Renal Flashcards
What is azotemia?
Azotemia is the term for increased blood concentrations of urea, serum creatinine (sCr), and other nonprotein nitrogenous substances.
What causes prerenal azotemia?
Prerenal azotemia is caused by decreased renal blood flow (RBF), such as dehydration, hypovolemic shock, or cardiac failure.
What causes renal azotemia?
Renal azotemia is caused by decreased glomerular filtration rate (GFR) due to renal injury.
What causes postrenal azotemia?
Postrenal azotemia is caused by the failure of excretion due to urinary tract obstruction or rupture.
What are many cases of AKI linked with?
inflammatory changes, toxic insults
Describe the continuum between prerenal and renal azotemia.
There is a continuum between prerenal and renal azotemia, where poor perfusion eventually leads to intrinsic kidney damage.
How is serum creatinine (sCr) processed by the kidneys?
Serum creatinine (sCr) is freely filtered by the glomerulus and is neither reabsorbed nor secreted.
What is the relationship between serum creatinine (sCr) and glomerular filtration rate (GFR)?
Serum creatinine (sCr) is inversely proportional to GFR and acts as a functional marker for it.
How does serum creatinine (sCr) respond to a decrease in GFR in advanced kidney disease?
In advanced disease, a small decrease in GFR results in a large increase in serum creatinine (sCr).
How does serum creatinine (sCr) respond to a decrease in GFR in early kidney disease?
In early renal disease, a large decrease in GFR results in only a small increase in serum creatinine (sCr).
At what point does serum creatinine (sCr) increase above reference limits?
Serum creatinine (sCr) does not increase above reference limits until GFR is reduced by nearly 75%.
How do heavily muscled animals affect serum creatinine (sCr) values?
Heavily muscled animals can have serum creatinine (sCr) values above reference limits.
How is creatinine production affected in humans with sepsis?
In humans, the production of creatinine is reduced in sepsis.
Has reduced creatinine production in sepsis been demonstrated in horses?
No
Why is blood urea nitrogen (BUN) a less specific estimator of GFR?
Blood urea nitrogen (BUN) is influenced by many factors, including dietary protein and protein metabolism, making it a less specific estimator of GFR and not useful for diagnosing AKI.
What does Acute Kidney Injury (AKI) represent?
AKI represents a spectrum of kidney damage, ranging from inapparent nephron injury to acute renal failure (ARF), involving a sudden decline in kidney function and a failure to excrete waste products and maintain fluid and electrolyte balance.
What is the prevalence of AKI in hospitalized horses?
AKI affects approximately 3% to 23% of hospitalized horses.
What are the risk factors for decreased renal blood flow and hypoxia in AKI?
Hypotension: Low blood pressure reduces renal perfusion.
Dehydration: Decreases overall blood volume, reducing renal blood flow (RBF).
Hypovolemia: Significant loss of blood volume, leading to reduced kidney perfusion.
Anemia: Lower oxygen-carrying capacity of the blood, leading to renal hypoxia.
What is Systemic Inflammatory Response Syndrome (SIRS) and its effects on kidneys?
SIRS causes systemic inflammation, often due to sepsis or endotoxemia, leading to:
Hypotensive injury: Decreased blood pressure affecting kidney perfusion.
Renal microcirculatory dysfunction: Impaired blood flow within the kidneys.
Thrombotic injury and infarction: Blood clots causing localized tissue death.
Fibrin deposition: Accumulation of fibrin protein, leading to kidney damage.
Renal cortical necrosis: Death of kidney tissue due to prolonged hypoxia.
What are the nephrotoxic agents that can cause AKI?
Aminoglycosides: Accumulate in the proximal tubular cells, causing nephrotoxicity.
Oxytetracycline: Causes AKI in high doses.
Bisphosphonates: Cause proximal tubule degeneration and glomerulosclerosis.
NSAIDs: Inhibit cyclooxygenase (COX), causing medullary crest necrosis and interstitial nephritis.
Other medications like omeprazole and hydroxyethyl starches are nephrotoxic in humans, but evidence in horses is lacking.
What endogenous nephrotoxins can lead to pigment nephropathy?
Myoglobin and hemoglobin released during muscle injury or hemolysis.
How can the risk of nephrotoxicity be managed?
Hydration: Initiate IV fluid treatment (IVFT) before administering nephrotoxic drugs.
Clinical judgment: Weigh benefits of prompt drug administration against AKI risk.
Combination therapy: Avoid simultaneous use of multiple nephrotoxic drugs.
What are other causes (rather than nephrotoxic drugs, decreased RBF and SIRS) of AKI in horses?
Immune-mediated injury: Conditions like purpura hemorrhagica causing glomerular damage.
Idiosyncratic hypersensitivity reactions: Leading to acute interstitial nephritis.
Infections: Actinobacillus spp. (especially in foals) and leptospirosis.
What are the clinical signs of AKI?
Oliguria: Reduced urine output (<0.5 mL/kg/h).
Inappetence and lethargy: Persisting beyond the resolution of the primary disease.
Neurological signs: Uremic encephalopathy in severe azotemia, manifesting as altered mental status or seizures.
What is the Veterinary Acute Kidney Injury (VAKI) System?
Stage 0: <150% change from baseline sCr.
Stage 1: 150%-199% change or absolute increase >0.3 mg/dL (26.5 µmol/L).
Stage 2: 200%-299% change.
Stage 3: ≥300% change or absolute increase to >4.0 mg/dL (>354 µmol/L).
What are common laboratory findings in AKI?
Electrolyte abnormalities: Hyponatremia, hypochloremia, hyperkalemia.
Urine Specific Gravity (USG): >1.035 in hypovolemic states, <1.020 in ARF despite hypovolemia.
Urinalysis: Detects microscopic hematuria, casts, and glucosuria.
What imaging techniques are used for diagnosing AKI?
Renal ultrasonography: Often unremarkable but useful for ruling out obstructions and evaluating kidney size and structure.
Renal biopsy: Rarely alters management and is not recommended due to risk and limited diagnostic value.
What are the initial treatment steps for AKI?
Focus on treating the underlying cause.
IV Fluid Therapy (IVFT): Essential to restore intravascular volume, blood pressure, and renal perfusion.
What is the approach to fluid therapy in AKI?
Response monitoring: Assess sCr levels and urine output within 24-72 hours.
Persistent hypotension: Use inotropes (e.g., dobutamine) and vasopressors (e.g., norepinephrine) if fluid replacement is insufficient.
How should urine output be monitored during IVFT in AKI?
Detect oliguria or anuria.
Furosemide challenge test to induce diuresis in euvolemic AKI patients. Avoid further doses unless a positive response is seen. Mannitol is no longer recommended due to nephrotoxicity.
What are the prognostic indicators for AKI?
Azotemia is a poor prognostic indicator if secondary to many conditions.
Early detection and management improve outcomes significantly.
Response to IVFT is a favorable prognostic indicator. Horses producing adequate urine and showing a decrease in sCr within 72 hours have a better prognosis.
What are the prevention strategies for AKI?
Close monitoring: Regularly check sCr levels in at-risk patients.
Prompt treatment: Correct primary diseases, hypovolemia, and hypotension quickly.
Nephrotoxic drugs: Use cautiously and avoid simultaneous use of multiple nephrotoxic agents.
Supportive measures: Maintain hydration and monitor for early signs of AKI.
Intravenous sodium bicarbonate: Often suggested to protect against pigment nephrosis through urine alkalinization, although its superiority to IVFT without sodium bicarbonate is not demonstrated.
What is the dose and mechanism of action for furosemide in horses?
Bolus 0.5-2 mg/kg IV/IM q4h-q6h or CRI 0.25-2 mg/kg/h; it decreases sodium, chloride, and potassium tubular reabsorption.
What are the adverse effects of high doses of furosemide in horses?
High doses can be nephrotoxic, causing an increase in sCr due to tubuloglomerular feedback and electrolyte disturbances.
What is the consensus on using furosemide in foals and adult horses?
Single high-dose furosemide test is the first-line treatment for normotensive foals and adults with anuria/oliguria.
What is the dose and mechanism of action for mannitol in horses?
A: 0.25-1 g/kg IV q4h-q8h (20% solution); it increases osmotic pressure in renal tubules.
Why is mannitol not recommended for use in horses?
It is associated with increased risk of AKI and can cause osmotic renal tubular injury.
What is the dose and mechanism of action for dobutamine in horses?
2-20 µg/kg/min; it is a beta-1 agonist with inotropic effects.
What are the consensus uses of dobutamine in foals and adult horses?
It is the first-line treatment for hypotension despite IVFT and for anesthesia-induced hypotension. Particularly foals.
What is the dose and mechanism of action for norepinephrine in horses?
0.2-0.3 µg/kg/min; it is an alpha-1 agonist causing peripheral vasoconstriction.
What are the consensus uses of norepinephrine in foals and adult horses?
Common treatment for hypotension despite IVFT and dobutamine, usually in conjunction with dobutamine, interchangeable with AVP.
What is the dose and mechanism of action for arginine vasopressin (AVP) in horses?
0.1-2.5 mU/kg/min; it increases water reabsorption in the distal tubule and collecting duct, vasoconstriction at high doses.
What are the consensus uses of arginine vasopressin (AVP) in foals and adult horses?
Treatment for hypotension despite IVFT and dobutamine, usually in conjunction with dobutamine, interchangeable with norepinephrine.
What is the dose and mechanism of action for fenoldopam mesylate in horses?
0.04 mg/kg/min; it is a selective dopamine (D1) agonist causing renal vasodilation.
What are the consensus uses of fenoldopam mesylate in foals and adult horses?
Potential treatment for normotensive foals and adults with anuria/oliguria.
What is the dose and mechanism of action for low-dose dopamine in horses?
1-5 µg/kg/min; it stimulates renal dopamine receptors causing vasodilation and natriuresis.
What are the consensus uses of low-dose dopamine in foals and adult horses?
Second-line treatment after unsuccessful furosemide challenge in normotensive foals and adults with anuria/oliguria.
What is the dose and mechanism of action for aminophylline in horses?
2-5 mg/kg slow IV q8h-q12h; it is an afferent arteriole vasoconstrictor with less potent and shorter action than theophylline. Adenosine antagonist.
What is the consensus use of aminophylline in foals and adult horses?
Potential treatment for normotensive foals and adults with ARF.
What is the dose and mechanism of action for theophylline in horses?
8 mg/kg IV q12h; it is an afferent arteriole vasoconstrictor.
What is the consensus use of theophylline in foals and adult horses?
Potential prophylactic treatment in foals with severe birth asphyxia; prophylactic treatment in adults is not established.
What is the mechanism of action for furosemide and its evidence of benefit in humans with AKI?
Furosemide decreases sodium, chloride, and potassium tubular reabsorption; it induces diuresis but without clinical benefit in AKI.
What adverse effects are associated with furosemide use in horses?
High doses can be nephrotoxic, causing increases in sCr through tubuloglomerular feedback and electrolyte disturbances.
What is the evidence of benefit for using dobutamine in humans with AKI?
Dobutamine has a beneficial effect on renal function for cardiorenal syndrome.
What adverse effects are associated with dobutamine use in horses?
: Increased blood pressure and arrhythmias.
What is the evidence of benefit for using norepinephrine in humans and its effects in horses?
Norepinephrine is recommended for treatment and prevention of AKI in humans with distributive shock; it increases blood pressure in anesthetized horses and critically ill foals.
What adverse effects are associated with norepinephrine use in horses?
Arrhythmias.
What is the mechanism of action for arginine vasopressin (AVP) and its adverse effects in horses?
AVP increases water reabsorption in the distal tubule and collecting duct, and causes vasoconstriction at high doses; adverse effects include arrhythmias and hyponatremia.
What is the mechanism of action and adverse effects of fenoldopam mesylate in horses?
Fenoldopam mesylate is a selective dopamine (D1) agonist causing renal vasodilation; it increases urine output in healthy foals but has no additional benefit to renal function when combined with norepinephrine.
What are the adverse effects of low-dose dopamine in horses?
Increased renal blood flow and urine production in healthy horses, and arrhythmias.
What is the evidence of benefit for using aminophylline in humans with AKI?
Aminophylline lowers sCr in pediatric patients with AKI but without improvement of urine production or outcome.
What adverse effects are associated with aminophylline use in horses?
Dose-related tachycardia, tachypnea, and nervous signs.
What is the mechanism of nephrotoxicity for aminoglycosides in horses?
Accumulation in proximal tubular cells caused by sustained drug exposure (frequent dosing), not individual high doses.
What are the risk factors for aminoglycoside nephrotoxicity in humans?
Risk factors include age, hypovolemia, preexisting renal dysfunction, and combination with furosemide. Gentamicin is more nephrotoxic than amikacin.
What is the evidence of nephrotoxicity for aminoglycosides in horses?
Reported nephrotoxicity; dosing schedules should be altered in neonates.
What is the panel recommendation for the use of aminoglycosides in at-risk patients?
Use aminoglycosides cautiously in at-risk patients.
What is the mechanism of nephrotoxicity for oxytetracycline in horses?
The mechanism of nephrotoxicity for oxytetracycline is unknown.
How common is nephrotoxicity from oxytetracycline in humans?
Nephrotoxicity from oxytetracycline is rare in humans.
What is the evidence of nephrotoxicity for oxytetracycline in horses?
AKI caused by high doses for flexural limb deformities in foals and normal antimicrobial doses in adults.
What is the panel recommendation for the use of oxytetracycline in at-risk patients?
Evaluate serum creatinine (sCr) before administration of high doses to foals.
What is the mechanism of nephrotoxicity for NSAIDs in horses?
Inhibition of COX blocks renal autoregulatory response to hypoperfusion, causing medullary crest necrosis and interstitial nephritis.
How common is nephrotoxicity from NSAIDs in humans?
Nephrotoxicity from NSAIDs is uncommon in humans.
What is the evidence of nephrotoxicity for NSAIDs in horses?
In healthy horses, phenylbutazone induced medullary crest necrosis with prolonged supraphysiological doses and AKI with normal doses. COX-2 selective drugs carry a similar but lower risk for nephrotoxicity.
What is the panel recommendation for the use of NSAIDs in at-risk horses?
NSAIDs, especially phenylbutazone, should be avoided in at-risk horses.
Which aminoglycoside is more nephrotoxic, gentamicin or amikacin?
Gentamicin is more nephrotoxic than amikacin.
What conditions in foals have been linked to AKI due to high doses of oxytetracycline?
Flexural limb deformities in foals have been linked to AKI due to high doses of oxytetracycline.
Which NSAID is specifically mentioned as inducing medullary crest necrosis in healthy horses?
Phenylbutazone is specifically mentioned as inducing medullary crest necrosis in healthy horses with prolonged supraphysiological doses.
What is Chronic Kidney Disease (CKD)?
An irreversible, progressive disease of the kidneys with a duration of more than 3 months, involving a gradual loss of kidney function over time.
What are the stages of CKD based on serum creatinine concentration?
Stage 1: <180 μmol/L (2.0 mg/dL), mild or absent clinical signs.
Stage 2: 180-250 μmol/L (2.0-3.0 mg/dL), mild clinical signs.
Stage 3: 251-450 μmol/L (3.1-5.0 mg/dL), moderate clinical signs.
Stage 4: >450 μmol/L (>6.0 mg/dL), severe clinical signs.
What are the congenital anomalies of development that can cause CKD?
Renal agenesis, hypoplasia, dysplasia, and polycystic kidney disease.
What is Chronic Interstitial Nephritis (CIN) and its causes?
A condition usually resulting from acute tubular necrosis due to ischemia or nephrotoxicity, adverse drug reactions, or progressing from AKI.
What is Pyelonephritis and how does it relate to CKD?
An ascending urinary tract infection causing inflammation of the kidney’s interstitial tissue, often a consequence of CKD.
What causes Nephrolithiasis and how is it related to CKD?
: Kidney stones, usually composed of calcium carbonate, found in the collecting ducts, often as a consequence rather than a cause of CKD.
What is Glomerulonephritis (GN) and what causes it?
A condition initiated by immune-mediated inflammation due to the deposition of immune complexes along the glomerular barrier, often associated with chronic infectious diseases.
What are the infiltrative causes of CKD?
Neoplasia (lymphoma, carcinoma, nephroblastoma), amyloidosis, and Halicephalobus gingivalis infection.
What is End-Stage Kidney Disease (ESKD)?
The final stage of CKD where kidneys are pale, shrunken, firm, with an irregular surface and adherent capsule, often with an indeterminate inciting cause.
What are the common clinical signs of CKD in horses?
Loss of body condition, polyuria/polydipsia (PU/PD), dental tartar accumulation, gingivitis/oral ulcers, decreased performance, hypertension, and ventral edema.
What laboratory findings are typically associated with CKD?
Moderate to severe azotemia, mild electrolyte imbalances, hypercalcemia (diet-dependent), hypophosphatemia, mild anemia, proteinuria, and isosthenuria.
What imaging techniques are useful in diagnosing CKD?
Rectal palpation and ultrasonography to evaluate kidney size, structure, presence of nephroliths, and cystic cavitation.
What are the main goals of dietary management in CKD?
Maintaining appetite and body condition, increasing carbohydrate and fat intake, monitoring BUN and serum protein levels, avoiding additional salt, and switching to low-calcium feeds for hypercalcemia.
What medications may benefit patients with CKD?
Corticosteroids for GN, ACE inhibitors (benazepril, ramipril) to control blood pressure and proteinuria, and nephrolith removal in specific cases.
What are the general management strategies for CKD?
IV fluid therapy (IVFT) as needed, free access to fresh water, appropriate dietary management, and careful use of medications.
How is CKD progression managed in horses?
Through long-term management including dietary adjustments, medication, regular monitoring, and individualized care to maintain quality of life until humane euthanasia becomes necessary.
What is pyelonephritis and how can it occur in horses?
Pyelonephritis is an uncommon condition characterized by bacterial infection of the renal pelvis and parenchyma, occurring via hematogenous spread or as an ascending infection from the lower urinary tract. Unilateral cases are more common than bilateral.
What mechanical obstructions or functional impairments can predispose horses to pyelonephritis?
Urolithiasis, recurrent cystitis, bladder paralysis, ectopic ureter, lower urinary tract neoplasia, urinary surgery, and foaling injury.
: What are the common bacterial isolates that cause pyelonephritis in horses?
Escherichia coli, Proteus spp., Klebsiella spp., Enterobacter spp., Streptococcus spp., Staphylococcus spp., Pseudomonas aeruginosa, Corynebacterium spp.
What are the general clinical symptoms of pyelonephritis in horses?
Fever, inappetence, lethargy, and weight loss.