Renal Flashcards
Dehydration in patient who is vomiting vs SIADH
What would you see for Una, Uosm, and Serum osm?
Hyponatremic dehydration
- Una is low (bc reabsorbing sodium to reabsorb water)
- Uosm is high (bc reabsorbing water)
- Serum osm is low (bc Na is biggest contributor to osm)
Urine sodium is an indicator of intravascular volume status and low urine sodium (< 20–25 mEq/L [20–25 mmol/L]) suggesting decreased perfusion even in patients without clinical features of dehydration (such as edematous pts in nephrotic syndrome, cirrhosis, CHF)
SIADH:
- Una is high (bc ADH causes increased water absorbtion
- Uosm is high
- low serum osms (bc more water circulating)
Some patients with chronic renal failure have a normal GFR
Serum creatinine and glomerular filtration rate (GFR) are not good indicators of the loss of functioning nephrons because of the compensatory increased function in the remaining nephrons and increased tubular secretion of endogenous creatinine.
The early stages of progression of chronic kidney disease (CKD) are accompanied by minimal elevation in serum creatinine, but a major decrease in GFR.
Increasing proteinuria, albuminuria, and/or new-onset or worsening hypertension is indicative of progressive CKD despite a stable GFR (especially in the early stages of CKD).
Variable urea production in patients with renal injury and tubular urea reabsorption make blood urea nitrogen a less reliable marker for GFR than creatinine.
Normal GFR > 90
Causes of hypochloremia
Hypochloremia is seen with Met Alkalosis
Urine chloride = helps assess intravascular status.
So if Urine chloride is low (<20) likely volume depletion
- vomiting, CF with loss of chloride rich sweat
If urine chloride is high (>40),
- renal tubular disorders with salt wasting (Bartter and Gitelman) will present with that, hypochloremia, hypoK, met alkalosis
- primary aldosteronism - HTN, hypoK, and meta alkalosis with high urinary chloride
Recurrent episodes of dehydration with FHX of males being affected
Nephrogenic DI
- ADH-R mutation is X-linked
- neonates with irritability, FTT< dehydration
- Hypernatremia with low urine osmolality
Other cuases of increased free water loss: diabetes mellitus (osmotic diuresis), diabetes insipidus (DI; antidiuretic hormone disorders), and psychogenic polydipsia
Tubulointerstitial injury associated with chronic kidney disease leads to reduced urinary concentration (acquired nephrogenic DI). These patients usually present with polyuria with or without enuresis.
How to treat HyperK
Diuretics, cation exchange resins, and dialysis remove excess potassium from the body.
Intravenous calcium gluconate (10%) is indicated for patients with severe hyperkalemia (> 7.0 mEq/L), widening of the QRS complex or absent P waves, and arrhythmias assumed to be secondary to hyperkalemia.
Inhaled β-adrenergic agonists, insulin-glucose infusion, and sodium bicarbonate move serum potassium from the extracellular to the intracellular compartment.
Gross hematuria DDX
file:///Users/vicky/Downloads/C188A.pdf
Na and K daily requirements.
Energy expenditure to meet daily needs is 100 kcal/kg which is associated with 100 mL/kg of sensible and insensible fluid loss
Na = 2-3 mEq per 100mL of fluid loss K = 1-2 mEq per 100mL of fluid loss
Metabolic Acidosis
Anion gap (NA - HCO3 - Cl)
Non-anion gap = 8-12
- RTA - loss of HCO3 from urine
- Diarrhea - loss of HCO3 from stool
- Urine anion gap is NEG in diarrhea vs. RTA
Urine anion gap = Na + K - Cl
- positive = low urinary NH4 (represented by Cl) = RTA
- negative = high urinary NH4 and excretion of H = diarrhea
Anion gap > 12
MUDPILES
Metabolic Alkalosis
Increased HCO3 (due to loss of Cl)
- Vomiting
- Diuretics
- Diarrhea
Hypertrophic Pyloric Stenosis
HypoCl HypoK Met Alkalosis
Can also have HypoNa!
Met Acidosis/Alkalosis Formulas
Metabolic acidosis
Winters:
pCO2 = 1.5 * HCO3 + 8 +/- 2
Resp:
HCO3 goes up 3.5 for every 10 mmHg in pCO2
Dehydration Tables
Mild-Mod-Severe: file:///Users/vicky/Downloads/C81A.pdf
ORS: file:///Users/vicky/Downloads/C81B.pdf
Respiratory Acidosis Compensation
In the acute phase of respiratory acidosis, serum bicarbonate rises slightly (approximately 1 mmol/L for every 10 mm Hg of increased partial pressure of carbon dioxide [Pco2]) due to buffering by intracellular proteins.
AKA carbonic anhydrase reaction
H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3-
In the chronic phase of respiratory acidosis, over days or longer, serum bicarbonate rises approximately 3.5 mmol/L for every 10 mm Hg of increased Pco2, because of the increased reabsorption of bicarbonate at the renal tubular level.
Hypernatremic Dehydration
Hypernatremic dehydration
- with gastrointestinal losses is more frequently associated with decreased water intake that occurs in patients with altered sensorium (ie, developmental delay) or infants who receive inadequate fluid intake from their caregivers
- diabetes mellitus
- diabetes insipidus
Sx: underestimation of the degree of dehydration.
Neurologic sequelae are frequently seen in infants with hypernatremic dehydration*
Free water deficit: 0.6 x wt x Na/140-1
Rate of lowering: 10 to 12 mEq/L/d (0.4-0.5 mEq/L/h) over 48 to 72 hours. to prevent cerebral edema
Hyponatremia
Plasma osmolality is tightly controlled between 280 and 295 mOsm/kg by osmostatic mechanisms in the posterior pituitary gland through regulation of the thirst mechanism and antidiuretic hormone (ADH).
mOSm/kg = 2NA + BUN/2.8 + Glucose/18
Increased ADH secretion:
- CHF, SIADH, neurologic conditions like TBI or surgery, pulmonary infections
Hypertonic HypoNa
- pseudohyponatremia = occurs in DKA when theres lots of glucose and it draws water out of cells
Alport Syndrome
Alport syndrome is an inherited disorder (often X-linked) of basement membrane collagen characterized by involvement of the kidneys (always), ears (often), and eyes (occasionally).
Sx: recurrent episodes of hematuria is the earliest manifestation and a universal symptom in patients with Alport syndrome.
In affected males, ESRD is common by 30 years of age. Females rarely develop end-stage renal disease but may still have intermittent microscopic hematuria.
VS: Asymptomatic isolated microscopic hematuria frequently seen in children, is usually transient and benign in etiology.
Anterior lenticonus is the conical protrusion of the lens and is pathognomonic of AS.
Renal stones - most common identified cause
Hypercalciuria
- Less commonly cystine, oxalate, and uric acid renal stones.
Urinary metabolic abnormality is the most commonly identified risk factor for renal stones. So should eval all pts with stones for this, with 24 hour urine collection.
Increased urinary excretion of citrate (most important), magnesium, and pyrophosphate is associated with decreased risk for renal stone formation, and a low level of these inhibitors is associated with an increased risk for nephrolithiasis in children and adults.
