Diagnostic Methods and Treatment Measures for Canine Urolithiasis: A Detailed Explanation
1 Clinical Symptoms
The symptoms of urolithiasis vary depending on the location of the stones. (1) Renal pelvic stones: The affected dog presents with weight loss, reduced food intake, poor spirits, unwillingness to move, and basically normal urination, sometimes with hematuria. A few dogs may show symptoms such as pain in the lower lumbar region and arching of the back. However, clinical symptoms are usually not obvious. (2) Bladder stones: Can cause lower urinary tract inflammation in the affected dog, presenting with frequent urination, urgency to urinate, hematuria, and painful dribbling of urine. (3) Urethral stones: In addition to the symptoms of bladder stones, the affected dog often also presents with difficulty urinating, urinary retention, bladder distension, and increased abdominal circumference; in severe cases, perineal hernia may develop. When the bladder is full of urine, male affected dogs often develop painful dribbling of urine and intermittent urinary incontinence.
2 Diagnosis
The diagnosis of urolithiasis is generally suspected based on clinical symptoms such as bladder distension, frequent urination, hematuria, and urinary retention combined with abdominal wall palpation, and then confirmed through X-ray imaging and B-ultrasound examination.
2.1 Palpation Examination In dogs with urethral stones, palpation may reveal pathological thickening of the urethra, and it is difficult to insert a urinary catheter during catheterization. In dogs with bladder stones, thickening of the bladder wall may be found, and sometimes the stones in the bladder can be palpated.
2.2 X-ray Examination During X-ray examination, place the dog in lateral recumbency with both hind legs pulled backward, select an appropriately sized film, and perform radiography of the pelvis and urethra. If bladder distension is seen and there are high-density foreign bodies in the renal pelvis, bladder, or urethra, a definitive diagnosis can be made. For fine sand-like small stones, careful observation is required to confirm. Sometimes some radiolucent stones, such as cystine stones and inflammatory exudates, cannot be seen on X-ray films and can be detected through B-ultrasound examination.
2.3 Differential Diagnosis Hematuria is a common symptom of the urinary system. Urolithiasis, cystitis, prostatitis, and injuries to the reproductive and urinary systems can all cause hematuria. (1) Cystitis: Scanty and frequent urination, hematuria, turbid and foul-smelling urine, and difficulty urinating; moreover, hematuria is particularly severe at the end of urination, palpation elicits a painful contractile response, the bladder wall is thickened, and X-ray examination shows no stone-like particles. (2) Reproductive system injury: Blood in the urine after parturition or with endometritis, etc., but symptoms such as urgency and frequency of urination are not obvious. (3) Urinary system injury: Hematuria caused by trauma or parasites; the former has a clear history of trauma, while the latter presents with weight loss, abdominal pain, constipation, and vomiting.
3 Conservative Treatment
For smooth, round stones with a diameter of less than 0.5 cm, without urinary tract obstruction or infection, and with good renal function, medication can be used.
3.1 Removing the Predisposing Causes of Kidney Stones Actively treating the causes of stone formation, such as: in primary hyperparathyroidism, removing the parathyroid glands; treating malignant tumors; controlling renal pelvic infection and relieving urinary tract obstruction, are all effective measures to prevent stone formation and recurrence.
3.2 General Treatment (1) Ensure adequate water intake: Especially in summer and at night, to avoid excessive concentration of urine at night, it is essential to emphasize drinking water before bedtime and to drink water again in the middle of the night. It is best to drink magnetized water containing minerals, so that the daily urine output is maintained at 2-3 L, which can dilute urine, reduce crystal precipitation, flush the urinary tract, and expel tiny stones. (2) Diet: The dietary composition should be determined according to the type of stone and urine pH. For idiopathic hypercalciuria, calcium intake should be restricted to reduce urinary calcium content. For recurrent oxalate stones without hypercalciuria, a low-calcium diet is not necessary. If a low-calcium diet increases urinary oxalate excretion and leads to stone formation, a low-calcium diet should also not be adopted. Control sodium intake; excessive sodium intake can increase urinary calcium excretion. In hyperuricemia and hyperuricosuria, a low-purine diet should be followed, avoiding animal offal and eating less meat.
3.3 Drug Treatment
3.3.1 Hypercalciuria (1) Thiazide diuretics: They can increase renal tubular reabsorption of calcium by reducing renal tubular reabsorption of water and sodium and through a direct effect on the renal tubular sodium and potassium ion transport system, thereby reducing urinary calcium excretion; the resulting increase in blood calcium can inhibit intestinal calcium absorption. Used for renal hypercalciuria and absorptive hypercalciuria. Hydrochlorothiazide 50-100 mg daily, or the corresponding dose of other diuretics. (2) Sodium cellulose phosphate: After oral administration, it binds with calcium in the intestine to limit calcium absorption, 2.5-5 g each time, taken with meals. Because calcium in the intestinal lumen is reduced, calcium binding with oxalate is reduced, leading to increased intestinal absorption of oxalate, so oxalate intake should also be appropriately restricted at the same time. It should not be used in primary hyperparathyroidism, renal hypercalciuria, conditions with increased bone calcium mobilization, or in growing dogs. (3) Phosphate salts: Neutral or alkaline soluble sodium or potassium phosphate binds with calcium to form calcium phosphate salts, reducing urinary calcium concentration and calcium oxalate saturation. It should not be used when the glomerular filtration rate is below 30 ml/min or in urinary tract infections, because it can cause metastatic soft tissue calcification and infectious stones.
3.3.2 Hyperoxaluria (1) Enteric hyperoxaluria: Restrict oxalate and fat intake, and supplement potassium citrate, which can lower urinary pH and increase citrate. (2) Primary hyperoxaluria: Some affected dogs occasionally respond to vitamin B6 (200 mg/d). Increasing urine output, using thiazide diuretics and citrate salts, and supplementing phosphorus are sometimes effective.
3.3.3 Hypocitraturic Calcium-Containing Kidney Stones Potassium citrate can effectively limit this