Renal Function and Urinalysis Practice Flashcards

A set of 40 practice flashcards covering renal anatomy, physiology, urinalysis methodologies, and clinical nephropathy based on lecture notes.

What is the normal consensus value for adult urine output per day?

$$800-1,200\,mL/day$$

Identify the average number of nephrons found in a single adult kidney.

$1,000,000$ nephrons

What percentage of cardiac output do the kidneys typically receive?

$$25\%$$

What are the three specific filtration barriers in the glomerulus?

1) Fenestrated endothelial cells, 2) Basement membrane (GBM), and 3) Epithelial cell projections (foot processes/filtration slits).

Plasma proteins smaller than what molecular weight are generally filterable?

$$< 60\,kDa$$

Why is albumin, which is approximately $60\,kDa$, largely prevented from entering the proximal tubule?

Due to negative charge repulsion (albumin has $>200$ negative charges) by the three filtration barriers and the glomerular glycocalyx.

What is the function of the glomerular glycocalyx?

A $200-1000\,nm$ thick negatively charged layer of glycoproteins and proteoglycans that acts as the primary, highly selective barrier to macromolecule leakage.

Which cells are responsible for keeping the glomerulus in the right conformation and can cause contraction?

Mesangial cells

What is creatinine a spontaneous, non-catalyzed decomposition product of?

Creatine ($Cr$) and creatine phosphate ($PCr$)

Where is creatine phosphate synthesized and stored for energy?

Skeletal muscle

Name four criteria for an ideal marker of filtration or clearance.

1) Freely filterable, 2) Not further metabolized, 3) Produced at a steady state level, and 4) Not secreted by tubules.

What is the reference range for plasma creatinine?

$$0.5-1.5\,mg/dL$$

Identify the novel filtration marker that is a cysteine protease inhibitor produced by all nucleated cells.

Cystatin C

What is the standard formula for calculating Glomerular Filtration Rate (GFR)/Creatinine Clearance?

$C = \frac{UV}{P}$ where $U$ is urinary creatinine, $V$ is 24-hour urine volume (usually divided by $1440\,min$), and $P$ is plasma creatinine.

What is the normal Renal Plasma Flow (RPF) per minute?

$$625\,mL/min$$

What plant polysaccharide is considered a perfect marker of filtration but is impractical for clinical use?

Inulin

What component of the distal tubule senses NaCl concentration delivery to help regulate blood pressure?

Macula Densa (MD)

Identify the three hormones/substances released or stimulated in the RAAS axis to increase sodium/water retention.

Renin, Angiotensin II, and Aldosterone

How is the Aldosterone-to-Renin Ratio (ARR) used clinically?

It is used to differentiate primary hyperaldosteronism (higher ratio) from secondary hyperaldosteronism (lower ratio).

What specific water channel does ADH recruit to the apical membrane of collecting ducts?

Aquaporin-2

Contrast SIADH and Diabetes Insipidus regarding urine concentration.

SIADH is characterized by increased urine osmolality (concentrated urine), while Diabetes Insipidus results in copious, dilute urine.

Who coined the term 'mellitus' to describe the 'honey sweet' urine of diabetic patients?

Thomas Willis

What is the methodology for the Nitrite patch on a UA reagent strip?

Greiss reaction: nitrite diazonium formation and colorimetry.

Which reagent is used on the test strip to detect Urobilinogen?

Ehrlich's reagent ($p$-dimethylaminobenzaldehyde)

What is the reported methodology for the Protein patch on typical UA dipsticks?

Dye binding (DIDNTB)

What does the specific gravity reagent pad indirectly measure?

Ionic strength (ionic concentration)

Which laboratory instrument is sensitive to glucose and contrast materials when measuring specific gravity, unlike the dipstick?

Refractometer

What is the methodology for the Glucose patch on a reagent strip?

Glucose oxidase reaction produces peroxide, which reacts with a chromogen.

Identify the backup test for detecting protein in urine that uses turbidometry.

Sulfosalicylic acid (SSA) precipitation test

What tablet test is used as a confirmatory test for Bilirubin and is four times more sensitive than the reagent strip?

Ictotest

What level of total protein excretion per day is defined as Nephrosis?

$> 3.0\,g$ of protein per day

What is the renal threshold for the urinary excretion of glucose?

$$\text{Plasma glucose} > 180\,mg/dL$$

Name the class of medications that inhibit the sodium-glucose cotransporter 2 in the proximal tubule.

Gliflozins (SGLT2 inhibitors)

Identify the 'clue cells' often found in cases of bacterial vaginosis.

Speckled Squamous Epithelial Cells (SECs) with Gardnerella vaginalis.

Where are hyaline casts formed, and what is their primary matrix?

Formed in the distal tubules in a matrix of Tamm-Horsfall protein.

What is the clinical significance of a Waxy or Broad cast?

Found in end-stage renal disease/indicative of tubular necrosis.

Which crystal is described as having a 'coffin lid' shape and is associated with urease-positive bacteria?

Triple phosphate (struvite)

Which pathological crystal appears as hexagonal plates and is associated with an aminoaciduria?

Cystine

What is 'Berger's disease'?

IgA nephropathy: caused by deposition of IgA immune complexes in the glomerulus.

Describe Goodpasture syndrome.

An anti-GBM autoantibody disease (anti-collagen Ig) that affects both the lungs and the kidneys.