September 22, 2018

Purdue 2018: Acute Kidney Injury in Small Animals

Timely recognition of this potentially severe disease and management of associated complications are critical for patient comfort and treatment success.
By Nicola M. Parry, BVSC, MRCVS, MSC, DACVP, FRSPH, ELS
Cat Fluid Kidney TreatmentAccording to Sarah Steinbach, Dr. med. vet, DACVIM, DECVIM, an assistant professor and director of the Purdue Veterinary Hemodialysis Service at Purdue University College of Veterinary Medicine in West Lafayette, Indiana, acute kidney injury (AKI) can be a serious disease that may carry a poor prognosis.

Presenting at the 2018 Purdue Veterinary Conference, which was held on the Purdue University campus, Dr Steinbach emphasized the need to “recognize that AKI represents a wide spectrum of disease,” ranging from mild (without azotemia) to severe (with high-grade azotemia and serious clinical manifestations). Additionally, animals can vacillate on the spectrum of disease severity during an AKI event, depending on how the animal is being treated, she noted. “It is a very dynamic disease.”

RELATED: DIAGNOSIS AND STAGING
In most cases, we do not identify the cause of AKI in our patients, despite extensive laboratory testing, Dr. Steinbach said. However, some of the most commonly reported causes of AKI in small animals have infectious, toxic, ischemic, or neoplastic origins.

A staging system for veterinary patients with AKI provides a mechanism to help identify animals with AKI and stage their disease, Dr. Steinbach said. However, she noted, no treatment recommendations are currently available to help guide the management of these patients.

Dr. Steinbach stressed that AKI is a multiorgan disease because the kidney affects many body systems. For example, about 80% of dogs with AKI develop hypertension, she said. So, the treatment plan must also be wide ranging, to address associated problems such as hypertension and gastrointestinal ulceration.

Indeed, the many complications that can arise in animals with AKI point to the intensive care needs of this condition. This disease cannot typically be managed on an outpatient basis, she stressed.

TREATMENT
Overall, timely recognition of AKI and management of its associated complications is critical for patient comfort and treatment success. Veterinarians should treat the primary cause of the AKI, if it is known, Dr. Steinbach said. Otherwise, treatment should aim to support the animal while its kidneys heal.

Although the goal is to restore and maintain hydration in an animal with AKI, she cautioned veterinarians to take care to avoid fluid overload in these patients. “In 99.9% of [cases] when we have excessive edema in these patients, it’s our fault,” she emphasized, “because we give them too much fluid.”

Fluid overload is bad, she explained, adding that in dogs, “the odds ratio for death increases by 1.08 with each 1% increase in fluid overload.” In critically ill people with AKI, fluid overload is independently associated with mortality, said Dr Steinbach, sharing the results of a study showing that patients with fluid overload at the time of their peak level of serum creatinine were significantly less likely to recover kidney function.  “You cannot just ‘flush’ the kidneys,” she stressed. Fluid diuresis does not improve the animal’s glomerular filtration rate.

If fluid therapy fails to restore urine output in veterinary patients with AKI, diuretic therapy may be used. In human medicine, diuretic therapy is contraindicated in such cases, Dr. Steinbach said, and these patients undergo hemodialysis.

However, because hemodialysis is not always an option for small animal patients, she noted that diuretic therapy may be used. Nevertheless, because it is the best practice treatment in these instances, the patient should undergo hemodialysis if an owner is able and willing to choose this option. In particular, in patients with AKI, insufficient urine output that results in either fluid retention and edema, or hyperkalemia, is an absolute indication for hemodialysis.

“The earlier we can intervene with dialysis, the better for the patient,” Dr. Steinbach stressed. Although no data are currently available to support this in veterinary patients, we know this from studies in human patients, she concluded.

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