Nephrology Flashcards
What is the emergency treatment of symptomatic hyponatremia?
IV infusion of hypertonic saline (3%) at a dose of 3 mL/kg. This will raise serum sodium concentration by 3-4 mEq/L. Can repeat dose every 10-20 minutes.
Why can correcting hypernatremia too quickly cause seizures?
When you have hypernatremia, fluid shifts out of brain cells. In reponse, brain cells make idiogenic osmoles that help minimize their water loss. Creating or getting rid of these osmoles takes about 24 hours. If you correct too quickly, water moves back into the brain cells and you get cerebral edema.
What is the maximum rate of sodium correction in hypernatremia?
Don’t decrease faster than 0.4 mEq/L per hour and more than 10-12 mEq/L per 24 hours!
What is the differential diagnosis of nephrogenic diabetes insipidus?
1) Inherited NDI: due to mutations in the arginine vasopressin receptor gene (AVPR2) or aquaporin gene (AQP2)
2) Acquired NDI: electrolyte disturbances (hypokalemia, hypocalcemia); medications (diuretics, lithium, cisplatin); CKD and tubulointerstitial disease.
3) Syndromic: renal Fanconi, RTA, Bartter syndrome
How does hypokalemia clinically present?
1) Muscle weakness
2) Paralysis (which can cause hypoventilation and apnea)
3) Constipation
4) Ileus
5) Arrythmia (especially ventricular ectopic rhythms and fibrillation)
6) Polyuria
What are the causes of hypokalemia?
1) Fluids and lytes: Diuretics, Laxatives, Metabolic alkalosis
2) GI: diarrhea
3) Endocrine: DKA, primary hyperaldosteronism, Cushing syndrome, adrenal tumour, CAH (rare forms), pituitary tumours producing ACTH)
4) Renal: RTA types I and II, Renal fanconi syndrome, Bartter syndrome, Gitelman syndrome, renal artery stenosis (hyperreninemic state)
Which foods are high in potassium?
Raisins, dates, avocado, beans, squash, tomatoes, lentils, baked potatoes, cocoa, oranges, bananas, french fries, chocolate, carrots
What are the causes of hyperkalemia?
1) Increased potassium intake: IV potassium, oral potassium, transfusion (when renal excretion is impaired 2/2 renal failure or in patients taking ACE inhibitors).
2) Decreased renal excretion: impaired renal function (when the GFR is <15 mL/min per 1.74 m2)
3) Potassium redistribution: metabolic acidosis, insulin deficiency
4) Tissue breakdown: trauma, asphyxia, rhabdomyolysis, chemotherapy (TLS), hemolysis, exercise, hyperkalemic periodic paralysis
5) Medication: beta blockers, potassium sparing diuretics, ACE inhibitors, angiotensin II receptor blockers (ARBs), digoxin, succinylcholine, arginine, NSAIDs, calcineurin inhibitors
6) Pseudohyperkalemia: hemolyzed sampling, severe thrombocytosis, severe polycythemia, leukocytosis
7) Aldosterone deficiency or resistance (pseudohypoaldosteronism): primary adrenal insufficiency, inborn errors of adrenal steroid metabolism
When are calcium infusions indicated for hyperkalemia and how does it work?
If serum potassium level is > 8 mEq/L or there is cardiac dysrhythmia.
It works by increasing the cell’s threshold potential, restoring the voltage difference between these two potentials and decreases the likelihood of dysrhythmia.
What are the key components of hyperkalemia treatment (3)?
1) Stabilize membrane potentials - use ten percent calcium gluconate
2) Promote potassium uptake into cells - can use glucose + insulin and sodium bicarbonate (in setting of acidosis), can also use IV or inhaled albuterol (beta 2 agonist)
3) Enhance the excretion of potassium - can use a cation exchange resin, loop diuretic, dialysis or exchange transfusion (neonates)
What is the differential for an elevated anion gap metabolic acidosis?
MUDPILES.
M = methanol (formic acid and formate)
U = uremia (guanidinosuccinic acid, phosphates, sulfates, other acids)
D = DKA (lactic acid, beta hydroxybutyrate, acetoacetate)
P = paraldehyde, phenformin
I - iron, isoniazid, inborn errors of metabolism
L = lactic acidosis (hypoxia, cardiorespiratory depression, shock, seizures, mitochondrial disease)
E = ethanol, ethylene glycol
S = salicylate
What is the differential for a metabolic alkalosis?
A) saline responsive: urine chloride low, volume depleted.
- vomiting, upper GI suctioning, congenital chloride diarrhea, laxative abuse, diuretics, cystic fibrosis, chloride deficient infant formulas, posthypercapnia syndrome, anion adminsitration (eg phosphate)
b) saline resistant: urine chloride high, volume normal or high.
- RAS, renin secreting tumour, steroids, hypokalemia, steroid hormone synthesis disorder, Liddle syndrome, Bartter syndrome, Gitelman syndrome, primary hyperaldosteronism, licorice
Describe the “paradoxical aciduria” of metabolic alkalosis.
Vomiting and dehydration causes loss of hydrogen ions (acid), sodium, potassium and chloride. RAAS is activated in an effort to increase blood pressure. To increase blood pressure, the kidney increases salt (and water) absorption in the distal nephron. In exchange, the kidney needs to give up other cations (esp hydrogen) to get sodium. Therefore, the urine is acidic.
How does hypocalcemia clinically present?
1) weakness
2) perioral numbness
3) paresthesias
4) carpopedal spasms
5) tetany
6) altered mental status
7) seizures
8) prolonged QT
9) Chvostek sign: tapping parotid gland over facial nerve (in front of ear) causes movement of upper lip.
10) Trousseau sign: carpopedal spasm when BP inflated greater than systolic for 2-5 minutes
How does hypercalcemia clinically present?
1) Bones: pain with osteolytic lesions
2) Stones: urolithiasis, hypertension, polyuria
3) Groans: nausea, vomiting, constipation, weakness
4) Psychiatric overtones: altered mental status
What is the stepwise approach to treating symptomatic hypercalcemia?
1) IV fluids with normal saline to increase urinary excretion +/- diuretic
2) Calcitonin or Bisphosphonates to inhibit bone resorption if present
3) Cinacalcet to activate calcium sensing receptors and decrease release of parathyroid hormone
4) Glucocorticoids to decrease intestinal absorption
In which clinical settings might be suspect hypophosphatemia?
1) Refeeding syndrome in a severely malnourished child
2) Hungry bone syndrome status post parathyroidectomy
3) Hyperparathyroidism (phosphate lost through kidneys)
4) Vitamin D deficiency or rickets
5) Primary renal phosphate wasting
6) Renal Fanconi syndrome
7) GI causes: reduced intake, increased loss (diarrhea), interference with absorption (certain antacids)
What are some laboratory studies that help distinguish prerenal oliguria from acute tubular necrosis?
Apart from volume status (clinical), you can look at:
1) Random urine sodium - prerenal < 20, renal > 20
2) Fractional excretion of sodium - prerenal < 1%, renal >1%
3) Urine osmolality - prerenal > 500, renal < 300
What is the most common cause of AKI in young children in the US?
Acute tubular necrosis 2/2 hypoxia, hypotension or hypovolemia or drug-induced injury.
It used to be caused by hemolytic uremic syndrome (HUS).
List 14 causes of prerenal AKI.
1) Diarrhea
2) Vomiting
3) Osmotic diuresis
4) Diuretics
5) Burns
6) Hemorrhage
7) Septic shock
8) Anaphylaxis
9) Nephrotic syndrome
10) CHD –> heart failure
11) Arrhythmia
12) Cardiomyopathy
13) Tamponade
14) Post cardiac surgery
List 10 causes of renal AKI.
1) Renal venous thrombosis
2) Vasculitis
3) NSAIDs
4) ACE inhibitors
5) Hemolytic uremic syndrome
6) Postinfectious glomerulonephritis
7) Lupus nephritis
8) HSP nephritis
9) IgA nephropathy
10) Crescentic glomerulonephritis
List 6 tubular causes of ATN (renal AKI).
1) Severe prerenal failure
2) Asphyxia/hypoxemia
3) Crystal obstruction
4) Medications
5) Toxins
6) Tumour Lysis Syndrome
List 5 causes of interstitial nephritis.
1) Allergic
2) TINU syndrome
3) Malignancy infiltrate
4) Pyelonephritis
5) Sarcoidosis
List 2 postrenal causes of AKI.
1) Bilateral nephrolithiasis
2) Neoplasm
What is the triad of clinical findings in hemolytic uremic syndrome?
1) Acute renal failure - oliguria, anuria, rare polyuria
2) Acute hemolytic anemia - microangiopathic, fragmented RBCs or schistocytes, DAT negative (nonimmune)
3) Thrombocytopenia
What is the most frequent cause of hemolytic uremic syndrome?
Shiga toxin producing E. coli OH157:H7 serotype. 15% of patients with this infection develop HUS within 2-14 days of diarrhea onset.
Toxin causes endothelial injury with secondary glomerular capillary microthrombi.
(Extra: You can also have genetic causes of atypical HUS, mutations that lead to uncontrolled activation of the complement system when triggered).
What is the prognosis of a child with HUS?
1) 50% require ICU
2) 70% recover completely
3) Approximately 4% die
4) Approximately 15% have long term complications (proteinuria, hypertension, chronic kidney disease)
5) Can develop extra-renal sequelae (colonic strictures, cholelithiasis, diabetes mellitus, brain injury).
In children with HUS, what are the two most important risk factors for poor renal outcome?
1) Anuria for over 10 days
2) Requiring dialysis for more than 3 weeks
How long must a child with HUS be followed as an outpatient?
5 years after the acute episode for all patients.
Indefinitely if there is proteinuria, hypertension or reduced eGFR.
What are the indications for dialysis in the setting of AKI?
Remember AEIOU.
A = acidemia (metabolic acidemia that you can't control with sodium bicarb) E = electrolyte abnormalities (rapid uncontrolled hyperkalemia, symptomatic hyponatremia, hypocalcemia, hyperphosphatemia and hyperuricemia) I = Increased BP (volume dependent HTN or CHF not responsive to diuretics) O = Overload (volume) (needs blood and already overloaded) U = Uremia (acute signs of symptoms of encephalopathy)
What is the definition of AKI versus CKD?
AKI: If it has been less than 3 months and a) the GFR is under 60, b) GFR is decreased by more than 35%, or c) the creatinine increases by over 50%.
CKD: Meets AKI criteria for over 3 months.
What are the GFR criteria for the different stages of Chronic Kidney Disease?
Stage 1: GFR over 90 but abnormal urine or imaging.
Stage 2: GFR 60-89.
Stage 3A: GFR 45-59.
Stage 3B: GFR 30-44.
Stage 4: GFR 15-29.
Stage 5: GFR < 15 or on dialysis.
What are the main causes of CKD in kids that result in kidney transplant?
1) Obstructive uropathy
2) Aplastic, hypoplastic or dysplastic kidneys (CAKUT)
3) Focal segmental glomerulosclerosis (FSGS)
What are four major medications that have improved the lives and outcomes for children living with CKD?
1) erythropoietin - reduces need for transfusions
2) 1,25 dihydroxycholecalciferol - helps prevent and treat osteodystrophy
3) recombinant GH - helps with growth and appetite
4) ACEi or ARB - helps with inhibition of RAAS and to control HTN, slow progression of glomerular fibrosis and ESRD
Explain how you get secondary hyperparathyroidism in CKD mineral and bone disorder.
Decreased GFR leads to decreased excretion of phosphate (ie. hyperphosphatemia) and decreased renal vitamin D production (low active vitamin D). The body doesn’t absorb as much calcium from the GI tract and the bones don’t respond as much to PTH, so there is hypocalcemia. Hypocalcemia causes more PTH to be released and more bone is broken down.
Osteodystrophy begins when the GFR is half the normal rate. It is important to intervene early for prevention and treatment with calcitriol, vitamin D and phosphate binders.
Please list some examples of single-gene ciliopathies with renal involvement.
Von Hippel-Lindau disease Autosomal recessive polycystic kidney disease Nephronopthisis Bardet-Biedl syndrome Retinal-Renal syndrome Senior-Loken syndrome Joubert syndrome Meckel syndrome Alstrom syndrome Sensenbrenner syndrome
What is nephronophthisis?
This is one of the single gene ciliopathies. It is the most common genetic cause of end stage kidney disease in the first 30 years of life.
Recessive mutations in NPHP1 to NPHP11 can cause cysts in the corticomedullary junction to form. Clinical features include anemia, polyuria, polydipsia, isosthenuria, growth failure and progression to ESRD.
What is autosomal dominant polycystic kidney disease and what are the associated genes?
How does ADPKD present and what is the treatment in kids?
Characterized by progressive enlargement of renal cysts, usually bilateral, that occur throughout the nephron. Can get cysts in other organs (liver, seminal vesicles, pancreas, arachnoid). Also associated with intracranial aneurysms, mitral prolapse, diverticulosis and aortic dilatation.
Can present with pain, hematuria, UTI, hypertension and stones. Can be picked up prenatally but usually presents in adulthood.
Diagnose with renal ultrasound. Genetic testing rarely indicated.
Monitor BP + urine, encourage PO water (suppress ADH and slow cyst growth) in kids with family history.
Two genes identified (PKD1, 85%), (PKD2, 15%).
What is autosomal recessive polycystic kidney disease?
What is the clinical spectrum?
What is the associated gene?
Mutations on chromosome 6, PKDHD1 gene cause dilatation of the renal collecting ducts and bilateral renal enlargement with microcysts.
The clinical spectrum includes liver problems such as congenital hepatic fibrosis and Caroli disease (dilation of the intrahepatic bile ducts). Can also have cholangitis, variceal bleeding and hypersplenism.
Many babies die before or at birth. In utero, renal insufficiency can cause oligohydramnios and lung hypoplasia.
