Endo-urological assessment and image guided interventions in the management of multiple cystic and urethral calculi in a dog

Introduction

Urolithiasis remains one of the most common urological conditions in dogs. While bladder stones were most frequently encountered, urethral calculi often resulted in acute obstruction, making timely intervention critical (Osborne et al., 2009) [1] . The etiology of urolithiasis remains multifactorial, involving urinary tract infections (UTIs), urinary pH, diet, genetic predisposition, and metabolic factors (Lulich et al., 2016 [2] , Houston et al., 2017 [3] ). In dogs, struvite and calcium oxalate stones predominate. Among the various types of uroliths, urate uroliths were less common but clinically significant due to their association with genetic predispositions, metabolic disorders, and hepatic dysfunction. They were typically present in breeds with defects in uric acid metabolism, most notably Dalmatian and English Bulldog (Bartges, 2016) [4] . Hyperuricosuria, concentrated urine, and acidic urine were the predominant factors for urolith formation. The diagnosis of urolithiasis remains based on clinical signs, urinalysis, urine culture, hematology, imaging modalities, and increasingly, cystoscopy. The diagnosis of urate uroliths relied on imaging modalities such as ultrasonography and radiography (where urate calculi may appear radiolucent) and confirmation were done with urolith analysis, (Hostutler, 2005) [5] . Flexible cystoscopy allowed direct visualization of uroliths and mucosal lesions, as well as minimally invasive retrieval of calculi (Berent and Weisse, 2011) [6] . Retrograde urohydropropulsion had been widely used for relieving urethral obstruction, thus avoiding invasive urethrotomy, (Hess et al., 2019) [7] .

Management involved medical dissolution with dietary modifications and pharmacological interventions (e.g., xanthine oxidase inhibitors like Allopurinol) as well as surgical or minimally invasive removal in obstructive cases, (Lulich et al., 2016) [2] . This study reports of the emerging strategies for management of multiple urinary stones in dogs.

Clinical and Laboratory findings

A 9-year-old intact male non-descript dog weighing 15 kg was presented to the Small Animal Medicine Out Patient Unit, Madras Veterinary College, Chennai with complaints in free flow of urine during micturition. Frequent red coloured urine was reported. The owner reported that the dog exhibited signs of discomfort, vocalization during urination, and dribbling of blood-tinged urine.

Clinical Evaluations

On physical examination, the dog was bright and alert, with normal body temperature, Stranguria, hematuria and urinary incontinence were observed. Abdominal palpation revealed a distended urinary bladder and discomfort upon palpation. Urinary system was examined on as per standard clinical protocols, (Ettinger et al, 2017) [8] and obstructive urinary stone disorders was diagnosed. Efforts were made to release the urine by catheterization. Catheterization was done as per standard protocols (Taylor, 2016) [9] . Resistance was noticed while inserting the urinary catheter at the level of penile urethra which indicated the possibility of obstructions. Blood samples were collected and analysed for hematology and serum biochemistry.both with and without EDTA for hematological and biochemical evaluation as described by Yogeshpriya et al., (2017) [10] . Hematological parameters were analyzed using an automated hematology analyzer (BC 2800 Vet, Mindray, China), while biochemical profiling was performed with an automated biochemical analyzer (Biosystem, Chennai) following standard clinical laboratory protocols (Kaneko, 2008) [11] . Hematology revealed a mild normocytic normochromic anemia, leukocytosis with neutrophilia. Serum biochemistry revealed a mild azotemia (BUN-28.3 mg/dL and 1.72 mg/dL), normal electrolytes profile.

Results and Discussion

Based on clinical findings, the case was diagnosed as obstructive urinary stone disorder. Urine samples were subjected to routine urinalysis, crystal studies and culture studies. Urine was found to be dark yellow with red of tinge; urinalysis done as per standard protocols which revealed an acidic urine and specific gravity of 1.030. Numerous RBC's, moderate WBC's and abundant urate crystals (Figure 1) were observed. Urine sediment was examined under microscope on low power (10X objective for identification of a microscopic crystals, total nucleated cell count, presence of cells, neoplastic cells, microorganism, renal tubular cast and epithelial cells as described by Callens, (2015) [12] and (Rizzi et al., 2017) [13] . Urine culture was undertaken as per standard protocols (Quinn et al., 2011) [14] for the diagnosis of urinary tract infection. Urine culture showed growth of Proteus spp. Antibiotic sensitivity test showed sensitivity to Amikacin, Gentamicin Ceftriaxone, and Ciprofloxacin while it was resistant to Amoxicillin and Cotrimoxazole (Figure 2). Imaging assessment is essential in detection of calculi and for planning calculi removal strategies. Radiographic examination of the abdomen was carried out in the lateral view at 66 kVp and 8 mAs using the AeroRad system (Konica Minolta Healthcare India Pvt. Ltd.). Abdominal radiography was done as per standard protocols (Thrall, 2018) [15] and it revealed calculi with intermittent radiodensity in the urinary bladder (Figure 3). A solitary radiopaque calculus was observed in the penile urethra. Abdominal ultrasonography was conducted with a convex probe (5-10 MHz) and a linear probe (2-10 MHz) using the Aeroscan-CD25 Ultrasound Scanner (Konica Minolta Healthcare India Pvt. Ltd.), following the standard procedures outlined by Sumathi et al., (2019) [6] and it confirmed the hyperechoic calculi with acoustic shadowing within the bladder (Figure 4). Clinical findings and Imaging investigations confirmed the presence of multiple calculi. Urine was relieved from the distended bladder using cystocentesis as per the standard protocol described by Taylor, (2016) [9] . After cystocentesis, the 5 mm urethral calculi was dislodged and displaced into the bladder using retrograde urohydropropulsion technique by flushing sterile saline through a urethral catheter with simultaneous compression of urethra. Considering the multiple nature of urinary stones, endourological assessment was planned. Uroendoscopic assessment and intervention was done using flexible ureteroscope Olympus URF-P5 system (Olympus Medical System, Tokyo, Japan), (Figure 5) with a distal end outer diameter 5.3Fr, insertion tube outer diameter 8.4Fr (2.8mm). The dog was premedicated for endoscopic intervention as per standard protocols Grimm et al., (2015) [17] with Atropine at 0.02 mg/kg, Butorphanol at 0.1 mg/kg and Xylazine at 1 mg/kg and induced with Ketamine at 5 mg/kg followed by Ketamine at 5 mg/kg and Diazepam 0.25 mg/kg for maintenance. The dog was placed in lateral recumbency and under general anesthesia, an urethrocystoscopy was performed as per standard protocols (Messer et al., 2005) [18] to remove the urolith in the bladder. Smaller uroliths in bladder were removed using stone basket (M/s Biorad Medisys Pvt. Ltd.) (Figure 6) as per standard protocols, (Butty et al., 2018) [19] . Image guided intervention in cystic and urethal calculi dog with stone basket retrieval procedure.

The flexible scope was gently inserted into the bladder through the urethra. Penile part of the urethra at the level of os penis was irregular with mild hemorrhage and the bladder mucosa was hyperemic with spots of erosions. Multiple black smooth-surfaced calculi of varying size was visualized with the cystoscope. Since multiple cystic calculi with variable sizes were in the bladder, 10 numbers of calculi which were smaller in size were retrieved using a stone basket. It was further decided to manage the urolithiasis by means of medical management based on the result of urinalysis. The image guided interventions were completed without any complications. The calculi retrieval were successful and the urethral obstruction was relieved with these interventions. The dog's clinical signs, including hematuria and stranguria resolved fully three after the post-procedure. The dog was administered with Ringes Lactate @ 10 ml/kg i/v, Inj. Meloxicam @ 0.2 mg/kg i/m for 3 days, and Tab.Enrofloxacin @ 5 mg/kg PO for one week. Dietary modification with a commercially available urinary care diet was advised, and the owner was instructed to maintain adequate hydration of the dog. No post procedural issues were encountered.

Follow up urinalysis at one month interval showed normal urine without any crystals, and there was no growth in the urine culture seen. Biochemistry showed normalization of BUN (8.19 mg/dL) and creatinine (1.02 mg/dL).

Discussion

Urolithiasis represents one of the most common day to day challenges in small animal practice and causes varying levels of affections urinary tract disorders in dogs. Effective management of uroliths is crucial because the disease significantly impacts animal health, welfare and even it leads to life-threatening complications if left untreated. Delayed diagnosis was commonly encountered in veterinary practice due to the nature of subclinical progression, inadequate routine screening, and low awareness among pet owners. Neglecting regular health monitoring not only contributed to late-stage presentation but also reduced the likelihood of successful, minimally invasive treatment and their outcomes. Interventional Endoscopy offers promising hope for early strategic care for urolithiasis management in small animals. Renal uroliths were frequently diagnosed as an incidental finding during imaging procedures performed for unrelated reasons and indicates their often-asymptomatic progression, (Lulich et al., 2013) [20] . This underscores the need for strategic screening protocols for dogs. Thus, regular urinalysis at least quarterly urinalysis per every year becomes essential for early identification of urolith risk factors. Urinalysis shall be made tool to serve as an effective prevention support tool.

The clinical and laboratory findings in this study were in accordance with similar findings in previous study by Lulich et al., (2000) [21] , Osborne et al., (1999) [1] , Bartges, (2015) [22] and Weese et al., (2019) [23] . Many leading authors in urological care like Lulich et al., (2016) [2] and Bartges (2015) [22] recommended for regular and procedural urine monitoring, ultrasound, and radiography every 3-6 months there by improving "recurrence surveillance". This study also highlighted the same. Retrograde urohydropropulsion had been widely recommended for dislodging urethral calculi ≤5 mm into the bladder, where they can be retrieved more safely (Hess et al., 2019) [7] . The successful use of this technique in the present case corroborated with the similar earlier findings. Manfredi et al., (2019) [24] observed that transurethral catheterization was unsuccessful in animals with urinary obstruction, and had advised of decompressive cystocentesis as a therapeutic intervention. In addition to reducing pressure on bladder wall and preventing rupture, it facilitated retropulsion of urethral plugs or urethroliths and improved the ease of catheterization in this case. Butty et al., (2018) [19] summarised that stones less than 3-4 mm in small female dogs were cases indicated for voiding urohydropropulsion and for male dogs it was limited by size of penile urethra. Flexible cystoscopy provided not only helped direct visualization of the calculi but allowed simultaneous minimally invasive retrieval of samples thereby helped to avoid open cystotomy and for managing the case effectively with medical treatments. Similar benefits have been reported, earlier (Bartges et al., 2013) [25] . The small caliber and flexible nature of the instrument facilitated atraumatic passage through the male urethra and enabled visualization of the bladder lumen, although the limited channel diameter restricted the retrieval of larger calculi, permitting only sampling with a stone basket for compositional analysis. Early identification of urolithiasis in dogs is the key element and is essential to make early efforts to prevent irreversible renal damage, urinary obstruction, and also the need for invasive surgical interventions. Many urinary stones form silently and were only become apparent when complications arise. Lulich et al., (2013) [20] identified a considerable number of uroliths in dogs incidentally on imaging and underscored the asymptomatic nature of early-stage disease. This is where we need to develop "early screening diagnostics" so as to ensure better prevention possibilities. The ACVIM consensus recommendations on the treatment and prevention of uroliths in dogs and cats also recommends for targeted surveillance in dogs at risk of recurrence or with prior history of urolithiasis, (Lulich et al., 2016) [26] . Hence breeds at risk shall be evaluated with very meticulous and planned screening strategies such as quarterly urinalysis or home care urinalysis using "dip stick" type diagnostics and enable early detections. Urinary stone disease in dogs will obstruct urine flow or induce infection and inflammation. Renal compromise occurs primarily due to obstructive uropathy caused by nephroltiths, ureteroltihs and urethroliths, leading to hydronephrosis, ischemic injury and tubular atrophy. This calls for better diagnostic skills to identify such changes. Berent and Weisse, (2015) [6] reported that obstructive uroliths had caused progressive renal damage due to backpressure and ischemic changes in the nephron architecture. Lulich et al., (2013) [20] documented that infection-induced uroliths had not only predisposed them to persistent bacteriuria but also to ascending infections that threaten renal architecture. Grauer, (2009) [27] observed that chronic ureteral obstruction had been shown to cause irreversible nephron loss and interstitial fibrosis within weeks if it was not relieved. Bartges, (2016) [4] highlighted that recurrent calcium oxalate nephroliths, if not managed aggressively were able to cause progressive renal insufficiency and eventual chronic kidney disease. Polzin, (2011) [28] emphasized that monitoring of renal biomarkers and urine concentrating ability remained essential in dogs with upper urinary tract stones to enable detection of early renal compromise. All these studies underscores that early and periodical screening with both urinalysis and imaging diagnostics are integral to improve urological care for pet animals. This case highlighted the importance of integrating urinalysis, culture, hematology, and imaging with minimally invasive endoscopic evaluations and need based interventional techniques for comprehensive management of canine urolithiasis and to prevent further complications.

Conclusion

This study demonstrated that Endourological assessment combined with stone basket retrieval and retrograde urohydropropulsion provided an effective, minimally invasive approach for managing cystic and urethral calculi in dogs. The presence of urate crystals and Proteus spp. infection underscored the importance of urinalysis and culture in guiding therapy. Although complete cystolith removal could not be achieved in this case, retrieval of intact calculi samples was beneficial for compositional analysis, which is crucial for guiding long-term dietary and medical management. The findings of this study emphasize that flexible cystoscopy enabled minimally invasive approach for both diagnosis and partial therapeutic interventions. A combination of endoscopic and conventional methods can help for better management of urinary stone disorders in dogs.

Acknowledgement

The technical support and facilities received from Dean, Madras Veterinary College, Chennai-600007 and Director of Clinics, TANUVAS is gratefully acknowledged.

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