Diagnosis and surgical management of ureteral calculi in dogs: 16 cases (1990-2003)

AIMS: To examine the clinical signs, laboratory and radiographic findings, surgical technique, ureterolith composition, and post-operative outcomes in dogs managed surgically for ureterolithiasis to determine whether surgical removal of ureteroliths in dogs resulted in a positive clinical outcome. METHODS: The medical record database of a university veterinary hospital in Pennsylvania, USA, was searched for dogs that underwent surgery to remove obstructive ureteral calculi between 1990 and 2003. Records were reviewed for signalment, clinical history and examination findings, radiographic and laboratory test results, surgical technique, and ureterolith analysis. Follow-up information was obtained from telephone interviews with owners or referring veterinarians, or by reviewing the medical record of subsequent hospital visits. RESULTS: Sixteen dogs were included in this study; ten were neutered females, two intact females and four castrated males. Abdominal radiography revealed ureteral calculi in 14/16 dogs, renal calculi in 8/16, cystic calculi in 8/16, urethral calculi in 1/16, renomegaly in 6/16 and renal mineralisation in 5/16. Ureterolith type included struvite in six dogs, calcium oxalate in five, calcium phosphate in one, and a mix of struvite, calcium phosphate and calcium oxalate in another. Compared to dogs with non-struvite ureteroliths, those with struvite ureteroliths had a higher pre-operative white blood cell (WBC) count (25.6, SD 7 vs 17.6, SD 6 x 103 cells/mul; p=0.046), and were more likely to have a purulent discharge from the ureteral incision noted at the time of surgery (p=0.015). Following discharge, 14/16 dogs were re-evaluated. Median survival time was 904 days (range 2-1,876). Two dogs required additional surgery on the urinary tract. Four dogs died or were euthanised because of azotaemia and clinical signs related to the urinary system or non-specific signs of illness (vomiting, lethargy) at 8, 90, 333 and 904 days post-operatively. CONCLUSIONS: Surgical management of ureteroliths was successful and resulted in good long-term survival in the majority of dogs examined in this small study population. Similar proportions of calcium oxalate and struvite ureteroliths were identified. CLINICAL RELEVANCE: The use of the ureteral surgery may increase as the frequency of diagnosis of ureteroliths in dogs increases.     

Nephroliths and ureteroliths: a new stone age

Nephroliths may obstruct the renal pelvis or ureter, predispose to pyelonephritis, or result in compressive injury of the renal parenchyma leading to progressive chronic kidney disease. Indications for removal of nephroliths in dogs include obstruction, recurrent infection, progressive nephrolith enlargement, presence of clinical signs (renal pain), and patients with nephroliths in a solitary functional kidney. The most common indication for removal of upper tract uroliths in cats is ureteral obstruction caused by ureteroliths. Nonobstructive nephroliths in cats are not usually treated unless they move into the ureter resulting in ureteral obstruction.

The treatment approach to nephroliths and ureteroliths is different for dogs versus cats. Surgical removal of nephroliths or ureteroliths by nephrotomy and ureterotomy respectively is associated with potential for complications in more than 30% of cats treated by ureterotomy; therefore, minimally invasive options should also be considered. Extracorporeal shock wave lithotripsy (ESWL) treatment of nephroliths results in small “passable” stone fragments in most dogs, whereas ESWL does not work effectively in cats. Ureteral stents are effective for relief of ureteral obstruction by ureteroliths in both dogs and cats. Ureteral stents may be left in place long-term to relieve ureteral obstruction by ureteroliths. Post-operative morbidity and mortality are substantially lower for ureteral stent placement compared to open surgical ureterotomy in cats.     

Validation and comparison of the use of diuresis cystometry and retrograde filling cystometry at various infusion rates in female Beagle dogs

OBJECTIVES: To compare retrograde filling cystometry at infusion rates of 5, 10, and 20 mL/min with diuresis cystometry for determination of an appropriate infusion rate and to confirm the reproducibility of measurements obtained by urethral pressure profilometry (UPP) and cystometry in female Beagles. ANIMALS: Adult female Beagles. PROCEDURE: Successive UPP and cystometry were performed by use of a water perfusion catheter on dogs anesthetized with propofol. Dogs randomly underwent each of the following at 1-week intervals: retrograde filling cystometry at 5, 10, and 20 mL/min, and diuresis cystometry. The maximum urethral pressure and closure pressure, functional and anatomic profile lengths, threshold pressure, threshold volume, and compliance were measured. RESULTS: For each UPP variable, significant differences were found among dogs, but no significant differences were found in intra- or interstudy measurements for individual dogs. For retrograde filling cystometry, threshold pressure was not significantly different between a 5 and 10 mL/min infusion rate. Threshold pressure was significantly higher during retrograde filling cystometry at 20 mL/min, compared with 5 and 10 mL/min, and was associated with bladder wall damages. Threshold pressure was significantly lower during diuresis cystometry, compared with retrograde filling cystometries. Threshold volume and compliance were not significantly different among retrograde filling cystometries but were significantly higher during diuresis cystometry. CONCLUSIONS AND CLINICAL RELEVANCE: Retrograde filling cystometry at 20 mL/min leads to unacceptable sudden increase in threshold bladder pressure. Retrograde filling cystometry at 10 mL/min can be recommended in a clinical setting, shortening the anesthesia time. However, diuresis cystometry approximates physiologic bladder filling most accurately.     

EVALUATION OF DIAPHRAGMATIC MOTION IN NORMAL AND DIAPHRAGMATIC PARALYZED DOGS USING M‐MODE ULTRASONOGRAPHY

Diagnosis of unilateral diaphragmatic paralysis in dogs is currently based on fluoroscopic detection of unequal movement between the crura. Bilateral paralysis may be more difficult to confirm with fluoroscopy because diaphragmatic movement is sometimes produced by compensatory abdominal muscle contractions. The purpose of this study was to develop a new method to evaluate diaphragmatic movement using M‐mode ultrasonography and to describe findings for normal and diaphragmatic paralyzed dogs. Fifty‐five clinically normal dogs and two dogs with diaphragmatic paralysis were recruited. Thoracic radiographs were acquired for all dogs and fluoroscopy studies were also acquired for clinically affected dogs. Two observers independently measured diaphragmatic direction of motion and amplitude of excursion using M‐mode ultrasonography for dogs meeting study inclusion criteria. Eight of the clinically normal dogs were excluded due to abnormal thoracic radiographic findings. For the remaining normal dogs, the lower limit values of diaphragmatic excursion were 2.85–2.98 mm during normal breathing. One dog with bilateral diaphragmatic paralysis showed paradoxical movement of both crura at the end of inspiration. One dog with unilateral diaphragmatic paralysis had diaphragmatic excursion values of 2.00 ± 0.42 mm on the left side and 4.05 ± 1.48 mm on the right side. The difference between left and right diaphragmatic excursion values was 55%. Findings indicated that M‐mode ultrasonography is a relatively simple and objective method for measuring diaphragmatic movement in dogs. Future studies are needed in a larger number of dogs with diaphragmatic paralysis to determine the diagnostic sensitivity of this promising new technique.     

Evaluation of the effects of nephrotomy on renal function in clinically normal cats

OBJECTIVE: To evaluate the effects of nephrotomy on renal function in clinically normal cats. ANIMALS: 20 specific-pathogen-free, 9- to 11-month-old female mixed-breed cats. PROCEDURE: Serum chemistry analyses, CBC determinations, urinalyses, microbiologic urine cultures, renal ultrasonography, abdominal radiography, and single-kidney and total glomerular filtration rate (GFR) determinations by use of renal scintigraphy and measurements of plasma disappearance of technetium 99m-diethylenetriaminepentaacetic acid were performed before surgery and at 3, 12, 26, 52, and 78 weeks after surgery in 10 cats that underwent unilateral nephrotomy and in 10 control cats that underwent a sham surgical procedure. RESULTS: Two cats (1 from each group) did not complete the study, and their data were eliminated from analyses. Unilateral nephrotomy resulted in a 10% to 20% reduction in mean single-kidney GFR, compared with that of nephrotomy contralateral control kidneys. However, mean total GFR in nephrotomy-group cats was not significantly different from that of sham-group cats. Over the 78 weeks of study, mean total GFR declined 34% and 40% in nephrotomy- and sham-group cats, respectively. Adverse events associated with nephrotomy included persistent microscopic hematuria, renal pelvis hyperechogenicity with distant shadowing on ultrasonographic evaluation, dilatation of renal pelves, and hydronephrosis. CONCLUSIONS AND CLINICAL RELEVANCE: Nephrotomy in normal functioning feline kidneys results in a modest relative reduction in renal function, compared with contralateral kidney controls, but has minimal effect on total GFR when compared with sham-operated control cats. However, any detrimental effects of nephrotomy may be magnified in cats with diseased kidneys, which may have little or no capacity for repair or compensation.     

LESIONS OF THE RENAL PELVIS AND PROXIMAL URETER IN VARIOUS NEPHRO-UROLOGICAL CONDITIONS: AN ULTRASONOGRAPHIC STUDY

The applicability of ultrasonography was studied in the diagnosis of lesions of the renal pelvis and ureter in 10 dogs. Ultrasonographic findings of processes associated with dilatation and concretion formation in the renal pelvis were described and the differential diagnosis of the lesions was discussed. The authors propose a new classification system for judging processes characterized by dilatation of the renal pelvis. Experience suggests that ultrasonography is an effective procedure in the diagnosis of certain diseases of the upper urinary tract in dogs.     

Objective determination of pelvic movement during hind limb lameness by use of a signal decomposition method and pelvic height differences

OBJECTIVE: To evaluate pelvic movement over a large number of strides in sound horses and in horses with induced hind limb lameness by applying methods to the pelvis that have been described for evaluating vertical head movement in horses with induced forelimb lameness. ANIMALS: 17 adult horses. PROCEDURE: Horses were filmed while trotting on a treadmill before and after induction of transient mild and moderate hind limb lamenesses. Vertical pelvic movement was measured by a signal decomposition method. The vertical pelvic signal was decomposed into a periodic component (A1) that occurred at half the stride frequency (representing vertical pelvic movement caused by lameness) and another periodic component (A2) that occurred at stride frequency (representing normal vertical pelvic movement of a trotting horse). Vertical pelvic and foot positions were correlated for each stride to compare the difference between the minimum and maximum heights of the pelvis during and after stance of the right hind limb to the minimum and maximum heights of the pelvis during and after stance of the left hind limb. RESULTS: Maximum pelvic height difference and lameness amplitude (A1) differed significantly between sound and mild or moderate hind limb lameness conditions. Mean A1 value for vertical pelvic movement in sound horses was less than that previously reported for vertical head movement. CONCLUSION AND CLINICAL RELEVANCE: Pelvic height differences and signal decomposition of pelvic movement can be used to objectively evaluate hind limb lameness in horses over a large number of strides in clinical and research settings.     

LAPAROSCOPIC SONOGRAPHY IN THE URINARY SYSTEM

This work reports the use of laparoscopic-transducer sonography for the examination of the urinary system in a swine model. Animals underwent a two-phase study. In the first phase, the urinary system was examined using laparoscopic sonography. In the second a partial ureteral obstruction was induced, and sonographic changes were recorded and evaluated. Sonography was used to evaluate kidneys, ureters, and bladder. Anatomic structures were evaluated and the following pathological findings were identified: renal cysts, one polycystic kidney, dilation of the renal pelvis, hydronephrosis, and one perirenal pseudocyst. Where necessary, contrast digital fluoroscopy (excretory urography and retrograde ureteropyelography) was also performed. Laparoscopic sonography mainly is used for evaluation prior to laparoscopic surgery to guide decisions relating to surgery. The quality of the images obtained laparoscopically is superior to that of percutaneous or transabdominal images, because artifacts are reduced and the contact surface of the transducer is placed directly over the study area. Laparoscopic sonography proved highly effective for studying renal and ureteral disorders prior to minimally invasive surgery.     

Renal pelvic rupture,intrapelvic haematoma and retroperitoneal haemorrhage associated with obstructive ureterolithiasis in a cat

A neutered female cat presented with a 9-day history of hyporexia and depression. The referring veterinarian had identified moderate non-regenerative anaemia, haematuria and suspected unilateral obstructive ureterolithiasis. Subsequent ultrasonography revealed moderate distension of the left renal pelvis with echogenic material, ureteral distension and ureterolithiasis. A partial ureteral obstruction was suspected. After 4 days of medical management, there was further distension of the renal pelvis with well-delineated echogenic material and an accumulation of perinephric fluid. A left nephroureterectomy was performed. Renal pelvic rupture with intrapelvic haematoma and retroperitoneal haemorrhage was confirmed by histopathology. Eighteen months following surgery, the cat remained clinically well with normal renal values.     

Computer-assisted kinematic evaluation of induced compensatory movements resembling lameness in horses trotting on a treadmill

OBJECTIVE: To characterize compensatory movements of the head and pelvis that resemble lameness in horses. ANIMALS: 17 adult horses. PROCEDURE: Kinematic evaluations were performed while horses trotted on a treadmill before and after shoe-induced lameness. Lameness was quantified and the affected limb determined by algorithms that measured asymmetry in vertical movement of the head and pelvis. Induced primary lameness and compensatory movements resembling lameness were assessed by the Friedman test. Association between induced lameness and compensatory movements was examined by regression analysis. RESULTS: Compensatory movements resembling lameness in the ipsilateral forelimb were seen with induced lameness of a hind limb. There was less downward and less upward head movement during and after the stance phase of the ipsilateral forelimb. Doubling the severity of lameness in the hind limb increased severity of the compensatory movements in the ipsilateral forelimb by 50%. Compensatory movements resembling lameness of the hind limb were seen after induced lameness in a forelimb. There was less upward movement of the pelvis after the stance phase of the contralateral hind limb and, to a lesser extent, less downward movement of the pelvis during the stance phase of the ipsilateral hind limb. Doubling the severity of lameness in the forelimb increased compensatory movements of the contralateral hind limb by 5%. CONCLUSIONS AND CLINICAL RELEVANCE: Induced lameness in a hind limb causes prominent compensatory movements resembling lameness in the ipsilateral forelimb. Induced lameness in a forelimb causes slight compensatory movements resembling lameness in the ipsilateral and contralateral hind limbs.     

A radiographic study of urine flow in the domestic fowl

The movement of radiopaque media in the ureters, cloaca, colon and caeca was studied radiographically in 12 in‐lay light hybrid hens. During direct screening of the conscious birds after intravenous administration of sodium diacetamidotriiodobenzoate, the contrast medium was observed to pass along the ureters to their distal extremity under the action of ureteral contractions. It accumulated in the coprodeum, which remained quiescent in some birds, but in others, periods of vigorous contraction of the coprodeum forced the material cranially into the colon. Retroperistaltic contractions of the colon which appeared to originate in the coprodeum were then seen to promote further retrograde movement and on several occasions the contrast medium entered the caeca. Retrograde movement of a suspension of barium sulphate from the coprodeum into the colon and caeca was also observed, but neither of the contrast media entered the ileum. Post‐mortem radiographs of the viscera confirmed the presence of the contrast media in the cloaca, colon and caeca. The findings are illustrated by radiographs and the contribution of retrograde flow to caecal filling is discussed.     

Correlation of histology of healed fractures and tissue surrounding implants with ultrasonographic and radiographic appearance

OBJECTIVES: To determine if there was histological correlation with ultrasonographic images of healed fractures and implant-associated tissue after fracture treatment by plate osteotomy. METHODS: Eight adult dogs were included in this retrospective study. Ultrasonography (B-mode and power Doppler) and radiography were performed before plate removal. Surgical biopsies were taken of the fracture site and the tissue adjacent to the plate. These were stained with haematoxylin and eosin to assess histomorphology and bone content and immunolabelled with CD31 to assess vascularity. RESULTS: Ultrasound and radiographic diagnoses of a healed fracture correlated with histological finding of bone healing. Ultrasonography and histology findings of vascularity were also highly correlated. The tissue surrounding the surgical implants was significantly more vascularised on both ultrasonography and histology than that at the fracture site itself. CLINICAL RELEVANCE: Ultrasonography can be used to diagnose fracture healing in plated fractures. Power Doppler ultrasonography examination of fracture healing should be performed away from surgical implants to avoid false-positive results of vascularisation.     

Detailed ultrasonographic mapping of the pelvis in clinically normal horses and ponies.

OBJECTIVE: To map the equine pelvis using ultrasonography, validated by use of computed tomography (CT), magnetic resonance imaging (MRI), and measurements of frozen cadaver slices. ANIMALS: 6 ponies and 6 horses. PROCEDURE: Ultrasonographic examination of the pelvis was performed on 6 clinically normal ponies. Measurements were obtained for imaged structures. Computed tomography, MRI, and measurements of frozen sections were performed after death and used to verify measurements. Linear regression determined the degree of correlation between measurements obtained ultrasonographically and the other modalities. Six clinically normal horses were then examined by use of ultrasonography. For each structure measured mean, SD, and range were calculated. RESULTS: Data obtained from ponies revealed high correlations between ultrasonographic findings and those of CT, MRI, and frozen section measurements (r2 = 0.97, r2 = 0.99, and r2 = 0.99, respectively). Differences between structures measured on each side of the pelvis were not significant. Variation in size of structures was not associated with weight of horses. A correlation was not found between weight of horses and ponies and size of structure. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasonography can be used to accurately measure and evaluate the musculoskeletal structures of the pelvis of horses. The use of CT, MRI, and measurements of frozen sections provided a means of validating the ultrasonographic measurements. Reference range values determined in our study can be used to evaluate horses with suspected pelvic disease.     

Management of traumatic urethral rupture in 11 cats using primary alignment with a urethral catheter

OBJECTIVE: To assess the management of traumatic urethral ruptures using a systematic attempt at urethral catheterisation. METHODS: Eleven cats that had been diagnosed with a traumatic urethral rupture over a five-year period were included in this study. Rupture was assessed by positive-contrast retrograde urethrography. An attempt was made to manage these ruptures by placing an indwelling urethral catheter. RESULTS: The placement of an indwelling urethral catheter, could be performed in 10 out of 11 cats, which indicated a partial rupture. In one cat, catheterisation was not possible because of complete urethral rupture. A urethral catheter was placed into the urinary bladder via the urethra in five animals. In the other five animals, urethral catheterization required cystotomy using a modified 'inside to outside' technique. Urethral catheter removal occurred between five and 14 days after placement. Urethral healing was accomplished in all cases of catheterisation with a good outcome in eight of the 10 cats. Two cats showed clinical signs related to stricture formation during the follow-up period (seven to 72 months). Retrograde urethrography provided a definitive diagnosis of partial rupture in only six of the 10 cases of partial rupture. CLINICAL SIGNIFICANCE: Results suggested that primary alignment with the placement of a urethral catheter should be attempted for the management of traumatic urethral ruptures in cats. Gentle urethral catheterisation seems to be an effective procedure for diagnosing and dealing with partial urethral rupture in cats. Clinical stricture formation can occur, but the risk does not seem to be high. Further studies are warranted in order to define the ideal duration for maintenance of an indwelling urethral catheter in cases of traumatic partial urethral rupture.     

Management and outcome of cats with ureteral calculi: 153 cases (1984-2002)

OBJECTIVE: To determine outcome of medical and surgical treatment in cats with ureteral calculi. DESIGN: Retrospective study. ANIMALS: 153 cats. PROCEDURE: Medical records were reviewed. Owners and referring veterinarians were contacted for follow-up information. RESULTS: All cats were initially treated medically before a decision was made to perform surgery. Medical treatment included parenteral administration of fluids and diuretics to promote urine production and passage of the ureteral calculus and supportive treatment for renal failure. Ureteral calculi in the proximal portion of the ureter were typically removed by ureterotomy, whereas ureteral calculi in the distal portion of the ureter were more likely to be removed by partial ureterectomy and ureteroneocystostomy. Ureterotomy could be performed without placement of a nephrostomy tube for postoperative urine diversion. Postoperative complication rate and perioperative mortality rate were 31% and 18%, respectively. The most common postoperative complications were urine leakage and persistent ureteral obstruction after surgery. Chronic renal failure was common at the time of diagnosis and continued after treatment, with serum creatinine concentration remaining greater than the upper reference limit in approximately half the cats. Twelve-month survival rates after medical and surgical treatment were 66% and 91%, respectively, with a number of cats dying of causes related to urinary tract disorders, including ureteral calculus recurrence and worsening of chronic renal failure. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that medical and surgical management of ureteral calculi in cats are associated with high morbidity and mortality rates. Treatment can stabilize renal function, although many surviving cats will continue to have impaired renal function.     

Unilateral renal agenesis associated with additional congenital abnormalities of the urinary tract in a Pekingese bitch

An eight-month-old Pekingese bitch with urinary incontinence was found to have three congenital anomalies of the urinary tract: left renal agenesis, bilateral ectopic ureters with a left cranial blind-ending ureter, and urinary bladder hypoplasia. The diagnoses were made by retrograde vaginourethrography, excretory urography, ultrasonography and duplex Doppler ultrasonography. Although urological anomalies associated with renal agenesis have been frequently observed, a cranial blind-end ectopic ureter has not, to the authors' knowledge, been described in the bitch. The dog was managed medically with a restricted protein diet because of a compromised unilateral kidney with hydronephrosis and hydroureter.     

Surgical management of gallbladder mucoceles in dogs: 22 cases (1999-2003)

OBJECTIVES: To describe preoperative, surgical, and postoperative findings and determine prognostic indicators and treatment recommendations in dogs treated surgically for gallbladder mucocele. DESIGN: Retrospective study. ANIMALS: 22 client-owned dogs. PROCEDURES: Medical records of dogs with gallbladder mucoceles that were treated surgically were reviewed. History, clinical signs, results of selected clinicopathologic analyses and abdominal ultrasonography, surgical procedure performed, results of histologic examination of a liver biopsy specimen, and survival time were recorded. Follow-up information was obtained via telephone interview with owners and referring veterinarians. RESULTS: Dogs were 7 to 15 years of age and had non-specific clinical signs (vomiting, anorexia, and lethargy). Physical examination findings included icterus, signs of depression, and signs of discomfort on palpation of the abdomen. Sixteen dogs had a definitive diagnosis and 6 dogs were strongly suspected of having a gallbladder mucocele on the basis of results of abdominal ultrasonography. Fifteen dogs survived after surgery; 3 of these dogs had bile-induced peritonitis, and 4 had pancreatitis. One dog was euthanatized as a result of severe pancreatitis, and 1 was euthanatized because of acute renal failure; 5 dogs died as a result of pancreatitis, cholecystitis, or bile-induced peritonitis. Hepatic abnormalities were detected histologically in all dogs. CONCLUSIONS AND CLINICAL RELEVANCE: No predictors of survival were identified. No associations between outcome of surgical treatment (survival vs nonsurvival) and preoperative findings, biliary rupture, surgical procedure performed, results of histologic examination of the liver, or development of pancreatitis were found. Cholecystoduodenostomy and cholecystectomy appear to be acceptable treatments for gallbladder mucocele.     

Semen-Matrix Calculi in a Juvenile Chinchilla (Chinchilla lanigera)

A 10-month-old, intact male chinchilla (Chinchilla lanigera) was diagnosed with urolithiasis, unilateral hydroureter, and hydronephrosis secondary to ureteral obstruction confirmed by radiography and ultrasonography. Nephrectomy and cystotomy were performed, and the urolith was suspected to be a semen-matrix calculus (mineralized copulatory plug) based on the discovery of sperm within the renal pelvis of the nephrectomized kidney on histopathology; this was later confirmed through a postmortem examination. Three months after initial presentation the chinchilla was diagnosed with recurrent urolithiasis, hydroureter, and hydronephrosis of the remaining kidney and ureter, and euthanized due to poor prognosis. Necropsy confirmed the presence of semen-matrix calculi in the ureter and urinary bladder. Veterinary clinicians should consider semen-matrix calculi as a differential diagnosis for radiopaque calculi within the bladder or urethra of male chinchillas. Pathogenesis may be formation of a coagulum secondary to retrograde ejaculation.     

Successful treatment of a pancreatic pseudocyst by omentalisation in a dog

CASE HISTORY: A 3-year-old male Labrador retriever was presented with a history of dietary indiscretion followed by vomiting and abdominal pain. CLINICAL FINDINGS AND TREATMENT: Abdominal ultrasonography revealed the presence of a fluid-filled cystic structure in the region of the pancreas. Flocculent, dark fluid was drained from the cystic structure during exploratory celiotomy prior to resection of the lateral cystic wall. Omentum was sutured into the cystic cavity to provide drainage and enhance immune response. A jejunostomy feeding tube was placed. Post-surgical care consisted of antibiotic therapy. The dog was clinically normal at 1 and 7 months post-operatively and the pancreas appeared normal on final ultrasonographic examination. CLINICAL RELEVANCE: This case describes the use of omentum to provide physiological drainage of a pancreatic pseudocyst. This surgical technique may help clinicians manage patients with this condition in the future.     

In vitro evaluation of canine and feline calcium oxalate urolith fragility via shock wave lithotripsy

OBJECTIVE: To test the hypothesis that feline calcium oxalate uroliths are intrinsically more resistant to comminution via shock wave lithotripsy (SWL) than canine calcium oxalate uroliths through comparison of the fragility of canine and feline uroliths in a quantitative in vitro test system. SAMPLE POPULATION: Calcium oxalate uroliths (previously obtained from dogs and cats) were matched by size and mineral composition to create 7 pairs of uroliths (1 canine and 1 feline urolith/pair). PROCEDURE: Uroliths were treated in vitro with 100 shock waves (20 kV; 1 Hz) by use of an electrohydraulic lithotripter. Urolith fragmentation was quantitatively assessed via determination of the percentage increase in projected area (calculated from the digital image area of each urolith before and after SWL). RESULTS: After SWL, canine uroliths (n = 7) fragmented to produce a mean +/- SD increase in image area of 238 +/- 104%, whereas feline uroliths (7) underwent significantly less fragmentation (mean image area increase of 78 +/- 97%). The post-SWL increase in fragment image area in 4 of 7 feline uroliths was < 50%, whereas it was > 150% in 6 of 7 canine uroliths. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that feline calcium oxalate uroliths are less susceptible to fragmentation via SWL than canine calcium oxalate uroliths. In some cats, SWL may not be efficacious for fragmentation of calcium oxalate nephroliths or ureteroliths because the high numbers of shock waves required to adequately fragment the uroliths may cause renal injury.