Nephrology Exam

What are the top 5 functions of the kidneys?

-remove waste
-control BP by secreting renin which initiates RAAS
-stimulates RBC production by secretion of EPO
-maintains bone health by secreting calcitriol --> reducing Ca2+ loss
-controls pH

What make up about 90% of all renal cancers?

renal cell carcinoma (parenchyma)- includes adenocarcinomas

What are the types of renal cancers?

-renal cell carcinoma (includes adenocarcinoma)
-transitional cell carcinoma - renal pelvis (linked with cigarette smoking)
-wilms' tumor
renal sarcoma- originated from vasculature or connective tissue of kidney

Describe the presentation of a patient with renal cell carcinoma.

-*gross or microscopic hematuria*
-flank pain or mass
-fever, weight loss
-solid renal mass on imaging
-night sweats, fever, malaise, weight loss
-*erythrocytosis but anemia is more common*
-*hypercalcemia*
-*stauffer syndrome* - hepatic dysfunction in absence of liver metastasis

What are risk factors for renal cell carcinoma?

-*cigarette smoking is the only environmental risk factor*
-obesity, HTN, acquired cystic kidney disease associated with dialysis, ADPKD
-familial causes

Which renal cancer is associated with paraneoplastic syndrome?

renal cell carcinoma
-Paraneoplastic syndrome is symptoms due to remote effects of cancer

What is the best initial test for renal cell carcinoma?

-US because it is inexpensive, without radiation and high sensitivity
-then do CT or MRI
-then *biopsy or nephrectomy*
-bone scan if metastasis is suspected

What is the treatment for renal cell carcinoma?

-*surgery is gold standard* - partial or radical- curative in stages 1-3
-resistant to chemo or radiation

Describe renal cell carcinoma staging.

I: confined to renal capsule and

What is Wilms' tumor?

-nephroblastoma
-most common renal malignancy in *children*
-African Americans are more at risk

Describe the presentation of a patient with Wilms' tumor?

-abdominal swelling or mass w/o other symptoms- rarely crosses midline
-abdominal pain
-hematuria
-HTN
-may have subcapsular hemorrhage (fever, rapid abd enlargement, anemia, HTN)

Which patients should be screened for Wilms' tumor?

-Beckwith-Wiedmann syndrome every 3 months until age 7
-WAGR syndrome every 3 months until age 5

Describe the workup in a patient with a Wilms' tumor?

-*US* then CT or MRI
-*evaluate for lung metastasis*
-SCr, CMP, UA, maybe coagulation studies if indicated

Describe the staging of a Wilms' tumor.

I: limited to kidney and completely excised w/o rupture or biopsy- renal capsule intact
II: tumor extends through renal capsule but all is removed- vessels outside kidney contain tumor - OR "local spillage on removal"
III: residual tumor confined to abd - involvement of abd lymph nodes- "diffuse" contamination by rupture- microscopic margins positive post resection
IV: hematogenous metastasis at any site
V: bilateral renal involvement

How are Wilms' tumors treated?

-*surgical excision*
-CTX (chemotherapy) with low risk tumors
-XRT (radiation) for advanced stage and histology

What is the prognosis of Wilms' tumor?

5 year survival of 90%
follow with CT - pulmonary and abdominal Q3mo/2 years then Q6mo/2 more years

What is ADPKD?

Autosomal dominant polycystic kidney disease
-cysts increase with age
-most common hereditary disorder in the US

Describe the presentation of ADPKD.

-often have HTN and abdominal mass (palpable kidneys)
-*family history*
-abdominal/ flank pain
-hematuria
-Hx of UTI/ nephrolithiasis

What genetic mutations were found for ADPKD?

PKD1 and PKD2
-PKD1 has worse prognosis and faster progression of disease

How is ADPKD treated?

treat symptoms
-Abd/ flank pain: *cyst decompression/drainage/ removal and analgesics*
-Hematuria: *bed rest, hydration*
-renal infection: *ABX- fluoroquinolones, bactrim, chloramphenicol*
-nephrolithiasis: *hydration*
-HTN: *cyst decompression and aggressive pharmacotherapy to prolong ESRD*
-cerebral aneurysms and other vascular problems may occur
-Vasopressin receptor antagonist can slow worsening of kidney function
-avoid caffeine, low protein, low salt diet

A patient has a urinalysis done and it comes back with Bence Jones protein, what might they have?

multiple myeloma
-Bence Jones protein is light chain Ig - causes renal toxicity and obstruction
-*hypercalcemia* is also found

How is multiple myeloma treated?

-correct hypercalcemia
-volume repletion
-chemo for MM

How much of the total body water does ICF make up? Which ions are found there?

2/3
K+, Phosphate, Sulfate

How much of the total body water does ECF make up? Which ions are found there?

1/3
Na+, Cl-, Bicarb

How much of the ECF does plasma make up?

1/4

How much of the ECF does the interstitial fluid make up?

3/4

What is a normal serum osmolality?

290 mosm/kg H2O

What is the gold standard for evaluating renal electrolytes?

24 hour urine collection

What does low (

-fractional excretion of Na+ (FENA)
-renal reabsorption (prerenal)

What does high (>1%) FENA indicate?

-fractional excretion of Na+ (FENA)
-renal wasting (intrinsic)

What is an osmolar gap?

-difference between serum osmolality and calculated osmolality *>10 mm/kg* indicated gap
-suggests unmeasured fluids such as ethanol, ethylene glycol, methanol

How is serum osmolality calculated?

should = 285-295 mmol/kg

What is the normal physiologic response to hypernatremia?

increased thirst mechanism

What usually causes hypernatremia?

-free water loss, hypotonic fluid loss (diabetes insipidus), urinary loss, GI loss, and insensible loss
-renal losses of glucose or osmotic diuresis with mannitol
-non renal losses such as excessive sweating, excessive bowel movements, osmotic diarrhea

Describe the presentation of a patient with hypernatremia.

-*dehydration
-positive orthostatic hypotension*
-flushed skin
-hyperthermia, fever
-*oliguria* and anuria
-hyperventilation
-hyperreflexia
-neurologic manifestations
-thirst, restlessness, irritability
-*lethargy, weakness*, disorientation
-*delirium, seizures, coma*

What findings occur in *central* diabetes insipidus?

low urine sodium and polyuria

What finding occur in *nephrogenic* diabetes insipidus?

antidiuretic stimulation does *not* increase urine osmolality

What is the formula for total body water?

TBW= patient weight in kg x % (based on gender and age)
usually 40-60% of patients weight
-Example =70kg*.55 for a 55 y/o male= 38.5L

How is total water deficit calculated for acute hypernatremia with acute volume loss?

water deficit= current TBW* ((serum [Na]/140)-1)

What is the total water deficit of a 70kg, 55 y/o male with a Na+ of 160 (water content 55% for this age/sex) who has acute hypernatremia?

(70kg x .55) x ((160/140)-1) = 5.4999L

How do you calculate flow rate in acute hypernatremia? What is considered acute?

-total water deficit is calculated them divided by 24 hours and multiply by 1000ml which gives you the hourly rate for a 24 hour infusion
-acute if under 48 hours

How do you calculate flow rate for chronic hypernatremia? What is considered chronic?

-patients weight in kg * 1.35mL/hr which will give you the hourly rate for a 24 hour infusion
-chronic >48 hours

Why is it important to not correct chronic hypernatremia too quickly?

it can cause increase in ICP (cerebral edema) and pulmonary edema

How is hypernatremia treated?

-underlying cause
-replace water orally preferred or IV *5% dextrose solution (D5W)*
•hypovolemic: replace with isotonic fluid (NS)
•euvolemic: 5% dextrose to allow excess Na+ to be excreted
•hypervolemic: loop diuretics or dialysis (if Na+ >200Eq/L)
-replace electrolytes if needed

How is hypovolemic hypernatremia treated?

-replace with normal saline (isotonic fluid)
-replacing electrolytes PRN

How is euvolemic hypernatremia treated?

-replace fluid with D5W to allow excess Na+ to be excreted
-replacing electrolytes PRN

How is hypervolemic hypernatremia treated?

-loop diuretics or dialysis (if Na>200mEq/L
-replacing electrolytes PRN

What is neurogenic diabetes insipidus?

-deficient secretion of arginine vasopressin (AVP) from posterior pituitary

What is nephrogenic diabetes insipidus? What causes it?

-kidneys are unresponsive to normal vasopressin levels
-inherited X-linked trait or acquired (lithium therapy, hypokalemia, hypercalcemia, or renal disease)

Describe the presentation of diabetes insipidus? What labs would be normal/ abnormal?

-*polyuria, nocturia, polydipsia*
-glucose - normal
-serum Na over 145 and urine osmolality < 300mOsm/kg

How can you differentiate between neurogenic and nephrogenic diabetes insipidus in a patient?

desmopressin challenge
-if urine osmolality improves (>400) then its central (neurogenic)
-if urine osmolality doesn't change them its nephrogenic

How is neurogenic diabetes insipidus treated?

-parenteral or intranasal desmopressin
-OR thiazide diuretics, chlorpropamide, carbamazepine for mild disease

How is nephrogenic diabetes insipidus treated?

-thiazide diuretics or indomethacin
-dietary measures, limiting salt and proteins intake can be helpful

What is the most common electrolyte abnormality in hospitalized patients?

hyponatremia

What levels of serum Na+ indicate a high mortality rate?

•

What is a corrected Na+?

Corrected Na+ = serum Na+ +. ( (glucose serum-100) * 0.016)
-use this if patient is hyperglycemic to get true Na value

What causes isotonic hyponatremia?

-hyper*protein*emia/ hyperalbuminemia - due to multiple myeloma or macroglobulinemia
-hyper*lipid*emia (milky appearing serum) - due to famlial hyperlipidemia or nephrotic syndrome
-Pseudohyponatremia - increase in plasma solids such as *lipid or protein* - lowers the proportion of each liquids per L of plasma which lowers the plasma Na+ concentration w/o altering the Na+ in the liquid compartment

What causes hypertonic hyponatremia?

-*hyperglycemia*
-mannitol administration
-these cause shift of H2O from the ICF to the ECF and lowers serum Na+ concentration

What causes hypervolemic hypotonic hyponatremia?

CHF, Nephrotic syndrome, Renal failure (late stage/ ESRD), Hepatic cirrhosis

What causes euvolemic hypotonic hyponatremia?

-severe hypothyroidism, drugs, psychogenic polydipsia, addison's disease
-*SIADH (most common)* can be due to malignancy or drugs
-renal failure- no excretion of free water
-post surgery
-HIV infection
-endurance exercise hyponatremia (combination of excess hypotonic fluid intake and continued ADH secretion)
-malignancy

What causes hypovolemic hypotonic hyponatremia?

-renal losses
diuretic use, nephropathy (salt wasting), addison's disease (adrenal insufficiency, GU obstruction)
-nonrenal sodium loss
•GI losses (diarrhea, vomiting), insensible losses (skin and respiratory tract), third spacing (ileus, burns)
-thiazide diuretics

What is ADH independent hyponatremia?

Uosm (urine osmolarity)

Describe the presentation of hypovolemic hypotonic hyponatremia? What labs would be normal/ abnormal?

-s/s: orthostatic hypotension, dry mucous membranes
-labs: increased BUN/ Creatinine (if renal), decreased urine Na+

Describe the presentation of hyponatremia.

-Symptoms: HA, lethargy, nausea, disorientation, marked confusion, emesis, seizures, coma, brain herniation, death
-chronic may be asymptomatic
-Signs: weakness, hyporeflexia, orthostatic hypotension, Cheyne-stokes respirations, delirium, coma, stupor

Describe the workup in a patient you suspect has hyponatremia?

-serum Na+

What is the urine Na+ content in euvolemic hypotonic hyponatremia?

>20mEq/L

A patient has low serum sodium, low plasma osmolality and decreased urine sodium. What is the cause?

*Nonrenal*
Hypervolemic hypotonic hyponatremia
-nephrotic syndrome, CHF, cirrhosis

A patient has low serum sodium, low plasma osmolality and increased urine sodium. What is the cause?

*Renal*
Hypervolemic hypotonic hyponatremia
-acute and chronic renal failure

How is hypovolemic hypotonic hyponatremia treated?

-*isotonic saline* to replace volume
-if 2º to diuretics may need K+ repletion

How is hypervolemic hypotonic hyponatremia treated?

-salt and fluid restriction + *loop diuretic*
-V2 receptor antagonist may be considered
-dialysis is last resort

How is euvolemic hypotonic hyponatremia treated?

-*free water restriction* is treatment of choice
-vasopressin antagonist (Tolvaptan/ Conivatan) if severe

When is Tolvaptan (Samsca)/ Conivaptan indicated and what is their action?

-euvolemic and hypervolemic hyponatremia
-*contraindicated* in hypovolemic
-V1A and V2 vasopressin receptor antagonist - induces both water and Na diuresis with improvement in plasma Na+ levels

How is severe symptomatic hyponatremia (Na

*hypertonic saline (3%)*
consult nephrology

How is chronic hyponatremia treated if it is unresponsive to fluid restriction?

demeclocycline - induces nephrogenic diabetes insipidus

What happens when hyponatremia is overcorrected too quickly?

-central pointe myelinolysis AKA iatrogenic cerebral osmotic demyelination or osmotic demyelination syndrome (ODS)

How is symptomatic acute hyponatremia managed?

-urgent correction by 4-6mmol/L (i think per day)
-if severe symptoms: 100mL of 3%NaCl infused over 10 min x 3 as needed
-mild-mod symptoms with low risk of herniation: 3% NaCl infused at 0.5-2mL/kg/h

How is symptomatic chronic hyponatremia managed?

minimum correction of serum Na+ by 4-8mmol/L per day with lower goal (4-6) if high risk of ODS
-max correction of 10-12mmol/L per day; 18mmol/L in 48 hours

How is hyponatremia due to SIADH managed?

-*fluid restriction at 1500mL to start* is first line
-if low renal electrolyte-free water excretion or if serum Na+ does not correct over 24-48 hours of fluid restriction --> consider demeclocycline, urea, and vasopressin receptor antagonist

How much plasma is filtered by the glomerulus?

20%

What are juxtaglomerular cells?

-"baroreceptors" sensing afferent arteriole pressure
-increase renin release when there is a drop in pressure

What are macula densa cells?

-cells of the early distal tubule- sense NaCl delivery (ion concentration)
-release vasoactive substances when there is a drop in solute levels

What is azotemia?

excess urea or other nitrogenous waste products in the blood as a result of kidney insufficiency- measured by BUN and/or creatinine

What is uremia?

clinical manifestation of azotemia (increased nitrogenous waste products in the blood)

What is the difference between oliguria and anuria?

oliguria: decreased urine output (100-400mL (cc) /day)
anuria:

What is an acute kidney injury?

-sudden increase in serum BUN and/or creatinine
-reversible
-results in inability to maintain acid-base, fluid and electrolyte balance or to excrete nitrogenous waste

What causes a postrenal AKI?

-urinary tract *obstruction* affecting both kidneys causing back pressure to bowman's space- afferent arteriole can dilate to compensate but will fail --> under perfused areas of the renal cortex and decrease of GFR
•Ureteric: caliculi, blood clots, papillary necrosis, cancer, external compression
•Bladder: neurogenic bladder, BPH, caliculi, blood clots, cancer
•Intratubular crystallization: uric acid, Ca oxalate, acyclovir, sulfonamide, methotrexate

What causes a prerenal AKI?

-*most common AKI*
-renal hypoperfusion with intact parenchyma- caused by impaired renal blood flow- normal compensatory mechanism is release of ATII --> afferent arteriole vasodilation and constriction of efferent arterioles to maintain GFR but this will fail if prolonged
•Hypovolemia: hemorrhage, GI fluid loss, renal fluid loss, extravascular sequestration (burns, pancreatitis, renal artery stenosis, severe hyperalbuminemia), decreased intake
•Low cardiac output
•systemic vasodilation: sepsis, anti hypertensives, anaphylaxis
•renal vasoconstriction: hypercalcemia, catecholamines, amphotericin B
•Impairment of renal autoregulatory responses: NSAIDS, ACEI, ARBs

What causes an intrinsic AKI?

-Parenchymal renal disease: *acute tubular necrosis* (most common- often after vascular surgery), cortical necrosis, acute glomerulonephritis, microvascular disease, allograft rejections, or interstitial disease
•aminoglycosides (neomycin, gentamycin, tobramycin)
•*radiocontrast media*
•chemotherapy - Cisplatin

What are the 4 categories of intrinsic AKI?

-Vascular- vasculitis, malignant HTN, TTP/HUS, emboli/thromboemboli vein or artery
-Glomerular- glomerulonephritis
-Tubular- ischemia, infection/sepsis, toxins (exogenous: radiocontrast, chemo or endogenous: rhabdomylysis, hemolysis)
-Interstitial-allergic/drug rxns, infiltration (lymphoma, sarcoidosis), inflammatory/ nonvascular (Sjogrens), intratubular obstruction (enodgenous or exogenous)

What are signs/symptoms of uremia?

What diagnostic studies are helpful to differentiate what kind of AKI?

-UA then 24 hour urine collection- to monitor fluid balance
-Electrolytes in serum and urine - look for *hyperkalemia*
-ABG for *metabolic acidosis*
-CBC for *infection or anemia*
-biopsy if needed
-EKG due to electrolyte imbalances
-US to visualize the kidney
-IV Urography : to evaluate urinary tract- IVP requires contrast
-CT scan: to evaluate solid or cystic lesions
-MRI: for glomerulonephritis, hydronephritis, and renal vascular occlusion
-Arteriography and venography

What is FENa and how is it calculated?

• Fraction Excretion of Sodium

• FENa = (urine Na+ x serum Cr)/ (serum Na+ x urine Cr) <1% = prerenal (or acute glomerulonephritis)

1% = intrinsic -Limitation: if taking diuretics

What does >20:1 BUN:Cr ratio indicate for AKI?

prerenal, post renal or acute glomerulonephritis

What does

intrarenal (ATN or acute interstitial nephritis)

Which AKI's have high urine Na+?

Acute tubular necrosis

Which AKI's have low urine Na+?

prerenal or acute glomerularnephritis

What indicates significant irreversible renal disease?

Why is Gadolinium contraindicated in stage 4-5 CKD, AKI, or a kidney transplant?

risk of nephrogenic systemic fibrosis

What is the gold standard for diagnosis of renal vein thrombosis?

venography

How is AKI treated?

depends on cause
-manage BP, treat infections, kidney rest
-consider drugs and metabolites not excreted
-low protein, high carb diet
-*primary goal is to maintain the individuals life until recovery*
-dialysis