Acute kidney injury (AKI) has been well recognized as one of the most threatening disease in small animals. The signs of azotemia such as anorexia, vomiting and oliguria are presented. Grading of AKI (2013) has been defined by International Renal Interest Society (IRIS)¹ from Stage I to IV depending upon plasma creatinine concentration. However, the rate of increase in plasma creatinine concentration may be more important. Moreover, the substage may be notified by clinician such as oliguria (O) or nonoliguric (NO) and whether they require renal replacement therapy.

The Causes of AKI

The causes of AKI in many countries may be related to poisoning such as ethylene glycol poisoning in dogs and lily poisoning in cats. Medication such as nonsteroidal anti-inflammatory drugs (NSAIDs) and antibacterial agents especially aminoglycoside group was well documented. However, in many cases, the known causes of kidney failure may not be demonstrated. In Thailand, AKI occurs in dogs regardless of sex, breed and age. In most of the cases, the blood parasite, especially Ehrlichia canis, were found. Other causes may include leptospirosis, pyometra, urinary tract infection or diuretic induced prerenal azotemia in dogs with congestive heart failure. Detection of E. canis was demonstrated mostly by snap 4Dx rather than from direct blood smear. Moreover, some dogs had coinfection with anaplasmosis. The dogs usually presented with mild anemia with decreased both bicarbonate and most of them had hypokalemia. The proteinuria was found in most of the cases infected with E. canis. The duration of treatment will be from 1 to 4 months by conventional supportive therapy.

Treatment Protocol

Animals which have acute rises in blood urea nitrogen and plasma creatinine concentration may be treated with many interventions coincided with treating specific causes. The most common treatment is conventional fluid therapy. The high techniques will include hemodialysis and peritoneal dialysis.

Intermittent Hemodialysis (IHD)

IHD has been introduced first case in dog on 2003. The machine was setup for using in animals with weight higher than 15 kg. The indication for HD is for dogs with acute onset of renal azotemia. However, it can be introduced in dogs with acute on top of chronic kidney disease (CKD).

Components of HD

The HD is composed of vascular access by using double lumen catheter introduced into the jugular vein. The dialyzer membrane was polysulfone. The delivery system included hemodialysis machine, dialysate and reverse osmosis water supply which installed as a single unit. The water system was checked to meet AAMI/ASAIO standards for HD water.

HD Prescription

The treatment intensity guideline was depending upon the blood urea nitrogen levels and the episode of treatments. Moreover, the dialyzer was chosen to match the body surface. The blood flow and dialysis time were estimated in corresponding to the desired urea reduction ratio as shown by the relationship between urea reduction ratio and blood process.² The extracorporeal volume was also calculated depending on the animal size.

Monitoring

The vital signs including body temperature, heart rate and respiratory rate have to be monitored throughout the dialysis period. Other measurement such as packed cell volume, plasma specific gravity, blood pressure have to be performed during dialysis period. Other special measurement such as electrocardiogram and blood gas may be needed. The activated clotting time has be measured since heparin has been introduce into the circuit.

Complications

The complications can occurs in animals or in the process of HD procedure. The vascular access may be difficult and animal may have bleeding at the point of the catheterization. Moreover, the catheter may not be patent for many days and partial blood clot may cause a difficult in pulling out the blood during HD.

One of the complications found in dogs is the condition called "disequilibrium syndrome". The dogs will show signs of restlessness, vomiting, tremor, confusion, stupor and even going to coma and death after intensive dialysis using IHD. The reason is the osmotic pressure in the plasma was dropped so quickly if the clinician removed the urea dramatically in short duration causing the brain edema thereafter. The mannitol should be administered to counteract the osmotic disequilibrium.

Advantages and Disadvantages

The IHD can be used with effective removal of nitrogenous waste within a short time period. The animals and personals can be relaxed and rest for a few hours before the dialysis begins on the next day. The continuous renal replacement therapy has been introduced to put the animal in slow dialysis for a long period of time which can avoid the osmotic complications but needs more attention times. However, the catheter, equipment and procedure for HD is expensive. The procedure also requires the trained personals. Some machine and accessory including the tubing line have limitation due to high extracorporeal volume and dialysis can be performed only in the large animals.

Although the HD is effective in treatment of AKI, it is not been performed in animals that have the chronic kidney disease. Unlike in human, the HD can be prescribed in all kinds of azotemia. Moreover, the HD and other dialysis procedures are conducted in patients awaited for renal transplantation. Thus, HD is still limit in veterinary practice.

Peritoneal Dialysis (PD)

The PD was first performed in dogs with acute kidney injury in Thailand on 1988. The procedure may not be as complicated as HD and the clinician can be trained to handle the PD procedure which is easier than HD. The concept of PD is removing the nitrogenous waste products and other substances such as potassium by diffusion through membrane into the dialysis solution inside the abdomen. The rate of diffusion is depending upon the size and charge of the particles and the concentration gradient. The convection can be occurred if the dialysis solution had higher osmolarity.

Contraindications

The PD shall not be performed in many conditions such as severe coagulopathy, peritonitis or peritoneal fibrosis, in animals with hernia or in those who have been passing the recent abdominal surgery.

PD Procedures

There are many type of PD catheter that was developed in order to get a good dialysis fluid drainage. The Blake catheter seems to be a good one. The catheter has to be introduced into the abdomen with sterile aseptic technique.

The location should be verified by radiography. The dialysis solution contains varying glucose concentration depending on the clinician needed. The fluid needs to be warmed to body temperature before putting into the animals. Timely interval between draining will vary from 20 minute to 6 hour depending on severity of azotemia and body fluid retention. Varying glucose concentration in the dialysis fluid or changing the frequency of indwelling time will change the outflow rate. The volume inflow may be between 10–30 ml/kg.

The heparin should be added into the dialysis fluid to prevent the fibrin formation and obstruction of outflow. Antibiotics need to be put in if the infection was suspicious or the while blood cell was found in the dialysate after draining. The most important is the precaution of infection during changing the bag of dialysis fluid.

Records

The body weight, packed cell volume, white blood cell count, total protein and plasma glucose should be measured periodically. The BUN and plasma creatinine concentration should be measured along with electrolytes such as potassium and phosphorus. Blood gas should be monitored for pH and bicarbonate concentrations. Finally, urine output has to be monitored to estimate the renal recovery.

Complications

The most common complication is the difficult in outflow of the dialysis fluid. This will occur at the beginning of dialysis procedure or a few days later. Catheter obstruction by omentum can be as quickly as a first few days. Positioning the catheter at the right location and remove some omentum are required. Other complications involve the infection after PD procedure. The hypoalbuminemia may be encountered if the infection develops. Some animals may have dialysis leakage at the exit site of the catheter. Finally, animals may develop peripheral edema or pleural effusion if the fluid is over retained in the body.

Discontinuation

Just like other treatments, the PD will be stopped after urine is produced and the azotemia was eradicated.

In conclusion, the renal replacement therapy either using HD or PD are an opened choice for treatment in animals suffering from AKI and fail to response to conventional supportive treatment with fluid therapy. However, the procedures should be used only in acute abrupt changes in renal functions and recovery is suspected to return within a few days. The appropriate procedure selected is varied depending upon the disease in each country and the environment of each practice. Once the clinician desires to setup the dialysis unit in their practice, the financial support, trained personals and the intensive care unit available for patients have to be in consideration.

References

1.  International Renal Interest Society. Grading of acute kidney injury. 2013. http://www.iris-kidney.com/guidelines/grading.html (VIN editor: Original link was modified as of 2-23-2016).

2.  Cowgill LD. Hemodialysis in veterinary medicine. The Dialysis Times Archive. 2013 Oct;20(3):1–5.