Nutritional Support of Renal and Urinary Tract Function
Renal and lower urinary tract disorders are frequently encountered in small animal practice, with conditions ranging from benign lower urinary tract inflammation to life-threatening renal failure. Clinical manifestations can vary widely, necessitating a thorough diagnostic approach to differentiate between functional and structural abnormalities.
Recognising Urinary Tract and Kidney Disorders
A wide spectrum of clinical signs may indicate underlying renal or urinary tract dysfunction, requiring prompt assessment to determine the etiology and appropriate intervention.
1. Micturition Abnormalities
Micturition abnormalities encompass dysuria (difficulty urinating), pollakiuria (increased frequency of urination), and stranguria (straining during urination). These signs often indicate lower urinary tract pathology, such as bacterial cystitis, idiopathic feline cystitis, or obstructive disorders like urolithiasis and neoplasia.
A study by Kruger et al. (1991) found that 54% of feline lower urinary tract disease (FLUTD) cases were idiopathic, with stress-related factors playing a significant role in disease onset.
2. Urinary Incontinence
Urinary incontinence is an involuntary loss of urine and may be classified as neurogenic (e.g., spinal cord injury, degenerative myelopathy) or non-neurogenic (e.g., urethral sphincter mechanism incompetence [USMI], ectopic ureters).
USMI is the most common cause of acquired urinary incontinence in spayed female dogs, particularly large breeds.
Congenital causes, such as ectopic ureters, account for up to 50% of urinary incontinence cases in young female dogs (Holt & Thrusfield, 1993).
3. Polyuria & Polydipsia (PU/PD)
Polyuria (PU) is defined as an increased urine output (>50 mL/kg/day), often accompanied by polydipsia (PD), which exceeds normal daily water intake (>100 mL/kg/day). PU/PD can be a primary disorder or secondary to systemic diseases such as:
- Chronic kidney disease (CKD) – characterized by progressive nephron loss, leading to reduced urine concentration ability.
- Diabetes mellitus – results in osmotic diuresis due to glucosuria.
- Hyperadrenocorticism (Cushing’s disease) – promotes water diuresis due to cortisol’s inhibitory effects on antidiuretic hormone (ADH).
Polzin (2011) highlighted that early detection of PU/PD in CKD can delay disease progression through dietary and pharmacological interventions.
4. Anuria & Oliguria
Anuria (complete absence of urine production) and oliguria (markedly reduced urine output) are critical conditions associated with:
- Acute kidney injury (AKI), often secondary to nephrotoxins (e.g., ethylene glycol, NSAIDs, aminoglycosides).
- Obstructive uropathy (e.g., urethral obstruction, bladder rupture).
- End-stage renal failure, where nephrons are no longer functional.
A retrospective study by Cowgill et al. (2016) found that aggressive fluid therapy and early intervention in AKI improved survival rates in 65% of canine cases.
5. Hematuria (Blood in Urine)
Hematuria can be macroscopic (visible) or microscopic (detected via urinalysis) and may originate from the upper or lower urinary tract. Key differentials include:
- Urinary tract infections (UTIs) – bacterial infections causing mucosal irritation.
- Urolithiasis – hematuria due to mechanical irritation by urinary calculi.
- Neoplasia – transitional cell carcinoma (TCC) of the bladder commonly presents with hematuria and dysuria.
Mutsaers et al. (2003) reported that TCC accounts for 50-75% of all canine bladder tumors, with Scottish Terriers being at 18-20 times greater risk.
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Dog diagnosis
Diagnosis Approach
A structured diagnostic approach is essential for identifying and managing kidney and urinary tract disorders in dogs and cats. Clinical signs such as polyuria, polydipsia, dysuria, hematuria, and incontinence necessitate a thorough workup, starting with urinalysis, bloodwork, and imaging.
1. Urinalysis
Remains the cornerstone of urinary disease diagnosis, assessing urine-specific gravity (USG) to determine concentrating ability and detecting abnormalities such as proteinuria, hematuria, pyuria, or crystalluria. The urine protein-to-creatinine (UPC) ratio is crucial for quantifying proteinuria, helping differentiate between glomerular and tubular disease. Persistent proteinuria with an elevated UPC ratio suggests glomerular disease, whereas mild proteinuria often accompanies lower urinary tract inflammation or infection.
2. Blood test
Including serum creatinine, blood urea nitrogen (BUN), and symmetric dimethylarginine (SDMA), provide insight into kidney function, with SDMA offering earlier detection of renal dysfunction than creatinine. Electrolyte imbalances, such as hyperkalemia in acute kidney injury (AKI) or hypokalemia in chronic kidney disease (CKD), can further guide clinical management.
3. Imaging Studies
Including abdominal radiographs and ultrasonography, help detect structural abnormalities such as urolithiasis, neoplasia, or congenital defects. Radiographs are useful for identifying radiopaque stones, while ultrasound provides superior visualization of renal parenchymal changes, bladder wall thickening, and radiolucent stones. For more complex cases, computed tomography (CT) urography offers advanced imaging of the urinary tract, particularly for diagnosing ectopic ureters, subtle uroliths, or renal pelvic masses. Cystoscopy is valuable for direct visualization of the bladder and urethra, especially in cases of recurrent hematuria or suspected neoplasia.
4. Microbiological Testing
Including bacterial culture and sensitivity, is essential in patients with suspected urinary tract infections (UTIs), particularly those with recurrent or complicated infections. A culture-confirmed diagnosis ensures appropriate antimicrobial selection, reducing the risk of antimicrobial resistance. In cases of persistent hematuria or lower urinary tract signs with negative culture results, additional testing such as bladder biopsy, urine cytology, or polymerase chain reaction (PCR) testing for infectious agents may be warranted.
Therapeutic Strategies
The management of kidney and urinary tract disorders in dogs and cats depends on the underlying cause, severity of disease, and individual patient factors. Treatment strategies typically involve a combination of dietary modifications, pharmacological therapy, and, in some cases, surgical or interventional procedures.
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In chronic kidney disease (CKD), dietary management plays a key role in slowing disease progression and maintaining overall health. Specialized diets formulated to support kidney function typically include controlled levels of protein, phosphorus, and sodium while incorporating beneficial nutrients such as omega-3 fatty acids, antioxidants, and B-complex vitamins. Evidence suggests that nutritional adjustments can improve quality of life and extend survival in affected pets.
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For conditions involving protein loss through the kidneys, medications that regulate blood pressure and reduce glomerular hypertension may be used to slow disease progression. Inflammatory and obstructive lower urinary tract disorders often require symptom-specific treatments, including muscle relaxants for urethral spasm, anti-inflammatory medications for bladder irritation, and analgesics for pain management. Careful selection and monitoring of these medications are essential, particularly in patients with pre-existing kidney dysfunction.
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Infectious urinary diseases, including bacterial urinary tract infections (UTIs), should be treated based on culture and sensitivity results to ensure appropriate antimicrobial use and prevent resistance. Treatment duration varies depending on whether the infection is uncomplicated or associated with an underlying condition such as urinary stones, anatomical abnormalities, or systemic disease.
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Surgical intervention or minimally invasive procedures may be necessary when medical management is insufficient. Urolith removal, correction of congenital abnormalities, and surgical treatment of obstructive conditions are commonly performed to restore normal urinary function. In cases of bladder tumors or chronic urinary tract obstructions, a multimodal approach combining medical therapy, surgical intervention, and supportive care may be required to maintain urinary health and improve long-term outcomes.
Innovative Veterinary Solutions
Adjunctive therapies and nutraceuticals play an increasing role in urinary health management. Omega-3 fatty acids have demonstrated renoprotective effects in CKD, reducing inflammation and slowing disease progression. Antioxidants, such as vitamin E and coenzyme Q10, may mitigate oxidative stress associated with kidney disease.
For lower urinary tract health, glycosaminoglycan (GAG) supplements, including glucosamine and chondroitin sulfate, are proposed to reinforce the bladder’s protective mucosal barrier, potentially benefiting patients with feline idiopathic cystitis (FIC). Cranberry extracts and D-mannose have been investigated for their ability to reduce bacterial adhesion in the urinary tract, serving as potential non-antibiotic preventive measures for recurrent UTIs.
Urinary pH modulation is an essential strategy for preventing urolithiasis. Diets formulated to maintain a urinary pH of 6.0–6.5 help prevent struvite crystallization, whereas calcium oxalate stone prevention often requires urine alkalization and increased water intake. Potassium citrate supplementation can be beneficial for managing calcium oxalate and urate stone formers by increasing urinary pH and reducing crystal formation.
Clinical Guidelines & Best Practices
Veterinarians should reference evidence-based guidelines to ensure optimal patient care. The International Renal Interest Society (IRIS) provides staging and treatment recommendations for CKD, emphasizing dietary modification, proteinuria control, and blood pressure management. The International Society for Companion Animal Infectious Diseases (ISCAID) offers antibiotic stewardship guidelines for UTIs, advocating for targeted therapy based on culture results and minimizing unnecessary antibiotic use. Additionally, ACVIM consensus statements outline best practices for managing conditions such as proteinuria, urinary incontinence, and leptospirosis.
Product selection for renal and UT support
- DiReNe contains a unique combination of natural ingredients with antioxidative, nitrogen- and phosphate binding, filtration promoting and anti-inflammatory properties.
- Dermoscent Uti-zen is formulated with the whole fruit of cranberries and recommended for the urinary comfort and well-being of animals prone to urinary discomfort (elderly, stressed animals…). Cranberry is known for its properties in limiting the adhesion of E. Coli bacteria* and also for its antioxidant effect.
- Dr. Baddaky Omega-3 is a high-quality marine-derived supplement designed to support overall kidney and urinary tract health in dogs and cats. Rich in EPA and DHA, it is commonly used in managing renal conditions and promoting bladder health as part of a comprehensive care plan.
