Kidney disease Flashcards
What is the mechanism behind proximal (type 2) and distal (type 1) renal tubular acidosis
- Proximal: decreased HCO3- reabsorption in proximal convoluted tubule (reduced transport maximum for HCO3-)
- Distal: decreased H+ secretion in late distal convoluted tubule / collecting duct (decreased HCO3- production)
What is the serum bicarbonate, urine pH (without treatment), urine pH after NaHCO3 administration, bicarbonate therapy requirement for proximal / distal RTA
- Proximal RTA:
- HCO3 = 15-18 mmol/L
- Urine pH < 6 (in steady state)
- Urine pH after NaHCO3 = alkaline
- NaHCO3 requirement = > 10 mEq/kg/d - Distal RTA:
- HCO3 = < 10-12 mmol/L
- Urine pH > 6
- Urine pH after NaHCO3 = no change
- NaHCO3 requirement = < 3 mEq/kg/d
Name causes of proximal and distal RTA
- Proximal:
- Aminoglycoside toxicity
- Fanconi syndrome (congenital: Basenjis)
- Acetazolamide treatment
- Cisplatin toxicity
- Ethylene glycol toxicity
- Leptospirosis
- Multiple myeloma
- Heavy metal toxicity - Distal:
- IMHA
- Pyelonephritis
- Multiple myeloma
- Amphotericin B toxicity
- Heavy metal toxicity
What is a consequence of alkali therapy in proximal RTA
Worsening hypokalemia (due to presence of HCO3- in the urine)
What is a possible complication of distal RTA
Urolithiasis due to:
- increased calciuresis due to bone resorption from chronic metabolic acidosis
- alkaline urine reducing the solubility of Ca and P
What is a possible alternative to sodium bicarbonate therapy in dogs with RTA
Potassium citrate
What is the histological finding with NSAID toxicity
Papillary necrosis
Name 5 toxins affecting the renal tubule
- Grapes
- Ethylene glycol
- Aminoglycosides
- Cisplatin
- Contrast agents
What are the 3 staging systems for AKI in humans
- Risk Injury Failure End Stage Kidney Disease (RIFLE)
- Acute Kidney Injury Network (AKIN)
- Kidney Disease: Improving Global Outcomes (KDIGO)
Describe the IRIS AKI grading system
- Grade I: Non-azotemic AKI (creat < 140 umol/L)
- Documented AKI (historical, clinical, lab, imaging) and/or
- Increase in creatinine > 26 umol/L in 48h and/or
- Oliguria < 1 mL/kg/h over 6h - Grade II: Mild AKI (creat 141 - 220 umol/L)
- Documented AKI and static or progressive azotemia and/or
- Increase in creatinine > 26 umol/L within 48h and/or
- Oliguria <1 mL/kg/h over 6h - Grade III: Moderate to severe AKI (creat 221-439 umol/L)
- Documented AKI and increasing severities of azotemia and functional failure - Grade IV: creat 440-880 umol/L
- Grade V: creat > 880 umol/L
Each grade subdivided with non-oliguric or oliguric, and need for RRT or no need
What are the 4 phases of the pathophysiology of AKI and their duration? What model are they based on?
Based on ischemic injury - might not apply to all types of injury
(0. Insult phase)
- Initiation phase (hours to days): cellular damage (decreased GFR but no clinical / biochemical changes)
- Extension phase (1-2 days): cellular death (biochemical and clinical manifestations start)
- Maintenance phase (days-weeks): simultaneous cell death and regeneration (GFR stabilizes, creatinine reaches a plateau)
- Recovery phase (weeks-months): improvement in GFR and tubular function
What is the pathophysiology of ischemic AKI
In initiation phase (hours - day):
1. Ischemia -> increase in intracellular Ca2+ -> ROS -> cellular damage + release of cytokines and chemokines
- Disruption of cytoskeleton and redistribution of Na/K ATPase to apical membrane -> entry of water in cells -> swelling -> tubular obstruction
- Relocation of integrins -> loss of cell anchorage to basal membrane ->cell desquamation, tubular obstruction + back-leakage of filtrate into interstitium
In extension phase (1-2 days):
1. Damaged endothelial cells -> expression of selectins, ICAM-1 responsible for leukocyte activation
- Endothelial glycocalyx shedding -> increased permeability -> edema -> hypoxia
- Sluggish flow in capillaries -> microthrombi -> capillary plugging -> ischemia
Maintenance phase (days-weeks):
- Stabilization of GFR
- Cell death vs regeneration
Recovery phase (weeks-months):
- Restoration of GFR
- reestablished cell polarity + tubular integrity
How is the ultrasonographic architecture of the kidneys in most cases of AKI? What are exceptions?
Normal in most cases (or sometimes enlarged kidneys +/- perirenal fluid).
Exceptions:
- Lymphoma: thickened cortex with hypoechoic perirenal halo
- AKI on CKD
- Ethylene glycol: hyperechoic renal cortices and medulla
- Obstruction
- Pyelonephritis
What are indicators of ethylene glycol toxicosis
- High anion gap metabolic acidosis
- Calcium oxalate crystalluria (especially Ca oxalate monohydrate)
- Hyperechoic renal cortices and medullary rim sign
- Hyperlactatemia in some analyzers
- Hypocalcemia
What are diagnostic criteria for Leptospirosis based on serology? Which serovar is the most at risk of false positive?
- Initial titers of >1:800 with clinical suspicion (L autumnalis most at risk of false positive from cross-reactivity with vaccines)
- OR 4-fold increase in titers after 2-4 weeks
What is the recommended rate of fluid tapering for patients recovering from AKI
Decrease rate by 10-25% per day as long as urine output decreases accordingly and weight and perfusion remain stable
(LOL)
What is the mortality rate from AKI in dogs and cats
- Dogs: 45% mortality (but survival up to 82-86% for lepto)
- Cats: 53% mortality
(Among surviving patients, about 50% will have chronic kidney disease)
What is the most common cause of CKD in cats and dogs
Cats: often unknown
Dogs: glomerular disease
What are the most common histologic lesions in cats and dogs with CKD
Cats: lymphoplasmocytic tubulointerstitial nephritis and fibrosis
Dogs: glomerular lesions and interstitial nephritis with common lipid infiltration
Described the IRIS CKD staging system
- Stage based on creatinine
- Stage I: creat < 125 (dogs) or 140 (cats)
- Stage II: creat 125-250 (dogs) or 140-250 (cats)
- Stage III: creat 251-440
- Stage IV: creat > 440 - Substage based on UPCR
- Nonproteinuric: UPCR<0.2
- Borderline proteinuric: UPCR 0.2-0.5 (dogs) or 0.2-0.4 (cats)
- Proteinuric: UPCR>0.5 (dogs) or 0.4 (cats) - Substage based on BP
- Normotensive: SBP<140
- Prehypertensive: SBP 140-159
- Hypertensive: SBP 160-179
- Severely hypertensive: SBP > 180
True or false: a USG>1.030 rules out CKD
False.
Some dogs and cats will have a CKD despite USG>1.030 (susp secondary to the presence of lipids in the urine)
What UPCR is suggestive of glomerular disease
UPCR >2
Name some congenital nephropathies in dogs and cats (with associated breeds)
- Dogs:
- Renal dysplasia (Lhassa Apso, Shih Tzu, Wheaten Terrier, Standard Poodle)
- Primary glomerulopathy (Cocker Spaniel Springer Spaniel, Bull Terrier)
- Polycystic kidney disease (Bull Terrier, Cairn Terrier, Westie)
- Amyloidosis (Shar Pei)
- Immune mediated glomerulonephritis (Bernese Mountain Dog, Brittany Spaniel)
- Fanconi syndrome (Basenji) - Cats:
- Plolycystic kidney disease (Persian)
- Amyloidosis (Abyssinian, Siamese)
What is the median pelvic width in dogs and cats with ureteral obstruction
Dogs: 15 mm
Cats: 6.8 mm
Name a renal disease potentially identified on renal aspirates (one in dogs, one in cats)
Dogs: renal lymphoma
Cats: FIP (and renal lymphoma)
Are antacids indicated in the treatment of CKD
No - there is no evidence of increased gastric acidity or gastric ulceration ; antacids increase the burden of medications and are associated with AKI in humans
What variables are associated with decompensation / mortality in cats and dogs with CKD
Creatinine, UPC, urine albumin-to-creatinine ratio, leukocytosis, hyperphosphatemia, weight loss
Name a few possible post-op complications of kidney transplantation in cats
- Graft rejection
- Retroperitoneal fibrosis (causing ureteral obstruction)
- Ureteral obstruction
- Infections
- Neoplasia (lymphoma)
- Diabetes mellitus
- Hemolytic uremic syndrome
What are mechanisms of pathogenesis of oligoanuria
- Decreased renal blood flow (hypovolemia, decreased CO, vasodilation, renal artery thrombosis)
- Tubular obstruction from casts or cells (pyelonephritis, acute interstitial nephritis, acute tubular necrosis)
- Backflow of glomerular filtrate in renal interstitium (tubular / pelvic / ureteral / urethral obstruction)
- Intrarenal RAAS activation (high Cl fluids)
- Altered permeability of glomerular capillaries (glomerulonephritis, vasculitis)
What should be the IV fluid plan for a normovolemic oligo-anuric patient
- Challenge with fluids to correct 3-5% dehydration (likely to be missed on physical exam)
- If responds, match INs/OUTs
- If does not respond, give fluids for insensible losses only (about 20 mL/kg/day, usually met with meds and flushes)
Why is furosemide unlikely to be effective in anuric patients
Furosemide needs to reach the tubular fluid to be inhibit the Na-K-2Cl pumps (by active secretion in proximal tubule +/- some glomerular filtration). If there is no urine production furosemide will likely not reach its site of action.
What medications can be given to attempt to convert oligoanuria to polyuria (+ mechanism of action and 1 adverse effect)
- Mannitol: osmotic diuretic, can help wash out tubules from casts etc.
Can worsen pulmonary edema and intracellular dehydration (not recommended in humans with AKI) - Furosemide: Na-K-2Cl transporter inhibitor (thick ascending limb of the loop of Henle).
Can cause ototoxicity. Might increase urine volume but not GFR. - Dopamine: stimulates DA-1, DA-1, and alpha and beta-adrenergic receptors ; leads to afferent arteriole vasodilation (at low doses) + increases natriuresis by inhibition of tubular transporters.
Can cause tachyarrhythmias. - Fenoldopam: selective dopamin receptor (DA-1) agonist leading to renal vasodilation.
Can cause hypotension from systemic vasodilation. - Diltiazem: calcium channel blocker leading to afferent arteriole vasodilation
Can cause hypotension.
Common bacteria responsible for UTIs in dogs
- E Coli
- Staphylococcus spp
- Enterococcus spp
- Proteus spp
- Streptococcus spp
- Klebsiella spp