Nephrology

Question 1

What is the emergency treatment of symptomatic hyponatremia?

Answer 1

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.

Question 2

Why can correcting hypernatremia too quickly cause seizures?

Answer 2

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.

Question 3

What is the maximum rate of sodium correction in hypernatremia?

Answer 3

Don’t decrease faster than 0.4 mEq/L per hour and more than 10-12 mEq/L per 24 hours!

Question 4

What is the differential diagnosis of nephrogenic diabetes insipidus?

Answer 4

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

Question 5

How does hypokalemia clinically present?

Answer 5

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

Question 6

What are the causes of hypokalemia?

Answer 6

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)

Question 7

Which foods are high in potassium?

Answer 7

Raisins, dates, avocado, beans, squash, tomatoes, lentils, baked potatoes, cocoa, oranges, bananas, french fries, chocolate, carrots

Question 8

What are the causes of hyperkalemia?

Answer 8

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

Question 9

When are calcium infusions indicated for hyperkalemia and how does it work?

Answer 9

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.

Question 10

What are the key components of hyperkalemia treatment (3)?

Answer 10

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)

Question 11

What is the differential for an elevated anion gap metabolic acidosis?

Answer 11

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

Question 12

What is the differential for a metabolic alkalosis?

Answer 12

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

Question 13

Describe the “paradoxical aciduria” of metabolic alkalosis.

Answer 13

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.

Question 14

How does hypocalcemia clinically present?

Answer 14

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

Question 15

How does hypercalcemia clinically present?

Answer 15

1) Bones: pain with osteolytic lesions
2) Stones: urolithiasis, hypertension, polyuria
3) Groans: nausea, vomiting, constipation, weakness
4) Psychiatric overtones: altered mental status

Question 16

What is the stepwise approach to treating symptomatic hypercalcemia?

Answer 16

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

Question 17

In which clinical settings might be suspect hypophosphatemia?

Answer 17

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)

Question 18

What are some laboratory studies that help distinguish prerenal oliguria from acute tubular necrosis?

Answer 18

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

Question 19

What is the most common cause of AKI in young children in the US?

Answer 19

Acute tubular necrosis 2/2 hypoxia, hypotension or hypovolemia or drug-induced injury.

It used to be caused by hemolytic uremic syndrome (HUS).

Question 20

List 14 causes of prerenal AKI.

Answer 20

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

Question 21

List 10 causes of renal AKI.

Answer 21

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

Question 22

List 6 tubular causes of ATN (renal AKI).

Answer 22

1) Severe prerenal failure
2) Asphyxia/hypoxemia
3) Crystal obstruction
4) Medications
5) Toxins
6) Tumour Lysis Syndrome

Question 23

List 5 causes of interstitial nephritis.

Answer 23

1) Allergic
2) TINU syndrome
3) Malignancy infiltrate
4) Pyelonephritis
5) Sarcoidosis

Question 24

List 2 postrenal causes of AKI.

Answer 24

1) Bilateral nephrolithiasis

2) Neoplasm

Question 25

What is the triad of clinical findings in hemolytic uremic syndrome?

Answer 25

1) Acute renal failure - oliguria, anuria, rare polyuria 2) Acute hemolytic anemia - microangiopathic, fragmented RBCs or schistocytes, DAT negative (nonimmune) 3) Thrombocytopenia

Question 26

What is the most frequent cause of hemolytic uremic syndrome?

Answer 26

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).

Question 27

What is the prognosis of a child with HUS?

Answer 27

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).

Question 28

In children with HUS, what are the two most important risk factors for poor renal outcome?

Answer 28

1) Anuria for over 10 days | 2) Requiring dialysis for more than 3 weeks

Question 29

How long must a child with HUS be followed as an outpatient?

Answer 29

5 years after the acute episode for all patients. Indefinitely if there is proteinuria, hypertension or reduced eGFR.

Question 30

What are the indications for dialysis in the setting of AKI?

Answer 30

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) ```

Question 31

What is the definition of AKI versus CKD?

Answer 31

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.

Question 32

What are the GFR criteria for the different stages of Chronic Kidney Disease?

Answer 32

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.

Question 33

What are the main causes of CKD in kids that result in kidney transplant?

Answer 33

1) Obstructive uropathy 2) Aplastic, hypoplastic or dysplastic kidneys (CAKUT) 3) Focal segmental glomerulosclerosis (FSGS)

Question 34

What are four major medications that have improved the lives and outcomes for children living with CKD?

Answer 34

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

Question 35

Explain how you get secondary hyperparathyroidism in CKD mineral and bone disorder.

Answer 35

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.

Question 36

Please list some examples of single-gene ciliopathies with renal involvement.

Answer 36

``` 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 ```

Question 37

What is nephronophthisis?

Answer 37

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.

Question 38

What is autosomal dominant polycystic kidney disease and what are the associated genes? How does ADPKD present and what is the treatment in kids?

Answer 38

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%).

Question 39

What is autosomal recessive polycystic kidney disease? What is the clinical spectrum? What is the associated gene?

Answer 39

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.

Question 40

How common is nocturnal enuresis and why does it persist in some kids?

Answer 40

At age 5, 20% of kids. At age 7, 20% of kids. At age 10, 5% of kids. At age 15, 1-2% of kids. Genetic influences are quite strong. If both parents had bed wetting, kid is 75% likely. If one parent, kid if 50% likely. Other thoughts about why it persists include small bladder, delayed neurodevelopment, sleep disorders.

Question 41

How do we treat nocturnal enuresis? What are the treatment side effects?

Answer 41

Will resolve on its own in 15% of patients. Can try dry bed training (self waking, cleanliness raining, bladder training, rewards), enuresis alarms. Medical options include desmopressin (increases distal tubular reabsorption of water and diminishes nighttime bladder volume), or imipramine (increases capacity and decreases detrusor excitability). Side effects of desmopressin include relapse, nasal irritation, hyponatremia, expensive. Side effects of imipramine include relapse, drowsiness, agitation, sleep disturbances.

Question 42

What is pollakiuria?

Answer 42

Excessive daytime urinary frequency (can be up to 50 times per day). Key features: limited to daytime, occurs after stressful life event. Self-resolves usually over 6 months. Provide reassurance. No treatment but need to exclude other causes.

Question 43

What is normal bladder capacity for a child?

Answer 43

Bladder capacity (mL) = [30 + (age in years x 30)] Can use formula up to age 12, after which the adult value is used which is 390 mL.

Question 44

How do we define nephrotic syndrome?

Answer 44

1) Proteinuria 2) Hypoalbuminemia 3) Edema 4) Hypercholesterolemia

Question 45

How is nephritis different than nephrosis?

Answer 45

Nephritis means that there is evidence of glomerular inflammation -- on biopsy, there is an increased number of cells within the glomerulus and/or leukocytes. The inflammation disrupts the glomerular membrane structure and function (ie stuff leaks out). Finding of RBC casts is usually diagnostic.

Question 46

12 year old female with sore throat AND simultaneous cola coloured urine for 2 days. A few days later, she has amber coloured urine, microscopic hematuria, 2+ protein, RBC casts. What is the most likely cause?

Answer 46

IgA nephropathy

Question 47

What is IgA nephritis and what are the clinical and histologic features?

Answer 47

Most common type primary glomerular disease. Most common type of glomerulonephritis that causes ESRD (25% will progress). Variable clinically and histologically. Microscopic hematuria, synpharyngitic hematuria, recurrent hematuria, proteinuria, nephrotic syndrome, nephritic syndrome, acute renal failure. Glomerular deposits of IgA.

Question 48

In patients with IgA nephropathy, what are risk factors for developing ESRD? How many go on develop ESRD?

Answer 48

25% develop ESRD over 25 years. Risk factors = elevated serum creatinine, proteinuria over 1g per day, hypertension, tubular atrophy, interstitial fibrosis severity, extent of glomerular sclerosis.

Question 49

What are the three major presentations of glomerular involvement?

Answer 49

1) Acute GN: edema, proteinuria of 1+ or more, hypertension, oliguria, dysmorphic RBCs or casts on urinalysis 2) Chronic GN: minimal acute symptoms; fatigue, FTT, anemia, hypertension, abnormal urinalysis, azotemia, metabolic acidosis, hypocalcemia, hyperphosphatemia 3) Nephrotic syndrome: proteinuria of over 40 mg/square metre per hour, edema, hypoalbuminemia and hypercholesterolemia

Question 50

What tests do you order for glomerulonephritis?

Answer 50

First line: urine dipstick, urine microscopy; serum electrolytes, BUN, Cr; serum C3 and C4; ASOT, throat culture, skin culture (if impetigo), serum albumin Second line: ANA, anti DNA (if suspecting lupus), Hep B and C serology; ANCA (if rapidly progressive GN or vasculitis)

Question 51

Which glomerular diseases have an underlying genetic cause?

Answer 51

1) Congenital nephrotic syndrome - recessive, NPHS1 2) Diffuse mesangial sclerosis - recessive, WT1 3) Denys-Drash syndrome - recessive, WT1 4) Frazier syndrome - recessive, KTS 5) FSGS - dominant or recessive; NPHS2, TRPC6, ACTN4, INF2, PLCE1 6) Alport syndrome - X linked r/d; COL4A5 7) Nail-patella syndrome - dominant, LMX1B 8) Steroid resistant NS with sensorineural deafness - dominant, COQ6 9) C3 Glomerulopathy - recessive; Factor H, CFHR

Question 52

When you have hypocomplementemia, which types of GN do you consider?

Answer 52

1) Postinfectious GN (acute post strep) 2) Lupus nephritis 3) Immune complex membranoproliferative glomerulonephritis 4) C3 glomerulopathy 5) Atypical HUS

Question 53

Does treating streptococcal skin or pharyngeal infections prevent acute post streptococcal glomerulonephritis?

Answer 53

No. It decreases spread to other kids from the index case, however.

Question 54

What is the usual time course of acute post streptococcal glomerulonephritis?

Answer 54

Symptoms start about 1-2 weeks after. It can be up to 6 weeks after a pyoderma. Acute phase includes HTN, gross hematuria, oliguria, edema and tea coloured urine) and can last up to 3 weeks. Serum C3 may be low for up to 8 weeks. Chronic microscopic hematuria can last for up to 2 years.

Question 55

Name that diagnosis: recurrent gross hematuria and persistently low C3, normal C4. What are the next steps for evaluation? What is the prognosis?

Answer 55

C3 glomerulopathy, including dense deposit disease and C3 glomerulonephritis. Evaluation includes genetic testing for alternative complement regulatory genes, checking for C3 nephritic factor and kidney biopsy. May lead to ESRD in ten years in 50% of patients.

Question 56

How common is hematuria in children?

Answer 56

Microscopic hematuria occurs in 0.5-2% of school age kids, often transient. No cause found in 70-80% of cases.

Question 57

What is the top cause of microscopic hematuria?

Answer 57

Hypercalciuria (>4 mg/kg per day)

Question 58

How to you distinguish upper versus lower tract GU bleeding?

Answer 58

Lower tract - bright red blood, clots. Upper tract - brown, tea/cola coloured. Glomerular - casts, small and dysmorphic RBCs.

Question 59

10 Y M with BRB at the end of micturition. What is the most likely diagnosis?

Answer 59

Urethroragia. Due to engorged vessels around the entry of the prostatic duct into the urethra. Benign condition associated with hormonal changes at adolescents. Resolves spontaneously in weeks to months.

Question 60

What is blue diaper syndrome and how is it different from pink diaper syndrome?

Answer 60

Blue = bad. Rare, autosomal recessive inborn error of amino acid metabolism. Due to defects in intestinal absorption of tryptophan. You get increased degradation of tryptophan by bacteria, more production and absorption of indican (a breakdown product). When they pee, they pee out indican (indicanuria). Exposure of this to air oxidizes the pee to an indigo blue colour. Can be associated with visual problems, hypercalcemia and nephrocalcinosis. Pink diaper syndrome is benign. Red brown spotting caused by normal urate crystals which turn pink on exposure to air, forming a powder that can be scraped from the diaper.

Question 61

What is the initial work up for coffee or cola coloured urine?

Answer 61

Do a urinalysis, r+m. If proteinuria and RBC casts, think GN. For GN, order serum BUN, Cr, electrolytes. Sent ASOT, C3, C4. If vasculitis, send ANCAs. If lupus, check ANA and antiDNA. If Alport on FHx, obtain hearing test.

Question 62

What is the initial workup if there is bright red, painless hematuria?

Answer 62

Renal US to rule out malignancy, calculi, trauma, large cyst, PCKD, HN. If suspecting SCD, obtain Hb electrophoresis.

Question 63

What is the initial workup of bright red hematuria with dysuria?

Answer 63

1) Renal US to rule out calculi 2) Calcium to creatinine ratio to rule out hypercalciuria. 3) Urine culture to rule out UTI.

Question 64

What is on the differential if the dipstick is positive for blood but microscopy is negative for RBCs?

Answer 64

Dyes from beets or candy, hemoglobinuria (hemolysis), myoglobinuria (rhabdomyolysis).

Question 65

How do we define hypertension in children 1 -12 years old?

Answer 65

Normal BP: <90th percentile Elevated BP: 90-95th percentile Stage 1 HTN: over 95th to 95th percentile + 12 Stage 2 HTN: over 95th percentile + 12

Question 66

How do we define hypertension in children over 13 years?

Answer 66

``` Like adults. Normal BP: <120/<80 Elevated BP: 120-129/<80 Stage 1 HTN: 130-139/80-89 Stage 2 HTN: 140/90 or above ```

Question 67

What are some common causes of artifactual blood pressure elevation?

Answer 67

``` BP cuff too small Arm below level of heart Child is talking Feet off the ground Child given no time to relax ```

Question 68

What are some common causes of artifactual low blood pressure?

Answer 68

Arm is above the level of the heart

Question 69

How much can we expect the blood pressure to fall between visits after white coat hypertension?

Answer 69

15/7 by the third visit. Note: If stage 2 at the first visit, then they need immediate evaluation off the bat.

Question 70

How do you determine the optimum cuff size for obtaining a blood pressure?

Answer 70

Inflatable bladder length encircles at least 80% of the arm. Height of the cuff should be the largest size that fits comfortably from axilla to elbow.

Question 71

How is hypertension defined in the neonate and when should it be treated?

Answer 71

Term neonate >90/60 Preterm neonate >80/45 Treat if sustained systolic >100

Question 72

What are the indications for pharmacologic treatment of HTN in children and adolescents?

Answer 72

1) Symptomatic HTN 2) Stage 2 HTN 3) Stage 1 HTN not responding to 4-6 mos of the non-pharmacologic therapy 4) Secondary HTN 5) Organ damage (eg LVH on Echo) 6) Type 1 and 2 Diabetes with BP >90th percentile

Question 73

What are some risk factors for HTN in children? List 7.

Answer 73

1) Family history (1 parent HTN = 25%, 2 parent HTN = 45%) 2) Genetic factors 3) Obesity 4) History of renal disease 5) Diet 6) Low birth weight 7) Additional cardiovascular risk factors: tobacco, diet, serum lipids, lack of exercise

Question 74

List five causes of secondary hypertension.

Answer 74

1) UTI 2) Vasculitis 3) Renal artery stenosis 4) Drug-induced (sympathomimetics, steroids, NSAIDS, OCPs, illicit drugs) 5) Adrenal disorder - hyperaldosteronism 6) Pheochromocytoma 7) Hyperthyroidism 8) Coarctation of the Aorta 9) OSA 10) CKD 11) Arteritis 12) Renal malformation, renal tumour 13) Lupus nephritis 14) Collagen vascular disease

Question 75

What is orthostatic proteinuria?

Answer 75

Usually in adolescents. Benign condition where there are normal rates of protein excretion when recumbent but have increased excretion rates when upright/ambulant. Confirm this with first morning urine specimen with a PCR < 0.25.

Question 76

What level constitutes significant proteinuria?

Answer 76

Protein excretion of >4 mg/metre squared/hour on a timed urine collection. Nephrotic range is >40. Urine CPR >0.5 in children under 2 years and >0.2 in children over 2 years is abnormal.

Question 77

At what serum albumin concentration does edema start to develop?

Answer 77

When serum albumin is less than 2.5 g/dL.

Question 78

What is the most common cause of nephrotic syndrome in children?

Answer 78

Minimal change nephrotic syndrome. Etiology unknown, thought to do with abnormal T cell function. Definitive way to prove it is with renal biopsy, but age at presentation is often indicative (ie. over age 1 year and under age 8).

Question 79

What are the clinical features, worrisome complications and typical treatment response of children with minimal change nephrotic syndrome?

Answer 79

1) Edema, normal or slightly increased BP, No gross hematuria. 1/3 will have microscopic hematuria without RBC casts. Normal BUN, Cr, Electrolytes. Low serum calcium and albumin. 2) Watch out for hypercoagulable state/thrombosis and peritonitis. (strep pneumo or Ecoli). 2) 90% of kids respond to daily prednisone within the first month of treatment and have SSNS (steroid sensitive NS). If prolonged for another month, another 4% will respond. Despite 2 months of therapy, 3% will be steroid resistant (SRNS). If SRNS, consider kidney biopsy and treatment with cyclophosphamide or tacrolimus.

Question 80

What are the indications for Lasix and Albumin in Nephrotic Syndrome and what are the doses of each when you administer it?

Answer 80

1) Severe edema with anasarca, cellulitis or skin breakdown 2) Respiratory decompensation from pleural effusions Infuse 25% albumin solution at 0.5 - 1 g/kg of albumin over 1-2 hours THEN furosemide 1-2 mg/kg.

Question 81

A 5 year old child presents with puffy eyes and lab features of nephrotic syndrome. He does not respond to steroids after 6 weeks. What is the most likely diagnosis and prognosis?

Answer 81

Focal segmental glomerulosclerosis (FSGS), 20% of cases of pediatric nephrotic syndrome. Very often genetic 2/2 mutations in podocytes. Can be AR (podocin) or AD (ACTN4). Can progress to ESRD. Might benefit from ACE inhibitors. Don't respond to steroids.

Question 82

Which kind of urinary crystals are always pathologic?

Answer 82

Cystine. Indicates cystinuria, amino acid transport defect where the dibasic amino acids (cystine, orthinine, arginine and lysine) are affected. Remember mnemonic COAL. You get cystine crystals and nephrolithiasis.

Question 83

What is the most common cause of urinary tract obstruction in the newborn?

Answer 83

Posterior urethral valves, persistent urogenital membranes only in boys. You often get high pressures and reflux, damaging the renal parenchyma. Can progress to ESRD.

Question 84

What is the most common renal abnormality detected on antenatal ultrasound?

Answer 84

Hydronephrosis. Incidence 0.5-1%. Cutoff is renal pelvic diameter of over 5 mm then grades 0-IV based on degree of dilation, number of calyces observed and evidence of any atrophy. Repeat US advised at 48-72 hours after birth and then again at 4-6 weeks after birth. After that, might need VCUG and urology referral.

Question 85

List a differential diagnosis for pathologic causes of prenatal hydronephrosis?

Answer 85

1) Ureteropelvic junction obstruction 2) Posterior urethral valves 3) VUR 4) Ectopic ureter 5) Ureterocele 6) Megaureter 7) Urethral atresia in prune belly syndrome

Question 86

What are signs and symptoms common in all types of renal tubular acidosis?

Answer 86

Growth failure, polyuria, polydipsia, recurrent dehydration, vomiting. Hyperchloremic metabolic acidosis, normal serum anion gap.

Question 87

What is the defect in Type 1 (distal) RTA?

Answer 87

Inability of the distal tubule to secrete hydrogen. K normal or low Frequent nephrocalcinosis Urine pH >5.5

Question 88

What is the defect in Type 2 (Proximal) RTA?

Answer 88

Decreased ability of the proximal tubule to reabsorb filtered bicarb. K normal or low Rare nephrocalcinosis Urine pH <5.5

Question 89

What is the defect in Type 4 RTA?

Answer 89

Acquired or inherited tubular insensitivity to aldosterone or to an absence of aldosterone. K high Rare nephrocalcinosis Urine pH <5.5

Question 90

What is the urine anion gap and how is it clinically useful in nephrology?

Answer 90

Urinary anion gap = (Urine) Sodium + Potassium - Chloride. Screening test for RTA, esp distal. Indirect estimate of urinary ammonium excretion (urine acid excretion). If negative, suggests large chloride excretion in urine and adequate acid excretion. It is negative in hyperchloremic MA due to diarrhea, untreated proximal RTA and prior administration of acid. If positive, suggests acidification defect like distal RTA. If you have a positive result, you should look at urine pH and plasma potassium. If urine pH is >5.5 and K is low-normal, distal RTA. If urine pH < 5.5 and high K, type 4 RTA. Results not reliable if large amounts of unmeasured anions like ketoacids, penicillin, salicylates.

Question 91

How to you treat renal tubular acidosis?

Answer 91

Alkali therapy using sodium citrate or sodium bicarbonate, with the goal of a normal plasma bicarbonate level. Patients with distal RTA only require 2-3 mEq/kg/day. Patients with proximal RTA require large quantities, 5-20 mEq/kg/day. For Type 4 RTA, usually need low dose alkali therapy, 1-3 mEq/kg/day plus a potassium restricted diet +/- mineralocorticoid therapy (if hypoaldosteronism).

Question 92

What is renal Fanconi syndrome?

Answer 92

Manifestation of multiple disorders that cause abnormal transport within the proximal tubule and you get abnormal excretion of glucose, phosphate, potassium, amino acids, bicarbonate. Cystinosis (lysosomal storage disease causing abnormal accumulation of cystine) is most common cause. Also consider galactosemia, tyrosinemia, fructose intolerance. Metabolic bone disease 2/2 phosphaturia and hypophosphatemia. Metabolic acidosis 2/2 bicarbonate loss.

Question 93

What is renal glucosuria?

Answer 93

Benign condition, commonly familial, usually due to genetic abnormalities in renal glucose reabsorption. Mild glucosuria is typical. Need to make sure that there are no other symptoms, hypokalemia, MA or elevated serum creatinine.

Question 94

What is the etiology and clinical presentation of acute interstitial nephritis (AIN)?

Answer 94

It is caused by an immune mediated inflammatory response. Involves the renal interstitium and tubules, usually spares the glomeruli and vasculature. Certain medications can cause it such as antibiotics (penicillin analogs, cephalosporins, sulfonamides, rifampin); NSAIDS, diuretics, PPIs. Can present in a spectrum - can get acute renal failure, isolated tubular disorders etc. Might get polyuria and polydipsia as well as hypersensitivity signs including fever, rash, arthralgias. Lab abnormalities depend on which area is affected. Proximal tubule = glucosuria, bicaronaturia, phosphaturia, aminoaciduria. Distal = hyperkalemia, sodium wasting. Medullary = sodium wasting, urinary concentrating defects.

Question 95

The risk is (BLANK) times more for UTI in uncircumcised vs circumcised male infants?

Answer 95

10x

Question 96

What can cause a falsely low colony count despite a culture positive UTI?

Answer 96

1) High urine volume 2) Recent antibiotics 3) Slow growing organisms (enterococcus, staph saprophyticus) 4) low urine pH and low specific gravity 5) ureter obstruction 6) chronic or indolent infection 7) inappropriate culture technique

Question 97

What pathogens are associated with UTIs in children?

Answer 97

E.coli is 80-90% of initial UTIs. Other organisms: Klebsiella pneumoniae, Enterobacter, Pseudomonas, Proteus Miribalis, some Staphylococcus species.

Question 98

How do you differentiate cystitis versus pyelonephritis?

Answer 98

Pyelonephritis has more constitutional symptoms