Renal and Urologic Systems Disorders

Starling’s Forces

The Starling equation calculates:

• Movement of edema fluid

• Depends on hydrostatic and oncotic pressure differences between capillaries and interstitium

• Glomerular filtration depends on same opposing forces that produce the exchange of fluids in every capillary in our body

Hydrostatic Pressure

• Force within a fluid compartment

• Major force that pushes water out of vascular system at capillary level

• Pushes out “bag chair crew”: blood pressure.

Oncotic Pressure

• Osmotic pressure exerted by colloids in solution

• albumin is a major colloid.

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Fluid Movement in Capillaries

Amount and direction of movement determined by

• Capillary hydrostatic pressure – pushes H2O out of capillary

• Plasma oncotic pressure- pulls H2O back into capillary

• Interstitial hydrostatic pressure- opposes movement of H20 out of capillary

• Interstitial oncotic pressure- pulls H20 out of capillary into interstitial spaces

Filtration: controls the outward movement of fluid from capillary

Reabsorption: pulls fluid back into capillary

WHY DOES IT MATTER?

• LOW BP = drop in hydrostatic pressure > drop in filtration > acute kidney injury

• LOW PROTEIN STATE = drop in oncotic pressure > fluid leaking out > edema

• edema in relation to solutes from liver and ascites.

Fluid Shifts

Plasma-to-interstitial fluid shift results in edema.

 __increase__ in hydrostatic pressure in capillaries

 __decrease___ in plasma oncotic pressure

 __increase___ in interstitial oncotic pressure

Interstitial fluid to plasma

 Fluid drawn into plasma space with increase in plasma osmotic or oncotic pressure

• Hypertonic solutions

• Osmotic diuretic- mannitol

• Colloids (albumin, dextran, or FFP)

 ___compression__ stockings decrease peripheral edema.

• how does it work

• increases interstitial hydrostatic pressure

A patient with low serum albumin is at risk for which complication related to Starling’s forces in the glomerulus?

A. Hypertension

B. Dehydration

C. Edema

D. Hyperkalemia

C. Edema

Fluid Distribution

Intracellular (ICF) = 2/3 of body fluid

Extracellular fluid (ECF) = 1/3 of body fluid

 Intravascular (Plasma) – inside blood vessels

 Interstitial- between cells

What is the difference between interstitial fluid and extracellular fluid?

• Edema - ↑ interstitial fluid volume

ELECTROLYTES AND OSMOTIC ACTIVE SOLUTES

ICF

• ↑ Potassium

• Moderate Magnesium

• ↓ Sodium, Chloride, Bicarbonate, Phosphorus

• Very little Calcium

ECF

• ↑ Sodium, Chloride

• Moderate Bicarbonate

• ↓ Potassium, Magnesium, Calcium, Phosphorus

Isotonic Fluid- used to increase fluid in vascular space

Isotonic Fluid- used to increase fluid in vascular space

• Cells stay the same

• And fluids stay in the intravascular space

Hypotonic fluid- uses hypovolemia with hypernatremia and/or dehydration

• Cells swell as fluid goes into the cells

• .45

• Could cause cells to burst (lyse)

Hypertonic fluid- used for severe hyponatremia or hypoglycemia

• 3NaCL

A nurse is administering Normal Saline (0.9% sodium chloride) and knows that this fluid type:

A) Has a higher concentration of solutes than the fluid inside the body’s cells

B) Has the same concentration of solutes as the fluid inside the body’s cells

C) Has a lower concentration of solutes than the fluid inside the body’s cells

B) Has the same concentration of solutes as the fluid inside the body’s cells

RAAS

What sparks the RAAS to activate?

 Dehydration

 Hyponatremia

 Hemorrhage

 Decreased cardiac output

 Decreased blood volume

 Decreased blood pressure.

RAAS & HIGH SODIUM DIET

• Consider how the RAAS responds to a high salt diet

• Increased salt→ keep water in → increased blood pressure→ increased blood flow to kidneys → renin decreased→ decrease salt reabsorption from tubules → decreased extracellular fluid → decreased blood pressure

Antidiuretic hormone

ANTIDIURETIC HORMONE

• ADH -also called vasopressin.

• Helps kidneys control the amount of water your body loses through the urine

• retains fluid

• Produced in the hypothalamus but released by the pituitary gland

• If too much is produced -Syndrome of Inappropriate Antidiuretic Hormone (SIADH))

 Kidneys hold onto too much water

 Hyponatremic because diluted by excess water

 Fluid overload

Fluid Volume Excess

FLUID VOLUME EXCESS - HYPERVOLEMIA

• Define: Too much fluid volume typically intravascular but can become interstitial.

• Nurses call these patients WET.

• Common causes:

  • Heart failure

  • Kidney disease- Chronic or acute renal failure or acute kidney injury

  • Liver disease- cirrhosis and ascites

  • Diabetes

• Manifestations:

  • Edema

  • Bloating

  • ↑ weight

  • Dyspnea

  • Hypertension

  • Crackles

Treatment

• Remove fluid without changing electrolyte composition.

• Give a diuretic!

Fluid Volume Deficit

FLUID VOLUME DEFICIT - HYPOVOLEMIA

• Define: Extracellular fluid volume deficit, can’t perfuse the body.

• Nurses call these patients “dry”. Think Hypovolemic Shock!

• Causes:

  • Diarrhea

  • Hemorrhage (blood loss)

  • Excessive sweating

• Manifestations:

  • Dizziness when standing

  • Dry skin and mucous membranes

  • Fatigue/weakness

  • Muscle cramps

  • Decreased urinary output, increase in urine specific gravity. (urine very concentrated)

• Treatment

  • Replace water and electrolytes with balanced IV solutions.

  • Replace whatever they are missing

RENAL CALCULI: NEPHROLITHIASIS

Also known as “kidney stones”

Complex etiology

• Increase in stone components in blood and urine

• Anatomic changes

• Metabolic, endocrine & dietary influences

• Infection

Risk factors:

• Family/personal Hx

• Dehydration

• Diet high in protein, Na & sugar

• Obesity

• Digestive diseases/surgery

Signs & symptoms

 Hematuria

 Pain

 Renal colic (spasms): acute, intermittent, excruciating pain

 May radiate down into groin for men

 Nausea/Vomiting

TREATMENT

Fluids- oral and IV

Pain management

Medications:

• Tamsulosin (Flomax) (releases sphincter action/quicker)

• Dutasteride and tamsulosin (Jalyn)

Procedures/surgeries

• Extracorporeal shock wave lithotripsy (ESWL)

• Percutaneous nephrolithotomy

• Ureteroscopy with or with/out stent placement

• Parathyroid gland surgery- if hyperparathyroidism caused

Types of Stones and causes

Calcium (most common)

• High doses of Vit D

• Intestinal bypass surgery (d/t metabolic changes)

• Metabolic disorders- renal tubular acidosis

Struvite- calcium, magnesium, ammonium and phosphate

• Usually caused by a UTI

Uric acid

• Chronic diarrhea or malabsorption

• High protein diet

• Diabetes

• Metabolic syndrome

Cystine (amino acid)

• Hereditary disorder - cystinuria

A 45-year-old male presents to the emergency department with sudden onset of severe flank pain radiating to the groin, accompanied by nausea and hematuria. A non-contrast CT scan reveals a 6 mm calculus in the left ureter.

Which of the following best explains the pathophysiological mechanism leading to his symptoms?

A. Inflammation of the glomerular basement membrane causing proteinuria

B. Obstruction of urinary flow causing increased intrarenal pressure and ureteral spasm

C. Autoimmune destruction of renal tubular cells causing acute tubular necrosis

D. Excess aldosterone secretion leading to sodium retention and hypokalemia

B. Obstruction of urinary flow causing increased intrarenal pressure and ureteral spasm