular access, biopsy and aspiration of lesions, thoracocentesis, abdominocentesis, embolization and ablation of tissues, placement of stents, angiography, angioplasty and intralesional therapy. Within the marine mammal community, thoracocentesis, abdominocentesis, venous catheterization, aspiration of lesions and tissue biopsy have been performed under ultrasound guidance.^1-4 In recent history, techniques in interventional radiology have been utilized more extensively by the U.S. Navy Marine Mammal Program, yielding multiple definitive diagnoses. Three such cases are discussed below, highlighting the impact that interventional radiology has made on the diagnosis of disease and overall case management.

Case #1, a 26 year-old female Tursiops truncatus, presented initially with marked leukocytosis and elevated erythrocyte sedimentation rate on routine blood analysis. Ultrasound of the thoracic cavity revealed an area of lung consolidation in the right dorsocaudal lung field measuring approximately 3 by 4 cm in diameter. Serial fine needle aspiration biopsies (FNA) were performed on the thoracic lesion and FNA was performed on the prescapular lymph nodes under ultrasound guidance. Coccidoides immitis was identified on histopathology from the thoracic lesion, and antifungal therapy was initiated. In the weeks following, survey CT scans were performed in order to assess the true extent of pulmonary involvement. CT guided biopsies of the area of lung consolidation were taken with a BioPince^TM (Angiotech, Vancouver, BC) biopsy instrument, and the diagnosis of pulmonary coccidiomycosis was confirmed. Follow-up ultrasound-guided biopsies of the pulmonary lesion were performed successfully a few months later in order to monitor response to therapy. The animal currently remains on long term antifungal therapy.

Case #2 is a 4 year old female Tursiops truncatus that presented initially with slight lethargy. Initial blood collection revealed a marked leukocytosis and elevated erythrocyte sedimentation rate. Antibiotic treatment was initiated and in the following days, a focal swelling became evident in the right prescapular region. Ultrasound of the swelling revealed enlarged prescapular lymph nodes. Additionally, a round, well demarcated hypoechogenic lesion was noted within the parenchyma of one of the lymph nodes. FNA of the hypoechogenic lesion was performed, revealing purulent discharge. Culture of the aspirate identified Streptococcus phocae, and the antibiotic regime was adjusted according to sensitivity results. The localized lymphadenitis persisted despite antibiotic treatment and follow-up ultrasound-guided biopsies were collected on two separate occasions, yielding tissue and purulent discharge. Bacterial and fungal cultures of the biopsies were negative. Following the second set of biopsies the prescapular lymph nodes slowly became smaller in size, and the inflammatory hemogram improved over time. Though lymphadenitis remains present, the animal's clinical picture continues to improve over time.

Case #3, a 25 year old female Tursiops truncatus, presented initially with a focal swelling in the cervical region near ventral midline. Bloodwork revealed a mild inflammatory hemogram. A well demarcated hypoechoic lesion within the parenchyma of one of the regional lymph nodes was noted on ultrasound. FNA of the lesion was performed under ultrasound guidance and purulent fluid was removed. Candida glabrata was identified on fungal culture and oral antifungal therapy was initiated based on culture and sensitivity results. As a chronic case, ultrasound guided aspiration and intralesional therapy has been performed a number of times since the onset of clinical signs in conjunction with oral antifungal therapy. Serial culture and sensitivity results have helped to guide oral and intralesional drug choices over time. Additionally, intralesional contrast studies were performed in order to assess the full extent of the lesion. The animal currently remains on long term oral and intralesional antifungal treatment.

Interventional radiology provides the clinician with useful diagnostic and therapeutic techniques that are less invasive than their traditional surgical counterparts. Techniques such as those described above have increased the number of definitive diagnoses obtained by the NMMP, expanded our diagnostic and therapeutic arsenal, and are recommended as viable clinical tools in the field of marine mammal medicine.

Acknowledgements

The authors would like to thank the veterinary and animal care staff of the U.S. Navy Marine Mammal Program and the staff of the Naval Medical Center San Diego for their guidance, support and dedication.

References

1.  Cassle S, Johnson S, Lutmerding B, Jensen E. 2009. Pulmonary brucellosis in an Atlantic bottlenose dolphin. Abstr Proc International Association of Aquatic Animal Medicine; p. 129.

2.  Rhinehart H, Townsend F, Gorzelany J, Broeker S. 1994. Ultrasound-aided thoracocentesis of a bottlenose dolphin. Abstr Proc International Association of Aquatic Animal Medicine; pp. 171-173.

3.  Van Bonn WG, Jensen ED, Miller WG, Ridgway SH. 1996. Contemporary diagnosis and treatment of bottlenose dolphins: a case study. Abstr Proc International Association of Aquatic Animal Medicine; pp. 40-42.

4.  Van Bonn WG, Jensen ED. 2001. Percutaneous thoracic fine needle aspiration biopsy in dolphins. Abstr Proc International Association of Aquatic Animal Medicine; pp. 69-72.