Missed Stones After Cystotomy: One in Five Dogs Still Have Uroliths Post-Op

Frequency of Incomplete Urolith Removal, Complications, and Diagnostic Imaging Following Cystotomy for Removal of Uroliths from the Lower Urinary Tract in Dogs: 128 Cases (1994–2006)

David C. Grant, Tisha A. M. Harper, Stephen R. Werre

Background:
Cystotomy is commonly performed for the removal of urocystoliths and urethroliths in dogs, yet its effectiveness in ensuring complete stone removal has not been rigorously assessed in large-scale studies. This study aimed to evaluate the frequency of incomplete urolith removal, the use of diagnostic imaging to confirm stone clearance, and postoperative complications, as well as to identify factors associated with surgical success or failure.

Methods:
A retrospective analysis of medical records was conducted for 128 dogs that underwent cystotomy for lower urinary tract urolith removal between 1994 and 2006. Data collected included signalment, stone type and location, imaging modalities used, number of uroliths removed, stone composition, surgical complications, and outcomes. Success was defined as removal of all radiographically or ultrasonographically identified uroliths. Multivariable logistic regression and Fisher's exact tests were used to identify predictors of surgical failure, imaging performance, and complications.

Results:
Of 44 cases where surgical outcome could be assessed, 9 (20%) had incomplete urolith removal. Only 19 dogs (15%) underwent appropriate postoperative imaging, 42% of which showed retained uroliths. Dogs with both urethroliths and urocystoliths were significantly more likely to experience failed cystotomy (odds ratio 31.8; P = 0.009). Postoperative complications were infrequent (4%) and minor. Imaging was more likely to be performed in dogs with non-urate uroliths. Surgeons often forewent postoperative imaging based on presumed complete removal, contributing to underdetection of failures.

Limitations:
This was a retrospective study with potential selection and reporting bias. Only a minority of dogs had complete outcome assessment via postoperative imaging. Urolith counts on imaging and during surgery may be inaccurate, and imaging choices were influenced by assumptions about stone composition, which may have been incorrect.

Conclusions:
Cystotomy is generally safe and effective for urolith removal, but incomplete removal occurs in a notable proportion of cases, particularly when urethroliths are present. Postoperative imaging is underutilized but crucial for confirming surgical success. Standardized imaging protocols and improved intraoperative assessment could enhance outcomes and reduce the risk of missed uroliths.

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