A Simple Urine Ratio Could Help Predict Which CKD Dogs Are Running Out of Time

Chronic kidney disease is one of the most common causes of death in dogs, and one of the most frustrating to manage not because treatment options don't exist, but because it is often difficult to know which patients are deteriorating faster than their bloodwork suggests. New research from North Carolina State University and the University of Florida may change that, at least in part.

The study, published May 28 in the Journal of Veterinary Internal Medicine, found that dogs with a urine ammonia-to-creatinine ratio (UACR) below 2.0 were three times more likely to die of renal failure, had significantly faster disease progression, and lived roughly half as long as dogs with higher UACR values. The difference was stark: median survival was 189 days in the low-UACR group versus 445 days in the higher-UACR group.

Terminology note: In veterinary medicine, UACR stands for the urine ammonia-to-creatinine ratio. In human medicine, a similar abbreviation (uACR) refers to urine albumin-to-creatinine ratio. These are different measurements — important to keep straight when reading across species literature.

Why Ammonia Excretion Matters in CKD

The underlying physiology here connects directly to what you already know about CKD progression. As kidney function declines, the tubular capacity to excrete acids — including ammonia — drops. In humans with CKD, this reduction in urinary ammonia excretion is closely linked to metabolic acidosis, which in turn accelerates disease progression and worsens outcomes. The relationship in dogs has been less well studied, which is exactly what this paper set out to address.

The research enrolled 50 client-owned dogs with IRIS Stage II–IV CKD who were already being managed on a therapeutic renal diet. Dogs were followed for up to 12 months with serial blood and urine sampling. The cohort was predominantly Stage II (82%), which makes the survival differences even more meaningful — these were not end-stage patients.

Most of the dogs had normal serum bicarbonate but abnormal UACR levels — suggesting ammonia dysregulation precedes the changes we catch on standard bloodwork.

CKD progression was defined as a greater than 25% increase in serum creatinine from baseline — a meaningful, clinically relevant threshold rather than a subtle statistical one.

The study also found that dogs with a urine protein-to-creatinine ratio (UPC) below 1.0 had a significantly lower risk of death (HR 0.351), reinforcing the value of urine protein assessment in this population — though that association is already more familiar in clinical practice.

What Makes This Finding Particularly Useful

The most clinically significant piece of this study is the timing of UACR changes relative to standard markers. In this cohort, most dogs had normal serum bicarbonate concentrations at enrollment — the conventional bloodwork marker for acid-base status — but already had abnormal UACR values. That means UACR may be detecting acid dysregulation in the kidney tubules before it has progressed to the point of showing up as metabolic acidosis on a standard chemistry panel.

For a clinician managing a dog with early-to-moderate CKD who looks reasonably stable on bloodwork, that is a meaningful window. If UACR is already below 2.0, you may be looking at an animal with a significantly compressed survival timeline that standard monitoring alone would not flag.

UACR could identify dogs at risk of faster progression before traditional bloodwork shows the change.

The Therapeutic Implication — Alkali Therapy

The study authors specifically flag alkali therapy as the intervention that a low UACR might help select for. The rationale follows directly from the pathophysiology: if the kidney is failing to excrete acid, supplementing with alkalizing agents — potassium citrate being the most common in small animal practice — may reduce the acid burden on the tubules and slow progression.

This is not a new concept. Alkali therapy is already used in some CKD patients. What this research adds is a way to identify which patients are most likely to benefit from it earlier in the disease course, before they deteriorate to the point where serum bicarbonate becomes abnormal. UACR below 2.0 may become a clinically useful trigger for initiating or escalating that conversation with clients.

Study Limitations Worth Knowing

Fifty dogs over 12 months is a meaningful prospective dataset for a nephrology study in veterinary medicine, but the numbers are still relatively small. The cohort was predominantly IRIS Stage II, which is useful for early detection insights but means the findings may not fully represent the Stage III–IV population. The study also enrolled only dogs already on therapeutic renal diets, so the findings apply specifically to a managed CKD population rather than newly diagnosed, untreated patients.

These are not reasons to dismiss the findings — they're reasons to watch for the larger validation studies that this work will hopefully generate.

The Bottom Line for Practice

UACR is a non-invasive, urine-based measurement. You are already collecting urine on your CKD monitoring patients. Adding ammonia quantification to your urinalysis panel is the kind of incremental test that, if this research holds up in larger studies, could meaningfully change how you stratify risk and time therapeutic interventions in dogs with CKD.

The cutoff to know is 2.0. Below it, the data suggest a patient that is progressing faster than their bloodwork may indicate and who may benefit from early alkali therapy. The study is published in the Journal of Veterinary Internal Medicine and was supported by the American Kennel Club Canine Health Foundation.

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