Bilateral Ureteral Stent Placement and Lithotripsy in an Asian Small-Clawed Otter (Aonyx cinerea) with Nephrolithiasis
Bilateral ureteral stent placement and lithotripsy were performed in a 12-year-old intact female Asian small-clawed otter (Aonyx cinerea) following a 7-year history of nephrolithiasis and increasing renal insufficiency. The otter had previously presented with acute abdominal pain due to suspected fracture of the left renal calculus. Renal scintigraphy at this time revealed a 50% decrease in renal function. Nephrectomy or nephrotomy were considered as surgical options, but not performed.
As the otter’s clinical condition continued to decline, interventional imaging was used for placement of ureteral stents to prevent obstruction of the ureters with stone fragments from subsequent extracorporeal shockwave lithotripsy. Nephrolith appearance was followed radiographically over 5 weeks post lithotripsy. Shifting in stone position was observed without significant decrease in stone mass. An initial increase in azotemia was observed immediately post procedure but normalized to pre-procedural values over 5 weeks.
Due to declining quality of life related to severe osteoarthritis, the otter was euthanatized at 5 weeks after the procedure. Postmortem analysis of the stones confirmed 100% calcium oxalate monohydrate, consistent with other reports in this species. Gross and histologic evaluation of the kidneys revealed moderately severe chronic interstitial nephritis and loss of functional parenchyma.
Extracorporeal shockwave lithotripsy was not successful at nephrolith disruption in this otter, possibly due to prolonged duration of the stones, extent of stone formation, and the resulting renal fibrosis. However, the technique may remain a useful tool for other Asian small-clawed otters presenting earlier in the course of disease.