Marine Mammal Diagnostic Imaging

Question 1

Describe your selection of the ideal imaging modality for various organs in marine mammals.

Answer 1

Question 2

Describe the use of ultrasonography in marine mammals.

What can be seen with pinnipeds?

What about cetaeans?

Answer 2

1. Ultrasonography
   
   1. Limitations in marine mammals: outdoors, near water, patient size
   2. No need for gel when in the water
   3. Pinnipeds: scan on dry land with alcohol, no shaving
      
      1. Ductus arteriosus remains open for up to 55 days in harbor seals
      2. Adults have struvite uroliths, neonates have urate uroliths
      3. Do not mistake normal hepatic sinus for an intrahepatic shunt
   4. Cetaceans
      
      1. Look at ventrolateral lung margins, often affected
      2. Healthy lymph nodes are isoechoic with liver parenchyma
      3. Liver should have triangular caudal margin
      4. Intrahepatic portal veins are very hyperechoic compared to hepatic veins
      5. Pancreas is hyperechoic to the liver
      6. Water per os can help differentiate forestomach from spleen
      7. Inactive ovaries = hypoechoic; old ovaries = echogenic
      8. Can use serial measurements of blubber depth to monitor recovery of emaciated patients
      9. Martony ME, Ivančić M, Gomez FM, Meegan JM, Nollens HH, Schmitt TL, Erlacher-Reid CD, Carlin KP, Smith CR. Establishing marginal lymph node ultrasonographic characteristics in healthy bottlenose dolphins (Tursiops truncatus). Journal of Zoo and Wildlife Medicine. 2017 Dec;48(4):961-71.
      10. Seitz KE, Smith CR, Marks SL, Venn-Watson SK, Ivančić M. Liver ultrasonography in dolphins: use of ultrasonography to establish a technique for hepatobiliary imaging and to evaluate metabolic disease-associated liver changes in bottlenose dolphins (Tursiops truncatus). Journal of Zoo and Wildlife Medicine. 2016 Dec;47(4):1034-43.

Question 3

Describe your technique for evaluating marine mammal respiratory systems by endoscopy.

Describe the anatomy the scope must be passed through.

Answer 3

RESPIRATORY ENDOSCOPY

• Bronchoscopy procedure on bottlenose dolphin fairly common
• Bronchoscopy - diagnostic value yet realize risk to patient - use caution in animals w/ obvious or suspected thoracic effusions, pulmonary masses, cardiovascular concerns, or questionable ventilation status
• Typically in conjunction w/ radiographs, CT
• Pharyngoscopy, tracheoscopy, and bronchoscopy can be done on conscious cetaceans - more commonly out of water - but use sedation as needed
• If introduction of scope through glottis is planned/expected - scope should be sterilized and procedure done aseptically
• Critical to orient image produced by equipment w/ animal’s position - once beyond blowhole - orientation becomes very difficult
• Brace hand feeding scope on melon 🡪 introduce quickly during a breath and hold still until scope is accepted without objection; lidocaine if needed given through operating channel
• Most efficient moves once in place - slow withdrawal, rotation, deflection of tip, and advancement (in order)
• Nasopharynx visualized 10-15 cm from blowhole in bottlenose; opening to auditory tube often visible just inferior to nasal septum
• In clinically normal animal - moderate amount of white froth commonly seen in dependent aspect of nasopharynx and may obscure anatomy
• To introduce into glottis - position tip superior to laryngeal cartilages and time passage w/ breath
• In bottlenose - tube diameters of 8-9 mm can be advanced to depth of ~70-80cm and 3 mm diameter to depth of ~90-110 cm
• Diagnostic cytology, washes, or BAL can be done but variable in marine mammals - interpretation is reliant on prior experience, comparison to more typical veterinary spp., and careful consideration of anatomy/physiology of marine mammals
• No standardization of anatomic nomenclature of cetacean airways yet
• Except pharynx and larynx - endoscopic anatomy of seals/sea lions very similar to dom. dog
  
  • Pinniped pharynx - abundance of pendulous soft tissues, often obscure visualization of laryngeal cartilages
  • Full extension of head/neck during scope introduction helps
• Manatees - flexible endoscopes used to facilitate endotracheal tube placement for general anesthesia; endoscope in one nasal passage to visualize while elongated endotracheal tube into other nasal opening that is guided into the glottis

Question 4

Describe the applications of flexible or rigid endoscopy in evaluating the respiratory systems of marine mammals.

Answer 4

Flexible

• Typically used for bronchoscopy
• In cetaceans, bronchoscopy now considered essential diagnostic modality and in some cases therapeutic
• Interestingly - odontocetes authors inspected had discrete openings w/in nasal passage to auditory tubes while mysticetes did not (small pores present, inaccessible by endoscopy)
• Case examples
  
  • ID location of fungus (Cunninghamella bertholletiae) w/ moderate mucoid exudate from L bronchus - used nebulization therapy and CT/radiograph monitoring in a bottlenose
  • Diagnosed focal stenosis of R accessory (tracheal) bronchus and R mainstem bronchus in bottlenose, used high-pressure balloons to dilate
  • Tracheal stenosis w/ nodules protruding into lumen in bottlenose, did needle aspiration through instrument channel 🡪 Aspergillus in nodules
  • Diagnosed intratracheal mucofibrinous sessile mass in bottlenose - used endoscopic N₂ cryosurgery probe and cauterizing w/ argon plasma unit to remove (Rhizopus etiology)
  • Diagnoses heavy load of mites in airways in CSL - Tx w/ ivermectin
  • Used for exploration of upper resp. in CSL following gunshot injury - retroflexion following oral introduction allowed evaluation of nasopharynx
  • Evaluated epistaxis in two walrus - nasal mites found in one; done behaviorally

Rigid

• Small-diameter rigid may be preferred to explore nasal passage of small pinnipeds and sea otters
• Presence of nasal mites (common) in sea otters easily detected via rhinoscopy
• Thoracoscopy has been performed in manatees using rigid scopes to evaluate lungs and pleural space following boat strike

Question 5

Describe the endoscopic evaluation of the cetacean upper GI.

What is the normal gastric emptying time? How long should animals be fasted for?

Describe the appropriate restraint for the procedure?

Describe the anatomy of the cetacean stomach.

Describe the peristaltic movement of the forestomach. How does this help digestion?

What does hypo- or hypermotlity indicate?

How can lower GI evaluation be performed?

Answer 5

GASTROINTESTINAL ENDOSCOPY

• Most commonly performed endoscopic procedure, esp. upper GI tract
• Stereotypical for presentation to be vague changes in behavior or nonspecific laboratory markers of inflammation
• Flexible endoscopy of upper GI commonplace and many marine mammals trained to accept
• Can visualize oral cavity, oropharynx, esophagus, esophageal sphincter, forestomach, cetacean fundic chamber lumen (to various degree) and on occasion, connecting channel and pyloric chamber of cetaceans
• For colonoscopy - complications can occur as mucosa of colon is relatively friable compared to esophagus, stomach 🡪 not possible to distinguish small intestine from colon via endoscopy
• Cetaceans
  
  • Sedation may be indicated
  • Fasting for at least 6 hours prior recommended
    
    • Normal gastric emptying time of dolphins <4 hours, solid food items observed at 6+ hours may indicate delayed gastric emptying
  • When using towels to hold maxilla/mandible apart - upper (maxillary) towel should be placed 1^st as mandibles are delicate *never restrain mandible without 1^st controlling maxilla*
  • If using rigid (PVC) speculum - make it padded to prevent oral mucosa damage
  • Speculums - gloved hands, PVC, ET tubes, molded rigid foam
  • Useful to orient scope prior to passing into pharynx
  • Once in esophagus, will need air insufflation
  • With scope in place most efficient moves (in order) - slow withdrawal, rotation, deflection of tip, advancement
    
    • indiscriminate advancing may lead to confusion and misdirection, can potentially traumatize patient
  • Upper GI contains thick, tenacious mucus - need properly functioning water irrigation
  • As advanced into oropharynx - numerous punctate openings visible in mucosa (openings of mucous glands - lubricates good before swallowing)
  • Normal cetacean esophagus - longitudinal folds, cardiac pulse often observed
  • Not a clear distinction b/w mucosa of forestomach and esophagus (sphincter not as pronounced as in pinnipeds)
  • Cetacean stomach (bottlenose as example)
    
    • 1^st chamber (forestomach)
      
      • Thick squamous epithelium-lined rugal folds
      • Often appear lighter in color than esophagus
      • Once in lumen - prominent fold seen along R wall
      • Moderate amount of cloudy greenish-brown fluid usually present
        
        • Can collect for cytology, diagnostics
      • In clinical normal animals - not unusual to observe waxy material floating on fluid surface and coating mucosa
      • Peristaltic motion was two waves
        
        • 1º wave moves from lower esophageal sphincter to fundus
        • 2º wave from fundus to lower esophageal sphincter
        • In dolphins, cycle @ 3-4 cycles/minute
      • Reduced peristalsis frequently seen w/ other indications of digestive disturbance (i.e. delayed gastric emptying, persistence of bones, elevated forestomach pH)
      • Hypermotility observed w/ forestomach impactions, foreign materials
      • During 1º wave - gastric fluid from glandular (2^nd) stomach refluxes into forestomach - w/ practice this reflux and opening can both be visualized by slow withdrawal of scope w/ scope retroflexed
    • 2^nd chamber (fundic)
      
      • Glandular, mucosal surface deep pink to red
      • Nondistensible, mucosa has distinct arrangement of roughly circular crypts - velvety-appearing deep red
      • Complete evaluation of lumen not possible (anatomy)
    • Ostium b/w forestomach and 2^nd chamber located cranially in L ventral quadrant, ~2.5 cm in diameter (mature bottlenose)
    • 3^rd chamber (pyloric)
      
      • Thin mucosal lining, mucus glands
    • Small tubular structure (connecting channel) connect fundic and pyloric
      
      • Intramural, small diameter, J-shaped
      • Not possible examine 3^rd chamber of stomach or proximal small bowel w/ current technologies
  • With liberal lubrication and cautious advancement - can introduce via anus and evaluate lumen and mucosa of rectum, colon
    
    • Recommend distension with fluid (isotonic)
    • Mucosa more friable than in terrestrial species
    • Indications for lower GI endoscopy are infrequent

Question 6

Describe cystoscopy in dolphins.

How is flexible endoscopy used in artificial insemination?

Answer 6

UROGENITAL ENDOSCOPY

Flexible

• Treatments utilizing cystoscopy in several cases in both pinnipeds and cetaceans
• Retrograde cystoscopy of urinary bladder in female dolphins and at least 1 animal trained to allow while stationed in water
  
  • Procedure requires small-bore, sterile scope
  • Urethral orifice of female dolphins located at apex of clitoris
  • Entire genital slit should be cleaned w/ antiseptic prior to introduction of scope
  • Use sterile technique
• Urethroscopy/cystoscopy of male cetaceans/pinnipeds not reported
• Routinely used to facilitate artificial insemination of cetaceans during application of advanced reproductive technologies for breeding programs
  
  • Semen generally deposited in lumen of uterine horns after passing scope via vaginal vault through pseudocervix and true cervix
  • Entire lumen of uterus of female dolphins can be visualized w/ sterile small-bore scopes
    
    • In addition to sterile technique, flushing entire vaginal vault w/ antiseptic wash to remove contamination should be included in patient preparation
    • Lateral recumbency - sterile speculum into vagina and advanced to pseudocervix
      
      • Scope advanced through this, distension of uterus w/ sterile fluid
• Urinary cystoscopy w/ retrograde ureteroscopy-guided laser lithotripsy to treat a bottlenose w/ urinary calculi and attempted in another dolphin
• Visualized urinary bladder tear in a walrus pup (treated w/ foley catheter) - healed w/out issue

Rigid

• In females, can be done directly or via laparoscopy
• Abdominal mass in CSL percutaneous core biopsy using laparoscopic visualization
• Laparoscopic surgeries used to evaluate or manage ovarian disease in female pinnipeds (gray seal, Patagonian sea lion, S. American sea lion) - both sea lions died w/in 24 hr, gray seal alive
• Urogenital tract of sea otters can be seen laparoscopically, laparoscopic ovariectomy feasible
  
  • Rigid scope can be used to visualize vaginal vault and cervix in female sea otters