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The Case: Retrobulbar Abscess or Something Else?

Clinician's Brief

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Initial Presentation

A 6-year-old neutered male Boston terrier was presented for lethargy and swelling around the right eye. The owner had awoken that morning to the dog’s yelping. The dog is indoor/outdoor with access to a large yard. There are no other pets in the household and the patient had not interacted with other animals that morning. No medications. 

Physical Examination

  • Heart/lungs: IV/VI left apical systolic heart murmur, strong synchronous pulses, lungs clear
  • Vital signs: temperature = 102.2⁰F, pulse = 150 bpm, respiration = 36 bpm
  • Eyes/ears/nose/throat: chemosis and hyperemia of conjunctiva OD, periocular swelling OD, third eyelid protrusion OD, right side of face swollen and painful

Pain precluded oral examination. After sedation (hydromorphone [0.1 mg/kg] IM, midazolam [0.25 mg/kg] IM), bleeding from the right maxillary fourth premolar and first molar (108 and 109) and severe calculus and gingivitis were noted.

Diagnostics

  • CBC: white blood cells––19.8 × 103 (range, 4.0–15.5), hematocrit––35% (range, 36–60), neutrophils––17,028/mL (range, 2060–10,600)
  • Serum chemistry panel: within normal limits
  • Urinalysis: no significant findings
  • Echocardiogram: advanced mitral valve disease 

Treatment 

  • Scheduled an appointment for oral examination and dental cleaning under general anesthesia to confirm suspected retrobulbar abscess and right maxillary fourth premolar (108) tooth root abscess
  • Amoxicillin/clavulanic acid: 13.75 mg/kg q12h PO × 14 days
  • Tramadol: 1 mg/kg q12h PO as needed
  • Carprofen: 4 mg/kg q24h PO × 3 days (until dental cleaning)

Second Presentation

DAY 1

When patient returned 2 days later for appointment, he was unable to close the right eye, demonstrated severe right ocular pain, and exhibited buphthalmos OD. According to the owner, the dog had worsened since the initial examination; he had to be carried up and down the stairs. Patient was still lethargic and exhibiting abnormal behavior. 

Procedure

  • Patient was induced with 0.1 mg/kg hydromorphone IV and 0.25 mg/kg midazolam IV, then intubated and maintained on sevoflurane
  • Right maxillary fourth premolar and first molar (108 and 109) were extracted
  • Superficial corneal ulcer and exposure keratitis noted OD; temporary tarsorrhaphy performed OD
  • During the procedure, the patient bled more than is typical. Physical examination under general anesthesia revealed diffuse bruising; large bruises on the right side of face, left hindlimb, both forelimbs, and right buccal mucosa.
  • Mucous membranes: very pale, unable to assess capillary refill time (unable to blanch)
  • Further questioning of the owner revealed that the patient had never had a bleeding problem; castration at 6 months was uncomplicated. However, it was revealed that the patient did have an occasional history of dietary indiscretion. Two weeks ago, the owner found a ball of “green stuff,” which the patient had vomited, and noticed that the dog’s stool was green. 

Diagnostics

  • PT/PTT: 18 sec (range, 6.3–13.3)/21 sec (range, 10.6–16.8)
  • PCV/TS: 9% (range, 35%–55%)/4.0 g/dL (range, 0–7.4)
  • Platelet estimate: 60 × 103/mL (range, 170–400 × 103)

Diagnosis:

Coagulopathy

Rule outs

  • Rodenticide toxicity
  • Primary clotting disorder
  • Clotting factor deficiency
  • Disseminated intravascular coagulopathy
  • Liver failure

Treatment

  • Fresh frozen plasma (FFP): 1 unit
  • Vitamin K: 2.5 mg/kg q12h SC
  • Oxygen: 40% in O2 cage
  • Ofloxacin 3 mg/mL drops: 1 drop OD q8h
  • Clindamycin: 11 mg/kg q12h PO
  • Tramadol: 1 mg/kg q8h PO

After initiation of treatment, the patient appeared stable with no evidence of further bleeding. No further transfusions were indicated. After the FFP transfusion, the following was noted:

  • PT/PTT = 16 sec (range, 6.3–13.3)/109 (range, 10.6–16.8)
  • PCV/TS = 27% (range, 35–55%)/4.6 g/dL (range, 5.0–7.4)

DAY 2

The patient was quiet, alert, responsive, and in sternal position; he had eaten overnight.

  • Heart/lungs: IV/VI left apical systolic heart murmur, strong synchronous pulses; lungs clear, eupneic but tachypneic.
  • Eyes/ears/nose/throat: clear AU. Severe swelling and bruising present OD with temporary tarsorrhaphy. Clear OS. Extensive bruising of the right maxillary buccal mucosa was noted.
  • Musculoskeletal: ambulatory × 4, bilateral grade I lateral luxating patellas
  • Integument: moderate to severe swelling with dark purple bruising noted from the right stifle extending distally, small ecchymoses/coalescing bruises on the abdomen, and bruising on both forelimbs were present.

Monitoring

PCV/TS: 20% (range, 35%–55%)/6.0 g/dL (range, 5.0–7.4)

Treatment

  • Vitamin K: 1.25 mg/kg q12h PO
  • Continue clindamycin, ofloxacin drops, and tramadol as previously prescribed.

DAY 3

The patient was bright, alert, and responsive, wagging tail, and had a good appetite. No further bleeding, bruising, or oral discharge was observed.

Physical Examination 

  • Heart/lungs: IV/VI left apical systolic heart murmur, strong synchronous pulses; lungs clear, eupneic but tachypneic.
  • Eyes/ears/nose/throat: clear AU. Temporary tarsorrhaphy OD, mild to moderate swelling of periocular region. Normal OS. Bruising in oral cavity improved but still present.
  • Musculoskeletal: ambulatory × 4
  • Integument: moderate swelling of left hindlimb with bruising evident. Bruises appear to be maturing normally.
  • Ophthalmology consult: retrobulbar abscess OD, blind OD. Temporary tarsorrhaphy OD. Corneal ulcer OD resolved. Recommend reevaluation in 3 weeks.

Diagnostics

PCV/TS: 28% (range, 35%–55%)/6.0 g/dL (range, 5.0–7.4)

Discharge instructions

Continue vitamin K, clindamycin, ofloxacin drops, tramadol, and artificial tear gel as prescribed. Recommend progress exam in 3 weeks. Recommend cardiology follow-up for complete cardiac evaluation.

Outcome

At the 3-week return visit, the patient was doing well. Coagulopathy secondary to rodenticide toxicity and retrobulbar abscess completely resolved. Blindness OD persisted. Artificial tear gel to be continued long-term, all other medications discontinued.


The Generalist’s Opinion

Barak Benaryeh, DVM, DABVP

“When you hear hoof beats coming around the corner, think horses, not zebras.”  This is generally true but, as we see in this case, not always.  

Initial Presentation

All signs pointed to a retrobulbar abscess when this patient first presented. Starting amoxicillin/clavulanic acid and planning a dental procedure to confirm the diagnosis was a sensible decision. Ideally, the dental examination would have been done that day or the next. Scheduling issues may have made that difficult and, given the presumptive diagnosis, postponing for 2 days did not seem harmful. Blood analysis, urinalysis, and an echocardiogram (for the heart murmur) were all part of a thorough and appropriate initial database.

Definitive Diagnosis

A tentative diagnosis needs to be recognized for what it is––a hypothesis. An attempt should be made, if possible, to make a definitive diagnosis. There was no mention of dental radiographs being taken to confirm the presence of an abscessed tooth/teeth. It’s possible that blood in the area may have mimicked an abscess radiographically and it’s also possible that teeth 108 and 109 were indeed abscessed. Intraoral dental radiographs are required by AAHA practice guidelines1 and are rapidly becoming standard of care for dentistry and extraction.  

Second Presentation 

The main oversight at the second presentation was reexamining the patient. If this dog had a PCV of 9% after dental bleeding, it would in all likelihood have had pale mucous membranes and some physical examination findings beyond what would be expected for a retrobulbar abscess. The owner reported that the dog had to be carried up and down stairs. The dog was lethargic and exhibiting abnormal behavior. If a thorough preoperative examination had been done, it might have been noticed that this case was not what it seemed.  

Tricky Presentations

This case was obviously difficult and may have initially led almost any practitioner down the wrong path. Presenting signs for rodenticide toxicity include epistaxis, melena, articular hemorrhage, hematemesis, pulmonary hemorrhage, and hemothorax. Some animals may have neurologic signs from subdural cranial or spinal canal hemorrhage.2 Patients can present with what seems like a mass but turns out to be a hematoma. We now know they can also present with what seems like a retrobulbar abscess. The most important learning point from this case is to recognize when a diagnosis is tentative versus definitive. Every recheck of a patient for any reason should include a thorough physical examination and a mental recalculation of the problem at hand. Questioning assumptions is what keeps us practicing top-quality medicine.

BARAK BENARYEH, DVM, DABVP, is the owner of Spicewood Springs Animal Hospital. He graduated from University of California Davis School of Veterinary Medicine in 1997 and completed an internship in Small Animal Medicine, Surgery, and Emergency at University of Pennsylvania. Dr. Benaryeh has also taught practical coursework to first-year veterinary students and was a primary veterinary surgeon for the Helping Hands Program, which trains assistance monkeys for quadriplegic people. Dr. Benaryeh is certified by the American Board of Veterinary Practitioners in Canine and Feline Practice.


The Specialist’s Opinion

Gretchen Statz, DVM, DACVECC

I think this case was handled well for the most part. The main issue was lack of recognition of rodenticide toxicity at the time of presentation. Luckily the dog ended up doing very well.  

Rodenticide toxicity was easy to miss initially because the presenting complaint and physical examination findings were not consistent with obvious hemorrhage. Understandably, the owner did not consider the green vomitus and stool from 2 weeks prior significant to the present problem, so this information was not shared with the veterinary staff. Both of these points are common pitfalls when dealing with anticoagulant rodenticide toxicity.

Rodenticide Toxicity

Anticoagulant rodenticides act by inhibiting activation of clotting factors II, VII, IX, and X. The intrinsic and extrinsic clotting cascade will be affected when these clotting factors are depleted, and the PT and PTT will be markedly prolonged. Because of the short half-life of fVII, which is involved in the extrinsic clotting cascade, the PT will often be elevated prior to the PTT. Bleeding usually takes place 3 to 5 days after ingestion of the toxin and can occur from any site, especially after trauma or a surgical procedure. It is important to consider rodenticide toxicity in any case involving unexplained bleeding or vague, unexplained clinical signs.  

Hemorrhage in this case occurred 2 weeks after the ingestion, making it more difficult to connect the events. One could argue that the bleeding from the gumline at initial presentation may have been the first clue of a clotting disorder. Bleeding from the gums is often associated with primary platelet disorders (ie, low platelet count or platelet dysfunction) but can occur with clotting factor deficiencies as well. Unexplained bleeding should prompt further evaluation of the primary and secondary clotting ability––a platelet count and PT/PTT at minimum. Given the level of dental disease, periodontal bleeding may not have seemed excessive. A platelet count was presumably normal on initial presentation but the actual number was not provided.  

Transfusion Therapy

Fresh frozen plasma is the main treatment for active hemorrhage secondary to rodenticide toxicity, while vitamin K1 allows for new clotting factor formation and helps prevent future bleeding.  Plasma works by providing active clotting factors and will immediately improve the PT and PTT as well as help to stop life-threatening hemorrhage. Dogs that bleed significantly and become anemic will also require packed red blood cells or whole blood transfusion.  

This dog would have benefited from a red blood cell transfusion in addition to the plasma if the hematocrit was indeed 9% after the dental procedure. Oxygen carrying capacity is diminished when the hematocrit drops below ~15% even if the patient appears stable; the more acute the drop, the more likely the animal is to develop clinical signs. It seems unlikely that the hematocrit would increase from 9% before plasma transfusion to 27% afterward without inclusion of packed cells. It is unclear how this occurred. It can take up to 6 days to mount a regenerative response after acute blood loss; absorption of red blood cells after hemorrhage also occurs slowly. It seems most likely that the 9% reading was an error or that a transfusion of packed red cells was given but not mentioned in the case presentation.  

Retrobulbar Abscess

It is not clear how the diagnosis of a retrobulbar abscess was made. There was no cytology or culture noted in the history. It is possible that this was a retrobulbar abscess and that the dog did not start bleeding until the surgical procedure was performed. It is also possible that the acute pain and ocular signs were actually a result of retrobulbar hemorrhage. Either way, the coagulopathy was discovered and the dog responded nicely to treatment, which is ultimately most important.

Conclusion

While common diseases occur commonly, less common diseases (like anticoagulant rodenticide intoxication) can present with uncommon clinical signs. The importance of keeping the differential list open is paramount; otherwise possibilities can be excluded prematurely.

GRETCHEN STATZ, DVM, DACVECC, is an internal medicine consultant for Antech Diagnostics and a clinician at Veterinary Emergency and Specialty Care in Indianapolis, Indiana. A graduate of University of Wisconsin – Madison, Dr. Statz interned at VCA West Los Angeles and then worked for several years at two emergency/referral hospitals in the Boston area. After completing a residency at VCA Veterinary Referral Associates in Gaithersburg, Maryland, she became boarded in emergency and critical care. Having a strong interest in internal medicine, she has been practicing in that field for the past several years.

References

For global readers, a calculator to convert laboratory values, dosages, and other measurements to SI units can be found here.

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