Detailed Study Notes on Urinary System Pathophysiology

Urinary System Pathophysiology and Pharmacology

  • Author: Roslyn Clapperton

  • Publication Date: August 2025

  • Acknowledgement: Recognizes the important role of Australia's First Nations Peoples and values Indigenous knowledge systems.

Polycystic Kidney Disease (PKD)

Chapter 17: Renal Neoplasms and Obstructions

Learning Objectives

  • Describe the pathophysiology, clinical manifestations, and management of polycystic kidney disease.

  • Suggested Readings: pp. 199-200

Overview of Polycystic Kidney Disease (PKD)

  • Definition: Genetic disorder characterized by the development of numerous cysts within the kidneys.

    • Types:

    • Autosomal dominant PKD (ADPKD) (adult PKD) - most common form.

    • Autosomal recessive PKD (ARPKD) (childhood/infantile PKD) - rarer variant.

  • Progression of Autosomal Dominant PKD:

    • Begins typically in teenage years, with kidneys swelling by early middle age (around 40s).

    • Kidney impairment becomes evident over time, often leading to kidney failure requiring transplant or lifelong dialysis.

    • Reference: Sorenson et al. (2019). Figure 46.6, p.1147.

Pathophysiology of PKD

  • Genetic Mutations:

    • Involvement of mutations in the PKD-1 and PKD-2 genes affecting protein formation of polycystin-1 and polycystin-2.

  • Effects of Abnormal Proteins:

    • Increase in tubular epithelial growth and fluid secretion.

    • Lead to cyst formation typically in the collecting ducts.

    • Cysts grow, which obstructs renal blood flow causing ischaemia and activation of the renin-angiotensin system.

Systemic Associations of PKD

  • Development of cysts in other organs (e.g., liver, pancreas) that may remain asymptomatic.

  • Potential for cerebral and aortic aneurysms, heart valve disorders, and diverticular disease.

    • Reference: Kumar et al. (2023). Figure 12.23, p.474.

Clinical Manifestations of PKD

  • Common Symptoms Include:

    • Hypertension

    • Flank pain

    • Enlarged and painful abdomen

    • Urinary tract infections

    • Hematuria (blood in urine)

Treatment Options for PKD

  • Disease Management:

    • Early Stage:

    • Annual renal function tests and ultrasound monitoring.

    • Diminished Kidney Function:

    • Aim to maintain blood pressure in normal range using antihypertensive medications and a low-sodium diet.

    • For excessive pain: cyst drainage and analgesics (avoiding NSAIDs).

    • Advanced Disease:

    • Dialysis is indicated as kidney failure progresses.

    • Kidney transplant is an option if chronic kidney failure develops.

Review Points

  • Students should be able to describe the pathophysiology, clinical manifestations, and management of polycystic kidney disease.

Urinary System Cancers

Chapter 17: Renal Neoplasms and Obstructions

Learning Objectives

  • Compare kidney cancer with Wilms’ tumor.

  • Describe the pathophysiology, clinical manifestations, and management of bladder cancer.

Kidney Cancer Overview

  • Commonality: The most prevalent type of kidney cancer among adults.

  • Types:

    • Renal Cell Carcinoma (RCC)

    • Origination from the epithelial cells of the proximal tubule.

    • Clinical Manifestations:

    • Hematuria, palpable mass, flank pain, hypertension, weight loss, fever.

    • Management:

    • Main treatment is surgical intervention.

    • Use of bisphosphonate medications to manage bone pain, hypercalcemia, and fractures with bone metastases.

    • References: Sorenson et al. (2019). Figure 45.10, p.1129; Kumar et al. (2023). Figure 12.26, p.478.

Comparison: Wilms’ Tumor

  • Commonality: Most prevalent in children; can be aggressive with poor prognosis.

  • Characteristics:

    • Determined by hereditary factors and typically present at birth.

    • Epithelial cells derived from embryonic kidney cells (nephroblastoma).

  • Clinical Manifestations:

    • Palpable mass or swelling in the flank or abdominal area, hypertension, abdominal pain, microscopic hematuria.

  • Management:

    • Surgery, chemotherapy, and radiotherapy.

Clinical Snapshot of Renal System Cancers

  • Comparative Summary:

    • Renal cell cancer primarily affects adults, while Wilms’ tumor is characteristic of pediatric cases.

    • Urinary bladder cancer typically arises from urothelium tissue in adults.

    • Management strategies are defined by the type of cancer and include surgery, chemotherapy, and immunotherapy where appropriate.

Bladder Cancer Overview

  • Description: Urothelial cell carcinomas originating from the bladder epithelium.

  • Structure:

    • Specialised epithelial lining (transitional epithelium): basal layer (cuboidal cells) and luminal layer (flattened cells).

    • Reference: Marieb & Keller. (2018). Figure 3.18, p.119.

Types of Bladder Cancer

  • Superficial Transitional Cell Carcinomas: Typically non-invasive, confined to urothelium.

  • Invasive Transitional Cell Carcinomas: Invade deeper layers (e.g., smooth muscle) with potential metastasis to lymph nodes, bones, lungs, and liver.

Pathophysiology of Bladder Cancer

  • Mechanism: Irritation of transitional epithelium/urothelium triggers rapid cell division (hyperplasia).

  • Contributing Factors: Activation of proto-oncogenes related to growth and division, induced inflammation fostering cancer cell survival.

Clinical Manifestations of Bladder Cancer

  • Symptoms include:

    • Hematuria

    • Dysuria and increased frequency and urgency of urination.

Diagnosis and Management of Bladder Cancer

  • Diagnostic Methods:

    • Urinalysis (to rule out UTI), imaging (X-ray, intravenous pyelogram), ultrasound, cystoscopy, and biopsy.

  • Management Options:

    • Surgery, chemotherapy (intravesical and intravenous), immunotherapy using interferons.

Review Points

  • Students should be able to compare kidney cancer with Wilms' tumor and describe the pathophysiology, clinical manifestations, and management of bladder cancer.

Renal Obstructions

Chapter 17: Renal Neoplasms and Obstructions

Learning Objectives

  • Describe the pathophysiology, clinical manifestations, and management of kidney stones.

  • Suggested Readings: pp. 205-207

Overview of Renal Obstructions

  • Definition: Obstruction can occur at any point from renal tubules to the external urethral opening.

  • Causes: Various factors leading to urinary stasis where filtration continues at the glomerulus despite blockage.

  • Consequences: Accumulation of urine leads to kidney distension (hydronephrosis), which can result in permanent damage if obstruction is not relieved.

    • Reference: Carlson & Clapperton (2025). Figure 17.9, p.205.

Kidney Stones Overview

  • Also known as renal calculi, they are a common cause of renal obstruction.

  • Formation Process: Insoluble stones form typically in the renal pelvis, known as nephrolithiasis or urolithiasis.

  • Major components include calcium ions (Ca^2+) combined with oxalate, phosphate, or urate ions leading to calcium oxalate, calcium phosphate, or calcium urate stones. Other stone types include uric acid crystals, cystine, and struvite stones.

    • Reference: Carlson & Clapperton (2025). Figure 17.11, p.206.

Pathophysiology of Kidney Stones

  • Contributing Factors:

    • Low urine volume (e.g., dehydration) and/or high concentration of substances (e.g., abnormal metabolism).

  • Kidney's inability to eliminate substances leading to supersaturation and crystal formation in nephrolithiasis.

  • Stones may travel causing obstruction leading to hydronephrosis or acute kidney injury.

Clinical Manifestations of Kidney Stones

  • Pain: Abrupt and severe onset (ureteral colic), with pain radiating from flank to groin as the stone moves.

  • Associated symptoms:

    • Nausea, vomiting, chills, fever, and hematuria may occur especially with infection.

    • Larger stones can cause obstruction damage to urinary tract structures.

Diagnosis and Management of Kidney Stones

  • Diagnostic Tools: Imaging studies (CT scan), blood tests (full count, electrolyte levels, renal function tests), urinalysis (detects hematuria, pyuria, struvite stones).

  • Management Strategies:

    • Pain control through NSAIDs (with nephrotoxicity considerations), opioids, antiemetics, and hydration via IV fluids.

    • Thiazide diuretics may be prescribed to counter hypercalciuria and prevent recurrence.

    • Extracorporeal shock wave lithotripsy or surgical interventions as necessary.

Review Points

  • Students should be able to describe the pathophysiology, clinical manifestations, and management of kidney stones.

Acute Kidney Injury (AKI)

Chapter 18: Acute Kidney Injury and Chronic Kidney Disease

Learning Objectives

  • Differentiate among the three types of AKI and their respective management.

  • Discuss clinical manifestations of AKI and the KDIGO classification system to determine kidney impairment.

  • Suggested Readings: pp. 209-211

Kidney Function Impairment Overview

  • Definition: Impairments are not evident until 80-90% of functional nephron mass is lost, with glomerular filtration rate as a key measurement (eGFR).

  • When kidney function is impaired:

    • Decreased urine volume

    • Increased retention of water, potassium, and hydrogen ions

    • Increased nitrogenous waste levels (e.g., urea, creatinine).

  • Acute Kidney Injury (AKI): Characterized by a rapid decline in glomerular function due to acute insults, often reversible.

Types of Acute Kidney Injury

  1. Prerenal AKI:

    • Causes: Factors disrupting renal blood flow leading to ischaemia (trauma, dehydration, heart disease).

    • Accounts for >80% of cases.

    • Effects: Abrupt reduction in GFR and potential tubular necrosis if blood supply is