Understanding Cystine Urolithiasis

Brief overview.

Bladder and urinary tract stones can be caused by diet, such as grains or peas.

In-depth overview.

Many books and medical texts have been written about the formation of "stones" in ferrets bladders, kidneys, and urinary tract. There are a few main ones covered by studies, they include struvite (magnesium ammonium phosphate or MAP) [oval, smooth and white], calcium oxalate (calcium salt of oxalic acid) [irregular shaped and white], and cystine (amino acid cysteine)[grainy and yellow].

Lesser referenced forms are calcium carbonate (as named), calcium phosphate (as named), and ammonium urate (Uric acid).

Though many have similar causes and lead to similar health concerns, they are formed by slightly different chemical methods.

Inherited traits.
Due to inbreeding, some ferrets will have a higher likelihood to produce stones. Because this is something an owner would need a pedigree history, this is the most we will dive into the genetics. (possibly at a later date we will extend this section)

Ferrets fed a diet which includes peas have a higher likely hood of cysteine stones, while those on a grain inclusive diet are more likely to get struvite stones. While removing both seems to be the best plan for action, another issue is deeper regarding the ferret's pH of its urine. Naturally, and to maintain proper health, a ferrets pH should be slightly acidic - however; plant protein and cereals (grains) will raise a ferret's pH making it more basic, which leads us onto our next subject.

If possible, ferrets should get food with no peas, no grains, and limited amount of/no plants.

This plays a major role in a ferret's health regarding the formation of stones.  A highly hydrated ferret will urinate more often, flushing any small stones their body has produced. They may still be producing them, but this constant good urination will help prevent the growth to where it may cause pain and/or blockage. The second is that by introducing new water into a ferret digestive system items which would have normally raised their pH can be equalised by it. This, of course, is all in well, if you have an average pH of your water.

If possible ferrets water should be a pH of 5 to match what their body wants.

Some ill ferrets have been found to develop stones due to an infection. The direct cause is quoted as being the actual bacteria raises the ferret's urine pH aiding in the formation of stones. It may also be made worse due to the lack of frequent urinations.

Following are direct quotes where the above information was derived from.

The second retrospective study from the Minnesota Urolith Center determined that between January 2010 and September 2012, 64% of ferret uroliths submitted for analysis were of the chemical cystine.6 Cystine is a non-essential amino acid composed of two cysteine molecules joined by a disulfide bond. Cystine uroliths are round to oval, light yellow to tan in color, and range from 0.5 mm to several cm in diameter. Cystine urolithiasis in the ferret has empirically been associated with diets containing sulfide amino acids.

Exotic Companion Mammal Urolithiasis
Peter G. Fisher, DVM, DABVP (Exotic Companion Mammal)
Pet Care Veterinary Hospital, Virginia Beach, VA, USA

Normally urolithiasis is related to diet, as plant proteins make the urine alkalinized (pH 6) which causes crystalluria and stone formation.

Conclusion by Debra Bourne MA VetMB PhD MRCVS and Bridget Fry BSc, RVN referencing Ferrets Health, Husbandry and Diseases, Ferrets, Rabbits and Rodents - Clinical Medicine and Surgery Second Edition, and Manual of Exotic Pet Practice

At this time, the only preventative option for urolithiasis in ferrets is to maintain adequate hydration and avoid feeding any diets that have been associated with cases of cystine urolithiasis.

Wellness and Environmental Enrichment, An Issue of Veterinary Clinics of North America: Exotic Animal Practice

The urine of ferrets is acidic (pH normally of 5). With infection the bacteria may cause the urine to become alkaline, which in turn may contribute to more bacterial growth. Often cystitis occurs due to presence of urolithiasis or due to incomplete voiding such as seen in males with enlarged prostates. Uroliths are usually struvite, except for ferrets on a no-grain, novel protein or diet with legumes such as peas. Ferrets on these no-grain diets seem to have cysteine stones.

Ferret Medicine and Surgery


Ferrets Health, Husbandry and Diseases, chapter "Urogenital Diseases" pages 111-115
Ferrets, Rabbits and Rodents - Clinical Medicine and Surgery Second Edition, chapter "Urogenital Diseases" pages 41-49 and chapter "Soft Tissue Surgery" pages 121-134
Manual of Exotic Pet Practice, chapter "Ferrets" pages 345-374
Wellness and Environmental Enrichment, An Issue of Veterinary Clinics of North America: Exotic Animal Practice, page 240
BSAVA Manual of Rodents and Ferrets, chapter "Ferrets: urogenital and reproductive system disorders" pages 291-302
Ferret Medicine and Surgery, page 136-138


Ferrets Dietary requirements

Ferrets need food high in meat protein, as they can not use plant proteins.

We expect to food to exceed 40% protein - solely provided by meat ingredients.
We expect 20% fat.