Introduction

Urolithiasis is defined as the formation of sediment, consisting of one or more poorly soluble crystalloids, in the urinary tract.

Microscopic sediment is referred to as crystals, and larger macroscopic precipitates are called uroliths.

Urolithiasis is a common problem in dogs. Uroliths can form anywhere in the urinary tract, although in dogs the vast majority occur in the bladder. Urolithiasis is responsible for about 18% of veterinary consultations in dogs with lower urinary tract disorders (Figure 1) (Lulich et al., 2000).

Figure 1. Main conditions responsible for the clinical signs of lower urinary tract disease in dogs (from Lulich et al., 2000).

Abigail STEVENSON
PhD, BSc, MIBiol, Cbiol

Abigail graduated from the University of Stirling with a BSc (Hons) in 1992. After working as a research assistant at the University of Anchorage in Alaska for 6 months Abigail was appointed as a research technician at the WALTHAM Centre for Pet Nutrition in 1993 to work on feline metabolism of vitamin A and taurine. In 1995, Abigail was promoted to the position of Research Scientist working in the area of urinary tract health, and obtained her PhD on this subject in 2002. From 2002 to 2005 Abigail was responsible for the bird and fish research programs at WALTHAM. Recently Abigail moved again to take up a position in Scientific Communications at WALTHAM.

Carolien RUTGERS
DVM, MS, Dipl ACVIM, Dipl ECVIM-CA, DSAM, MRCVS

Carolien graduated from Utrecht State University (Hons) with a DVM in 1985, and then completed an internship at the University of Pennsylvania and a residency and Masters degree at Ohio State University. She has worked in both general and referral small animal practice. She joined the University of Liverpool as a Lecturer in Small Animal Medicine In 1985 and moved to the Royal Veterinary College in 1990, where she became a Senior Lecturer. Carolien has published more than 100 scientific papers and book chapters, and has lectured widely in the UK and internationally. Her major research interest is in gastroenterology. She is a Diplomate of the American College of Veterinary Internal Medicine (ACVIM), a Founding Diplomate of the European College of Veterinary Internal Medicine - Companion Animals (ECVIM-CA), and a RCVS Diplomate in Small Animal Medicine (DSAM). Carolien has been a Board member of the ECVIM-CA and a member of the RCVS Small Animal Medicine and Surgery Board, and an Diploma examiner for both.

1. Introduction

The four most common minerals found in canine uroliths are magnesium ammonium phosphate (struvite), calcium oxalate, ammonium urate and cystine (Osborne et al., 1995; Osborne et al., 1999b; Houston et al., 2004) (Figure 2 & Figure 3, Table 1). Less common urolith types are calcium phosphate, silicate, drugs and drug metabolites.

Figure 2. Calcium oxalate crystal. (© Waltham Centre for Pet Nutrition).

Figure 3. Struvite crystal. (© Waltham Centre for Pet Nutrition).