03-08-2009 - Cystoscopic removal of a urolith from a pet guinea pig
Cystoscopic removal of a urolith from a pet guinea pigR. Pizzi, BVSc, MSc, DZooMed, FRES, MACVSc, MRCVS1
1 Zoological Medicine, 79A Garvock Hill, Dunfermline, Fife KY12 7UT
Correspondence: E-mail for correspondence: email@example.com
THE guinea pig (Cavia porcelles) is a domesticated monogastric herbivorous hystricomorph rodent originating from South America. Believed to have been domesticated as early as 5000 BC in the Andean region of South America, they were used as a food item, predominately during ceremonial meals (Morales 1995). No longer extant in the wild, several related species occur in the grass plains of the region (Nowak 1999). First described in the West by Konrad Gesner in 1554 (Gmelig-Nijboer 1977), traders brought guinea pigs to Europe in the 16th century, where they became a popular exotic pet among the upper classes and royalty, including Queen Elizabeth I (Morales 1995).
A pet female guinea pig aged two years and seven months and
weighing 1·058 kg was referred for recurrent haematuria
over the previous two months. The guinea pig demonstrated pain
on caudal abdominal palpation, and a small thickened bladder
was discovered. Previous treatment with two 10-day courses of
5 mg/kg oral enrofloxacin (Baytril 2·5 per cent oral solution;
Bayer) twice daily resulted in clinical improvement, but haematuria recurred
Urine collected by catheterisation revealed marked haematuria (Fig 1), degenerate neutrophils and a small amount of calcium oxalate crystals, and was submitted for microbiological culture. Serum urea and creatinine levels were normal. Anaesthesia was induced with 4 per cent isoflurane (Isoba; Schering-Plough Animal Health) in an induction chamber after premedication with 0·1 mg/kg subcutaneous atropine (Atropine Sulphate; Hameln Pharmaceuticals). Anaesthesia was maintained with 2 per cent isoflurane using a face mask (Longley 2008), with analgesia provided by 0·6 mg/kg subcutaneous meloxicam (Metacam; Boehringer Ingelheim). A radiodense urolith was seen on lateral and dorsoventral abdominal radiographs (Fig 2).
A rigid endoscope 2·7 mm in diameter, 180 mm length and 30° forward oblique, with a 14·5 Fr (4·83 mm) operating sheath (Karl-Storz), was gently passed into the urinary papilla and directed into the bladder. The bladder was flushed with sterile 0·9 per cent saline via the operating sheath. The bladder wall appeared thickened, with a hyperaemic mucosa, ecchymosis and free haemorrhage. The urolith, which had an uneven surface (Fig 3), was grasped on the second attempt with 5 Fr (1·66 mm) forceps via the operating sheath. The operating sheath was removed with the forceps. The entire cystoscopy and removal of the urolith took just under six minutes, according to the video cystoscopy recording. The procedure was quicker and less invasive than surgical removal via cystotomy.
On recovery the guinea pig was given 30 mg/kg oral trimethoprim-sulphonamide (Septrin Paediatric Suspension, GlaxoSmithKline) twice daily for two weeks (Morrisey and Carpenter 2004, Carpenter 2005) and 0·6 mg/kg oral meloxicam (Metacam; Boehringer Ingelheim) twice daily for five days. There was no microbial growth from the urine culture. The guinea pig remained free from any clinical abnormalities six months after the procedure.
Quesenberry and others (2004) reported guinea pigs as hardy animals with few disease problems. As a prey animal they may conceal clinical signs of disease (Riggs 2008), or show non-specific signs (Flecknell 2002). Urolithiasis may not result in clinical signs notable to owners, unless they are associated with cystitis or cause urinary obstruction (Flecknell 2002, O'Rourke 2004).
There is conflicting information in the literature on urolithiasis in guinea pigs. While Riggs (2008) and O'Rourke (2004) have reported urinary tract calculi occurring commonly in pet guinea pigs, Flecknell (2002) instead reported uroliths as being relatively uncommon. O'Rourke (2004) and Flecknell (2002) state that uroliths most commonly consist of calcium oxalate, while Riggs (2008) found uroliths to be predominately calcium carbonate. Both are radioopaque. While the underlying causes are not completely understood, Riggs (2008) believed a genetic predisposition and an association with high calcium diets was likely. Other authors have thought cystitis, which is common in older females, to be an important predisposing factor (Peng and others 1987, Percy and Barthold 2001, Flecknell 2002). Okewole and others (1991) have also described a number of laboratory guinea pigs that developed calcium oxalate urolithiasis during an outbreak of systemic and urinary tract infection with Streptococcus pyogenes. In the author's experience, urolithiasis is common in older guinea pigs of both genders and is commonly associated with urinary tract infections.
Most texts recommend removal of uroliths by cystotomy (Flecknell 2002, O'Rourke 2004, Riggs 2008) and while cytoscopy of pet guinea pigs has been described (Lennox 2005), this is, to the author's knowledge, the first report of cystoscopic removal of a urolith performed in a pet guinea pig. Although the use of potassium citrate to prevent the formation of uroliths has been reported (O'Rourke 2004), no efficacy has been proven, and as guinea pigs cannot remove an acid load, urinary acidifiers are not indicated (Harkness and Wagner 1989).
The separate urinary papilla present in guinea pigs (Breazile and Brown 1976, Quesenberry and others 2004, Lennox 2005) made introduction of the cystoscope into the bladder simpler in this case than in dogs and cats (McCarthy 2005, Hotston Moore and England 2008).
This procedure is a rapid and less invasive alternative to surgical cystotomy in some female guinea pigs with urolithiasis.
The author thanks Elizabeth Grant and Kirsty Moir for their assistance with this case, and Adam Tjolle and Ken Davison for support of the endoscopy service.
BREAZILE, J. E. & BROWN, E. M. (1976) Anatomy. InThe Biology of the Guinea Pig . Academic Press. pp53 -62
CARPENTER, J. W. (2005) Exotic Animal Formulary. 3rd edn. Elsevier Saunders. p382
FLECKNELL, P. (2002) Guinea pigs. In Manual of Exotic Pets. 4th edn. Eds A. Meredith, S. Redrobe. BSAVA Publications. pp 52-64
GMELIG-NIJBOER, C. A. (1977) Conrad Gessner's "Historia Animalum": an Inventory of Renaissance Zoology. Krips Repro B. V. pp 69-70
HARKNESS, J. E. & WAGNER, J. E. (1989) The Biology and Medicine of Rabbits and Rodents. 3rd edn. Lea and Febiger. p 201
HOTSTON MOORE, A. & ENGLAND, G. (2008) Rigid endoscopy: urethrocytoscopy and vaginoscopy. In BSAVA Manual of Endoscopy and Endosurgery. Eds P. Lhermette, D. Sorbel. BSAVA Publications. pp 142-157
LENNOX, A. M. (2005) Endoscopy of the distal urogenital tract as an aid in differentiating causes of urogenital bleeding in small mammals. Exotic DVM 7·2,43 -47
LONGLEY, L. A. (2008) Rodents. In Anaesthesia of Exotic Pets. Ed L. Longley. Elsevier Saunders. pp63 -66
MCCARTHY, T. C. (2005) Cystoscopy. InVeterinary Endoscopy for the Small Animal Practitioner . Ed T. C. McCarthy. Elsevier Saunders. pp 49-135
MORALES, E. (1995) History. In The Guinea Pig: Healing, Food and Ritual in the Andes. University of Arizona Press
MORRISEY, J. K. & CARPENTER, J. W. (2004) Formulary. In Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. 2nd edn. Eds K. E. Quesenberry, J. W. Carpenter. Elsevier Saunders. pp 436-444
NOWAK, R. M. (1999) Cavia. In Walker's Mammals of the World. 6th edn. John Hopkins University Press. pp1213 -1714
OKEWOLE, P. A., ODEYEMI, P. S., OLADUNMADE, M. A., AJAGBONNA, B. O., ONAH, J. & SPENCER, T. (1991) An outbreak of Streptococcus pyogenes infection associated with calcium oxalate urolithiasis in guinea pigs (Cavia porcellus). Laboratory Animals 25,184 -186[Abstract/Free Full Text]
O'ROURKE, D. P. (2004) Disease problems of guinea pigs. In Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery. 2nd edn. Eds K. E. Quesenberry, J. W. Carpenter. Elsevier Saunders. pp 245-254
PENG, X., GRIFFITH, J. W. & LANG, C. M. (1987) Cystitis and cystic calculi in aged guinea pigs. Laboratory Animal Science 34,527
PERCY, D. H. & BARTHOLD, S. W. (2001) Guinea pig. In Pathology of Laboratory Rodents and Rabbits. 2nd edn. Blackwell Publishing. pp 209-247
QUESENBERRY, K. E., DONNELLY, T. M. & HILLYER, E. V. (2004) Biology, husbandry, and clinical techniques, guinea pigs and chinchillas. In Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery. 2nd edn. Eds K. E. Quesenberry, J. W. Carpenter. Elsevier Saunders. pp 245-254
RIGGS, S. M. (2008) Guinea pigs. In Manual of Exotic Pet Practice. Eds M. A. Mitchell, T. N. Tully. Missourri, Elsevier Saunders. pp 456-473