Removal of lower urinary tract stones by percutaneous cystolithotomy: 68 cases (2012-2017).

OBJECTIVE: To describe the use and outcome of percutaneous cystolithotomy (PCCL) for removal of urethral and bladder stones in dogs and cats. STUDY DESIGN: Retrospective case series. ANIMALS: Sixty-eight client-owned dogs and cats. METHODS: Records were reviewed and analyzed for dogs and cats that underwent PCCL between January 2012 and December 2017. Signalment, clinical presentation, laboratory and imaging data, procedure time, use of lithotripsy, biopsy, perioperative and immediate postoperative complications, hospitalization times, stone composition, and urine culture results were recorded. Owners were contacted by phone or email 3 weeks after the procedure. Follow-up communications with the owner and referring veterinarian were also recorded. RESULTS: Seventy percutaneous cystolithotomies were performed in 59 dogs and nine cats. The median duration of the procedure was 95 minutes (45-420), and lithotripsy was required in 3% (2/70) of PCCL. Complications during the procedure were reported in one case. In eighty-three percent of procedures (58/70), animals were discharged within 24 hours postoperative. Twenty-four percent (16/68) of animals had minor complications (lower urinary tract signs), and one dog had a major complication (surgical wound dehiscence) during the 3 weeks after the operation. Long-term follow-up revealed stone recurrence in 21% of cases followed more than a year after the procedure (7/33). CONCLUSION: Percutaneous cystolithotomy allowed removal of bladder and urethral stones with rapid postoperative recovery and few major perioperative or short-term postoperative complications. CLINICAL SIGNIFICANCE: Percutaneous cystolithotomy provides an attractive minimally invasive surgical alternative for removal of lower urinary tract stones in small animals.

Radiographic features of suspected suture-associated cystic calculi in dogs.

This retrospective case series describes the radiographic features of suspected suture-associated cystic calculi in six dogs with a history of at least one or multiple prior cystotomies. One of the dogs presented twice. Suspected suture-associated cystic calculi were multifocal, short, predominantly linear mineral opacities localized in the center of the urinary bladder on abdominal radiographs. One patient (n = 1) presented with multifocal round, pin point, and linear radiopaque calculi. The calculi were all calcium oxalate in composition. On gross examination, the calculi had a hollow center. Six cystotomies used monofilament absorbable suture material (polydioxanone [n = 4] or poliglecaprone 25 [n = 1]) in prior cystotomies. Suture material in two of the cases was unknown. Suspected suture-associated cystic calculi are a rare occurrence in veterinary medicine but should be considered in dogs that have a history of prior cystotomy, hollow core on gross analysis, and radiographic evidence of mineral opaque, predominantly linear, cystic calculi.

Evaluation of a dry therapeutic urinary diet and concurrent administration of antimicrobials for struvite cystolith dissolution in dogs.

BACKGROUND: Struvite urolithiasis with bacterial urinary tract infection (UTI) is commonly reported in dogs; few data exist to describe successful dissolution protocols in dogs with naturally occurring disease. We hypothesized that a dry therapeutic urinary diet combined with targeted antimicrobial therapy can effectively dissolve presumptive struvite cystolithiasis in dogs with naturally occurring urease-producing bacterial UTI. RESULTS: Ten dogs with presumed infection-induced struvite cystolithiasis based on lower urinary tract signs (LUTS), radiodense cystoliths, and urease-producing bacterial UTI were enrolled. At enrollment, antimicrobials and dry therapeutic urinary diet were dispensed. In addition to lack of radiographic resolution of urolithiasis, dogs with persistent clinical signs were considered non-responders. There was no significant difference in pH between responders and non-responders; USG was significantly higher in the responder group. Recheck visits continued until radiographic dissolution or failure was documented. Five of the 10 dogs achieved radiographic dissolution of cystolithiasis within a median of 31 days (range 19-103). In the other 5 dogs, surgical urolith removal was necessary due to persistent LUTS (3 dogs within 2 weeks) or lack of continued dissolution noted radiographically (1 dog with numerous cystoliths failed at day 91; 1 dog failed by day 57 with questionable owner compliance). CONCLUSIONS: Dissolution of urinary tract infection induced struvite cystoliths can be accomplished in some dogs fed this dry therapeutic urinary diet in conjunction with antimicrobial therapy. Case selection could increase the likelihood of successful dissolution; however, if calcium phosphate is present, this could also prevent stone dissolution. If clinical signs persist despite diet and antimicrobials, stone removal is advised.

Evaluation of 21 426 feline bladder urolith submissions to the Canadian Veterinary Urolith Centre (1998-2014).

This study reports emerging trends in feline urolithiasis in Canada during the past 16.8 y, evaluates associations of breed and gender with urolith types, and reports on feline submissions from outside of Canada. Struvite and calcium oxalate uroliths comprised > 90% of all uroliths submitted. In cats, oxalate submissions outnumbered struvite submissions from Canada, Hong Kong, Denmark, and the United Arab Emirates, while Australian struvite submissions outnumbered calcium oxalate submissions. In Canada, the majority of urolith submissions were from domestic cats followed by Himalayan, Persian, and Siamese cats. Males were more likely to form calcium oxalate uroliths and females were more likely to develop struvite uroliths. Compared to domestic short-haired cats, Tonkinese, Burmese, Devon rex, Himalayan, Persian, and Siamese cats were significantly associated with calcium oxalate urolith submission. Egyptian mau, Birman, ocicat, and Siamese breeds were over-represented amongst urate submissions.

Évaluation de 21 426 soumissions d'urolithes de vessie au Centre canadien d'urolithes vétérinaires (1998­2014). Cette étude présente un rapport sur les tendances émergentes pour l'urolithiase féline au Canada pendant les 16,8 dernières années, évalue les associations avec la race et le sexe pour les types d'urolithes et établit un rapport sur les soumissions félines provenant de l'extérieur du Canada. Les urolithes de struvite et d'oxalate de calcium représentaient > 90 % de tous les urolithes soumis. Chez les chats, les soumissions d'oxalate étaient supérieures aux soumissions de struvite pour les échantillons provenant du Canada, de Hong Kong, du Danemark et des Émirats arabes unis, tandis que les soumissions de struvite provenant de l'Australie étaient supérieures aux soumissions d'oxalate de calcium. Au Canada, la majorité des soumissions d'urolithes provenaient de chats domestiques suivis des chats himalayens, persans et siamois. Il était plus probable que les mâles aient des urolithes d'oxalate de calcium et il était plus probable que les femelles développent des urolithes de struvite. Comparativement aux chats domestiques à poil court, les chats tonkinois, burmese, Devon rex, himalayens, persans et siamois présentaient une association importante avec une soumission d'urolithes d'oxalate de calcium. Les races de chat Mau égyptien, birman, ocicat et siamois étaient surreprésentées parmi les soumissions d'urate.(Traduit par Isabelle Vallières).

ASSOCIATIONS BETWEEN ULTRASOUND AND CLINICAL FINDINGS IN 87 CATS WITH URETHRAL OBSTRUCTION.

Urethral obstruction is a life-threatening form of feline lower urinary tract disease. Ultrasonographic risk factors for reobstruction have not been previously reported. Purposes of this retrospective cross-sectional study were to describe urinary tract ultrasound findings in cats following acute urethral obstruction and determine whether ultrasound findings were associated with reobstruction. Inclusion criteria were a physical examination and history consistent with urethral obstruction, an abdominal ultrasound including a full evaluation of the urinary system within 24 h of hospitalization, and no cystocentesis prior to ultrasound examination. Medical records for included cats were reviewed and presence of azotemia, hyperkalemia, positive urine culture, and duration of hospitalization were recorded. For medically treated cats with available outcome data, presence of reobstruction was also recorded. Ultrasound images were reviewed and urinary tract characteristics were recorded. A total of 87 cats met inclusion criteria. Common ultrasound findings for the bladder included echogenic urine sediment, bladder wall thickening, pericystic effusion, hyperechoic pericystic fat, and increased urinary echoes; and for the kidneys/ureters included pyelectasia, renomegaly, perirenal effusion, hyperechoic perirenal fat, and ureteral dilation. Six-month postdischarge outcomes were available for 61 medically treated cats and 21 of these cats had reobstruction. No findings were associated with an increased risk of reobstruction. Ultrasonographic perirenal effusion was associated with severe hyperkalemia (P = 0.009, relative risk 5.75, 95% confidence interval [1.54-21.51]). Findings supported the use of ultrasound as an adjunct for treatment planning in cats presented with urethral obstruction but not as a method for predicting risk of reobstruction.

Laparoscopic-assisted cystotomy for urolith removal in dogs and cats - 23 cases.

This report describes the outcomes of a modified laparoscopic-assisted cystotomy for urolith removal in dogs and cats. Modifications of the original techniques included a temporary cystopexy to the abdominal wall, utilization of a laparoscope instead of cystoscope, and retrograde flow of saline in the bladder with pressurized saline. The medical records of 23 client-owned animals for which laparoscopic-assisted cystotomy was used for urolith extraction were reviewed. Twenty-six procedures were performed in 23 animals. There were intraoperative complications in 19.2% of cases leading to open conversion in 11.5%. Rate of complications directly related to the procedure was 11.5%. Four cases had documented urolith recurrence with a mean time to recurrence of 335 days.

Cystotomie assistée par laparoscopie pour l'enlèvement des urolithes chez les chiens et les chats ­ 23 cas. Ce rapport décrit les résultats d'une cystotomie assistée par laparoscopie pour l'enlèvement des urolithes chez les chiens et les chats. Les modifications des techniques originales ont inclus une cystopexie temporaire à la paroi abdominale et un flux rétrograde de la solution saline dans la vessie avec une solution saline sous pression. Les dossiers médicaux de 23 animaux appartenant à des propriétaires pour lesquels la cystotomie par laparoscopie avait été utilisée pour l'extraction des urolithes ont été examinés. Vingt-six interventions ont été réalisées chez 23 animaux. Il y a eu des complications peropératoires dans 19,2 % des cas causant une conversion ouverte à 11,5 %. Le taux des complications directement reliées à l'intervention était de 11,5 %. Pour quatre cas, il y a eu une récurrence documentée des urolithes avec une durée moyenne de 335 jours.(Traduit par Isabelle Vallières).

Progressive urethral dilation in male horses undergoing perineal urethrotomy for cystolith removal: 22 cases.

This retrospective case series describes the use of progressive urethral dilation in 22 client-owned male horses undergoing perineal urethrotomy (PU) for cystolith removal. Medical records of horses undergoing PU and urethral dilation for treatment of cystolithiasis were reviewed. Dilation of the pelvic urethra was performed following PU and using customized dilators with the same length (30cm) and with various outer diameters (25 to 45mm). Analyzed data included: signalment, cystolith size, renal ultrasound findings, method used for cystolith removal, diameter of urethral dilators, intra- and post-operative complications, and hospitalization time. Cystolith size ranged between 37mm and 90mm. Dilation of the pelvic urethra was as follows: 35mm (n=8), 25mm (n=6), 39mm (n=3), 33mm (n=2), 28mm (n=2) and 45mm (n=1). In 6 cases, the cystolith was removed without fragmentation. In the remaining 16 horses, lithotripsy was performed with forceps (n=9) or a pneumatic scaler (n=7). In 15 horses a retrieval device was used to aid in calculi removal. Hospitalization time ranged between 1 and 5 days. Intra-operative complications occurred in one horse. No post-operative complications were recorded. Follow-up information was available for 21 horses (range 1-8 years). Urethral dilation via PU may be a viable option for cystolith removal in male horses.

Pseudomembranous cystitis in cats with presumed or confirmed mineralization: A retrospective study of 26 cases (2016-2021).

BACKGROUND: Pseudomembranous cystitis (PMC) in cats is a recognized disease, but concurrent mineralization is reported rarely and its outcome is poorly described. HYPOTHESIS AND OBJECTIVES: Describe a population of cats with PMC and the prevalence of concurrent mineralization. ANIMALS: Twenty-six cats with PMC. METHODS: Medical records were retrospectively reviewed (January 2016 to December 2021). Cats with an ultrasound diagnosis of PMC were included. Clinicopathologic results, imaging, treatment, and outcome were reviewed. RESULTS: All cats were male and 21 (80%) were diagnosed with urethral obstruction (UO). Five cats (23.8%) had positive urine culture (Staphylococcus felis, 3/5; Proteus mirabilis, 2/5) with a median urine pH of 8 (range, 6-9). All cats had ultrasonographic changes suggestive of mineralization. On ultrasound examination, 10 cats (38.5%) had pseudomembranes with acoustic shadowing suggestive of mineralization, 15 (57.7%) had changes indicative of ulceration, and 8 (31%) had changes compatible with of a urachal anomaly. Twenty-two cats received medical treatment, 4 underwent surgery (3 percutaneous cystolithotomy, 1 cystotomy). Twenty cats (77%) survived to discharge. Follow-up ultrasound examination indicated resolution of PMC in 6/7 cats, 4 had persistent hyperechoic bladder lining. Five of 12 cats with follow-up had a relapse of lower urinary tract signs. CONCLUSIONS AND CLINICAL IMPORTANCE: Pseudomembranous cystitis was diagnosed mainly in male cats with UO and imaging findings suggestive of mineralization were present in all cases. Frequent negative urine culture suggests a different etiology than encrusting cystitis related to urease-positive bacteria. Good outcomes can be achieved with medical management.

Laparoscopic-assisted cystotomy and cystostomy for treatment of cystic calculus in a gelding.

OBJECTIVE: To report laparoscopic-assisted cystotomy and inguinal cystostomy for treating bladder urolithiasis in a gelding. STUDY DESIGN: Clinical report. ANIMALS: Twelve-year-old Appaloosa gelding. METHODS: A laparoscopic approach was used to locate and grasp the bladder, which was exteriorized through an enlarged instrument portal for cystotomy to remove the calculus. During withdrawal, the calculus fragmented into multiple pieces. To avoid urethral occlusion and facilitate elimination of these fragments, an inguinal cystostomy was created. The seromuscular layer of the bladder was circumferentially secured to the abdominal fascia and bladder mucosa margins were sutured to the skin. RESULTS: At 2-year follow-up, the gelding was in good condition with mild urine scald of the left ventral abdomen. CONCLUSION: Laparoscopic-assisted cystotomy was used for calculus removal and inguinal cystostomy for successful fragment elimination.

Endoscopic-assisted electrohydraulic shockwave lithotripsy in standing sedated horses.

OBJECTIVE: To report use of transendoscopic electrohydraulic shockwave lithotripsy for fragmentation of urinary calculi in horses. STUDY DESIGN: Case series. ANIMALS: Male horses (n = 21). METHODS: Fragmentation of cystic calculi (median, 6 cm diameter; range, 4-11 cm diameter) was achieved by transurethral endoscopy in standing sedated horses using an electrohydraulic shockwave fiber introduced through the biopsy channel of an endoscope. The fiber was advanced until it contacted the calculus. Repeated activation of the fiber was used to disrupt the calculus into fragments <1 cm diameter. Visibility within the bladder was maintained by repeated lavage with saline solution. RESULTS: Complete calculus removal was achieved in 20 horses (95%) with mean total surgical time of 168.6 minutes (range, 45-450). In the 20 horses with single calculi, 1-6 sessions were required to completely fragment the calculus. Except for 1 horse, in which perineal urethrotomy was eventually performed for complete fragment removal, fragments calculi were excreted via the urethra. Postoperative complications included hematuria because of severe mucosal erosion (n = 2), dysuria because of a trapped urethral fragment (2), small amount of urinary debris (1). One horse was euthanatized because of bladder rupture. Complete clearance of calculi and urinary debris was confirmed endoscopically 20 (3-45) days after the last session. Telephone follow-up (mean, 18.8 months; range, 7-24 months) revealed that horses had returned to previous activity levels without recurrence of clinical signs. CONCLUSIONS: Transendoscopic electrohydraulic lithotripsy appears to be an effective method for fragmentation of low-density calcium carbonate cystic calculi in male horses.

Local anesthesia and hydro-distension to facilitate cystic calculus removal in horses.

OBJECTIVE: To report a technique for improving surgical access to the bladder for removal of cystic calculi in male horses. STUDY DESIGN: Retrospective case series. ANIMALS OR SAMPLE POPULATION: Geldings (8) with cystic calculi. METHODS: After catheterization of the bladder through the penis, 100 mL 2% lidocaine hydrochloride solution was instilled. After 10 minutes, the bladder was distended with sterile, warmed Hartmann's solution to a pressure of ≈ 40 cm H(2) O, using gravity feed. This was left in place until abdominal access was gained at surgery, then the fluid siphoned off via the catheter. RESULTS: Calculi were 3-11 cm in diameter (median, 6 cm). Bladder capacity ranged from 1.4 to 2.5 L (median, 1.8 L). Exteriorization time from placing a hand in the abdomen to having the bladder in a surgically accessible position was <5 minutes. CONCLUSION: The described technique facilitates exteriorization of the bladder for removal of cystic calculi.

Cystine urolithiasis in a caracal (Caracal caracal).

In July 2009, a 14-yr-old male caracal (Caracal caracal) at the National Zoological Gardens of South Africa was found, on abdominal ultrasound, to have a single large cystolith. The cystolith was removed, and the composition was determined to be 100% cystine. Blood and urine samples were also collected from three other apparently healthy caracals at the zoo and were submitted, together with the samples from the affected animal, for analysis using gas chromatograph mass spectrometry for cystine, lysine, alanine, and ornithine levels. The cystine levels in the urine, the fractional excretion of cystine, and the normalized excretion of cystine (micromol/g of creatinine) were all higher in the affected caracal than in the healthy animals. Only a single other case of cystine urolithiasis has been previously reported in any wild felid in the literature.

Bladder wall adhesion causing a vesicular septum in a dog following surgical cystotomy.

CASE DESCRIPTION: An 8-year-old spayed female Yorkshire Terrier-Poodle dog was evaluated for persistent pollakiuria and stranguria following routine cystotomy for calcium oxalate cystoliths. CLINICAL FINDINGS: The dog presented for a cystotomy with intermittent hematuria. Postoperative radiographs revealed no remaining cystoliths. Urine, cystolith, and bladder mucosal aerobic cultures were negative. Pollakiuria, stranguria, and hematuria developed immediately after surgery and persisted despite antibiotics. Ultrasound revealed suspected fibrous adhesions within the urinary bladder lumen connecting the dorsal and ventral bladder wall creating a septum. This was confirmed cystoscopically 4 weeks after surgery. TREATMENT AND OUTCOME: Cystoscopic-guided laser ablation was performed to incise abnormal tissue connecting the ventral and dorsal bladder wall using a holmium:yttrium-aluminum-garnet laser. Three weeks later, ultrasound revealed adhesion resolution though mild pollakiuria and stranguria persisted. Oxybutynin was prescribed and clinical signs resolved. At 27 months after ablation, hematuria occurred with recurrent cystoliths. These cystoliths were removed by percutaneous cystolithotomy, documenting a cystoscopically normal bladder wall. The patient had normal urination for 55.5 months after ablation, with normal bladder wall thickness on ultrasound repeated at 27 and 36 months after ablation. CLINICAL RELEVANCE: To the authors' knowledge, an adhesion creating a septum between the dorsal and ventral bladder wall has not been previously reported as a complication after cystotomy in any species and should be considered as a cause of persistent lower urinary signs after surgery. Ultrasound identified the lesion in this dog. Because bladder abnormalities can develop quickly after surgery, ultrasound might be considered if urine testing is not supportive of infection. Cystoscopic-guided laser ablation was a successful minimally invasive treatment in this case.

Comparison of percutaneous cystolithotomy and open cystotomy for removal of urethral and bladder uroliths in dogs: Retrospective study of 81 cases (2014-2018).

OBJECTIVE: Compare percutaneous cystolithotomy (PCCL) and open cystotomy (OC) for removal of bladder and urethral uroliths. DESIGN: Retrospective study. ANIMALS: Client-owned dogs and cats that underwent PCCL (n = 41) or OC (n = 40) between January 1, 2014 and February 28, 2018 at a referral center. METHODS: Medical records of dogs and cats that underwent a PCCL or an OC were reviewed. History, signalment, physical examination, diagnostic tests, length of the procedure and anesthesia, complications, and duration of hospitalization were recorded. RESULTS: A total 17 cats (PCCL = 10; OC = 7) and 64 dogs (PCCL = 31; OC = 33) were included. There was no significant difference, regardless of species, in the mean surgical time (45 min [24-160 min] and 48.5 min [15-122 min] with P = .54 in dogs, P = .65 in cats) nor mean duration of anesthesia (90 min [50-120 min] and 98 min [54-223 min] with P = .87 in dogs, P = .08 in cats) in the PCCL and OC groups respectively. Number of uroliths did not affect duration of surgery in either group. Complete urolith removal was achieved in 98% of dogs and cats in both groups. The median hospitalization time was significantly shorter in the PCCL group for dogs (11.3 hours [range 4 to 51.3] in the PCCL vs 56.6 hours [range 7.3 to 96] in the OC group; P < .001) but did not differ for cats (24.5 hours [range 8.3 to 30] in the PCCL vs 56.6 hours [range 10.1 to 193.2] in the OC group; P = .08). CONCLUSION AND CLINICAL RELEVANCE: Bladder urolith removal by PCCL procedure is no longer than OC. Further studies are needed to compare the pain related to procedure between PCCL and OC.

Small ruminant urinary obstruction: decision trees for treatment.

Urolithiasis is the most common cause of urinary tract disease in small ruminants and has significant economic and production impacts worldwide. Urolithiasis is multifactorial in origin and generally begins with the formation of cystoliths followed by urethral obstruction. The condition is most common in males. Clinical signs are variable depending on the severity of the obstruction. Uroliths can be calcium, struvite, or silicate based; however, struvite and amorphous magnesium calcium phosphate are the most common urolith types observed in small ruminants. Although urethral process (vermiform appendage) amputation is widely considered the first line of treatment, reobstruction is common within the first 36 hours. Surgical interventions such as temporary tube cystostomy, perineal urethrostomy (PU), modified proximal perineal urethrostomy, vesico-preputial anastomosis (VPA), and urinary bladder marsupialization (BM) are reported to carry an improved prognosis for long-term survival. PU carries a lower proportion of long-term success (> 12-month survival time) when compared with VPA and BM. Stoma stricture and urine scald are the most commonly observed surgical complications. Currently, the literature provides minimal direction for clinician decision-making in managing these cases while accounting for patient history, client financial ability, composition of calculi, and potential treatment complications. Small ruminant urinary obstructions are challenging and complicated conditions to treat, due to their multifactorial etiology, ruminant urogenital anatomy, and the variety of imperfect treatment options available. The purpose of this article this article is to provide veterinary practitioners with decision trees to guide management and treatment of urolithiasis in small ruminants.

A diet with a struvite relative supersaturation less than 1 is effective in dissolving struvite stones in vivo.

Magnesium ammonium phosphate (struvite) is one of the most common minerals found in feline uroliths. Previous studies have shown the efficacy of acidifying calculolytic diets (inducing urine pH < 6.5), in dissolving struvite stones in cats. Recent work in our laboratory found that wet and dry test diets induce a struvite urinary relative supersaturation (RSS) < 1 and that the urine of healthy cats fed the dry test diet dissolved feline struvite stones in vitro. The objective of the present study was to demonstrate the efficacy of those test diets on naturally occurring struvite urocystoliths in cats. A total of twenty-one cats were used, of which seventeen completed the study. Of the seventeen cats, eight were fed the wet test diet and nine the dry test diet. Uroliths dissolved in a median of 18 (10-55) d. In the remaining four cats, uroliths failed to dissolve and were removed surgically. Quantitative analysis showed that these uroliths contained either calcium oxalate or calcium phosphate. The present study demonstrates that diets that induce a struvite RSS < 1 result in struvite stone dissolution in vivo.

Mouse barley awn (Hordeum murinum) migration induced cystolithiasis in 2 male dogs.

Two male dogs were presented with cystic uroliths composed of magnesium ammonium phosphate (struvite). Each had an atypical nidus, a mouse barley awn (Hordeum murinum). To our knowledge, this is the first report of grass awns located in the bladder lumen of dogs. The composition of uroliths and the pathophysiology of grass awn migration to the urinary bladder are discussed.

Efficacy of medical dissolution for suspected struvite cystoliths in dogs.

BACKGROUND: Medical dissolution of struvite uroliths in dogs is commonly recommended, but data on success rates and complications are limited. OBJECTIVES: To evaluate the efficacy of medical dissolution for suspected struvite cystoliths in dogs. ANIMALS: Fifty client-owned dogs fed a therapeutic dissolution diet, with or without administration of antimicrobials, for treatment of suspected struvite cystoliths. METHODS: Single institution, retrospective case series. Medical records were reviewed for dogs with at least 1 follow-up visit. Dissolution success, complications, and possible predictors of success were evaluated. RESULTS: Full dissolution of cystoliths was achieved in 58% (29/50) of dogs within a median of 35 days (range, 13-167). Of 21 dogs without success, 7 each had partial dissolution, no dissolution, or undetermined outcome. Uroliths containing >10% nonstruvite mineral were common in the nonsuccess group (11/16 analyzed). Maximum urolith diameter, number of uroliths, and baseline urine pH did not differ significantly between dogs with and without success. Dissolution was more likely in dogs receiving antimicrobial therapy (OR = 16.3, 95% confidence interval 1.9-787.4, P = .002). Adverse events occurred in 9 dogs (18%); urethral obstructions were the most common, but 3 of 4 dogs with this complication were obstructed on presentation, before trial initiation. CONCLUSIONS AND CLINICAL IMPORTANCE: Results support a medical dissolution trial for dogs with suspected struvite cystoliths. If no reduction in urolith size or number occurs by 1 month, a nonstruvite composition is likely, and alternative interventions should be considered. Dogs presenting with urethral obstructions should not be considered candidates for medical dissolution.

Effect of a struvite dissolution diet in cats with naturally occurring struvite urolithiasis.

OBJECTIVES: The aim of the study was to determine the efficacy of the low struvite relative supersaturation diet in dissolution of feline struvite cystoliths. METHODS: This was a prospective, open-label, two-center study. Twelve client-owned cats were enrolled based on the radiographic appearance of their uroliths and urinalysis parameters. Cats were fed the test diet exclusively for up to 56 days. Cats were radiographed every other week until radiographic evidence of dissolution occurred or the end of the study period was reached. Cats with radiographically apparent uroliths at the end of the study period underwent cystotomy for stone retrieval and analysis. RESULTS: Nine of the 12 cats completed the study. Eight experienced radiographic dissolution; seven of these had complete dissolution within the first month of treatment. One cat, whose owner declined cystotomy after partial dissolution at day 56, had complete radiographic resolution at 70 days of treatment. Two calcium oxalate urolith cores were removed from a cat that had partial radiographic dissolution. CONCLUSIONS AND RELEVANCE: The test diet was successful in dissolving suspected struvite cystoliths. As this diet is suitable for maintenance feeding of adult cats, it may be a suitable choice for long-term prevention of feline struvite urolithiasis.

In vitro comparison of plain radiography, double-contrast cystography, ultrasonography, and computed tomography for estimation of cystolith size.

OBJECTIVE: To compare accuracy of estimates of cystolith size obtained by means of plain radiography, double-contrast cystography, ultrasonography, and computed tomography. SAMPLE POPULATION: 30 canine cystoliths ranging from 1 to 11 mm in diameter with various mineral compositions. PROCEDURES: A bladder phantom model was created by filling a rubber balloon with saline (1% NaCl) solution and positioning it on top of a 2% gelatin cushion at the bottom of a water-filled 4-quart container. Cystoliths were individually placed in the bladder phantom and imaged by each of the 4 techniques. For each image, cystolith size was measured by 2 radiologists with computerized calipers, and size estimates were compared with actual cystolith size. RESULTS: Mean cystolith size estimates obtained by means of radiography, cystography, and computed tomography did not differ significantly from each other. However, for ultrasonographic images, mean +/- SD difference between actual and estimated cystolith size (2.95 +/- 0.73 mm) was significantly higher than mean difference for radiographic, cystographic, and computed tomographic images. For ultrasonography, mean +/- SD percentage overestimation in cystolith size was 68.4 +/- 51.5%. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that measurements of cystolith size obtained by means of ultrasonography may overestimate the true size. This suggests that cystolith size estimates obtained by means of ultrasonography should be interpreted with caution whenever cystolith size may influence patient management.