Cystic Calculus and Cystotomy in a Hoffmann’s Two-toed Sloth (Choloepus hoffmanni)

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A 25 year old captive female Hoffmann’s two-toed sloth (Choloepus hoffmanni) housed at a zoological institution in the United States was observed exhibiting increased defecation frequency, white-pink discolored feces, perineal staining, and increasing lethargy over a period of one week. To evaluate the patient, general anesthesia was induced with ketamine (4 mg/kg) and maintained with isoflurane. Physical exam revealed urine perineal staining, and palpation of a large firm caudal abdominal mass eliciting pain. Blood analysis revealed a neutrophilia with a left shift and an unremarkable blood chemistry. A toxoplasmosis titer was negative and a rectal swab bacterial culture yielded no significant organisms. Radiographs revealed a spherical multi-layered structure localized presumptively in the bladder. Abdominal ultrasound showed hyperechoic bladder contents and indistinct wall margins. The following treatments were initiated in preparation for surgery: Lactated Ringer's Solution (50 ml/kg tapered to 25 ml/kg once daily subcutaneously (SC)), cefovecin (8 mg/kg SC every 14 days), ceftiofur (6 mg/kg SC every 5 days), meloxicam (0.1 mg/kg SC every 2 days), and buprenorphine (0.02 mg/kg SC once daily).

Four days after her initial exam, the patient was re-anesthetized for an exploratory laparotomy and cystotomy. Cystotomy revealed a single large firm calculus (6 cm diameter) and thickening of the bladder mucosa and wall. The calculus was successfully removed, the bladder was flushed, and the bladder wall was sutured closed as follows: mucosa in a simple continuous pattern, seromuscular layer in a Cushing pattern and oversewn in a Lembert pattern. Post-operatively, the patient recovered well and was housed in a large crate for three days to limit exercise. She continued to receive buprenorphine, meloxicam, and subcutaneous fluids. She was moved to a small cage 3 days after surgery, continued to do well, and 4 days later was reintroduced to conspecifics uneventfully.

Histopathology of the bladder wall revealed subacute plasmacytic and lymphocytic cystitis with submucosal edema. No significant organisms were isolated on the urine culture, however, culture of the bladder wall yielded Trueperella spp. that was susceptible to several antibiotics including cefovecin. Analysis of the calculus revealed its composition was 100% magnesium calcium phosphate apatite. This case report will outline unique physiological features and management challenges in two-toed sloths. In addition, the development of cystic calculi and the principles of surgical treatment will be discussed.

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Cystotomy, cystic calculus, urolithiasis, Xenarthra, sloth


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