THE SCIENCE OF SOFT TISSUE SURGERY


respectively. These included two horses with ob- structive ureteroliths.


Ultrasonographic Findings


Transrectal ultrasound identified bladder stones in all horses. Transcutaneous ultrasound alone was used to visualize the bladder stone in the lone don- key in the study. Bladder stones measured 1–11 cm (median, 6 cm) and all showed a rounded, smooth to slightly irregular, hyperechoic appearance and cast hard shadows. Twenty of 33 cases (61%) had concurrent uroliths identified in either the kidney (19) and/or ureters (3). Nephroliths were found in the left kidney in 7


cases, the right kidney in 5 and both kidneys in 7 cases. Nephrolithiasis was graded as mild in 12 kidneys, including 3 horses that were bilaterally affected and 3 horses that were unilaterally affected as the primary renal finding. Two horses also showed mild pelvic distention, and one horse showed moderate nephrolithiasis in the opposite kidney. Two additional horses showed moderate unilateral nephrolithiasis as the primary renal finding. Small, difficult-to-recognize, and distorted end-stage kidneys were identified in 7 horses, including 4 horses where the opposite kidney was enlarged and had increased cortical echogenicity and thickness, 2 horses whose opposite kidney was normal or showed only mild changes (increased cortical thickening and echogenic- ity) and another horse that appeared bilaterally end stage. Nearly all end-stage kidneys showed promi- nent mineralization and/or evidence of nephrolith for- mation. Two horses showed severe hydronephrosis, including one described below with an obstructive ure- terolith and an enlarged opposite kidney. Two horses showed evidence of moderate renal disease involving one or both kidneys, including mild enlargement, in- creased renal cortical thickening, and echogenicity but with easily recognizable renal parenchyma. One horse showed bilateral renal pelvic distention as a lone renal finding. Kidneys appeared within normal lim- its bilaterally in 10 cases and unilaterally in an addi- tional 7 horses. Ureteroliths were identified in three patients, all


within the proximal third of the right ureter. Sig- nificant obstruction of the ureter along with severe thickening and distention cranial to the ureterolith was seen in all three cases (Fig. 5). All demon- strated severe renal abnormalities, including severe hydronephrosis (same horse as mentioned above), bilateral nephrolithiasis and an end-stage contralat- eral kidney in the second horse and an endstage ipsilateral kidney in the third horse. While two of these horses showed azotemia, BUN and creatinine were normal in the horse with hydronephrosis. This horse also had an enlarged contralateral kid- ney, severe bilateral ureteral thickening and the largest cystolith in this study. Most horses showed mild-to-severe ureteral thickening that often ex- tended the length of the ureters.


406 2019  Vol. 65  AAEP PROCEEDINGS Treatment and Outcome


Surgical procedures were performed in 29 patients. This included standing procedures in 19 cases, including transurethral removal in 8 mares and perineal urethrotomy in 11 geldings, of which 9 also underwent lithotripsy to facilitate stone re- moval. Surgery was performed under general an- esthesia in the remaining 10 patients using a parainguinal8 or ventral midline2 approach. One of these horses was euthanized on the table after discov- ering multiple tears of the bladder wall. Another 2 horses were euthanized due to obstructive ureteroli- thiasis and evidence of severe urinary tract disease. Thirty horses were discharged from the hospital, in- cluding two horses that received no treatment due to the small size of the cystolith.


4. Discussion


Of the 33 equids with cystoliths over this 10-year study period, ultrasonographic evaluation of the uri- nary tract identified additional findings in nearly 70% of cases (23/33). Ultrasound was able to iden- tify severe pathology in several study horses, includ- ing many with normal BUN and creatinine. These included horses with obstructive ureteroliths, end- stage kidneys and evidence of chronic renal failure, which would be expected to significantly affect short- and long-term prognosis. Whereas findings were considered mild in several horses, these in- cluded small to moderate size nephroliths in at least one kidney. It would seem possible that the pres- ence of nephroliths would increase the risk for re- current bladder stones; however, this was not evaluated in this study due to the relatively low numbers of horses that returned to the authors’ hospital in subsequent years. For many owners, cystolith removal was performed to relieve the horse’s current clinical signs and they were willing to accept the risk of possible recurrence. The abil- ity for owners to make an informed decision was especially important in horses with obstructive ure- teroliths and/or extensive urinary tract disease from which they were unlikely to recover, even with blad- der stone removal. Although ultrasonographic findings did not often dissuade owners from pursuing surgical removal of cystic calculi, this information was felt to be impor- tant in the decision-making process. Long-term follow up to determine the rate of recurrence and/or relationship between additional ultrasonographic findings and life expectancy would be beneficial in the future. Certainly, visualization of concurrent obstructive ureteroliths was felt to be a significant finding, seen in 2 of the 3 horses with azotemia. One of these horses underwent lithotripsy fragmen- tation of the ureterolith in addition to standing blad- der stone removal. The other two horses with ureteroliths were euthanized due to the extent of renal pathology which was confirmed on necropsy examination.


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