Urinary System Disorders Flashcards

Functions of the Urinary System

• Removal of Metabolic Waste: The system is responsible for eliminating nitrogenous wastes and acidic components from the body.

• Excretion of Foreign Materials: It facilitates the removal of hormones, drugs, and other foreign substances.

• Regulation of Internal Balance: It maintains homeostasis through the regulation of water content, electrolyte levels, and acid-base balance (pH).

• Endocrine and Metabolic Functions:     

• * Erythropoietin Secretion: Produces the hormone necessary for red blood cell production.     * Vitamin D Activation: Participates in the conversion of Vitamin D to its active form.    

•  * Blood Pressure Regulation: Utilizes the Renin-Angiotensin-Aldosterone System (RAAS) to control blood pressure.

Anatomy and Physiology of the Urinary System

• Structural Pathway: The system follows a specific flow: Kidneys → Ureters → Bladder → Urethra.

• Urine Formation Process:     

• * Filtration: A large volume of fluid, including nutrients, electrolytes, dissolved substances, and waste, passes from the blood into the tubules. This process occurs in the glomerulus. Notably, cells and large proteins remain in the blood. If filtration pressure increases, more filtrate is formed, leading to increased urine production.     

• * Tubular Structure: The filtrate flows through three primary parts of the tubule:         

• 1. Proximal Convoluted Tubule (PCT).         

• 2. Loop of Henle.         

• 3. Distal Convoluted Tubule (DCT).     

• * Reabsorption and Secretion: The tubules reabsorb essential nutrients (water and electrolytes) back into the blood and secrete certain wastes and electrolytes into the filtrate.     * Collection: The collection ducts transport the final urine to the renal pelvis.

Hormonal Control of Reabsorption

• Antidiuretic Hormone (ADH):     

• * Source: Secreted by the posterior pituitary gland.     

• * Function: Controls the reabsorption of water specifically in the distal convoluted tubules and the collecting ducts.

• Aldosterone:    

•  * Source: Secreted by the adrenal cortex.     

• * Function: Controls sodium reabsorption. It occurs in exchange for the secretion of potassium ($K^+$) or hydrogen ($H^+$) ions.

• Atrial Natriuretic Hormone (ANH):     

• * Source: Produced by the heart.     

• * Function: Reduces the reabsorption of sodium ($Na^+$) and fluid, thereby increasing urine output.

Glomerular Filtration Rate (GFR) and Control Mechanisms

• Definition: GFR measures the flow rate of filtered fluid through the kidney's filters, known as the glomeruli. It is the primary indicator of how efficiently the kidneys remove waste and excess fluid from the blood.

• Factors Controlling Arteriolar Constriction:     

• 1. Local Autoregulation: Internal reflex adjustments to the diameter of arterioles in response to minor changes in blood flow, maintaining a normal filtration rate.     

• 2. Sympathetic Nervous System (SNS): Stimulation of the SNS increases vasoconstriction in both the afferent and efferent arterioles.    

• 3. Renin: Secreted by the juxtaglomerular cells when blood flow in the arteriole is reduced for any reason.

• Emergency Response: If blood flow is seriously impaired (e.g., significant drop in blood pressure), both the SNS and the Renin-Angiotensin mechanism activate to restore blood flow to vital areas.

Urinary Incontinence and Retention

• Incontinence Definitions:     

• * Incontinence: The loss of voluntary control over the bladder.     

• * Enuresis: Involuntary urination by a child older than $4$ years of age. It is often linked to developmental delays, sleep pattern disturbances, or psychosocial factors (regression).     * Stress Incontinence: Common in women after multiple pregnancies due to relaxed sphincter muscles. Increased intra-abdominal pressure (from coughing, laughing, or lifting) forces urine through the sphincter.     

• * Overflow Incontinence: Caused by an incompetent bladder sphincter. In older adults, a weakened detrusor muscle may prevent complete emptying, leading to frequency and leakage.

• Neurological Causes: Spinal cord injuries or brain damage can disrupt the micturition reflex, leading to incontinence or retention.

• Retention:     

• * Definition: The inability to empty the bladder.     

• * Causes: Spinal cord injuries at the sacral level blocking the micturition reflex, side effects of anesthesia, immobility, or an enlarged prostate (prostatic hypertrophy) in men obstructing flow.

Diagnostic Tests for Urinary Disorders

• Urinalysis (UA):     

• * Appearance: Normal urine is straw-colored with a mild odor.     

• * Specific Gravity: Normal range is between $1.01$ and $1.05$.     

• * Cloudiness: Indicates large amounts of protein, blood (hematuria), bacteria (bacteriuria), or pus (pyuria).     

• * Color Indicators: Dark urine may indicate hematuria, excessive bilirubin, or highly concentrated urine (dehydration).     

• * Odor: Foul or unpleasant odors may indicate infection, dietary intake, or medications.

• Microscopic and Chemical Abnormalities:    

•  * Hematuria: Small amounts indicate infection, inflammation, or tumors; large amounts indicate increased glomerular permeability or hemorrhage.    

•  * Proteinuria/Albuminuria: Leakage of albumin or plasma proteins into the filtrate.    

•  * Urinary Casts: Microscopic molds of tubules that indicate inflammation of the kidney tubules.    

•  * Low Specific Gravity: Indicates dilute urine, often seen with normal hydration.     

• * High Specific Gravity: Highly concentrated urine; can be related to renal failure where the kidney fails to clear solutes.     

• * Glucose and Ketones: Found when diabetes mellitus is poorly controlled.

• Blood Tests:     

• * Decreased GFR: Leading to failure to excrete nitrogenous waste.     

• * Metabolic Acidosis: Characterized by decreased serum pH (less than $7.35$) and decreased serum bicarbonate, indicating tubular failure to manage acid-base balance.     * Anemia: Low hemoglobin levels; indicates decreased erythropoietin secretion or bone marrow depression due to waste accumulation.     

• * Antibody Levels: Anti-streptolysin O (ASO) and Anti-streptokinase (ASK) titers are used to diagnose post-streptococcal glomerulonephritis.     

• * Renin Levels: High levels indicate a potential cause of hypertension.

• Advanced Investigations:     

• * Culture and Sensitivity: Identifies the specific causative organism and the appropriate antibiotic treatment.     

• * Radiologic Tests: Imaging such as ultrasound, CT, MRI, angiography, and intravenous pyelography to visualize structures.     

• * Clearance Tests: Creatinine or inulin clearance tests are used to assess GFR (often involving a $24$-hour urine collection).     

• * Cystoscopy: Visualization of the lower urinary tract; allows for biopsies or stone removal.

Diuretic Drugs

• Function: Known colloquially as "water pills," these remove excess sodium ions and water from the body, reducing fluid volume in tissues (edema) and blood.

• Indications: Prescribed for renal disease, hypertension, congestive heart failure, liver disease, and pulmonary edema.

• Classification:    

•  * Potassium-Wasting: Examples include Hydrochlorothiazide (HCTZ) and Furosemide (Lasix).     

• * Potassium-Sparing: Example includes Spironolactone (Aldactone).

• Specific Agents:     

• * Hydrochlorothiazide (HCTZ).     

• * Furosemide (Lasix).     

• * Spironolactone (Aldactone).     

• * Acetazolamide (Diamox).     

• * Mannitol (administered intravenously).

Dialysis

• Purpose: Provides an artificial kidney function to sustain life after renal failure.

• Hemodialysis:     

• * Setting: Hospital, dialysis center, or home with specialized training.     

• * Procedure: Blood is removed via an implanted shunt or catheter (often in the arm), passed through a machine with a semipermeable membrane, and returned to the vein. Waste and electrolytes exchange between the blood and dialysis fluid.     

• * Schedule: Typically performed $3$ times a week for $3$ to $4$ hours per session.     

• * Complications: Shunt infection, sclerosed blood vessels, and blood clots (requiring blood thinners). There is a risk of Hepatitis B, C, or HIV if precautions are not followed.

• Peritoneal Dialysis:     

• * Setting: Usually outpatient/home, often performed overnight during sleep.     

• * Mechanism: The peritoneal membrane acts as the semipermeable membrane. Dialyzing fluid is instilled into the peritoneal cavity via a catheter and then drained by gravity back into a bag.     

• * Complications: The primary risk is infection leading to peritonitis.

Urinary Tract Infections (UTIs)

• Classification:     

• * Lower UTI: Cystitis (bladder wall) and Urethritis (urethra).     

• * Upper UTI: Pyelonephritis (kidney infection).

• Etiology: The common causative organism is Escherichia coli (E. coli), which is resident flora in the GI tract.

• Predisposing Factors:     

• * Gender: More common in women due to a shorter urethra and proximity to the anus.     * Age: Prostatic hypertrophy (enlarged prostate) in older men leads to retention and bacterial growth.     

• * Hygiene: Incorrect wiping (back to front) can pull E. coli into the urethra.

• Clinical Manifestations:     

• * Cystitis/Urethritis: Dysuria (painful urination), urgency, frequency, nocturia, and cloudy/foul-smelling urine. Systemic signs include fever, malaise, nausea, and leukocytosis.     

• * Pyelonephritis: Involvement of one or both kidneys. Purulent exudate fills the renal pelvis. Manifests with dull, aching flank pain, high fever, and urinary casts in the urinalysis. Chronic infection can lead to scar tissue, hydronephrosis, and renal failure.

• Treatment: Antibiotics such as Bactrim, Nitrofurantoin (Furadantin), Cephalosporins (Keflex, Duricef), Amoxicillin, and Fosfomycin (specifically for pregnancy).

Glomerular Disorders

• Post-Streptococcal Glomerulonephritis:     

• * Pathophysiology: Formation of antigen-antibody complexes (Type III hypersensitivity) that activate the complement system, leading to an inflammatory response in the glomeruli. This causes congestion, decreased GFR, and fluid/waste retention.     

• * Signs: Dark/cloudy urine, periorbital edema followed by generalized edema, hypertension (due to renin secretion), and flank pain.     

• * Labs: Elevated serum urea and creatinine, decreased complement levels, and metabolic acidosis.

• Nephrotic Syndrome:     

• * Pathophysiology: Increased glomerular permeability allows massive amounts of plasma protein (primarily albumin) to escape into filtrate. This leads to hypoalbuminemia, decreased plasma osmotic pressure, and generalized edema. Low blood volume triggers aldosterone, worsening the edema.     

• * Minimal Change Disease (Lipoid Necrosis): A primary nephrotic disease in children aged $2$ to $6$.     

• * Manifestations: Frothy urine, massive edema (ascites, pleural effusion), weight gain, and pallor. High cholesterol (hyperlipidemia) and lipiduria are also present.     

• * Treatment: Glucocorticoids (e.g., Prednisone), ACE inhibitors (e.g., Ramipril), sodium restriction, and increased protein intake.

Urinary Tract Obstructions

• Urolithiasis (Calculi/Kidney Stones):     

• * Composition: $75\%$ are calcium salts (forming in alkaline urine). Other types include uric acid stones (associated with gout, high purine diets, or cancer/chemo in acidic urine).     * Predisposing Factors: Insufficient fluid intake and UTIs.     

• * Manifestations: Often asymptomatic until they obstruct flow. Obstruction causes intense, radiating pain (into the groin), nausea, vomiting, and frequency/retention.     

• * Treatment: Small stones may pass naturally. Large stones require lithotripsy (shockwave or laser) or surgical removal. Stents may be used to keep tubes dilated.

• Hydronephrosis:     

• * Definition: Secondary problem where back pressure from an obstruction (stone, tumor, BPH) causes a dilated, urine-filled area in the kidney.    

•  * Outcome: Prolonged pressure causes necrosis of renal tissue and can lead to chronic renal failure.

Tumors of the Urinary System

• Renal Cell Carcinoma:    

•  * Source: Tubal epithelium, usually in the renal cortex.     

• * Risk Factors: More frequent in men and smokers over age $45$.    

•  * Manifestations: Painless hematuria, dull flank pain, palpable mass, and unexplained weight loss. Often silent until it metastasizes (lung, liver, bone).     

• * Treatment: Nephrectomy (surgical removal), as it is often resistant to radiation/chemo.

• Bladder Cancer:     

• * Source: Commonly arises from transitional epithelium.     

• * Risk Factors: Men over $50$, exposure to aniline dyes (rubber/aluminum industries), and cigarette smoking.     

• * Characteristics: Multiple tumors, invasive through the wall to pelvic lymph nodes.     

• * Treatment: Surgical resection, chemotherapy, and radiation.

Vascular, Congenital, and Genetic Disorders

• Nephrosclerosis: Vascular changes similar to arteriosclerosis (thickening/narrowing of arterioles), reducing blood supply and triggering renin, which increases blood pressure. Often secondary to essential hypertension.

• Congenital Abnormalities:     

• * Vesicoureteral Reflux.    

•  * Agenesis: Failure of one kidney to develop.     

• * Hypoplasia: Failure to develop to normal size.     

• * Ectopic Kidney: Displacement of the kidney/ureter.     

• * Horseshoe Kidney: Fusion of the two kidneys.

• Adult Polycystic Kidney Disease (PKD):     

• * Genetics: Autosomal dominant gene on chromosome $16$.     

• * Manifestations: Symptoms usually appear around age $40$. Multiple cysts develop in both kidneys, leading to enlargement and eventual renal failure.

• Wilms Tumor (Nephroblastoma):     

• * Target: Children aged $3$ to $4$.     

• * Genetics: Defects in tumor suppressor genes on chromosome $11$.    

•  *Manifestations: Large abdominal mass, unilateral bulge, and potentially high blood pressure.

Renal Failure

• Acute Renal Failure:     

• * Causes: Sudden onset from bilateral kidney disease (Glomerulonephritis), circulatory shock, heart failure, nephrotoxins, or mechanical obstructions.    

•  * Indicators: Sudden increase in serum urea/creatinine, metabolic acidosis, and hyperkalemia.

• Chronic Renal Failure:     

• * Stages:         

• 1. Decreased Renal Reserve: GFR decreases, no clinical symptoms.         

• 2. Renal Insufficiency: GFR drops to $20\%$ of normal, excretion of large volumes of dilute urine, and elevated blood pressure.         

• 3. End-Stage Renal Failure: GFR is negligible. Fluid, electrolytes, and waste (azotemia) are retained. Marked oliguria (small amounts of urine) or anuria (no urine).     

• * Uremic Manifestations: Metabolic acidosis (pH less than $7.35$), severe anemia, dry/itchy skin (pruritus), possible uremic frost on the skin, encephalopathy, and congestive heart failure.     * Treatment: Dialysis or kidney transplantation is required to maintain life. Restricted fluid, electrolyte, and protein intake; medications for erythropoiesis and cardiovascular issues.