ACVIM Small Animal Consensus Recommendations on the Treatment and Prevention of Uroliths in Dogs and Cats PDF

ACVIM Consensus Statement J Vet Intern Med 2016;30:1564–1574 Consensus Statements of the American College of Veterinary Internal Medicine (ACVIM) provide the veterinary community with up-to-date information on the pathophysiology, diagnosis, and treatment of clinically im...

ACVIM Consensus Statement J Vet Intern Med 2016;30:1564–1574 Consensus Statements of the American College of Veterinary Internal Medicine (ACVIM) provide the veterinary community with up-to-date information on the pathophysiology, diagnosis, and treatment of clinically important animal diseases. The ACVIM Board of Regents oversees selection of relevant topics, identification of panel members with the expertise to draft the statements, and other aspects of assuring the integrity of the process. The statements are derived from evidence-based medicine whenever possible, and the panel offers interpretive comments when such evidence is inadequate or contradictory. A draft is prepared by the panel, followed by solicitation of input by the ACVIM membership which may be incor- porated into the statement. It is then submitted to the Journal of Veterinary Internal Medicine, where it is edited before publication. The authors are solely responsible for the content of the statements. ACVIM Small Animal Consensus Recommendations on the Treatment and Prevention of Uroliths in Dogs and Cats J.P. Lulich, A.C. Berent, L.G. Adams, J.L. Westropp, J.W. Bartges, and C.A. Osborne In an age of advancing endoscopic and lithotripsy technologies, the management of urolithiasis poses a unique opportu- nity to advance compassionate veterinary care, not only for patients with urolithiasis but for those with other urinary dis- eases as well. The following are consensus-derived, research and experience-supported, patient-centered recommendations for the treatment and prevention of uroliths in dogs and cats utilizing contemporary strategies. Ultimately, we hope that these recommendations will serve as a foundation for ongoing and future clinical research and inspiration for innovative problem solving. Key words: Calcium Oxalate; Lithotripsy; Stent; Struvite. or the past century, treatment for urolithiasis in Methodology F dogs and cats has been the province of the surgeon, but with the advent of new technologies, urolith man- A panel of 6 specialists convened to formulate recom- agement is evolving. Several minimally invasive proce- mendations by constructing common clinical scenarios dures are performed daily in veterinary hospitals of dogs and cats with uroliths paired with suitable con- around the world. Not all management strategies are temporary management strategies. The panelists were suitable for every patient or every situation. The chal- from different veterinary institutions around the country lenge for clinicians is to move beyond traditional surgi- with various experiences and skill sets, although all are cal care and consider less invasive alternatives. For well versed in the management of urolithiasis. Each clients to be properly educated and informed of their panelist cast an independent vote as to the appropriate- options, clinicians must understand these options and ness of the strategy. The panelists then met to conduct their associated indications and risks. an iterative group discussion to reach consensus. Dur- ing this discussion, the treatment decision for each clini- cal scenario was debated with the assumption that urolithiasis was the patient’s primary problem. The committee recognized that not all veterinary care facili- ties have the technology or expertise to perform all min- From the Department of Veterinary Clinical Sciences, University imally invasive procedures. This issue was not of Minnesota, Saint Paul, MN (Lulich); The Animal Medical Center, New York, NY (Berent); the Department of Veterinary considered in the panelists’ treatment decision; treat- Clinical Sciences, Purdue University, West Lafayette, IN (Adams); ment decisions were selected in the patient’s best inter- the Department of Veterinary Medicine and Epidemiology, est as if all options were available. The committee University of California, Davis, CA (Westropp); the Department of recognized that cost and willingness to travel to centers Small Animal Medicine and Surgery, University of Georgia, Athens, of expertise affect treatment choices, but the panelists GA (Bartges); and the Department of Veterinary Clinical Sciences, did not include these variables in proposing a standard University of Minnesota, Saint Paul, MN (Osborne). Corresponding author: J.P. Lulich, Department of Veterinary of care. The committee recognized that exceptions to Clinical Sciences, University of Minnesota, Saint Paul, MN 55108; each recommendation always will exist, especially dur- e-mail: [email protected] ing emergency presentations. Therefore, the committee Submitted June 16, 2016; Revised July 8, 2016; Accepted made its decisions on the assumption that any unex- July 11, 2016. pected emergency situation would be sufficiently stabi- Copyright © 2016 The Authors. Journal of Veterinary Internal lized before urolith management. Medicine published by Wiley Periodicals, Inc. on behalf of the Ameri- It was requested that treatment justifications be sup- can College of Veterinary Internal Medicine. This is an open access article under the terms of the Creative ported by published research evidence when available. Commons Attribution-NonCommercial License, which permits use, If published research was not available, then the pan- distribution and reproduction in any medium, provided the original elists used research available from human medicine, as work is properly cited and is not used for commercial purposes. well as clinical expertise and experience. After the DOI: 10.1111/jvim.14559  19391676, 2016, 5, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/jvim.14559 by INASP/HINARI - INDONESIA, Wiley Online Library on [24/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Uroliths in Dogs and Cats 1565 iterative group discussion, a consensus recommendation with alkaline urine and a urinary tract infection caused was formulated. This recommendation was followed by by urease-producing bacteria (such as Staphylococcus a final vote of acceptance. Therefore, the panelists’ col- spp), and moderately radiopaque uroliths in cats with lective personal experiences and interpretations of the approximately neutral urine pH) should be medically published data constitute the basis for these guidelines. dissolved unless (1) medications or dissolution foods The guidelines are divided into 3 sections: treatment cannot be administered or are contraindicated, (2) the of lower tract (bladder and urethra) uroliths, treatment uroliths cannot be adequately bathed in modified urine of upper tract (kidney and ureter) uroliths, and urolith (eg, urinary obstruction, large solitary urocystoliths prevention (regardless of location). It was not the com- occupying almost all of the urinary bladder), or (3) mittee’s goal to address every urolith type or combina- uncontrollable infection despite appropriate medical tion of precipitating minerals, but to provide sufficient management and owner compliance. Most struvite cys- recommendations for the more common uroliths man- toliths can be safely dissolved with minimal risk, includ- aged in practice. The less common clinical situations ing urinary obstruction (Table 1). could be adequately addressed by extrapolation of a Rationale: Medical dissolution for both sterile and combination of this consensus statement, as well as by infection-induced struvite uroliths is highly effective and referring to the literature that has been published avoids the risks and complications of anesthesia and previously. surgery. In many cases, dissolution is less expensive than surgery. Sterile struvite urocystoliths usually dis- Part 1 solve in less than 2–5 weeks.1–6 Standards of Care for Dogs and Cats with Lower Avoiding cystotomy and closure of the bladder with Urinary Tract Uroliths sutures will eliminate the risk of suture-induced uro- lith recurrence, which may be responsible for up to Recommendation 1.1: Struvite Uroliths should be Med- 9% of urolith recurrences.7,8 Although some believe ically Dissolved. Uroliths consistent with a composition that medical dissolution places the patient at high risk of struvite (ie, moderately radiopaque uroliths in dogs for urethral obstruction, this complication has not Table 1. Summary of consensus recommendations for the treatment and prevention of uroliths in dogs and cats. Recommendation 1.1: Struvite uroliths should be medically dissolved Recommendation 1.2: Urocystoliths associated with clinical signs should be removed by minimally invasive procedures Recommendation 1.2a Consider medical dissolution of urate uroliths before removal Recommendation 1.2b Consider medical dissolution of cystine uroliths before removal Recommendation 1.3: Nonclinical urocystoliths unlikely to cause urinary obstruction do not require removal Recommendation 1.4: Nonclinical urocystoliths likely to cause urinary obstruction should be removed by minimally invasive procedures Recommendation 1.5: Urethroliths should be managed by intracorporeal lithotripsy and basket retrieval Recommendation 1.6: Urethral surgery to manage urolithiasis is discouraged Recommendation 2.1: Only problematic nephroliths require treatment Recommendation 2.2: Struvite nephroliths should be medically dissolved Recommendation 2.3: Dissolution should not be attempted in cats with obstructive upper urinary tract uroliths Recommendation 2.4: Problematic nephroliths should be removed by minimally invasive procedures Recommendation 2.5: Hydronephrosis and hydroureter proximal to an obstructive lesion are sufficient to diagnose ureteral obstruction Recommendation 2.6: Ureteral obstructions require immediate care Recommendation 2.7: Medical treatment for obstructive ureterolithiasis is rarely effective, consider minimally invasive removal Recommendation 2.8: Obstructive ureteroliths in cats should be managed by subcutaneous ureteral bypass or ureteral stenting Recommendation 2.9: Obstructive ureteroliths in dogs should be managed by ureteral stenting Recommendation 2.10: Ureterolith composition will affect management decisions Recommendation 2.11: Routinely culture urine of dogs with ureteral obstruction and consider antimicrobial treatment Recommendation 3.1: Prevent sterile struvite uroliths by feeding therapeutic maintenance foods with low magnesium and phosphorus that acidify urine Recommendation 3.2: Primary prevention of infection-induced struvite uroliths is persistent elimination of urinary tract infection Recommendation 3.3: To minimize calcium oxalate urolith recurrence, decrease urine concentration, avoid urine acidification, and avoid diets with excessive protein content Recommendation 3.3a: Feeding high-sodium dry foods should not be recommended as a substitute for high-moisture foods Recommendation 3.3b: Consider potassium citrate or other alkalinizing citrate salts for dogs and cats with persistently acidic urine Recommendation 3.3c: Consider thiazide diuretics for frequently recurrent calcium oxalate uroliths Recommendation 3.4: To minimize urate urolith recurrence, decrease urine concentration, promote alkaline urine, and limit purine intake Recommendation 3.4.A: Consider xanthine oxidase inhibitors for dogs homozygous for genetic hyperuricosuria that have failed therapeutic diet prevention Recommendation 3.5: To minimize cystine urolith recurrence, decrease urine concentration, limit animal protein intake, limit sodium intake, increase urine pH, and neuter Recommendation 3.5.A: In recurrent cystine urolith formers, add 2-mercaptopropionylglycine (tiopronin, Thiola) to previously recommended prevention strategies to further lower cystine concentration and increase cystine solubility  19391676, 2016, 5, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/jvim.14559 by INASP/HINARI - INDONESIA, Wiley Online Library on [24/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 1566 Lulich et al been reported in the veterinary literature and is likely 15 mg/kg PO q12 h).14,15 In 1 study, medical dissolu- to occur with the same frequency or less frequently tion was effective in approximately 40% of Dalmatians, than when attempts at surgical removal are partial dissolution occurred in approximately 30%, and incomplete.1–6 no dissolution occurred in approximately 30%.16 Disso- Recommendation 1.2: Urocystoliths Associated with lution has not been possible in dogs and cats with Clinical Signs should be Removed by Minimally Invasive uncorrected liver disease (ie, hepatic porto-vascular Procedures. Urocystoliths small enough to pass through shunt). There are no data for the dissolution of urate the urethra should be removed by medical dissolution, uroliths in cats. voiding urohydropropulsion, basket retrieval, or other Recommendation 1.2b: Consider Medical Dissolution extraction procedures that do not involve surgical of Cystine Uroliths before Removal. Cystine uroliths intervention. form, in part, because of the decreased proximal tubu- Rationale: Incision-less procedures are associated with lar reabsorption of cystine. Dissolution is achieved by shorter hospitalization, shorter anesthesia time, and fas- increasing cystine solubility and may be attempted in ter patient recovery. Avoiding cystotomy and closure of dogs unless (1) medications or dissolution foods cannot the bladder with sutures will eliminate the risk of be administered or tolerated or (2) the urolith cannot suture-induced urolith recurrence, which may be a pri- be adequately bathed in modified urine (eg, urinary mary causal factor in approximately 9% of recurrent obstruction, urethroliths). urocystoliths.7,8 Rationale: In 1 study performed on cystinuric dogs, Urocystoliths too large to pass through the urethra the consumption of a decreased protein, urine-alkalinizing, should be removed by medical dissolution, intracor- canned fooda resulted in a 20–25% decrease in 24-hour poreal laser lithotripsy, or percutaneous cystolitho- urine cystine excretion compared with a canned mainte- tomy instead of cystotomy. The committee recognizes nance food.17 This same food with the addition of 2- that the urethras of small male dogs (eg, Yorkshire mercaptopropionylglycine (Thiolaâ, tiopronin) at a terriers, Maltese, Chihuahua) and almost all male dosage of 15–20 mg/kg PO q12 h successfully dissolved cats may be too narrow to accommodate currently cystine stones in 18 of 18 episodes.17 Cystine solubility available cystoscopes, and the selection of which mini- increases with increasing urine pH.18 In vitro studies mally invasive procedure to perform will depend on that achieved a urine pH > 7.5 increased the efficacy of urolith type, experience of the operator, availability of thiol-binding drugs to solubilize cystine in the urine equipment, urolith burden, and appropriateness of from cystinuric humans.19 Therefore, potassium citrate the patient to undergo a second procedure to com- or other alkalinizing salts should be administered to pletely clear the lower urinary tract of uroliths, if dogs and cats with persistently acidic urine. The dosage needed. should be gradually increased to achieve a urine pH of Rationale: Minimally invasive procedures are associ- approximately 7.5, if possible. Studies showed that the ated with shorter hospitalization, and perceived fewer administration of 2-mercaptopropionylglycine without adverse effects, fewer residual stones because of modifying the diet is associated with dissolution.17,20 improved visualization, and possibly lower stone recur- Dissolution should be attempted cautiously in cats rence rates compared to surgical cystotomy.9–13 because of their perceived intolerance of 2-mercaptopro- Recommendation 1.2a: Consider Medical Dissolution pionylglycine. of Urate Uroliths before Removal. Hyperuricosuria, con- In some forms of cystinuria, neutering has been asso- centrated urine, and acidic urine are the predominant ciated with the decreases in urine cystine concentration factors driving urate urolith formation. In most dogs as the result of a potential androgen-dependent effect, and cats, uric acid, an intermediate product of purine but this is not universal.21 This uncertainty raises the metabolism, is transported to the liver where it is fur- question of whether or not neutering alone will result in ther metabolized by intracellular hepatic uricase to urolith dissolution, or whether the combination of neu- allantoin, an innocuous nitrogenous compound with rel- tering and cystotomy is a medically economical atively high water solubility. A defective uric acid trans- approach for intact dogs with cystine uroliths. porter (ie, SLC2A9 genetic mutation) and hepatic Recommendation 1.3: Nonclinical Urocystoliths porto-vascular anomalies have been identified as com- Unlikely to Cause Urinary Obstruction do not Require mon causes for hyperuricosuria and subsequent urate Removal. Dogs and cats without clinical signs but with urolithiasis. However, for some animals, especially cats, nondissolvable uroliths too large to pass into the ure- the cause for hyperuricosuria and urate urolith forma- thra or too irregular to cause urethral obstruction tion remains idiopathic. Dissolution may be attempted need only periodic monitoring and appropriate client for urate uroliths unassociated with liver disease unless education. With the onset of clinical signs (eg, hema- (1) medications or dissolution foods cannot be adminis- turia, dysuria, urinary tract infection [UTI]), urolith tered or tolerated, or (2) the urolith cannot be ade- removal should be considered. Imaging modalities quately bathed in modified urine (eg, urinary including ultrasonography and radiology should be obstruction, urethroliths). performed to assess urolith size and position as well as Rationale: Dissolution of urate uroliths in dogs usu- to predict mineral composition, as needed. Increasing ally is accomplished within 4 weeks by feeding a stone size may limit the type of minimally invasive purine-restricted, alkalinizing, diuretic diet,a and admin- procedure that can be performed for future stone istration of a xanthine oxidase inhibitor (ie, allopurinol: removal.  19391676, 2016, 5, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/jvim.14559 by INASP/HINARI - INDONESIA, Wiley Online Library on [24/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Uroliths in Dogs and Cats 1567 Rationale: Watchful waiting minimizes unnecessary clients to access minimally invasive care, urethral stric- intervention, especially for urolith types that are highly ture where alternative interventions are not an recurrent (eg, calcium oxalate, cystine, urate).22 Client option).25–27 education about the clinical signs of urinary obstruction is essential so that clients seek timely and appropriate care in the event of obstruction. Part 2 Recommendation 1.4: Nonclinical Urocystoliths Likely Standard of Care for Dogs and Cats with Upper to Cause Urinary Obstruction should be Removed by Urinary Tract Uroliths Minimally Invasive Procedures. Animals without clinical signs diagnosed with smooth uroliths that have a high Recommendation 2.1: only Problematic Nephroliths likelihood of urethral obstruction (ie, diameter approxi- Require Treatment. Only those nephroliths contributing mating the diameter of the urethral lumen) should have to outflow obstruction, recurrent infection, pain, and their uroliths removed or dissolved. those enlarging to the point of causing renal parenchy- Rationale: Urolith removal is indicated as a precau- mal compression, should be considered for removal in tion in patients that are likely to succumb to life- dogs and cats. Dissolution only should be considered threatening urinary obstruction so that careful medical for nonobstructive nephroliths or if the obstruction can intervention can be implemented at the time of diagno- be concomitantly alleviated or bypassed (eg, urethral sis as opposed to less carefully planned removal on an stenting). emergency basis. To minimize patient discomfort and Rationale: The presence of nephroliths in cats with unnecessary damage to healthy tissues, nonsurgical chronic kidney disease did not significantly affect the removal methods (eg, dissolution, basket retrieval, progression of renal disease, and the same has been lithotripsy, percutaneous cystolithotomy) should be observed clinically in dogs.13,28 considered. Recommendation 2.2: Struvite Nephroliths should be Recommendation 1.5: Urethroliths should be Man- Medically Dissolved. Nephroliths and ureteroliths con- aged by Intracorporeal Lithotripsy and Basket sistent with a composition of struvite (ie, moderately Retrieval. Whether causing urethral obstruction or not, radiopaque uroliths in a dog with alkalinuria and a uri- urethroliths are quickly and safely managed by intracor- nary tract infection with urease-producing bacteria poreal lithotripsy and basket retrieval. (such as Staphylococcus spp.) should be medically dis- Rationale: Intracorporeal lithotripsy was 100% effec- solved. When ureters are obstructed, they should be tive in the removal of urethroliths.23 The median time stented to (1) improve kidney function, (2) allow medi- to complete initial evaluation, urethrolith removal, and cated urine to reach the ureterolith, (3) allow antimicro- postprocedural radiography was 36 minutes in dogs; no bial access to eradicate bacteriuria, and (4) allow dog experienced adverse events. The committee recog- evacuation of bacteria and inflammatory debris. Treat- nizes that the urethra of small male dogs and most male ment for other nephroliths potentially amenable to dis- cats may be too narrow to accommodate appropriate solution (eg, cystine, purine) should be addressed on a cystoscopes to manage urethroliths by minimally inva- case-by-case basis considering the stability of kidney sive procedures. In these situations, urethroliths can be function and the likelihood of complete removal or urohydropropulsed retrograde back into the bladder dissolution. and retrieved by percutaneous cystolithotomy or Rationale: Approximately 20–30% of upper urinary cystotomy.24 tract uroliths in dogs are suspected to be struvite for Recommendation 1.6: Urethral Surgery to Manage which dissolution should be effective. Rapid control of Urolithiasis is Discouraged. Urethrotomy and urethros- infection while avoiding surgical urolith extraction tomy are salvage procedures that may result in perma- should maximally preserve kidney function.b ,29 Dissolu- nent alterations in the anatomy and function of the tion requires that uroliths be bathed in appropriately urethra. Urethroliths should be repositioned (retrograde medicated urine that is undersaturated for struvite. urohydropropulsion) into the urinary bladder and Obstructive uroliths are not surrounded by appropriate removed by minimally invasive procedures (eg, frag- urine conditions unless a ureteral stent is placed mented in the urethra by laser lithotripsy) and retrieved concurrently.b,30 (by voiding urohydropropulsion, basket retrieval or per- Recommendation 2.3: Dissolution Should not be cutaneous cystolithotomy if possible). Urethrostomy Attempted in Cats with Obstructive Upper Urinary Tract can be considered to minimize future urethral obstruc- Uroliths. Rationale: Over 90% of nephroliths and ure- tion in highly recurrent stone-forming animals. Rigid teroliths in cats are composed primarily of calcium oxa- adherence to strategies to prevent urolith recurrence, late. Calcium oxalate uroliths are not amenable to however, should be considered first. medical dissolution. Delaying appropriate care may Rationale: Because of the high frequency of morbidity contribute to an irreversible decrease in kidney and adverse effects associated with urethral surgery (eg, function.31–33 stricture, urine leakage, recurrent UTI, hemorrhage), Recommendation 2.4: Problematic Nephroliths should be urethral surgeries are discouraged except under few cir- Removed by Minimally Invasive Procedures. Nephroliths cumstances that go beyond the recommendations of should be removed by (1) dissolution, (2) endoscopic sound medical judgment (eg, client inability to afford nephrolithotomy (ie, for nephroliths too large for extra- additional care with recurrent obstruction, inability for corporeal shock wave lithotripsy and for nephroliths in  19391676, 2016, 5, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/jvim.14559 by INASP/HINARI - INDONESIA, Wiley Online Library on [24/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 1568 Lulich et al cats), and (3) extracorporeal shockwave lithotripsy (for Rationale: Experimental ureteral occlusion in healthy nephroliths in dogs only).c dogs is associated with a rapid and lasting decrease in Rationale: Minimally invasive urolith removal is less renal function. A 35% permanent decease in glomerular likely to adversely affect glomerular filtration filtration rate was noted after 7 days, 54% after rate. Extracorporeal shockwave lithotripsy has minimal 14 days and 100% after 40 days, but some studies sup- effects on renal function, but is reserved for nephroliths port a return to normal function after 150 days.38–41 ≤1.5 cm in diameter. Nephroliths >1–1.5 cm often Evidence-based data over the past 6 years support that require concurrent ureteral stent placement.34,35 In interventional procedures, such as ureteral stents and human medicine, endoscopic nephrolithotomy is the subcutaneous ureteral bypass, have a lower morbidity most effective minimally invasive treatment option for and mortality rate for ureteral obstruction than do tra- large stone burdens and has the highest stone-free rate ditional surgical options in both dogs and cats, respec- when compared to alternative therapies.35 Endoscopic tively.b,30,33,42–47 Referral should be considered nephrolithotomy has been successfully performed in whenever possible for each patient if minimally invasive dogs and cats.36 options cannot be performed locally. In animal models, Recommendation 2.5: Hydronephrosis and Hydroureter renal function was maximized by relieving the obstruc- Proximal to an Obstructive Lesion are Sufficient to Diag- tion of any functional kidney after it was partially nose Ureteral Obstruction. A diagnosis of a ureteral obstructed for >8 weeks.48,49 Over 80–90% of ureteral obstruction should be based on ultrasonographic find- obstructions in cats are considered partial based on ings of hydronephrosis and associated hydroureter antegrade ureteropyelography.33 proximal to an obstructive ureterolith regardless of Data currently are not available to determine the the degree of the renal pelvic dilatation. If renal pel- amount of renal function that may return after the vic dilatation is 25% of been found to predict the extent of renal recovery after cats). decompression; the majority of kidneys seem to recover Antegrade contrast pyelography is not necessary for well.43 the diagnosis of ureteral obstruction if an obstructive Recommendation 2.7: Medical Treatment for Obstruc- ureterolith is seen at the distal termination of hydrour- tive Ureterolithiasis is Rarely Effective, Consider Mini- eter. Likewise, advanced imaging studies such as com- mally Invasive Removal. Medical management of stable puterized tomography and intravenous pyelography in obstructive ureterolithiasis can be considered for 24– patients with suspected ureteral obstruction do not typi- 72 hours. However, clients should be informed of the cally provide more clinical information than that high rate of medical failure. Medical treatment should obtained from the combination of ultrasound examina- include fluid diuresis and mannitol continuous rate infu- tion and survey radiographs. sion treatment, if tolerated. Alpha adrenergic antago- Rationale: In a study evaluating the causes of nists and tricyclic antidepressants also have been used hydronephrosis, all renal pelves >13 mm were associ- with anecdotal reports of improvement in some cases ated with ureteral obstruction and those >7 mm were and can be considered if not contraindicated. Medical likely associated with ureteral obstruction. Many treatment should not be continued in animals that are