Renal Physiology, Kidney Injury, and Transplant Lecture

A comprehensive set of Q&A flashcards reviewing renal anatomy, physiology, laboratory values, kidney injury etiologies, dialysis modalities, transplant considerations, and diuretic pharmacology.

Give examples of pre-renal causes of acute kidney injury.

Hypovolemic states (hemorrhage, GI losses, renal losses, burns), systolic heart failure, hypoalbuminemia, and medications such as NSAIDs, ACE inhibitors, ARBs, cyclosporine, or iodinated contrast.

Give examples of intra-renal causes of acute kidney injury.

Acute tubular necrosis, nephrotoxins (aminoglycosides, methotrexate, lead, ethylene glycol, radiocontrast dye), rhabdomyolysis, glomerular disease, and acute interstitial nephritis.

Give examples of post-renal causes of acute kidney injury.

Kidney stones, benign prostatic hyperplasia (BPH), and intra-abdominal tumors obstructing urine flow.

What is considered normal urine output per kilogram per hour in an adult?

0.5 mL/kg/hr.

What is the renal capsule and its function?

Three layers of connective tissue and fat that protect, stabilize, and anchor the kidney to surrounding structures.

Where do nephrons begin and which hormone is produced there?

In the renal cortex; the cortex produces erythropoietin for red blood cell production.

Approximately how many nephrons does each kidney contain?

About one million nephrons per kidney.

Which region of the kidney holds the nephrons, glomeruli, and renal tubules?

The renal medulla.

What is the role of the renal tubules?

To carry forming urine from the nephron to the renal pelvis.

What is the function of the renal pelvis?

It collects urine and passes it to the ureters.

Define a nephron.

The functional unit of the kidney that filters blood and forms urine.

What is the glomerulus?

A bundle of capillaries inside Bowman’s capsule where filtration begins.

Where in the nephron are two-thirds of water and electrolytes reabsorbed?

The proximal convoluted tubule.

Which arteriole brings blood into the glomerulus?

The afferent arteriole.

Which arteriole carries blood away from the glomerulus?

The efferent arteriole.

Compare pressures in the afferent versus efferent arterioles.

Afferent arteriole has higher pressure and a higher initial filtration rate; the efferent arteriole has lower pressure and continues into the vasa recta.

Define filtration in renal physiology.

Mass movement of water and solutes from plasma into the renal tubule at the glomerulus.

Define reabsorption in renal physiology.

Movement of solutes and water from the renal tubule back into the bloodstream.

Define secretion in renal physiology.

Active transport of unwanted substances (e.g., creatinine, H⁺, K⁺, drugs) from blood into the tubule.

Define excretion in renal physiology.

The final elimination of filtrate as urine after filtration, reabsorption, and secretion.

What is the normal serum creatinine range in adults?

0.6 – 1.2 mg/dL.

What is the normal blood urea nitrogen (BUN) range?

10 – 20 mg/dL.

What is the normal BUN-to-creatinine ratio?

Approximately 10 : 1.

What GFR value is considered normal?

Greater than 125 mL/min.

List classic EKG changes associated with hyperkalemia.

ST-segment elevation, peaked T waves, prolonged PR interval, and a widened QRS complex.

At what GFR does stage 1 chronic kidney disease begin?

GFR of 90 mL/min or greater.

How long must complete loss of renal function persist to diagnose ESRD?

More than three months.

What is the induction goal of immunosuppression before kidney transplantation?

To completely deplete T-cells in the immediate pre-transplant period to reduce acute rejection risk.

Describe early and late clinical manifestations of end-stage renal disease (ESRD).

Early: often asymptomatic. Late: oliguria, decreased mental sharpness, muscle cramps, edema, persistent pruritus, immune dysfunction with high cytokines, shortness of breath, fluid overload, hypertension, hyperkalemia, hyponatremia, hypoalbuminemia, and hypocalcemia.

Outline the timeline of serum creatinine changes after iodinated contrast exposure.

Creatinine rises at 48-72 hours, peaks at 3-5 days, and returns to baseline in another 3-5 days.

List contraindications to kidney transplantation.

Age > 65 years, ventilator dependence, high-dose steroid therapy, active infection, multi-organ dysfunction, cancer, ongoing smoking, poor rehabilitation potential (e.g., homelessness), and significant psychiatric issues.

Compare hemodialysis with continuous renal replacement therapy (CRRT).

Hemodialysis: short-term vascular access or long-term fistula/graft; 3–4 hours per session, 3×/week; rapid fluid shifts (0.5–3 L), risk of hypotension/bleeding/infection; not ideal for unstable patients. CRRT: slower, gentler, preferred for hemodynamically unstable patients; less effective with poor cardiac output.

Where do thiazide diuretics work and what do they block?

In the early distal convoluted tubule; they block sodium and chloride reabsorption, thereby reducing water reabsorption.

Where do loop diuretics act and what is their primary effect?

In the loop of Henle; they block sodium and chloride reabsorption, increasing excretion of water, Na⁺, K⁺, Cl⁻, Mg²⁺, and Ca²⁺.

How do potassium-sparing diuretics achieve diuresis without causing potassium loss?

They antagonize aldosterone, leading to sodium and water excretion while promoting potassium retention.

What is the renal mechanism of action of desmopressin (DDAVP)?

It is an ADH analog that promotes water reabsorption in the kidney and induces vasoconstriction.