Urinary System Notes: PKD, Cancers, Obstructions, AKI, CKD, ESKD, Erythropoietin, and Diuretics
Polycystic Kidney Disease (PKD)
Definition
Genetic disorder that causes numerous cysts to develop inside the kidney.
Two main types:
Autosomal dominant PKD (adult PKD) – most common
Autosomal recessive PKD (childhood/infantile PKD) – more rare
Key characteristics by type
Autosomal dominant PKD
Begins in teenage years; kidneys become swollen by early middle years (around the 40s).
Kidney impairment eventually appears and may progress to kidney failure requiring transplant or lifelong dialysis.
Autosomal recessive PKD
Occurs in childhood/infancy; less common than the dominant form.
Pathophysiology
Mutations in PKD-1 and PKD-2 genes affect the formation of polycystin-1 and polycystin-2 proteins.
Abnormal proteins cause increases in tubular epithelium and fluid secretion, leading to cyst formation.
Cysts typically form from the nephrons, usually in the collecting ducts.
Cysts enlarge, blocking renal blood flow and causing ischaemia and activation of the renin-angiotensin system (RAAS).
Cysts can grow systemically and be associated with other organ involvement (see below).
Cysts may cause hypertension and progressive renal function decline.
Systemic associations and complications
Cysts can develop in liver, pancreas, and other organs; many cysts can be asymptomatic.
May be associated with cerebral aneurysms, aortic aneurysms, heart valve disorders, and diverticular disease.
These associations can contribute to morbidity beyond renal disease.
Clinical manifestations
Hypertension
Flank pain
Enlarged painful abdomen
Urinary tract infections
Haematuria
Readiness for monitoring and prognosis
PKD can be monitored with regular renal function tests and ultrasound, especially in less severe (simple) disease.
Progression to renal impairment varies; ongoing assessment is required.
Management and treatment strategies
Depends on disease progression:
Simple disease: annual renal function tests and ultrasound.
Diminished kidney function: maintain blood pressure within normal range; use antihypertensive medicines and follow a low-sodium diet.
Excessive pain: cyst drainage and analgesics (NSAIDs should be avoided).
Extreme disease: dialysis or kidney transplant if chronic kidney failure develops.
General considerations
Control of hypertension is important to slow disease progression.
Pain management strategies may involve procedures like cyst drainage.
Involvement of transplant services for end-stage disease.
Key figures/references (for context)
PKD-related cyst formation and progression illustrated in Sorenson et al. (2019), Fig. 46.6, p. 1147.
Systemic associations and organ involvement illustrated in Kumar et al. (2023), Fig. 12.23, p. 474.
Urinary System Cancers
Overview
Chapter focus: Renal neoplasms and obstructions.
Main cancers discussed: kidney cancer, Wilms’ tumour, bladder cancer.
Kidney cancer (Renal cell carcinoma)
Epidemiology: Most common in adults; relatively uncommon; aggressive with a poor prognosis.
Origin: Comes from epithelial cells of the proximal tubule.
Clinical manifestations: Haematuria, palpable mass, flank pain, hypertension, weight loss, fever.
Management: Surgery is main treatment; bisphosphonates used to prevent bone pain, hypercalcaemia, and fractures with bone metastases.
Notes: Figure references include Sorenson et al. (2019), Fig. 45.10, p.1129 and Kumar et al. (2023), Fig. 12.26, p.478.
Wilms’ tumour (Nephroblastoma)
Epidemiology: Most common renal tumour in children; relatively uncommon in adults.
Origin: From embryonic kidney cells that persist beyond birth.
Clinical manifestations: Haematuria, palpable mass or flank pain, hypertension, weight loss, fever.
Management: Surgery, chemotherapy and radiotherapy.
Distinguishing features: Hereditary associations and pediatric onset differ from adult renal cell carcinoma.
Note: Wilms’ tumour differs from renal cell carcinoma in origin and typical patient age group.
Bladder cancer
Type: Urothelial (transitional cell) carcinomas.
Onset: Usually begins in the bladder epithelium (urothelium).
Subtypes: Can be superficial (non-invasive) or invasive.
Superficial transitional cell carcinomas – tend to remain confined to the urothelium; less invasive.
Invasive transitional cell carcinomas – invade deeper layers (e.g., smooth muscle) and may metastasise to lymph nodes, bones, lungs and liver.
Pathophysiology: Transitional epithelium irritation can lead to hyperplasia; proto-oncogenes may be activated; inflammation can promote pro-tumour factors.
Clinical manifestations: Haematuria; sometimes dysuria and increased frequency/urgency of urination.
Diagnosis: Urinalysis; imaging (X-ray, IV pyelogram, ultrasound); cystoscopy and biopsy for diagnosis and grading.
Management: Surgery; chemotherapy (intravesical or intravenous); immunotherapy (e.g., interferons).
Visual context
A clinical snapshot (Figure 17.3) summarizes renal cancers and their clinical features (Carlson & Clapperton, 2025).
Prostate cancer and broader carcinogenesis pathways appear in the clinical diagrams but are not the primary focus of the renal cancer sections.
Renal Obstructions and Kidney Stones
Renal obstructions (kidney stones and related issues)
Can occur anywhere from renal tubules to external urethral opening.
Causes wide range of factors; obstruction leads to urine stasis upstream.
Filtration at the glomerulus continues, resulting in urine accumulation in the renal pelvis and calyces.
Prolonged obstruction causes hydronephrosis and potential permanent kidney damage if not relieved.
Figure reference: Carlson & Clapperton (2025) Fig. 17.9, p.205.
Kidney stones (nephrolithiasis, urolithiasis)
Major component is calcium ions (Ca^{2+}).
Calcium can combine with oxalate, phosphate, or urate to form calcium oxalate, calcium phosphate, or calcium urate stones.
Stones can also consist of uric acid crystals, cystine, and struvite.
Pathophysiology: Forms when urine calcium concentration is high (hypercalciuria), often due to dehydration or loop diuretic use; supersaturation causes crystal formation; stones form in kidney/renal pelvis and may travel to ureters.
Clinical manifestations: Large stones may cause urinary tract obstruction, severe pain (renal colic) radiating to the groin, nausea, vomiting, fever; small stones may be asymptomatic.
Diagnosis: CT imaging; full blood count; electrolyte levels; renal function tests (urea and creatinine); urinalysis (haematuria, pyuria, struvite stones, pH > 7); stone analysis after passage.
Management: Pain control (NSAIDs or opioids; NSAIDs may have nephrotoxicity); antiemetics; IV fluids if dehydrated; thiazide diuretics to oppose hypercalciuria and prevent recurrence; extracorporeal shock wave lithotripsy (ESWL); surgery when needed.
Reference: Carlson & Clapperton (2025) Fig. 17.11, p.206.
Clinical considerations
Hydration and electrolyte balance are central to prevention and treatment.
Recurrent stones require metabolic evaluation to identify and treat underlying causes.
Acute Kidney Injury (AKI) and Chronic Kidney Disease (CKD)
Acute Kidney Injury (AKI)
Learning objectives recap
Differentiate the three types of AKI and discuss appropriate management for each type.
Discuss clinical manifestations and KDIGO classification for kidney impairment.
Kidney function impairment (overview)
AKI involves a sudden impairment in kidney function with reduced GFR and/or urine output.
eGFR (estimated GFR) is used to monitor kidney function; a drop in GFR indicates impairment.
Acute insults to kidneys may be prerenal, intrarenal, or postrenal in origin.
Types of AKI
Prerenal AKI
Develops upstream of the kidneys; usually due to disruptions in renal blood flow.
Intrarenal AKI
Direct damage to kidney structures (e.g., tubules, glomeruli).
Postrenal AKI
Obstruction to urine flow distal to the kidneys.
Figure reference: Craft et al. (2023) Fig. 30.12, p.938.
Prerenal AKI (key features)
>80% of AKI cases.
Common causes include renal ischaemia from trauma, major surgery, dehydration, burns, heart disease with low cardiac output, arterial stenosis, atherosclerosis, microemboli.
Mechanism: abrupt decrease in GFR due to reduced renal perfusion; tubular cells are highly sensitive to hypoxia; tubular necrosis can occur if blood supply is not restored; glomerulus survival supports regeneration.
Intrarenal AKI
Direct kidney tissue damage (e.g., acute glomerulonephritis, acute pyelonephritis).
Potential causes: immune hypersensitivity, infections, toxins, certain medications (e.g., NSAIDs).
Pyelonephritis leads to inflammation and exudate that impedes tubular function.
Glomerulonephritis leads to increased glomerular permeability, haematuria, and proteinuria, with reduced GFR.
Figure reference: Craft et al. (2023) Fig. 30.12, p.938.
Postrenal AKI
Obstruction of urine flow from both kidneys (e.g., kidney stones, prostatic hypertrophy, tumors).
Urine accumulates proximal to obstruction, causing urinary stasis and increased pressure in renal pelvis/calyses.
If obstruction persists, nephron loss may occur due to compromised renal blood supply.
Figure reference: Craft et al. (2023) Fig. 30.12, p.938.
Clinical manifestations and KDIGO framework
General AKI manifestations include oliguria or possibly anuria.
Prerenal AKI may present with hypotension; intrarenal/postrenal AKI may present with hypertension, flank pain, edema, and hyperkalemia.
KDIGO classification evaluates kidney impairment using serum creatinine and urine output (and GFR considerations).
Diagnosis and treatment are AKI-type dependent; treatment targets the underlying cause and may include temporary dialysis.
Figure: Clinical snapshot (Figure 18.2) illustrates management pathways.
Treatment principles
Prerenal: correct fluid volume deficits.
Intrarenal: treat underlying cause (e.g., infection, toxin exposure).
Postrenal: relieve obstruction.
Dialysis may be required in the short term for severe cases.
Review cue
You should be able to differentiate the three AKI types and discuss their management, and understand the KDIGO framework for kidney impairment.
Chronic Kidney Disease (CKD)
Readings and learning objectives
Discuss progression of CKD to end-stage kidney disease (ESKD) in relation to CKD stages.
Discuss clinical manifestations and consequences of CKD.
CKD definition and characteristics
CKD is kidney impairment persisting for > months.
Characterised by progressive nephron loss and reduced GFR.
Proteinuria is an important clinical sign.
Clinical manifestations may not be apparent until renal function reduces by ~ of normal.
Common causes include chronic glomerular disease, chronic pyelonephritis, diabetes mellitus, hypertension, polycystic kidney disease, among others.
ANZDATA 2023 data (Australia & New Zealand): Diabetes mellitus 44%, Hypertension 15%, Glomerulonephritis 24%, Other kidney disease 17% as causes among dialysis patients.
CKD classification (GFR-based stages)
Stage 1: GFR > mL/min/1.73m^2 with kidney damage
Stage 2: GFR mL/min/1.73m^2 with kidney damage
Stage 3A: GFR mL/min/1.73m^2
Stage 3B: GFR mL/min/1.73m^2
Stage 4: GFR mL/min/1.73m^2
Stage 5: GFR < mL/min/1.73m^2 or on dialysis
GFR stands for glomerular filtration rate.
Pathophysiology of CKD progression
Multitude of causes lead to progressive nephron loss.
Surviving nephrons undergo compensatory hypertrophy and hyperfunction of filtration, reabsorption, and secretion.
Continued nephron loss drives inflammation, fibrosis, and sclerosis, reducing GFR over time.
End-stage kidney disease (ESKD)
End-point of CKD; occurs when GFR < mL/min/1.73m^2 for at least months (Stage 3 onward).
Clinical manifestation when > of nephron function is lost.
No possibility of nephron function recovery; requires regular dialysis or transplant.
Reference image: VanMeter & Hubert (2018), Fig. 18-17, p.510.
Multisystem consequences of severe kidney impairment (CKD/ESKD)
Fluid and electrolyte imbalances: high potassium, sodium retention, and water retention with edema; metabolic acidosis.
Cardiovascular: hypertension, hyperlipidaemia, atherosclerosis, heart failure.
Haematological: anaemia and platelet dysfunction.
Gastrointestinal/Endocrine: nausea, vomiting, anorexia, malnutrition, insulin resistance.
Skeletal: vitamin D deficiency, hypocalcaemia, hyperphosphatemia, osteopathies, higher fracture risk.
Neurological: peripheral neuropathy, encephalopathy.
Renal: oliguria or anuria.
Immune and hormonal effects: immune suppression, reduced sex hormone levels, decreased libido, infertility.
Systematic summary table (Table 18.3) lists systemic consequences of severe sustained kidney impairment.
CKD clinical manifestations (early to late)
Azotaemia: accumulation of nitrogenous wastes; progresses to uraemia (blood urea) with associated pruritus, dry skin, infection risk.
Other symptoms: hypertension, nocturia, restlessness, haematuria, dyspnoea, fatigue, anorexia, weight loss.
CKD progression and end-organ consequences – schematic view
Progressive nephron loss leads to compensatory changes and eventual systemic effects.
Key drivers include proteinuria and RAAS-mediated hypertension, which contribute to renal scarring and further decline.
Management of CKD and progression to ESKD
Goals: slow disease progression, manage complications, and prepare for possible dialysis or transplant.
End-stage kidney disease management focuses on dialysis and associated systemic management:
Hypertension control to protect residual renal function.
Anemia management with erythropoietin therapy.
Electrolyte management (hyperkalemia, hypocalcaemia, hyperphosphataemia) with diet and phosphate binders.
Urine and dietary management (low-protein diet; dietician involvement).
Dialysis: two main modalities – hemodialysis and peritoneal dialysis.
Vascular access for dialysis: AV fistula (surgically created by joining a vein and an artery) to provide extended access for cannulation.
Peritoneal dialysis: catheter remains in place; can be performed at home.
Erythropoietin in CKD/ESKD
Indication: management of anaemia associated with CKD.
Mechanism of action: stimulates differentiation of erythrocytes from bone marrow stem cells.
Time to effect: about two weeks for Hb to rise after initiation.
Adverse effects: hypertension, skin rashes, flu-like symptoms.
Clinical considerations:
Target Hb increase: about .
Check baseline iron, vitamin B12, and folic acid levels.
Monitor urea, creatinine, phosphate, and potassium during therapy.
Injection pain can be reduced by warming the injection before administration.
Dialysis modalities (overview)
Haemodialysis: removes blood, filters it through a dialysis machine to remove waste and excess fluid; typical session lasts hours, usually three times per week.
Peritoneal dialysis: uses the peritoneal membrane as a filter; requires a catheter; can be performed at home; less equipment/training required.
End-stage kidney disease management principles
CKD cannot be cured; management aims to slow progression and manage complications.
Comprehensive, systematic plan needed to address diverse effects of disease.
Erythropoietin in CKD (Additional Details)
Chapter/section reference: Chapter 20: Antianaemic agents.
Erythropoietin is used for CKD-related anaemia.
Mechanism, adverse effects, and clinical considerations summarized above (see CKD section).
Diuretics and Other Renal Medications
Overview
Purpose: describe sites and mechanisms of action of various diuretics and related renal medicines.
Types covered: loop diuretics, thiazides and thiazide-like diuretics, potassium-sparing diuretics, osmotic diuretics, carbonic anhydrase inhibitors, and urinary alkalisers/acidifiers.
Loop diuretics
Site of action: thick ascending limb of the loop of Henle; inhibits Na^+-K^+-2Cl^- cotransporter (NKCC2).
Examples: furosemide (frusemide), bumetanide, ethacrynic acid.
Mechanism: blocks NKCC2, reducing reabsorption of Na^+, K^+, and Cl^-; creates hypotonic interstitial fluid and diuresis.
Uses: oedema due to heart failure, renal disease, cirrhosis; can be used for hypertension.
Adverse effects: dehydration; electrolyte losses; hypokalaemia; possible ↑ uric acid (gout).
Clinical considerations: IV use for rapid effect in oedema; give earlier in the day to avoid nocturnal diuresis; monitor fluids/electrolytes; start at low dose and adjust.
Visual aid: Carlson & Clapperton (2025) Fig. 19.1, p.222.
Thiazide and thiazide-like diuretics
Site of action: early distal convoluted tubule; inhibits Na-Cl cotransporter.
Common types: hydrochlorothiazide, indapamide; thiazide-like diuretics have similar mechanism.
Mechanism: reduces Na^+-Cl^- reabsorption, delivering more Na^+ to late distal tubule; diuresis.
Common adverse effects: dehydration, electrolyte imbalances; increased uric acid; potential negative effects on lactation/impotence; caution in sulfonamide sensitivity.
Clinical considerations: often first-line for mild–moderate hypertension in people >65 years; not recommended as monotherapy for younger patients (<65 years);
Visual aid: Marieb & Hoehn (2023) Fig. 25.6, p. 1013.
Potassium-sparing diuretics
Site of action: collecting tubule (late distal tubule/collecting duct).
Types and mechanisms:
Aldosterone antagonists (e.g., spironolactone) – inhibit aldosterone action at late distal convoluted tubule and collecting tubule.
ENaC blockers (e.g., amiloride) – block luminal sodium channels in distal convoluted/tubules.
Purpose: to prevent potassium loss from other diuretics and to promote sodium/water excretion.
Common adverse effects: hyperkalaemia; nausea and vomiting.
Clinical considerations: monitor potassium levels during dosing; once-daily morning dosing recommended to avoid nocturnal diuresis.
Visual aid: Marieb & Hoehn (2023) Fig. 25.6, p. 1013.
Osmotic diuretics
Site of action: proximal convoluted tubule and descending limb of the loop of Henle.
Mechanism: increases renal blood flow and alters tonicity of medullary interstitium; reduces tubular water reabsorption.
Common agents: mannitol, glucose (as osmotic agents).
Common adverse effects: dehydration and electrolyte imbalances.
Clinical considerations: usually given IV; mannitol may crystallise at low temperatures and requires warming; glucose provides calories.
Visual aid: Marieb & Hoehn (2023) Fig. 25.6, p. 1013.
Carbonic anhydrase inhibitors
Examples: acetazolamide (e.g., for congestive heart failure) and dorzolamide.
Mechanism: inhibits carbonic anhydrase → loss of bicarbonate and sodium ions with water (alkaline urine); reduces hydrogen secretion.
Common adverse effects: hepatic effects, paresthesias, anorexia, polyuria, polydipsia, headache, drowsiness, fatigue.
Clinical considerations: monitor fluid balance, glucose, and electrolytes; weigh patient to detect rapid fluid loss; diuresis diminishes in acidotic conditions; caution with respiratory disease.
Urinary alkalisers and acidifiers
Urinary alkalisers: used to raise urine pH; can relieve dysuria in cystitis by reducing acidity and bacterial growth; useful in poisoning with acidic medicines to increase excretion.
Urinary acidifiers: used for overdose of basic drugs to promote excretion; ammonium chloride or ascorbic acid used to acidify urine.
Summary notes on diuretics
The major diuretic classes differ by nephron segment targeted and tonicity effects.
Selection depends on the clinical indication (edema, hypertension, electrolyte balance) and patient comorbidities.
References for diuretics content
Adams, Urban & Sutter (2019); Marieb & Hoehn (2023); Carlson & Clapperton (2025).
Important LaTeX and numeric references used in these notes
CKD staging thresholds (glomerular filtration rate, GFR):
Stage 1: GFR > \,\mathrm{mL\,min^{-1}\,1.73\,m^{-2}}
Stage 2: GFR \,\mathrm{mL\,min^{-1}\,1.73\,m^{-2}}
Stage 3A: GFR \,\mathrm{mL\,min^{-1}\,1.73\,m^{-2}}
Stage 3B: GFR \,\mathrm{mL\,min^{-1}\,1.73\,m^{-2}}
Stage 4: GFR \,\mathrm{mL\,min^{-1}\,1.73\,m^{-2}}
Stage 5: GFR < \,\mathrm{mL\,min^{-1}\,1.73\,m^{-2}}
CKD progression terms with timeframes
Chronic impairment defined as persists for >3 months.
ESKD defined as GFR < for at least months.
Erythropoietin therapy timing
Hb rise time: about after initiation.
Hb increase target: .
Dialysis specifics
Haemodialysis session duration: hours, typically times per week.
End-stage disease terminology
End-stage kidney disease (ESKD) denotes the stage where nephron function is severely compromised and dialysis or transplantation is required.
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