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Hematochezia in a Dog

Samantha Parkinson, DVM, University of Tennessee

M. Katherine Tolbert, DVM, PhD, DACVIM (SAIM), Texas A&M University

Parasitology

|
July 2016
|
Peer Reviewed

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Molly, a 6-year-old spayed bichon frise, was presented with a 2-month history of hematochezia and a 3-day history of inappetence and vomiting.

History

Hematochezia was initially mild but had progressed in severity. At presentation, Molly was defecating mostly frank blood with little discernible fecal material. Metronidazole (10 mg/kg PO twice a day), amoxicillin (10 mg/kg PO twice a day), and sulfasalazine (20 mg/kg PO 3 times a day) were previously prescribed for treatment of diarrhea but were discontinued 10 days before presentation after no apparent improvement. Heartworm and flea and tick preventives had also been discontinued.

Mollys left eye 5 weeks before presentation. Complete bullous retinal detachment with a right subretinal exudate (arrow) can be observed.

Molly’s left eye 5 weeks before presentation. Complete bullous retinal detachment with a right subretinal exudate (arrow) can be observed.
Molly’s left eye 5 weeks before presentation. Complete bullous retinal detachment with a right subretinal exudate (arrow) can be observed.

Molly’s left eye 5 weeks before presentation. Complete bullous retinal detachment with a right subretinal exudate (arrow) can be observed.

Molly had a previous history of acute blindness, diagnosed as bilateral retinal detachment 5 weeks before presentation (Figure 1). Blood pressure was mildly elevated at 160 mm Hg. Tests for infectious disease were negative. Additional testing was offered but declined. Immunosuppressive doses of prednisone (1 mg/kg PO twice a day) were prescribed for suspected steroid responsive retinal detachment. When retinal reattachment did not occur after 1 week of corticosteroid therapy, further evaluation was recommended but was declined by the owner.

Related Article: Retinal Detachment

Physical Examination

Molly had a lean BCS of 4/9 and was 5% dehydrated. Frank blood was found on rectal examination, and the ophthalmic examination remained unchanged. Temperature, pulse, and respiration were normal. No additional abnormalities were identified.

Diagnostic Results

Serum chemistry profile revealed hyperglobulinemia (globulin, 4.1 g/dL; reference interval, 2.0-3.2 g/dL) and hypoalbuminemia (albumin, 2.7 g/dL; reference interval, 3.2-4.1 g/dL). A CBC and rectal scrape were unremarkable. Urinalysis was initially considered to be normal, with a urine specific gravity of 1.030, absence of protein, and an inactive sediment. Abdominal ultrasonography revealed moderate thickening of the intestinal wall (up to 0.41 cm thick; normal thickness, <0.3 cm), which originated at the ileocecal junction and extended the length of the colon. Numerous lymph nodes surrounding the colon were also enlarged. Ultrasound-guided fine-needle aspiration of the thickened colonic mucosa and intraabdominal lymph nodes was performed; however, cytologic evaluation was nondiagnostic because of low cellularity.

Single Prototheca zopfii organism observed in a cytologic preparation of subretinal fluid. P zopfii is a round-to-oval organism with a thin, clear cell wall and granular, blue-gray-to-purple interior structures. The organism can be observed above the magnification legend. The red-to-purple round structures (arrow) represent endospores, which can sometimes be observed. (100 objective)

Single Prototheca zopfii organism observed in a cytologic preparation of subretinal fluid. P zopfii is a round-to-oval organism with a thin, clear cell wall and granular, blue-gray-to-purple interior structures. The organism can be observed above the magnification legend. The red-to-purple round structures (arrow) represent endospores, which can sometimes be observed. (100× objective)
Single Prototheca zopfii organism observed in a cytologic preparation of subretinal fluid. P zopfii is a round-to-oval organism with a thin, clear cell wall and granular, blue-gray-to-purple interior structures. The organism can be observed above the magnification legend. The red-to-purple round structures (arrow) represent endospores, which can sometimes be observed. (100× objective)

Single Prototheca zopfii organism observed in a cytologic preparation of subretinal fluid. P zopfii is a round-to-oval organism with a thin, clear cell wall and granular, blue-gray-to-purple interior structures. The organism can be observed above the magnification legend. The red-to-purple round structures (arrow) represent endospores, which can sometimes be observed. (100× objective)

Definitive Cytology Results

A subretinal tap was performed with the patient under general anesthesia. Cytology of the subretinal fluid (Figure 2) and reevaluation of urine sediment by the clinical pathologist revealed Prototheca spp-like organisms. Growth of P zopfii was evident on fungal culture of the urine.

Diagnosis

Protothecosis

Ask Yourself

Question 1

What is protothecosis?

Question 2

What are the most common ways Prototheca spp infection manifests clinically?

Question 3

How is protothecosis diagnosed, and what is the appropriate treatment?

Question 4

How should I monitor a patient receiving amphotericin B and itraconazole?

Prognosis

Poor-to-grave. There is a single reported case of a dog surviving 12 months.1 This dog had both colonic and ophthalmologic involvement; it is likely that previous immunosuppression from prednisone caused an acute worsening of the condition. Prognosis can likely worsen with neurologic and/or ophthalmic system involvement.1

Treatment

Molly was initially treated with amphotericin B colloidal dispersion (ABCD; 0.5 mg/kg IV over 4-6 hours) every 48 hours for 4 treatments. On the fourth day of treatment, Molly also received itraconazole (5 mg/kg twice a day). Prototheca spp infection is generally considered a progressive, terminal disease; thus, daily itraconazole was continued long-term.

Related Article: Large Bowel Diarrhea

Outcome

Mollys hematochezia improved dramatically with ABCD and itraconazole treatment. Her stool remained soft for several weeks, but her appetite and feces returned to normal within the first month of treatment. Five months into treatment, Molly developed neurologic signs, including vocalization and ataxia; terbinafine at a low dose (10 mg/kg PO once a day; because of itraconazole continuation) was added to the treatment protocol because of suspicion of advanced disease. Neurologic signs resolved following treatment, and at the time of this publication (2 years after diagnosis), the patient is alive and being treated with itraconazole (5 mg/kg twice a day) and terbinafine (10 mg/kg PO once a day). The authors have recommended she continue this treatment for life.

Did You Answer?

Question 1

What is protothecosis?


Question 2

What are the most common ways Prototheca spp infection manifests clinically?


Question 3

How is protothecosis diagnosed, and what is the appropriate treatment?


Question 4

How should I monitor a patient receiving amphotericin B and itraconazole?

ABCD = amphotericin B colloidal dispersion,BCS = body condition score

References and Author Information

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