Cystic calculi
Synonym(s): Bladder stones, Urolithiasis, Urinary calculi, Urinary stones
Introduction
- Cause: concretions of insoluble urate salts in the urinary bladders of tortoises and in those lizard species that possess a urinary bladder.
- Signs: lethargy, anorexia, dysuria, tenesmus, hind limb weakness, cloaca organ prolapse, dystocia.
- Diagnosis: radiography, ultrasonography, cystoscopy.
- Treatment: removal per cloaca or via surgical coeliotomy and cystotomy. Management changes to prevent recurrence.
- Prognosis: generally good although dependent on underlying cause.
Presenting signs
- Usually non-specific.
- Anorexia and lethargy most common.
- Hindlimb weakness and altered gait is a common presenting sign in chelonia.
- Dysuria, constipation Constipation and dyspnea are sometimes seen.
- Blood stained urine may be seen.
- Posturing and straining may be notes, and in chelonians the cloaca organ may be come prolapsed.
- Dystocia may occur in females.
- Poor growth may be observed in younger reptiles, particularly tortoises.
Acute presentation
- Urolithiasis is a chronic disease, but owners may present animals as being suddenly anorexic or more lethargic than usual.
Geographic incidence
- Common in captive animals worldwide.
Age predisposition
- Seen in all age groups, including young animals.
Breed/Species predisposition
- No confirmed specific predisposition however often seen in:
- Herbivorous animals fed on high protein, especially animal protein, diets, eg Testudo spp Hermann's tortoise Marginated tortoise Spur-thighed tortoise, Iguana spp Green iguana.
- Omnivorous species that have been fed excessive amounts of animal protein, eg Red footed tortoises (Geochelone carbonaria) Red-footed tortoise.
- Desert dwelling or arid species that may be more uricotelic combined with owners that do not provide a constant water source in the mistaken belief that it is not required, eg Uromastyx spp Uromastyx.
Cost considerations
- Many cases will require surgical celiotomy, hospitalization and assisted feeding or esophagostomy tubes.
- Husbandry and environmental deficits will need to be corrected and appropriate equipment will likely require expenditure.
Special risks
- Underlying renal disease increases anesthetic risks.
- Underlying renal disease may restrict drug choices.
- Many of these animals are chronically dehydrated and should be stabilized first.
Pathogenesis
Etiology
- Concretion of insoluble urate compounds in the urinary bladder.
- Can be caused by a number of factors listed below.
Predisposing factors
General
- Excessive dietary protein, particularly in herbivorous species.
- Excessive oxalate consumption has been proposed.
- Chronic dehydration is the most common cause.
- Renal disease Renal disease.
- Bacterial cystitis.
- Retropulsed eggs that have entered the urinary bladder may act as a nidus.
Pathophysiology
- In contrast to mammals, terrestrial reptiles are uricotelic.
- Uric acid is the main waste product of protein metabolism.
- Increased uric acid production, eg due to diet, or decreased excretion, eg with renal disease, or chronic dehydration, leads to increased levels of urate monohydrate crystals in the urine .
- Urate crystals are relatively insoluble and as a result, easily form urate salts which can then form concretions in the urinary bladder.
- As the size of the calculi increases, they cause inflammation of the bladder wall and discomfort.
- Some may exert a space occupying effect and interfere with GI function, breathing and locomotion.
- Anorexia Anorexia and lethargy follow.
Timecourse
- Usually chronic over many weeks to months but often only noticed once significant lethargy and anorexia or mobility problems become evident.
Epidemiology
- Disease is often secondary to husbandry therefore more than one animal in the same environment may be affected.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Di Girolamo N (2016) Reptile soft tissue surgery. Vet Clin North Am Exotic Anim Pract 19 (1), 97-131 PubMed.
- Reavill D R & Schmidt R E (2010) Urinary tract diseases of reptiles. J Exotic Pet Med 19 (4), 280-289 VetMedResource.
Other sources of information
- Doneley B, Monks D, Johnson R & Carmel B Eds (2018) Reptile Medicine and Surgery in Clinical Practice. Wiley-Blackwell, UK.
- Hochleithner C & Holland M (2014) Ultrasonography. In: Current Therapy in Reptile Medicine and Surgery. Eds: Mader D R & Divers S J. Elsevier Saunders, USA. pp 107-127.
- Mader D R et al (2006) Surgery. In: Reptile Medicine and Surgery. 2nd edn. Saunders Elsevier, USA. pp 581-630.
- Johnson J D (2004) Urogenital System. In: BSAVA Manual of Reptiles. Eds: Girling S J & Raiti P. BSAVA, UK. pp 261-272.
- McArthur S, Wilkinson R & Meyer J (2004) Diagnostic Imaging Techniques. In: Medicine and Surgery of Tortoises and Turtles. Blackwell Publishing, UK. pp 187-238.
- McArthur S & Hernandez-Divers S (2004) Surgery. In: Medicine and Surgery of Tortoises and Turtles. Blackwell Publishing, UK. pp 403-464.