Renal and Urologic Pathophysiology: Structure, Function, and Disorders

Vocabulary practice flashcards covering normal anatomy, glomerular filtration, tubular transport, adult and pediatric renal pathologies, and clinical frameworks based on McCance and Huether's Pathophysiology.

Hilum

The medial anatomical indentation of the kidney through which renal blood vessels, lymphatic vessels, nerves, and the ureter pass into and out of the kidney.

Juxtamedullary Nephrons

A subtype of nephrons located adjacent to the corticomedullary junction with long loops of Henle extending deep into the inner medulla, essential for the concentration of urine.

Podocytes

Specialized epithelial cells forming the visceral layer of Bowman capsule that possess interdigitating foot processes and filtration slits to modulate glomerular filtration.

Juxtaglomerular Apparatus (JGA)

A regulatory complex comprising the renin-secreting juxtaglomerular cells surrounding the afferent arteriole and the sodium-sensing macula densa cells of the distal convoluted tubule.

Principal Cells

Specialized transport cells located in the collecting duct that reabsorb sodium and water while secreting potassium, regulated primarily by aldosterone and antidiuretic hormone.

Intercalated Cells

Specialized cells of the collecting duct responsible for secreting hydrogen ions into the tubular lumen and reabsorbing potassium and bicarbonate to maintain acid–base homeostasis.

Vasa Recta

A hairpin-loop network of peritubular capillaries parallel to the loops of Henle that provides the only vascular blood supply to the renal medulla and maintains the osmotic gradient.

Renal Autoregulation

The intrinsic physiologic capability of the kidneys to sustain a stable glomerular filtration rate and renal blood flow across systemic arterial pressures between $80\text{--}180\,\text{mmHg}$.

Tubuloglomerular Feedback

An autoregulatory feedback loop wherein increased sodium chloride delivery sensed by the macula densa triggers afferent arteriolar vasoconstriction to reduce glomerular filtration rate.

Urodilatin

A natriuretic peptide secreted by the distal convoluted tubules and collecting ducts in response to increased blood pressure and circulating volume, producing renal vasodilation and natriuresis.

Net Filtration Pressure (NFP)

The combined physical pressure governing ultrafiltration, determined by the capillary hydrostatic pressure favoring filtration minus opposing forces (capillary oncotic pressure and Bowman capsule hydrostatic pressure).

Countercurrent Exchange System

The passive and active transport mechanism occurring in parallel loops of Henle and vasa recta flowing in opposing directions, establishing a hyperosmotic medullary gradient for urine concentration.

Tamm–Horsfall Glycoprotein (Uromodulin)

The most abundant urinary protein, produced by epithelial cells of the thick ascending limb and early distal tubule, which defends against urinary tract infections and stone formation.

Renalase

An enzymatic hormone synthesized and secreted by the kidney that metabolizes circulating catecholamines, thereby aiding in systemic blood pressure regulation.

Plasma Creatinine Concentration

A blood test derived from skeletal muscle breakdown with a normal adult range of $0.7\text{--}1.2\,\text{mg/dL}$, serving as a stable clinical index for tracking progressive chronic renal disease.

Blood Urea Nitrogen (BUN)

A serum indicator reflecting urea levels with an adult normal range of $10\text{--}20\,\text{mg/dL}$, which fluctuates with protein intake and catabolism and serves primarily as an index of hydration status.

Hydronephrosis

Dilation and enlargement of the renal pelvis and calyces proximal to a site of urinary tract obstruction.

Ureterohydronephrosis

Dilation of both the ureter and the renal collecting structures (pelvis and calyces) secondary to downstream urinary obstruction.

Postobstructive Diuresis

A rapid, high-volume diuresis that occurs following the relief of severe or prolonged urinary tract obstruction, potentially causing dehydration and electrolyte imbalances.

Nephrolithiasis

The condition of having kidney stones (renal calculi), consisting of mineral salts, crystals, or proteinaceous matrices formed via supersaturation, precipitation, and crystallization in urine.

Staghorn Calculi

Extensive, branched renal stones that fill the minor and major renal calyces and pelvis, most commonly composed of struvite (magnesium, ammonium, phosphate).

Detrusor Sphincter Dyssynergia

A form of neurogenic bladder caused by upper motor neuron lesions wherein the detrusor muscle and external urethral sphincter contract simultaneously, causing functional outlet obstruction.

Detrusor Areflexia

A hypotonic, underactive, or atonic bladder state resulting from lower motor neuron injury to the sacral micturition center, leading to urinary retention and overflow incontinence.

Renal Cell Carcinoma

The most common primary malignant renal neoplasm, frequently associated with mutations in the $VHL$ gene on chromosome $3\text{p}25$, presenting with hematuria, flank pain, and a palpable flank mass.

Interstitial Cystitis (Painful Bladder Syndrome)

A chronic nonbacterial inflammatory bladder condition lasting longer than $6\text{ weeks}$ characterized by bladder pain, urgency, and frequency with negative urine cultures.

Crescentic Glomerulonephritis

A rapidly progressive form of glomerulonephritis characterized pathologically by cellular proliferation forming crescent-shaped lesions in Bowman space that causes rapid renal failure.

Nephrotic Syndrome

A clinical constellation resulting from glomerular injury characterized by massive proteinuria ($\ge 3.5\,\text{g/day}$), hypoalbuminemia, hyperlipidemia, and peripheral edema.

Nephritic Syndrome

A syndrome caused by inflammatory glomerular barrier disruption, marked by hematuria with red blood cell casts, mild to moderate proteinuria, oliguria, and hypertension.

Azotemia

A biochemical abnormality characterized by increased levels of blood urea nitrogen, serum creatinine, and other nitrogenous waste compounds resulting from reduced glomerular filtration.

Uremia

The systemic toxic syndrome of renal failure featuring elevated urea and creatinine along with nausea, vomiting, pruritus, fatigue, electrolyte imbalances, and neurologic dysfunction.

Acute Tubular Necrosis (ATN)

The most frequent intrarenal etiology of acute kidney injury, resulting from severe ischemia or nephrotoxins leading to tubular cell necrosis, cast formation, and luminal obstruction.

Intact Nephron Hypothesis

The pathophysiologic concept postulating that surviving, undamaged nephrons undergo compensatory hypertrophy and hyperfiltration to sustain total renal function as nephron mass decreases in CKD.

Uremic Fetor

A distinctive, urine-like breath odor observed in individuals with advanced uremia, generated by salivary bacterial enzymes breaking down urea into ammonia.

Metanephros

The third and permanent embryonic precursor of the kidney, formed from the ureteric bud and metanephrogenic mesenchyme, which initiates urine production by the third month of gestation.

Potter Syndrome

A fatal congenital syndrome caused by bilateral renal agenesis and oligohydramnios, characterized by facial anomalies such as wide-set eyes, parrot-beak nose, low-set ears, and a receding chin.

Polycystic Kidney Disease (PKD)

A genetic disease causing parenchymal destruction via renal cysts; autosomal dominant PKD involves $PKD\text{-}1$ (chromosome $16$) or $PKD\text{-}2$ (chromosome $4$), while autosomal recessive PKD causes renal and hepatic cysts in youth.

Hypospadias

A congenital malformation in male infants where the urethral meatus opens abnormally on the ventral surface (undersurface) of the penis.

Epispadias

A congenital anomaly wherein the urethral opening is located on the dorsal surface of the penis in males or presents as a ventral urethral cleft extending to the bladder neck in females.

Exstrophy of the Bladder

A severe midline defect where the bladder protrudes externally through the anterior abdominal wall due to failure of abdominal and pelvic skeletal structures to fuse during development.

Poststreptococcal Glomerulonephritis (PSGN)

An immune complex-mediated glomerulonephritis appearing after a throat or skin infection with group A α-hemolytic streptococci, presenting with sudden hematuria, edema, and hypertension in children aged $5\text{--}15\,\text{years}$.

Henoch–Schönlein Purpura Nephritis

An immune-mediated IgA vasculitis involving glomerular small vessels, characterized clinically by palpable purpura, arthritis, abdominal pain, and gross or microscopic hematuria.

Congenital Nephrotic Syndrome (Finnish Type)

A rare autosomal recessive disorder caused by a mutation in the $NPHS1$ gene encoding the slit diaphragm protein nephrin, presenting with severe steroid-resistant proteinuria before $3\,\text{months}$ of life.

Hemolytic-Uremic Syndrome (HUS)

The most common community-acquired pediatric acute renal failure, linked to verotoxin-producing $Escherichia\,\text{coli}\,O157:H7$, characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury.

Nephroblastoma (Wilms Tumor)

An embryonal renal neoplasm derived from metanephric blastema presenting between $1\text{ and }5\,\text{years}$ of age as an asymptomatic abdominal mass, associated with $WT1$ and $WT2$ gene mutations on chromosome $11$.

Vesicoureteral Reflux (VUR)

The retrograde backflow of urine from the bladder into the ureters and collecting systems graded from $I\text{ through }V$, predisposing pediatric patients to recurrent pyelonephritis and renal scarring.

Primary Enuresis

Involuntary urinary bedwetting during sleep in a child aged $5\,\text{years}$ or older who has never previously established nighttime urinary continence.

Prerenal Acute Kidney Injury

An abrupt reduction in renal excretory function induced by transient renal hypoperfusion (e.g., volume depletion, hypotension) without structural parenchymal damage to the kidney.

Chronic Kidney Disease (CKD)

A persistent structural or functional abnormality of the kidneys lasting $\ge 3\,\text{months}$, characterized by reduced eGFR, pathological albuminuria, and progressive loss of homeostatic functions.