Quantitative urolith analysis: A standard of practice?

Quantitative urolith analysis: A standard of practice?

Carl A. Osborne
A quarter-century ago, analysis of uroliths removed (usually by surgery) was optional. In fact, rather than have the stones analyzed, some veterinary practitioners gave them to their clients as a topic of conversation. What about today? Is it an acceptable standard of practice to give stones retrieved from the urinary tract to owners without knowing their composition? What would be your response to a physician who gave you stones retrieved from your urinary tract? Believe it or not, we have received uroliths for analysis formed by our veterinary colleagues that were given to them by a physician. Of course, we did not perform the requested analysis because we did not want to cross the line of practicing medicine without a license. Instead, we sent them to a laboratory licensed to provide that service.

Jody P. Lulich
The question that we pose to you is whether making a choice not to request quantitative analysis of uroliths is ethical. Should failure to request quantitative urolith analysis be considered negligence?

Recall that negligence may be defined as the act of doing (or not doing) something that a person of ordinary prudence would or would not have done in similar circumstances. Negligence implies that a veterinarian did not follow a reasonable standard of care. The standard applies not only to what you do (commission), but also to what you don't do (omission).

Figure 1: Fragments of a mixture of ammonium urate and struvite that formed around a catheter. (Photo: courtesy of Dr. Carl A. Osborne)
The law says that reasonable practitioners, not the most highly skilled professionals, set the standard of care. If an error occurs despite the exercise of due care, negligence is not an issue. In this context, should failure to request quantitative urolith analysis be considered negligence?

What are uroliths?

Figure 2: Calcium oxalate monohydrate that formed around suture material.
Uroliths (also known as calculi) are aggregates of mineral and/or non-mineral substances in the urinary tract. They may vary in size and number, and may form in one or more locations within the urinary tract when urine becomes oversaturated with crystallogenic substances. Uroliths may be composed of one or more biogenic minerals, including magnesium ammonium phosphate (struvite), calcium phosphate (calcium apatite), calcium oxalate monohydrate (Whewellite), calcium oxalate dihydrate (Weddellite), uric acid or salts of uric acid (e.g., ammonium, sodium and calcium urate), silica, cystine and/or xanthine. Also, they may be partly or completely composed of drugs or drug metabolites. If foreign substances (such as suture material, hair or plant material) are present within the lumen of the urinary tract, they often become the nidus for urolith formation (Figures 1 and 2).

Why should uroliths be analyzed?