Introduction

The most common Dalmatian urinary stones are urates (also classified as "purines") whereas the most common in all other breeds of dogs is struvite (also known as "infection stones"). These two frequent culprits of abnormal canine stone-forming spotlight the need to, first, diagnostically confirm their presence so that subsequent treatment is not incorrect and misdirected. For example, urates thrive in acidic urine whereas infection stones thrive in alkaline urine and so, one treatment option of acidifying or alkalinizing the urine could be either beneficial or detrimental depending on the type of abnormal stone or crystals the Dalmatian is forming. 

Breeders and fanciers now are reluctantly aware that every one of our beloved breed is born with the potential of urate stone-forming because of breed-specific defects of urine production in Dalmatian livers and kidneys. I join with them in unhappily accepting this deplorable fact which has been known and taught to veterinarians for 81 years. It is especially disturbing considering Dalmatians are the only breed of dog with these inborn defects. Bulldogs, for example, also have a high incidence of urate stone-forming but not for the reasons Dalmatians do. Most breeders now are also aware of being able to minimize and even prevent overt Dalmatian urate stone-forming by (1) reducing purine-yielding foods in adult Dalmatian diets, (2) by monitoring via dipsticking to determine and to correct abnormal urinary pH, and (3) by routine repetitive urinalyses to detect the onset of abnormal urinary crystals before they progress into stone formation and the dreaded urinary obstruction. 

As recognition of this breed-specific health problem has grown during these years, breeders inevitably ask, "If all Dalmatians are born with the defect, how do we know which ones will shift from potential stone-formers to overt ones?" The answer is no one knows nor is any kind of data gathering even possible which could lead to plausible suggestions. There simply are overwhelmingly too many factors influencing overt stone-forming to be surveyed in order to come to any sort of statistically significant trends from which to draw even preliminary answers to the question. Yes, it is known that diet and perhaps the quality of local water purification can be two influences to push the potential Dal into overt stone-forming but lurking in the background and complicating any appraisal of a meaningful database of Dalmatians are many other contributing factors, such as: 

• how often each Dal is permitted to void,
• how "normally" concentrated its urine is,
• in the case of show entries, how often it leaves its home environment and to where,
• how accurate was the identification of abnormal crystals and stones (reported to be 65 percent in error according to a published veterinarian survey of U.S. assay methods).

I know some breeders claim "I have never had a stone-former in my line." I sincerely and fervently wish this were so but what they really should be saying is "I have never produced an overt stone-former" - or - "I have never produced a Dalmatian who has shown abnormal urate crystals." Until every puppy of every litter tests with no abnormal urinary crystals, until those puppies grow up to become adults and, regardless wherever they live and whatever they're fed and whatever they drink, continue to test without abnormal urinary crystals, an unequivocal statement "I have never produced a stone-former" is open to question.

Perhaps in some future Dalmatian Utopia these insurmountable discouragements will be overcome but until then, no meaningful conclusions can even be suspected why some Dalmatians become overt stone-formers and others do not. What we do have are the two U.S. veterinary centers who specialize in canine stone-forming and from them, invaluable statistics thoughtfully and cooperatively made available to the DCA Study Group on Dalmatian stone-forming. In 1993, the Urinary Stone Analysis Laboratory of the U. of California at Davis, and its chief, Gerald V. Ling, DVM, published an article in the Journal of the American Veterinary Medicine Association on a retrospective statistical analysis of 275 Dalmatian cases of stone-forming. A bulletin was immediately issued to all regional DCA clubs with the pagination of that article. 

We now have, through the courtesy of Carl A. Osborne, DVM, PhD, chief of the Minnesota Urolith Center of the U. of Minnesota Veterinary School in St. Paul, the latest of their retrospective data on almost 3,000 Dalmatian stones over the past fifteen years. The purpose of this article is to brief the Dalmatian community on this latest statistical compilation and to see if there were any changes in Dalmatian trends during the past eleven years since Dr. Osborne published two 1986 volumes of a veterinary teaching text on stone-forming. The following graphic data must be qualified: readers should remember that the numbers, while statistically significant, are those only of stones sent to Dr. Osborne's Minnesota Urolith Center or only of stone-forming Dalmatians treated there. If the reader projects the data into breedwide Dalmatian conclusions, they should remember none of the data includes Dalmatians who were what Dr. Osborne terms "silent stone formers" without symptoms or those whose stones were sent elsewhere for assay. The graphic data provide invaluable information but within the confines of confirmed stone-forming Dalmatians only.

Three percent of all urinary stones reported by Dr. Osborne's Center in 1986 were from Dalmatians. The current data shows an increase to 5 percent but does not necessarily mean the health problem has ominously increased within our breed. Teaching information during the past five years from the DCA Study Group on Urinary Stones to the Dalmatian community has urged abnormal urinary crystals or stones to be assayed by the Minnesota or California centers because of the reported 65 percent error by local, provincial testings. Therefore, it is entirely possible this increase in the Dalmatian component mostly reflects more stones being supplied for assay and not an increase in overt stone-forming in our breed.

Some definitions, first - the "urethra" is the single tube carrying urine from the bladder to the outside; the "ureters" are bilateral tubes carrying urine from each of the kidneys to the bladder. The lower urinary system (bladder, urethra or both) remains the most prevalent location of stones as it was in Dr. Osborne's 1986 textbook statistics (then grouped for all stone-forming breeds, Dalmatians included). By adding in data on expelled stones, the sum means 97.3 percent of Dalmatian stones are anatomically located in the lower system where many can be treated non-surgically, easily and less expensively as compared to stones in the upper urinary system. 

The newly reported category of 12.3 percent Dalmatian stones "passed" provides hope. The most common type of Dalmatian stone, urates, architecturally tend to be rounded and smooth which facilitates their moving down the urinary system as compared to other types of stones which can be barbed and lodge more unmovingly. On a positive note, many urate stones are reported as frequently being expelled and "passed." On a negative note, large urate stones can be moved easily by the urinary stream to jam within the penis at the narrowing of cartilage, the "os penis," thereby creating the dreaded urinary obstruction in males. If the Dalmatian is obstructed, the smooth urate stones are equally capable of being similarly and successfully moved to be "back flushed" into the bladder thereby re-opening the urinary flow. A non-surgical attempt via diet and anti-urate medication to dissolve urate stones thereby reducing their size so they can pass may well be worth the effort, time and veterinary expense. 

Renal surgery of the upper system (kidneys, ureters or both) is major, drastic surgery requiring skilled experienced surgeons. It may be prohibitively expensive whereas bladder surgery is no more complicated, if unavoidable, than an appendix removal in humans. In 1986, stones in the upper system of all breeds was 3 percent. These fifteen year data show the upper system was confirmed in only 1.2% of Dalmatians and in both upper and lower systems in 1.5 percent of Dals. Please note the data does not identify which type of stones were lodged in the upper system of these Dalmatians. 

The total of 97.3 percent of stones in the lower system is an eloquent explanation why indiscriminately calling the health problem "Dalmatian kidney stones" is misleading and unnecessarily threatening. The Study Group suggests it more properly be termed "Dalmatian urinary stones." 

"Purine" stones include the most common mineral found in Dalmatian stones, the "urates" of which there are several forms. It is the urates which are automatically prognosed by many veterinarians to be Dalmatian stones. The purine group also includes "xanthine." This purine is a side effect of uninterrupted overdosage with the anti-urate drug, allopurinol (see discussion under Chart No. 4). Unlike the other purines, xanthine stones cannot be dissolved and must be removed surgically.

Knowing that Dalmatians do not metabolize purine-yielding foods properly, it is not surprising that purine stones represent a whopping 94 percent of all Dalmatian stones assayed by Minnesota over the 15 year period. A comparison of this stone - most common in Dalmatians - to struvite, the most common one in all other breeds of dogs, is dramatic. In 1986, Dr. Osborne's textbooks published a world survey of 1,700 stones from all stone-forming breeds which showed struvite ("infection stones") to represent 63 percent whereas urate stones were identified from only 6 percent of all breeds. In comparison, this graph shows the exact opposite of those allbreed statistics - Dalmatians can indeed form the "infection stones" but only 1 percent of Dalmatian stones were found to be struvite as compared to 94 percent of Dalmatian stones confirmed as purines. Remembering that Dalmatians are the only breed of dog with their type of urate stone-forming defect, their reversal of the most frequently-found stone is not surprising. However, it does not justify presuming any stone-forming Dalmatian is producing urates despite their overwhelming preponderance. Identifying which abnormal crystal or stone is being formed should not be avoided and still must routinely be done before correct and successful treatment can be assured. Your overt Dalmatian, for example, may just be forming struvite or calcium oxalate stones. 

A monstrous 99 percent of Dalmatian purine stones - not surprisingly because of the breed's defect - were the urates. Of those, 83 percent of stone-forming Dalmatians produced ammonium acid urate, a form of urates happily very responsive to non-surgical treatment with anti-urate diet and anti-urate medication. In 1986, only 80 percent of Dalmatian stones were reported as urates, of which 76 percent were ammonium acid urate. This increase, like Chart No. 1, may be a result of more Dalmatian specimens being sent to Minnesota for assay. We may not know why some Dalmatians become overt stone-formers but with this preponderance of those forming urates, we do know methods by which urates can be detected early in their onset in order to be minimized and ultimate stone-forming avoided: 

(1) dipsticking to detect as soon as possible an abnormally acidic urine in which urates thrive, (2) urinalysis to confirm as soon as possible the presence of abnormal urate crystals, (3) diet formulations with low amounts of purine-yielding foods, including home cooked recipes, (4) the anti-urate drug, allopurinol, in short periods of high dosage to dissolve existing urates or in long-term low dosage for prevention, and (5) the use of distilled water to guarantee fluid intake which does not influence abnormal urinary crystals or stones. 

Such early detection and the prompt starting of known preventative methods can often minimize and reverse the ongoing growth of urate stones in the urine thereby aborting the dreaded urinary obstruction.

Note the 1 percent of xanthine which shows up as a mineral in the stones for the first time in these new data. It was only in 1991 that the report of xanthine as a side effect of allopurinol overdosage was first published in the veterinary literature. Dalmatian stones consisting of a center core of urates surrounded by outer layers of xanthine due to allopurinol overdosage are extremely difficult to assay and require advanced laboratory procedures like "high pressure liquid chromatography" available at the two U.S. centers but rarely if ever for local, provincial assay. Remembering the 65 percent error around the country in assaying any urinary stone, it is quite possible that xanthine stones have existed for many years but have never been identified. More importantly, it is then possible that some previous failures attributed to non-surgical but unsuccessful treatment with allopurinol of urate stone-forming in Dalmatians may have been because of overdosage and the laying down of non-dissolvable xanthine. Allopurinol still is reported to be the anti-urate drug-of-choice but its dosage for long-term use to be knowledgeably prescribed. 

This chart of all breeds is included only as a comparison to the next, Chart No. 6, representing only Dalmatian data. Note that because all minerals are combined for this data, the chart includes that for struvite ("infection") stones, the most common one for all stone-forming breeds of dogs except for Dalmatians. The preponderance of almost 60 percent bitches perhaps may be a result of those struvite data because bitches are allegedly more prone than males to urinary tract infections. While on the subject of infection stones, it may be of interest to know that - of the bacterial species known to frequently cause urinary tract infections - E. coli is reported to be the most prevalent but it has not been incriminated as a stone-forming bacterium. The others, Proteus and Staphylococcus have been incriminated as stone-formers, such as "coagulase-positive Staphylococcus, " for which Ampicillin has been reported to be the antibiotic-of-choice. 

Compared to Chart No. 5, a gender shift to almost 97 percent male Dalmatians may be explained because stone-forming symptoms and most certainly urinary obstruction in males is immediately visible to the observer as a result of their urinary anatomy. Bitches uneventfully pass many stones including urates without detectable symptoms because their urinary anatomy permit passing of large stones more easily than males. Many female stone-formers therefore remain undetected and unreported but these data nonetheless dispel the misconception that bitches do not become stone-formers. 

In 1986, Dr. Osborne's textbooks showed three years to be the most prevalent age for all breeds to show stone-forming symptoms. These current data shift to a range of one-to-four years as the most prevalent Dalmatian ages. Younger Dalmatians now significantly showing up may be a result of an increased awareness to the health problem and more frequent observation of their urinating. Remember the prevalence of those ages merely means when stones were sent to the Minnesota Center for assay or when the dogs entered there as patients. We do not know how many of these data represent the first onset of stone-forming. 

The entire graph shows Dalmatian stone-forming can occur at any age - in any puppy, in any adult and in older senior citizens. I am not struck by the dwindling data after four years-of-age so much as the mere presence of old Dalmatians in the data. Years or even a lifetime of no overt stone-forming symptoms clearly does not justify complacency. 

These data are not from Minnesota but from the California ten-year database published in 1993. They logically follow Chart No. 7 showing age of stone-formers and are included to amplify those data for you. Not surprisingly, the graph shows the majority of Dalmatians formed stones in a once-or-twice pattern of recurrence. Thereafter, any Dalmatian forming stones for a third-to-sixth time drops off precipitously. Several possible explanations come to mind: 

• Repetitive stone-formers may have been euthanized the more frequently they recurred;
• Owners became more conscientious (and thereby more successful) in following an anti-stone regimen;
• New knowledge for successful treatment became available as years went on;
• Stones were not returned for assay as they recurred.

1. Every Dalmatian is born with the breed-specific potential of urate stone-forming because of defects in urine production in the Dalmatian liver and kidney. It is not known why some Dalmatians become overt stone-formers as compared to others including littermates.
2. Improper diet containing potent purine-yielding foods or large amounts of them have been incriminated in Dalmatian urate stone-forming. Environmental factors such as quality of local water purification systems may be an added, significant influence.
3. The vast majority of Dalmatian urinary stones reveal urates as their most prevalent mineral as compared to struvite ("infection stones") in all other breeds. This underscores the necessity to first identify what kind of abnormal urinary crystal or stone the Dalmatian is forming before effective and appropriate treatment can be dependable.
4. Architecturally, urates are smooth-walled so that treatment directed to dissolving them for passing or to reopen blocked urinary flow by non-surgical "back-flushing" carries hope for a high degree of success.
5. Male Dalmatians are susceptible to the dreaded urinary obstruction but bitches have definitely been confirmed as stone-forming too.
6. Early detection of abnormal urinary crystals may be invaluable to abort the progression into stones and their dreaded urinary obstruction. The earliest sign can be an abnormal urinary pH easily monitored by Dalmatian owners using dipsticks. The simple, inexpensive but confirming diagnosis is a standard urinalysis to detect if abnormal urinary crystals are present and continue to be present over repetitive testings. A published veterinary survey revealed a 65 percent error in identifying abnormal urinary crystals and stones throughout the U.S. Accordingly, the DCA Study Group on Urinary Stones currently is working up a wallchart of abnormal urinary crystals, planning on its distribution to their veterinarians by Dalmatian owners.
7. Overzealous and overly protective owners of Dalmatians without symptoms of abnormal urinary crystals or stones need not feel compelled to adhere to the extremes of diet and water intake urged for known stone-formers. The absence of symptoms, however, should be periodically confirmed by ongoing urinalyses.

Bartges, J.W., and coauthors: Prevalence of cystine and urate uroliths in Bulldogs and urate uroliths in Dalmatians, Journal of the American Veterinary Medicine Association 204: 1914-1918 (June 15) 1994. 

Case, L.C., and coauthors: Urolithiasis in Dalmatians: 275 cases (1981-1990), Journal of the American Veterinary Medicine Association 203: 96-100 (July 1) 1993. 

Ling, G.V., and others: Xanthine-containing urinary calculi in dogs given allopurinol, Journal of the American Veterinary Medicine Association 203:1933-1940 (June 1) 1991. 

Osborne, C.A.: Data on some 3,000 Dalmatian stones, personal communication. 

Osborne, C.A., editor: Volume I, Canine Uroliths: Etiopathogenesis, Detection, Treatment and Prevention, The Veterinary Clinics of North America, W.B. Saunders Co., Publishers, Philadelphia, January 1986.

Osborne, C.A., editor: Volume II, Canine Urolithiasis, The Veterinary Clinics of North America, W.B. Saunders Co., Publishers, Philadelphia, March 1986. 

Osborne, C.A., and coauthors: Analyzing the mineral composition of uroliths from dogs, cats, horses, cattle, sheep, goats and pigs, Veterinary Medicine 84:750-764, 1989. 

Osborne, C.A. and others: Canine and feline urolithiasis: Relationship of etiopathogenesis to treatment and prevention, in: Bojrab, M.D., editor: Disease Mechanisms in Small Animal Surgery, Lea & Febiger, Philadelphia, 1992. 

Sorenson, J., and Ling, G.V.: A literature survey of urate urolithiasis in Dalmatian dogs: Metabolic and genetic aspects, Journal of the American Veterinary Medicine Association 203: 857-869 (Sept. 15) 1993.