Abstract

Renal calculi have been reported from free-ranging harbor seals as well as those living under human care. Most commonly, urate nephrolithiasis has been reported in multiple pinniped species. Chronic dehydration and diet as well as age may be contributing factors to development of renal calculi. Pinnipeds have a multilobulated reniculate renal anatomy with numerous collection systems that funnel into a common renal pelvis and ureter. Because of this unique anatomy, traditional methods of calculi treatment including ureteroscopic laser lithotripsy are often ineffective.

A 22-year-old male harbor seal living at the Vancouver Aquarium presented with intermittent signs of inappetence and abdominal pain. Renal calculi in both kidneys were diagnosed by ultrasound examination, and the extensive number and position of nephroliths was confirmed via computed tomography (CT). Due to failure of treatment with allopurinol and a guarded prognosis based on previous cases, alternative treatment methodologies were investigated. The recent development of a noninvasive lithotripsy procedure based on delivering ultrasound-guided focused sound energy (Break Wave™, SonoMotion Inc, San Mateo, CA) to calculi from the external surface of the abdomen was suggested as a potential treatment modality.

Break Wave™ lithotripsy was performed noninvasively on several calculi with the animal under general anesthesia and placed in right lateral recumbency, allowing sonographic visualization of the left kidney from the left flank. Real-time ultrasound image guidance from the SonoMotion Break Wave™ system showed complete fragmentation of the primary targeted 1-cm stone, which was confirmed on postoperative CT scan. In addition, numerous stones in the vicinity of the main stone targeted were also reduced substantially and were not observed in the postoperative CT scan. The seal had some hematuria and mild abdominal pain postoperatively, but all clinical signs resolved within 4 days after the procedure.

The seal will require multiple procedures to remove all renal calculi. However, Break Wave™ therapy appears to be a promising treatment modality for renal calculi in species with complex reniculate renal anatomy.

Acknowledgements

The authors wish to thank the Vancouver Aquarium husbandry staff, and veterinary technicians Sion Cahoon, Gabrielle Beer, Natalie Sacks for their dedication to providing the best care possible for the animals at the Vancouver Aquarium. We are indebted to the University of British Columbia medical faculty and animal care staff. SonoMotion Inc. provided all equipment, consultation, and support for these procedures.

*Presenting author