Introduction
Urine retention is defined as inability of animal to empty its bladder which may be partial or complete. Multiple causes including calculi, neoplasms, strictures and atony of bladder may result in urine retention. Obstructive urolithiasis is the most common urinary tract disease in breeding rams and goats (Radostits et al., 2007). The urethral occlusion due to calculi is more common in males than females due to more length of urethra (Samal et al., 2011). 

There are different types of urine stones including struvite, calcium oxalate, calcium carbonate, calcium phosphate, silica, uric acid, cystine and tyrosine crystals (Samal et al., 2011). Alkaline pH (pH>8.0) of the urine favors the formation of phosphate, carbonate and struvite calculi while acidic urine (pH<7.0) predisposes the animal to urate and silicate calculi (Pugh, 2002). 
 
Urolithiasis is diagnosed on the basis of careful history, clinical signs and physical examination. The history must include diet history, water intake, water mineral contents, previous problem and duration of the problem. The urine analysis may also indicate presence of crystals, change in pH (acidic or alkaline) and change in color of the urine (Pugh, 2002). 

Even though almost all the calculi are amenable to surgical intervention, in a considerable proportion of operated animals, post-surgical complications like urethral stricture (Samal et al., 2011; Kinjavdekar et al., 2005) may ensue. Treatment with antispasmodics and tranquilizers leading to relaxation of retractor penis muscles with straightening of the sigmoid flexure is useful only in a few cases (Radostits et al., 2007). Dictated by the pH of the urine, urinary acidifiers (e.g. ammonium chloride) or urinary alkalizers (e.g. sodium bicarbonate) can be used to treat urinary calculi (Samal et al., 2011). Animals with urate crystals and urate calculi are candidate for treatment with allopurinol (Bishop, 2008). Reports on the use of this agent are extremely scanty. The present communication describes the successful treatment of urate associated urolithiasis in 2 sacrificial bucks with allopurinol.
 
Case No. 1
A 2 ½ years old sacrificial buck of beetle breed weighing 80 kg was presented to Veterinary Teaching Hospital (VTH), Dept. of Clinical Medicine and Surgery, Faculty of Veterinary Science, University of Agriculture, Faisalabad, Pakistan with a primary complaint of urine retention of three days standing.
 
At the start, there was dribbling of urine indicated that the retention was partial. Then on the advice of some local healer, the owner gave ammonium chloride (25 gm, per os) which resulted in complete retention of the urine. The buck was being fed with 4~5 kg chickpea along with concentrate (1~2 kg) and wheat straw (5~6 kg) per day. It was tethered and provided with water twice a day. There was reduction in feed and water intake accompanied by depression. Prior to referral, the buck had previously been treated by excision of urethral process, medicated with diazepam and ammonium chloride but to no avail.
 
At the time of presentation to VTH, the animal was depressed and standing with its head down. Ventral side of the abdomen was swollen due to distention of urinary bladder. Other signs observed were treading of hind feet, twitching of tail and restlessness. On close physical examination, a firm mass at the level of sigmoid flexure accompanied by swelling and pain was detected. The hairs at prepuce were dry along with adhered whitish crystals. Readings of rectal temperature, respiration and pulse rates were 39.2℃, 26 breaths per minute accompanied by dyspnea and 96 beats per minute, respectively.
 
A diagnosis of urolithiasis was reached on the basis of composite of history and clinical signs. The history reflected that the animal was medicated with a urine acidifier ammonium chloride (25 gm, per os) which resulted into complete obstruction of urine outflow, so the urolithiasis was due the crystals more common in acidic pH.
 
Allopurinol (Zyloric^® GSK, Ltd. Pakistan) was administered @10 mg/kg of body weight per os, bid for 3 days, along with Ketoprofen (Leads Pharma^®, Ltd. Pakistan) @ 3 mg/kg of body weight I/M, sid. The animal started urination 3 hours after the first dose of medication and completely recovered after treatment of 3 days. 
 
Case No.2
A 12 months old sacrificial buck (cross of beetle and teddy) weighing about 35 kg was presented to VTH, Dept. of Clinical Medicine and Surgery, University of Agriculture, Faisalabad, Pakistan, with a primary complaint of dysuria and partial retention of urine 1 day standing.
 
The animal was kept tethered along with 2 animals of same species. It was managed on 2.5 kg concentrates and 2 kg chickpea along with 3~4 kg green fodder (Alfalfa) per day. After the beginning of this problem, the animal was drenched with lassi (considered as diuretic) but it did not show any response. There was no other previous medication history.
 
The clinical signs observed were restlessness, vocalization, reluctance to move and depression. There were no adhered crystals around prepuce and no painful swelling could be detected on palpation of the urethra. The parameters (rectal temperature: 39.4℃, respiration: 32 bpm and pulse rate: 86 per min.) were recorded. Few drops of urine were collected for urine analysis.
 
A clinical diagnosis of urate associated urolithiasis was reached on the basis of history, physical examination and urine analysis (Table 1). 
 

Table 1 Urine analysis* before and after treatment with allopurinol

 
The buck was treated by using allopurinol (Zyloric^® GSK, Ltd.) @ 10 mg/kg of body weight PO, bid in combination with Ketoprofen (Leads Pharma^®, Ltd. Pakistan) @ 3 mg/kg of body weight I/M, sid for 3 days.
 
After 8 hours of the start of treatment, the buck voided urine without any difficulty but the color of urine was still whitish yellow. The animal recovered completely after treatment of 3 days. The urine was again analyzed after the recovery (Table 1).
 
Discussion
Obstructive urolithiasis is the most common urinary tract disease in breeding rams and goats (Radostits et al., 2007). The urethral occlusion due to calculi is more common in males than females due to more length of urethra (Samal et al., 2011). 
 
In this study, both the cases of bucks were being fed with high amount of protein diet. The animals were kept for fattening and the ration was not balanced (comprised of high protein contents). Goats are more commonly affected by the urolithiasis followed by cattle, cats and dogs (Samal et al., 2011). The animals are at high risk of developing urolithiasis fed on high grain diets with roughly 1:1 calcium to phosphorous ratio, high magnesium contents in diet and high mineral level in the drinking water (Kahn, 2005; Radostits et al., 2007).
 
The specific type of crystals depends upon the nature of diet and chemical composition like pH of the urine (Samal et al., 2011). Alkaline pH (pH>8.0) of the urine favors the formation of phosphate, carbonate and struvite calculi while acidic urine (pH<7.0) predisposes the animal to urate and silicate calculi (Pugh, 2002). One of the treated animals had a history of ammonium chloride administration, a known urine acidifier (Samal et al., 2011) while in case of other animal, pH of the urine was acidic (pH=5.8) which showed that there was problem of calculi common in acidic urine, and presence of urate crystals (hexagonal, barrels, rosettes in shape and amber in color) in urine further confirmed urate associated urolithiasis (Pugh, 2002).
 
There are few approaches to handle the urolithiasis like surgical methods and use of different medicines. Surgical approaches may involve excision of urethral process, urethrotomy and bladder marsupialization but these may be followed by many complications (Kahn, 2005; Kinjavdekar et al., 2005; Samal et al., 2011). Allopurinol was used to treat the urinary calculi found in acidic urine as depicted by the history and urine analysis. Oxypurines are converted into uric acid (urate crystals) in the presence of an enzyme xanthine oxidase leading to obstruction of the urine outflow if lodged in the urinary tract. Allopurinol and its metabolite (oxypurinol) inhibit the enzyme xanthine oxidase (Plumb, 2008) result into decreased production of uric acid. The fallouts in both of the cases were successful and the animals recovered after treatment.
 
Conclusion
This manuscript suggested that the clinician may found uroliths in small ruminant’s urine which are normally present in acidic urine and these can be successfully treated by using allopurinol and ketoprofen.
 
References
Bishop Y., 2008, The veterinary formulary, 6^th Ed., Pharmaceutical Press, London, U.K.
 
Kahn C.M., 2005, The merck veterinary manual, 10^th Ed., Merck Sharp & Dohme Corp., A subsidiary of Merck & Co., Inc., N.J, USA 
 
Kinjavdekar P., Amarpal, H.P. Aithal, A.M. Pawde, K. Partap, T. Singh, and K. Singh, 2005, Management of urolithiasis in goats (Capra hircus)-A retrospective study of 25 cases, Indian J. Anim. Res., 39 (1): 8-13 
 
Plumb D.C., 2008, Plumb’s Veterinary Drug Handbook, 6^th Ed., Blackwell Publishing Professionals, Ames, Iowa, UAS
 
Pugh D.G., 2002, Sheep and Goat Medicine, 1^st Ed. Elsevier Publishing Co., Philadelphia, USA 
 
Radostits O.M., C.C. Gay, K.W. Hinchchlif, and P.D. Constable, 2007, Veterinary Medicine; A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses, 10th Ed. Elsevier Publishing Co., London 
 
Samal L., A.K. Pattanaik, C. Mishra, B.R. Maharana, L.N. Sarangi, and R.K. Baithalu, 2011, Nutritional strategies to prev- ent urolithiasis in animals, Veterinary World 4(3): 142-144
http://dx.doi.org/10.5455/vetworld.2011.142-144