D115 Unit 6 Cohort Notes: RAAS, Kidney Disorders, and GI Pathophysiology

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Western Governors University 

D115 Advanced Pathophysiology for the Advanced Practice Nurse

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Unit 6: Renin–Angiotensin–Aldosterone System (RAAS)

Purpose and Physiological Role of RAAS

The Renin–Angiotensin–Aldosterone System (RAAS) is an essential hormonal pathway that regulates systemic blood pressure, extracellular fluid volume, and electrolyte balance. This system serves as a compensatory mechanism activated in response to low blood pressure, reduced renal blood flow, or decreased sodium levels. Through RAAS activation, the body restores hemodynamic stability and maintains internal equilibrium.

What Triggers RAAS Activation?

RAAS is stimulated primarily when the kidneys detect:

• A drop in arterial blood pressure

• Reduced sodium concentration delivered to the distal renal tubules

• Decreased circulating blood volume

These conditions signal the body to conserve sodium and water, thereby supporting the restoration of adequate blood pressure and ensuring proper tissue perfusion.

Step-by-Step Mechanism of RAAS Activation

What Are the Physiological Effects of Angiotensin II?

Angiotensin II acts as the primary effector hormone and exerts several effects:

• Stimulates aldosterone release, enhancing sodium and water reabsorption in the kidneys

• Facilitates potassium excretion to maintain electrolyte balance

• Causes arteriolar vasoconstriction, which increases systemic vascular resistance and elevates blood pressure

Acute Pyelonephritis

What Is Acute Pyelonephritis?

Acute pyelonephritis is a bacterial infection involving one or both kidneys, targeting the renal pelvis, calyces, interstitial tissues, and renal tubules. It is a severe upper urinary tract infection that, if left untreated, can lead to irreversible kidney damage.

Who Is Most at Risk?

Factors increasing susceptibility include:

• Urinary tract obstructions such as kidney stones or strictures

• Vesicoureteral reflux, particularly in children

• Female anatomical characteristics that facilitate ascending infections

Which Microbes Are Responsible?

The infection commonly arises from bacteria ascending from the lower urinary tract, primarily:

• Escherichia coli (most common pathogen)

• Proteus species

• Pseudomonas aeruginosa

What Pathological Changes Occur?

The infection primarily damages renal tubules, resulting in:

• Inflammatory fibrosis and scarring

• Tubular atrophy due to repeated injury

• Permanent loss of renal function after multiple infections

What Are the Symptoms?

Typical signs include:

• High-grade fever and chills

• Flank or groin pain

• Dysuria (painful urination) and increased frequency

• Tenderness over the costovertebral angle

Older adults may show atypical symptoms such as fatigue or mild fever instead of classic presentations.

How Is It Diagnosed and Treated?

Diagnosis depends on urinalysis showing white blood cell casts, urine culture, blood cultures, and imaging for complicated cases. Treatment includes a 2–3 week course of targeted antibiotics, with repeat cultures if symptoms persist.

Acute Glomerulonephritis

What Defines Acute Glomerulonephritis?

This condition involves inflammation and injury to the glomeruli, either as a primary renal disease or secondary to systemic disorders.

What Causes It?

Etiologies include:

• Immune-mediated processes such as post-infectious glomerulonephritis

• Infectious agents

• Ischemia

• Toxic exposures

• Vascular diseases

How Does It Affect Kidney Function?

Inflammation damages the glomerular filtration barrier (endothelial cells, basement membrane, podocytes), reducing filtration efficiency and causing progressive nephron loss.

What Is the Clinical Course?

Symptoms may develop gradually, allowing significant renal damage before diagnosis. Severe cases can show oliguria (low urine output) and rapid renal function decline.

Diabetes Insipidus: Diagnosis and Management

How Is Diabetes Insipidus Diagnosed?

What Are the Treatment Strategies?

Neurogenic DI:

• Desmopressin replacement via oral, nasal, or intravenous routes

• Treat underlying causes such as trauma or tumors

Nephrogenic DI:

• Discontinue causative agents (e.g., lithium)

• Ensure hydration and correct electrolyte imbalances

• Use thiazide diuretics to reduce urine output

• Modify diet by restricting sodium and protein intake

Gastroesophageal Reflux Disease (GERD)

What Is GERD?

GERD is a chronic condition characterized by the reflux of acidic stomach contents into the esophagus, leading to mucosal injury and inflammation.

How Does GERD Develop?

GERD results from failure of the lower esophageal sphincter (LES) to maintain adequate tone, allowing acid and pepsin to reflux. This may occur due to transient LES relaxations or anatomical weaknesses.

What Factors Exacerbate GERD?

Factors increasing intra-abdominal pressure, such as obesity, pregnancy, coughing, vomiting, or heavy lifting, worsen reflux symptoms.

What Are the Common Symptoms?

• Heartburn and epigastric discomfort post-meals

• Chronic cough and hoarseness

• Asthma exacerbations and sinus infections

How Is GERD Diagnosed?

Upper endoscopy with biopsy is utilized to assess esophageal mucosal damage and rule out premalignant lesions like Barrett’s esophagus.

What Treatments Are Available?

Glomerulonephritis Overview

What Is Glomerulonephritis?

A group of inflammatory disorders affecting the glomeruli, leading to impaired filtration and fluid regulation.

Types and Causes

Common causes encompass infections, autoimmune disorders, drug toxicity, hypertension, diabetes, genetics, and malignancies.

Clinical Features

• Acute: hematuria, edema, hypertension

• Chronic: proteinuria, nocturia, fatigue, generalized edema

Diagnosis and Management

Diagnosis includes laboratory tests, imaging, and renal biopsy. Treatment ranges from antibiotics to immunosuppressants, combined with blood pressure control and dietary adjustments. Advanced cases may need dialysis or transplantation.

Nephrotic Syndrome

Definition and Features

Characterized by heavy proteinuria (>3.5 g/day), low plasma albumin, widespread edema, and elevated lipid levels.

Pathophysiology

Damage to the glomerular filtration barrier increases permeability, causing protein loss and lowered oncotic pressure. This promotes fluid movement into tissues and activates RAAS, aggravating edema.

Causes

• Primary: minimal change disease, focal segmental glomerulosclerosis

• Secondary: diabetes, amyloidosis, infections, systemic diseases

Complications

Increased risk of infections, blood clots, malnutrition, and cardiovascular disease.

Management

Peptic Ulcer Disease (PUD) Overview

What Is PUD?

PUD involves erosions or ulcers in the mucosa of the lower esophagus, stomach, or duodenum caused by acid and pepsin injury.

Risk Factors

• Helicobacter pylori infection

• Chronic NSAID or aspirin use

• Smoking and alcohol use

• Other factors: chronic illness, obesity, older age, socioeconomic status, genetics

Types and Symptoms

Diagnosis

Upper GI endoscopy with biopsy, H. pylori testing (biopsy or stool antigen), and blood tests for anemia.

Treatment

Pyelonephritis Overview

What Is Pyelonephritis?

An infection affecting the kidney pelvis, calyces, and interstitial tissue, presenting either acutely or chronically due to recurrent infections.

Etiology and Progression

Most often caused by E. coli, with Proteus and Pseudomonas as other pathogens. Acute infections cause inflammation and purulent urine; chronic cases lead to fibrosis and impaired concentrating ability.

Clinical Features

• Acute: fever, chills, flank pain, urinary symptoms

• Chronic: hypertension, renal failure, metabolic disturbances

Diagnosis and Treatment

Confirmed by urinalysis and culture; imaging for chronic cases. Treatment includes prolonged antibiotics and correction of anatomical abnormalities.

Renal Calculi (Kidney Stones)

Overview and Formation

Kidney stones are crystalline aggregates formed in supersaturated urine. Their formation depends on factors like supersaturation, crystal nucleation and growth, and reduced inhibition by substances such as citrate.

Urine pH and Stone Type

Management and Prevention

Treatment includes pain control, hydration, facilitating stone passage, lithotripsy, or surgery for large stones. Prevention involves increased fluid intake, sodium restriction, moderated animal protein consumption, and balanced calcium intake.

Renal Failure Overview

Acute vs. Chronic Renal Failure

Renal failure impairs filtration and fluid/electrolyte balance. Acute renal failure may be prerenal, intrarenal, or postrenal, while chronic kidney disease (CKD) progresses irreversibly over time.

Dialysis Modalities

Hemodialysis and continuous renal replacement therapies assist in waste and fluid removal but do not restore kidney function.

Urinary Tract Infections (UTIs)

What Are UTIs?

UTIs are bacterial infections of the urinary tract, predominantly caused by Escherichia coli.

Risk Factors

Include sexual activity, pregnancy, menopause, urinary obstruction, and poor hygiene.

Clinical Presentation and Management

Diagnosis relies on urinalysis and culture, with treatment tailored to the causative pathogen and patient status.

Summary of RAAS

Pharmacological inhibitors such as ACE inhibitors and angiotensin receptor blockers (ARBs) are pivotal in treating hypertension and renal diseases by interrupting this cascade.

References

Centers for Disease Control and Prevention. (2023). Urinary tract infection (UTI). https://www.cdc.gov

Feldman, M., Friedman, L. S., & Brandt, L. J. (2021). Sleisenger and Fordtran’s gastrointestinal and liver disease (11th ed.). Elsevier.

Guyton, A. C., & Hall, J. E. (2021). Textbook of medical physiology (14th ed.). Elsevier.

Kasper, D. L., Fauci, A. S., Hauser, S. L., Longo, D. L., Jameson, J. L., & Loscalzo, J. (2022). Harrison’s principles of internal medicine (21st ed.). McGraw-Hill.

Kumar, V., Abbas, A. K., & Aster, J. C. (2020). Robbins and Cotran pathologic basis of disease (10th ed.). Elsevier.

D115 Unit 6 Cohort Notes: RAAS, Kidney Disorders, and GI Pathophysiology

McCance, K. L., & Huether, S. E. (2019). Pathophysiology: The biologic basis for disease in adults and children (8th ed.). Elsevier.

National Institute of Diabetes and Digestive and Kidney Diseases. (2023). Kidney disease and renal failure. https://www.niddk.nih.gov

Sung, J. J. Y., Kuipers, E. J., & El-Serag, H. B. (2020). Systematic review: The global incidence and prevalence of peptic ulcer disease. Alimentary Pharmacology & Therapeutics, 29(9), 938–946.

UpToDate. (2024). Management of nephrotic syndrome, pyelonephritis, and renal calculi. Wolters Kluwer.