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Also known as: '''''Urethral Calculi — Urinary Calculi'''''
==Introduction==
==Introduction==
Urolithiasis is the main cause of obstruction in the lower urinary tract. Although it occurs in both males and females, urolithiasis is '''more common in males''' due to their long, narrow urethra.
[[File:Struvite crystals dog with scale 1.JPG|200px|right|thumb|Struvite crystals (sourced from Wikipedia.org)]]
[[File:Calcium oxalate crystals in urine.jpg|200px|right|thumb|Calcium oxalate (sourced from Wikipedia.org)]]
Urolithiasis is the main cause of obstruction in the lower urinary tract. Although it occurs in both males and females, urolithiasis is '''more common in mammalian males''' due to their long, narrow urethra.
Common sites of obstruction in the different species include:
Common sites of obstruction in the different species include:
In '''birds''', the condition arises during breeding or following egg incubation. Some birds sit very tight on their eggs and fail to void their cloacal contents regularly. Urates can precipitate in the cloaca and lead to the formation of a urolith.
In '''birds''', the condition arises during breeding or following egg incubation. Some birds sit very tight on their eggs and fail to void their cloacal contents regularly. Urates can precipitate in the cloaca and lead to the formation of a urolith.
===Types of uroliths===
'''Definitions:'''
:'''Urolithiasis''' - the presence of calculi, or uroliths, in the urinary passages.
:'''Urolith''' (calculus, stone) - polycrystalline concretion of precipitated urinary solutes, urinary proteins and proteinaceous debris.
===Types of Uroliths===
'''Struvite'''
'''Struvite'''
most common urolith in small animals
:most common urolith in small animals commonly associated with '''infection''' by urease producing organisms such as [[:Category:Staphylococcus species|''Staphylococcus'']] or ''[[Proteus]]''
:more common in females due to increased susceptibility to urinary tract infections
commonly associated with infection by urease producing organisms such as ''Staphylococcus'' or ''Proteus''
:formation enhanced by the presence of alkaline urine
:struvite uroliths may contain calcium and become '''radiodense''' on radiographs
more common in females due to increased susceptibility to urinary tract infections
formation enhanced by the presence of alkaline urine
'''Calcium oxalate'''
'''Calcium oxalate'''
form due to supersaturation of urine with calcium
:form due to supersaturation of urine with calcium
:often have spine-like projections
often have spine-like projections
:markedly '''radiodense''' on radiographs
'''Urate'''
'''Urate'''
Dalmations predisposed, urolith of birds
:'''Dalmations''' predisposed, urolith of birds
:urolith associated with hepatic disease, especially [[Portosystemic Shunt|'''portosystemic shunts''']]
:'''radiolucent''' on radiographs
'''Cystine'''
'''Cystine'''
occurs with cystinuria
:occurs with cystinuria
:'''radiodense''' on radiographs, but may occasionally be radiolucent
'''Calcium carbonate'''
'''Calcium carbonate'''
occurs in horses
:occurs in horses
:'''radiodense''' on radiographs
'''Silica'''
'''Silica'''
occurs in pastured ruminants
:occurs in pastured ruminants, development may be related to diet
:'''radiodense''' on radiographs
development may be related to diet
==Clinical signs==
==Clinical Signs==
Clinical signs are due to the macroscopic uroliths in the lower urinary tract which interfere with the flow of urine or irritate the mucosal lining. This leads to signs such as: '''dysuria, stranguria and haematuria'''.
Clinical signs are due to the macroscopic uroliths in the lower urinary tract which interfere with the flow of urine or irritate the mucosal lining. This leads to signs such as: '''dysuria, stranguria and haematuria'''.
'''Nephroliths''' are often asymptomatic unless pyelonephritis develops or the stone passes into the ureter.
'''Nephroliths''' are often asymptomatic unless [[pyelonephritis]] develops or the stone passes into the ureter.
'''Ureteroliths''' may present as pain which is difficult to detect, or signs of vomiting, lethary, especially if there is distension of the renal capsule and developing hydronephrosis. Clinical signs may not be apparent unless both ureters are affected, there is contralateral chronic kidney disease, or a renal infection develops.
'''Ureteroliths''' may present as pain which is difficult to detect, or signs of vomiting, lethargy, especially if there is distension of the renal capsule and developing [[hydronephrosis]]. Clinical signs may not be apparent unless both ureters are affected, there is contralateral chronic kidney disease, or a renal infection develops.
'''Urethral obstruction''' may occur suddenly or may develop over days or weeks. There will be dysuria and stranguria, and complete obstruction leads to: depression, anorexia, vomiting, dehydration, coma and death.
'''Urethral obstruction''' may occur suddenly or may develop over days or weeks. There will be dysuria and stranguria, and complete obstruction leads to: depression, anorexia, vomiting, dehydration, coma and death.
'''Contrast studies''' include: excretory urogram for nephroliths and ureteroliths, double contrast radiography for bladder stones, retrograde urethrogram for urethroliths.
'''Contrast studies''' include: excretory urogram for nephroliths and ureteroliths, double contrast radiography for bladder stones, retrograde urethrogram for urethroliths.
'''Urinalysis''', including examination of urine, '''urine culture and sensitivity''' and cristal identification on microscopic exmination, is also indicated.
'''Urinalysis''', including examination of urine, '''urine culture and sensitivity''' and crystal identification on microscopic examination, is also indicated.
Urethral obstruction is diagnosed by palpating a distended, hard and painful bladder.
Urethral obstruction is diagnosed by palpating a distended, hard and painful bladder.
'''In birds''', cloacal urolithiasis is treated by breaking up the urolith with a pair of forceps and removing it piecemeal. Antibiotics should be administered for 3-5 days after due to the local trauma which can be caused by the removal.
'''In birds''', cloacal urolithiasis is treated by breaking up the urolith with a pair of forceps and removing it piecemeal. Antibiotics should be administered for 3-5 days after due to the local trauma which can be caused by the removal.
{{Learning
{{Learning
|flashcards = [[Avian Medicine Q&A 18]]
|flashcards = [[Feline Medicine Q&A 21]]<br>[[Avian Medicine Q&A 18]]
}}
{{Chapter}}
{{Mansonchapter
|chapterlink = http://www.mansonpublishing.co.uk/book-images/9781840761283_sample.pdf
|chaptername = Struvite stones
|book = A Colour Handbook - Urinary Stones in Small Animal Medicine
|author = Albrecht Hesse, Reto Neiger
|isbn = 9781840761283
}}
}}
==References==
Kahn, C. (2005) '''Merck veterinary manual''' ''Merck and co''
Kahn, C. (2005) '''Merck veterinary manual''' ''Merck and co''
Syme, H. (2009) '''Urogenital system: urolithiasis''' ''RVC student notes''
Syme, H. (2009) '''Urogenital system: urolithiasis''' ''RVC student notes''
{{review}}
{{OpenPages}}
[[Category:Urological Diseases - Dog]]
[[Category:Urological Diseases - Cat]]
[[Category:Urological Diseases - Horse]]
[[Category:Urological Diseases - Cattle]]
[[Category:Urological Diseases - Sheep]]
[[Category:Expert Review]]
[[Category:Lower Urinary Tract - Pathology]]
[[Category:Lower Urinary Tract - Pathology]]
[[Category:To Do - Urinary]]
[[Category:Urological Diseases - Birds]]