Toxicology – Caustic Ingestion: Alkaline Agents

Sources

Common alkaline caustic products include:

• Drain cleaners
• Lye
• Oven cleaners
• Ammonia-containing cleaners
• Some concentrated cleaning solutions
• Bleach, although household bleach is usually less corrosive than strong alkalis

Typical Presentation

A young child is found after getting into a household cleaner and develops:

• Coughing
• Sore throat
• Drooling
• Pain with swallowing

Severity depends on the concentration, amount, and duration of contact.

Clinical Features

Possible findings include:

• Oral or pharyngeal burns
• Drooling
• Nausea and vomiting
• Hematemesis
• Dysphagia
• Odynophagia
• Chest pain
• Abdominal pain
• Dyspnea or stridor

Serious complications include:

• Upper-airway edema
• Esophageal or gastric injury
• Perforation
• Mediastinitis or peritonitis
• Later esophageal stricture formation

Importantly, the absence of visible mouth burns does not exclude serious esophageal injury.

Mechanism of Action

Alkaline substances cause liquefactive necrosis and saponification of fats.

This allows deeper tissue penetration and can produce significant injury to the esophagus and surrounding structures.

Management

Initial priorities include:

• Airway assessment and protection
• Supportive care
• Evaluation for perforation or significant internal injury
• Early consultation with gastroenterology, surgery, and toxicology when severe exposure is suspected

Endoscopy is commonly used in selected symptomatic patients to assess the extent of injury, usually after stabilization and within an appropriate early time window.

Avoid:

• Inducing vomiting
• Gastric lavage
• Activated charcoal
• Attempting to neutralize the alkali with an acid

These measures can worsen tissue injury or increase aspiration risk.

Routine administration of milk or water after significant caustic ingestion is not generally recommended without poison-center or specialist guidance, especially once symptoms are present.

Key Points

• Alkalis cause liquefactive necrosis and can penetrate deeply.
• Drooling, dysphagia, odynophagia, chest pain, or respiratory symptoms suggest significant injury.
• A normal-looking mouth does not rule out esophageal burns.
• Do not induce emesis or attempt chemical neutralization.
• Airway compromise and GI perforation are the most dangerous early complications.
• Corticosteroids are not routinely recommended solely to prevent strictures; their use depends on the specific clinical situation.

Toxicology – Hydrocarbon Ingestion

Sources

Hydrocarbons are found in many fuels, solvents, and petroleum products. Examples include:

• Propane and butane
• Hexane and octane
• Gasoline
• Kerosene
• Motor oil

Typical Presentation

A person drinks a small amount of gasoline and immediately begins gagging and coughing. The main danger is often not absorption from the stomach, but aspiration into the lungs.

Clinical Features

Possible symptoms include:

• Coughing
• Gagging
• Vomiting
• Shortness of breath
• Hypoxia
• Altered mental status
• Syncope

Aspiration can cause:

• Chemical pneumonitis
• Pulmonary edema
• Respiratory distress

Inhalation of hydrocarbon vapors may also cause:

• CNS depression or intoxication
• Dizziness and impaired coordination
• Cardiac dysrhythmias

Repeated inhalational abuse can lead to chronic neurologic injury.

Mechanism of Action

Hydrocarbon toxicity depends greatly on the physical properties of the product.

Low-viscosity hydrocarbons spread easily and are more likely to enter the airway during swallowing or vomiting.

Once aspirated, they:

• Directly injure pulmonary tissue
• Disrupt surfactant
• Trigger inflammation and chemical pneumonitis

Some inhaled hydrocarbons can also sensitize the heart to catecholamines, increasing the risk of dangerous dysrhythmias.

Aspiration Risk

Aspiration risk is generally higher with low-viscosity hydrocarbons.

Examples:

• Gasoline and kerosene: relatively high aspiration risk
• Motor oil: lower aspiration risk because of higher viscosity

Management

Treatment is mainly supportive:

• Remove the patient from further exposure
• Support airway and breathing
• Provide supplemental oxygen if needed
• Monitor for respiratory deterioration

There is no specific antidote for hydrocarbon aspiration.

Inducing vomiting is avoided because it can increase the risk of aspiration. Activated charcoal is generally not useful for uncomplicated aliphatic hydrocarbon ingestion.

Key Points

• The major danger after ingestion is often aspiration, not systemic absorption.
• Low viscosity = higher aspiration risk.
• Chemical pneumonitis may develop after coughing or choking during ingestion.
• High-viscosity products such as motor oil usually pose less aspiration risk.
• Treatment is primarily supportive, with attention to respiratory symptoms and cardiac rhythm abnormalities.

Toxicology – Hydrofluoric Acid (HF) Exposure

Sources

Hydrofluoric acid is used in several industrial and commercial processes, including:

• Glass etching
• Semiconductor and computer-chip manufacturing
• Oil refining
• Chemical production
• Metallurgy
• Some rust removers and wheel-cleaning products

Typical Presentation

A worker exposed to HF develops severe, deep pain several hours after skin contact, despite relatively minor-looking surface burns.

Pain that seems out of proportion to the visible injury is an important clue.

Clinical Features

Skin exposure may cause:

• Severe burning or throbbing pain
• Tissue destruction that can extend deeply beneath the skin
• Delayed symptoms, particularly with more dilute solutions

Significant exposure can produce systemic electrolyte abnormalities, especially:

• Hypocalcemia
• Hypomagnesemia

These may cause:

• Muscle cramps or spasms
• Tetany
• Chvostek or Trousseau signs
• QT prolongation
• Ventricular dysrhythmias
• Cardiovascular collapse in severe poisoning

Inhalational exposure can also cause significant respiratory tract and pulmonary injury.

Mechanism of Action

HF toxicity is unusual because both components contribute to injury.

The hydrogen ion produces local corrosive damage, while absorbed fluoride ions penetrate deeply and bind calcium and magnesium.

This sequestration can cause profound electrolyte disturbances and disrupt cardiac electrical activity.

Management

HF exposure is a medical emergency. Initial treatment includes:

• Immediate removal from the source
• Prompt removal of contaminated clothing
• Copious water irrigation of exposed skin
• Early cardiac monitoring for significant exposures
• Serial monitoring of calcium, magnesium, potassium, and ECG findings

After initial decontamination, calcium gluconate is used to bind fluoride and limit ongoing tissue injury. The route of calcium treatment depends on the location and severity of exposure and should be directed by experienced clinicians or a poison center.

Severe exposures may require intensive treatment of electrolyte abnormalities, dysrhythmias, and respiratory complications.

Key Points

• Severe pain out of proportion to the visible burn is characteristic of HF exposure.
• HF can penetrate deeply even when the surface injury initially appears mild.
• Fluoride binds calcium and magnesium, potentially causing life-threatening electrolyte disturbances.
• Significant exposure can produce QT prolongation and dangerous ventricular dysrhythmias.
• Rapid decontamination and calcium-based treatment are central to management.
• Because deterioration can be delayed, significant HF exposure requires urgent medical evaluation and toxicology guidance.

Toxicology – Magnesium Toxicity

Sources

Hypermagnesemia may result from excessive exposure to magnesium-containing products such as:

• Magnesium sulfate
• Magnesium citrate
• Milk of magnesia
• Other magnesium-containing antacids or laxatives

Risk is increased in patients with renal impairment, because magnesium is primarily eliminated by the kidneys.

Typical Presentation

A patient receiving magnesium therapy, such as during treatment of preeclampsia, develops:

• Weakness
• Nausea
• Flushing
• Diminished reflexes
• Hypotension
• Bradycardia

Severe toxicity may progress to respiratory depression and cardiac conduction abnormalities.

Clinical Features

As magnesium levels rise, findings may include:

• Nausea and vomiting
• Flushing
• Thirst
• Generalized weakness
• Lethargy
• Decreased or absent deep tendon reflexes
• Hypotension
• Bradycardia
• Respiratory depression
• Prolonged cardiac conduction
• Wide QRS complexes
• Complete heart block
• Cardiac arrest in extreme cases

Loss of deep tendon reflexes is an important early bedside clue during magnesium therapy.

Mechanism of Action

Excess magnesium depresses neuromuscular and cardiac function.

It:

• Reduces acetylcholine release at the neuromuscular junction
• Interferes with calcium-dependent processes
• Alters sodium and potassium channel activity
• Slows cardiac conduction
• Produces peripheral vasodilation

Management

Treatment includes:

• Immediately stopping the magnesium source
• Airway and respiratory support when needed
• IV fluids and cardiovascular support
• Continuous ECG monitoring in significant toxicity

IV calcium, usually calcium gluconate, can temporarily antagonize the cardiac and neuromuscular effects of magnesium.

Patients with adequate renal function may eliminate excess magnesium with supportive care. Hemodialysis is particularly useful in severe toxicity or when renal failure prevents magnesium excretion.

Key Points

• Think of weakness + diminished reflexes + hypotension/bradycardia in a patient receiving magnesium.
• Renal failure greatly increases the risk of magnesium accumulation.
• Calcium antagonizes the physiologic effects of magnesium and is used for significant toxicity.
• Severe hypermagnesemia can cause respiratory failure and heart block.
• Magnesium-containing laxatives should be used cautiously in patients with impaired renal function.

 Toxicology – Thallium Poisoning

Sources

Thallium exposure may occur from:

• Certain industrial processes
• Some older rodenticides
• Fireworks or pyrotechnic materials
• Contaminated products
• Intentional poisoning

Historical medical uses are largely obsolete.

Typical Presentation

Thallium poisoning often begins with gastrointestinal symptoms, followed days later by characteristic neurologic and skin findings.

A classic clue is the combination of:

• Abdominal pain
• Painful peripheral neuropathy
• Hair loss

Clinical Features

Early findings

• Nausea
• Vomiting
• Abdominal pain
• Diarrhea
• Occasionally GI bleeding
• Tachycardia
• Hypertension
• Chest discomfort

Neurologic findings

• Painful paresthesias
• Peripheral neuropathy
• Headache
• Ataxia
• Visual disturbances
• Altered mental status
• Seizures in severe cases

Delayed skin and hair findings

• Alopecia, often developing days to weeks after exposure
• Scaling or abnormalities of the palms and soles
• Acneiform or pustular skin eruptions
• Abnormal nail growth

Mechanism of Action

Thallium behaves similarly to potassium and can enter cells through potassium transport pathways.

It interferes with:

• Potassium-dependent cellular processes
• Mitochondrial energy production
• Sulfhydryl-containing enzymes
• Protein and keratin synthesis

These effects help explain its prominent neurologic toxicity and characteristic abnormalities of the hair, skin, and nails.

Management

Treatment includes:

• Immediate removal from the exposure source
• Supportive care
• Management of seizures, cardiovascular instability, and electrolyte abnormalities
• Gastrointestinal decontamination in selected recent exposures

Prussian blue is the specific antidotal therapy. It binds thallium in the gastrointestinal tract and interrupts enterohepatic and enteric recycling, increasing fecal elimination.

Repeated-dose activated charcoal may also be considered in selected cases under toxicology guidance.

Extracorporeal removal may be considered in severe poisoning, particularly early in the course.

Key Points

• Think of GI symptoms + painful neuropathy + delayed alopecia.
• Thallium mimics potassium and disrupts mitochondrial and enzymatic function.
• Prussian blue is the key specific antidote.
• Hair loss is often delayed and may become a major diagnostic clue.
• Conventional chelators are generally not useful for thallium poisoning.

Toxicology – Arsenic Poisoning

Sources

Arsenic exposure may occur from:

• Contaminated groundwater or food
• Certain traditional or nonstandard medicines
• Some pesticides and industrial products
• Pigments and manufacturing processes
• Contaminated occupational environments

Inorganic arsenic is generally responsible for the most significant systemic toxicity.

Typical Presentation

A patient with substantial arsenic exposure may develop severe gastrointestinal illness followed by cardiovascular and neurologic toxicity. Chronic exposure can produce characteristic skin changes and a painful stocking-glove peripheral neuropathy.

A garlic-like odor on the breath has traditionally been described but is neither sensitive nor specific.

Clinical Features

Acute poisoning may cause:

• Severe nausea and vomiting
• Profuse watery diarrhea
• Abdominal pain
• Dehydration
• Tachycardia
• Hypotension and shock
• Altered mental status
• Seizures
• Peripheral neuropathy, sometimes developing after the initial illness
• Cardiac dysrhythmias and QT prolongation
• Cardiovascular collapse in severe cases

Chronic poisoning may cause:

• Hyperkeratosis, especially of the palms and soles
• Abnormal skin pigmentation
• Peripheral neuropathy
• Metabolic abnormalities, including increased risk of diabetes
• Cardiovascular disease
• Increased risk of several cancers, particularly skin, lung, and bladder cancers

Mechanism of Action

Arsenic disrupts cellular energy production. Inorganic arsenic can inhibit enzymes such as pyruvate dehydrogenase, interfering with formation of acetyl-CoA and ATP.

It can also impair:

• Oxidative phosphorylation
• Glucose metabolism
• Other essential enzyme systems

The result is widespread cellular dysfunction affecting the gastrointestinal, cardiovascular, neurologic, and other organ systems.

Management

Treatment includes:

• Immediate removal from the exposure source
• Aggressive supportive care
• IV fluids and cardiovascular stabilization
• Correction of electrolyte abnormalities
• ECG monitoring in significant acute poisoning

Chelation may be required for clinically important poisoning. Agents include:

• Dimercaprol (BAL) in selected severe acute cases
• Succimer (DMSA)
• DMPS, where available

Chelation decisions should be made with a medical toxicologist or poison center because the preferred agent depends on the type and severity of exposure.

Key Points

• Acute arsenic poisoning often begins with severe GI symptoms and can progress to shock, dysrhythmias, and neurologic injury.
• Painful stocking-glove neuropathy is an important clue.
• Chronic exposure can cause hyperkeratosis and characteristic pigmentation changes.
• Arsenic interferes with cellular energy production.
• Chronic inorganic arsenic exposure is associated with increased cancer risk.
• Groundwater contamination remains an important source of arsenic exposure worldwide.

Toxicology – Mercury Poisoning

Sources

Mercury exists in several forms, and toxicity depends strongly on the form and route of exposure.

• Elemental mercury: thermometers, some older thermostats, dental amalgam, industrial processes, and gold extraction
• Inorganic mercury salts: some industrial chemicals, older disinfectants, pigments, and manufacturing processes
• Organic mercury compounds: especially methylmercury, which can accumulate in large predatory fish

Typical Presentation

A person with chronic occupational mercury exposure may develop:

• Tremor
• Irritability or personality change
• Memory problems
• Excessive sweating
• Gingivitis or inflammation of the mouth

Clinical Features

Elemental mercury vapor inhalation

• Cough
• Dyspnea
• Chemical pneumonitis
• Noncardiogenic pulmonary edema in severe exposure

Chronic vapor exposure can produce the classic combination of:

• Neuropsychiatric changes
• Tremor
• Gingivostomatitis

Neuropsychiatric symptoms may include irritability, insomnia, poor concentration, memory impairment, and emotional instability.

Inorganic mercury salts

Ingestion can cause:

• Severe nausea and vomiting
• Abdominal pain
• Hemorrhagic gastroenteritis
• Acute tubular injury
• Acute kidney failure

Chronic exposure can also produce neurologic abnormalities.

Organic mercury

Methylmercury primarily damages the nervous system and may cause:

• Paresthesias
• Ataxia
• Tremor or other movement abnormalities
• Visual impairment
• Hearing impairment
• Hyperreflexia
• Cognitive dysfunction

Developing fetuses and young children are particularly vulnerable to the neurologic effects of methylmercury.

Mechanism of Action

Mercury binds strongly to sulfhydryl groups in proteins.

This interferes with:

• Enzyme activity
• Cellular metabolism
• Membrane function
• Antioxidant defenses

The nervous system and kidneys are major targets of toxicity.

Management

Treatment includes:

• Immediate removal from the exposure source
• Supportive care
• Respiratory support for severe inhalational injury
• Renal monitoring after significant inorganic mercury exposure

Chelation may be considered in clinically significant poisoning, commonly with agents such as:

• Succimer (DMSA)
• DMPS

Choice of therapy depends on the mercury compound, exposure severity, symptoms, and specialist guidance.

Key Points

• Mercury toxicity differs markedly between elemental, inorganic, and organic forms.
• Swallowed liquid elemental mercury is poorly absorbed from an intact GI tract, whereas inhaled mercury vapor can be highly toxic.
• Chronic elemental mercury exposure classically causes tremor + neuropsychiatric changes + gingivostomatitis.
• Inorganic mercury mainly causes severe GI and renal toxicity.
• Methylmercury predominantly causes neurologic toxicity.
• Significant suspected mercury poisoning should be discussed with a medical toxicologist or poison center.

Toxicology – Lead Poisoning

Sources

Common sources of lead exposure include:

• Older lead-based paint and contaminated household dust
• Batteries
• Ceramics and pottery glazes
• Plumbing and contaminated water
• Certain toys, jewelry, figurines, and imported products
• Some traditional or nonstandard medicines
• Occupational or industrial exposure

Typical Presentation

A child living in an older home may present with:

• Developmental delay
• Learning difficulties
• Behavioral problems
• Fatigue
• Vague abdominal complaints

Chronic exposure is often subtle and may be discovered only after screening.

Clinical Features

Acute lead toxicity may cause:

• Nausea and vomiting
• Abdominal pain
• Diarrhea
• Hemolysis
• Acute kidney injury
• Severe neurologic toxicity in major exposures

Chronic lead toxicity may cause:

• Recurrent abdominal pain
• Constipation
• Fatigue
• Headache
• Cognitive and learning impairment
• Behavioral changes
• Anemia
• Peripheral neuropathy
• Motor weakness, including wrist drop

Children are particularly vulnerable to the neurodevelopmental effects of lead.

Mechanism of Action

Lead disrupts multiple cellular processes and can damage several organ systems, especially:

• Central and peripheral nervous systems
• Kidneys
• Bone and bone marrow
• Gastrointestinal tract
• Cardiovascular system

It also interferes with enzymes involved in heme synthesis, contributing to anemia.

Laboratory Findings

Diagnosis is based primarily on an elevated blood lead level.

Other possible findings include:

• Microcytic or normocytic anemia
• Basophilic stippling on peripheral blood smear
• Increased erythrocyte protoporphyrin in significant chronic exposure

These findings support the diagnosis but are not as specific as the blood lead concentration.

Characteristic Findings

Classic but less commonly seen findings include:

• Burton lines: blue-gray discoloration along the gingival margin
• Lead lines: dense metaphyseal bands seen on radiographs of growing bones in chronically exposed children

Management

The most important intervention is to identify and eliminate the source of exposure.

Chelation may be required for significant poisoning. Agents used include:

• Succimer (DMSA)
• Calcium disodium EDTA
• Dimercaprol in selected severe cases

The choice of chelator depends on the blood lead level, symptoms, and severity of toxicity. Severe neurologic toxicity requires urgent specialist management.

Key Points

• Children are especially susceptible to lead-related cognitive and developmental injury.
• Chronic poisoning may present with abdominal pain, constipation, anemia, and behavioral or learning problems.
• Basophilic stippling is a classic clue but is not diagnostic by itself.
• Treatment begins with removal of the exposure source.
• Chelation is reserved for sufficiently elevated blood lead levels or clinically significant poisoning.

Medicine – Causes of Proteinuria

Proteinuria means an abnormal amount of protein in the urine. It may be temporary and benign, or it may indicate significant renal disease. The causes are most usefully understood according to whether the proteinuria is transient, glomerular, tubular, overflow, or post-renal.

1. Infection and Febrile Illness

The original notes correctly include:

Fever.

Acute febrile illness can cause:

Transient proteinuria.

This usually resolves once the acute illness settles.

Therefore, a small amount of protein detected during fever does not automatically indicate chronic kidney disease.

2. Urinary Tract Infection

A UTI can produce mild proteinuria because inflammation within the urinary tract allows protein and inflammatory material to enter the urine.

It is often associated with:

Pyuria.

Bacteriuria.

Dysuria.

Frequency.

Proteinuria from uncomplicated UTI is usually:

Mild rather than nephrotic-range.

3. Chronic Pyelonephritis

Chronic pyelonephritis and chronic tubulointerstitial scarring can cause:

Persistent low-grade proteinuria.

Because the main pathology affects:

Tubules and interstitium,

the amount of protein is usually less than in major glomerular disease.

4. Renal Tuberculosis

Genitourinary tuberculosis can cause:

Proteinuria.

However, its more characteristic urinary finding is:

Persistent sterile pyuria.

Microscopic haematuria may also occur.

Therefore:

RENAL TB → THINK STERILE PYURIA MORE THAN HEAVY PROTEINURIA.

5. Glomerular Disease

Glomerular disease is the major cause of:

Moderate to heavy proteinuria.

Damage to the glomerular filtration barrier allows excessive plasma proteins, especially:

Albumin,

to enter the urine.

6. Diabetes Mellitus

The original notes correctly include:

Diabetes mellitus.

Diabetic kidney disease causes:

Glomerular hyperfiltration.

GBM thickening.

Mesangial expansion.

Intraglomerular hypertension.

These changes lead to increasing urinary albumin loss.

7. Proteinuria in Diabetic Kidney Disease

The traditional sequence is:

Normal albumin excretion

↓

Moderately increased albuminuria

↓

Severely increased albuminuria

↓

Heavy proteinuria

↓

Progressive CKD.

However, some patients can develop declining GFR without marked albuminuria.

8. Hypertension

Long-standing hypertension can cause:

Hypertensive nephrosclerosis.

This may produce:

Persistent proteinuria.

Usually the amount is:

Low to moderate.

If proteinuria is very heavy, another glomerular cause should be considered.

9. Pre-Eclampsia

The original notes include:

Pre-eclampsia.

Pre-eclampsia occurs after approximately:

20 weeks of pregnancy

and causes:

Hypertension with maternal organ dysfunction.

Proteinuria is common.

10. Mechanism in Pre-Eclampsia

The renal lesion classically involves:

Glomerular endotheliosis.

This increases glomerular permeability and produces:

Proteinuria.

In severe disease, proteinuria may become:

Nephrotic-range.

11. Acute Glomerulonephritis

Acute GN may cause:

Proteinuria.

However, the classic nephritic pattern also includes:

Haematuria.

Dysmorphic RBCs.

RBC casts.

Hypertension.

Reduced GFR.

Proteinuria is usually less marked than in nephrotic syndrome, though overlap can occur.

12. Chronic Glomerulonephritis

Chronic GN may cause:

Persistent proteinuria

with gradual progression to:

Chronic kidney disease.

The quantity depends on the underlying glomerular lesion.

13. Nephrotic Syndrome

The original notes list:

Nephrotic syndrome.

This is not a single disease, but a clinical syndrome characterised by:

Heavy proteinuria.

Hypoalbuminaemia.

Generalised oedema.

Hyperlipidaemia.

14. Common Causes of Nephrotic-Range Proteinuria

Important causes include:

Minimal change disease.

FSGS.

Membranous nephropathy.

Diabetic kidney disease.

Amyloidosis.

Membranous lupus nephritis.

15. Neoplastic Causes

The original notes include:

Renal tract tumour

and

Multiple myeloma.

These cause proteinuria through very different mechanisms.

16. Renal Tract Tumour

Tumours of the kidney or urinary tract may cause protein to appear in urine because of:

Bleeding.

Inflammation.

Parenchymal disruption.

However, the more characteristic finding is:

Haematuria.

Marked isolated proteinuria is not usually the main presentation.

17. Multiple Myeloma

Multiple myeloma can produce:

Overflow proteinuria.

This occurs because large quantities of monoclonal:

Free light chains

are produced and filtered by the kidney.

18. Bence Jones Protein

The older term:

Bence Jones protein

refers to urinary monoclonal free light chains.

Modern assessment commonly uses:

Serum free light chains.

Serum immunofixation.

Urine studies when indicated.

19. Important Dipstick Limitation in Myeloma

Standard urine dipsticks detect mainly:

Albumin.

Therefore a patient with large amounts of:

Light-chain proteinuria

may have substantial total urinary protein despite only modest dipstick positivity.

This is an important clue to:

Paraprotein-related kidney disease.

20. Acute Tubular Injury

The original notes include:

ATN, more accurately often termed:

Acute tubular injury – ATI.

Tubular injury can cause:

Tubular proteinuria.

21. Mechanism of Tubular Proteinuria

Normally, small low-molecular-weight proteins are filtered and then reabsorbed by:

Proximal tubular cells.

When tubular function is damaged, reabsorption falls.

Therefore these proteins remain in the urine.

22. Amount of Protein in Tubular Disease

Tubular proteinuria is usually:

Mild to moderate.

It is generally less severe than:

Glomerular proteinuria.

Therefore nephrotic-range proteinuria should usually suggest:

A glomerular process.

23. Acute Interstitial Nephritis

Acute interstitial nephritis can cause:

Mild-to-moderate proteinuria.

It is often associated with:

Sterile pyuria.

WBC casts.

Microscopic haematuria.

AKI.

24. NSAID-Associated AIN

An important exception is:

NSAID-related acute interstitial nephritis.

This can occasionally cause:

Heavy or nephrotic-range proteinuria,

especially when associated with:

Minimal-change-like glomerular injury.

25. Transient Proteinuria

An important category missing from the original list is:

Transient proteinuria.

Possible causes include:

Fever.

Strenuous exercise.

Acute illness.

Seizures.

Severe physiological stress.

It usually resolves when the trigger disappears.

26. Orthostatic Proteinuria

Another important benign cause is:

Orthostatic proteinuria.

This occurs mainly in:

Adolescents and young adults.

Protein appears when the patient is upright but falls or disappears during:

Overnight recumbency.

27. Orthostatic Pattern

A typical pattern is:

Daytime urine → protein present.

First-morning urine → normal or minimal protein.

This is generally benign.

28. Glomerular Proteinuria

Glomerular proteinuria occurs when the filtration barrier becomes abnormally permeable.

The dominant urinary protein is usually:

Albumin.

Important causes include:

Diabetes.

Primary GN.

Secondary GN.

Nephrotic syndromes.

Pre-eclampsia.

29. Tubular Proteinuria

Tubular proteinuria results from impaired proximal tubular reabsorption.

Causes include:

Acute tubular injury.

Acute interstitial nephritis.

Chronic tubulointerstitial disease.

30. Overflow Proteinuria

Overflow proteinuria occurs when excessive amounts of small proteins circulate in plasma and overwhelm tubular reabsorption.

The classic cause is:

Multiple myeloma.

Other examples include:

Myoglobin in rhabdomyolysis.

Haemoglobin in intravascular haemolysis.

31. Post-Renal Proteinuria

Protein can also enter urine from inflammation or bleeding after it has left the glomerulus.

This is called:

Post-renal proteinuria.

Examples include:

UTI.

Urinary tract inflammation.

Tumours.

Bleeding.

This usually produces relatively modest proteinuria.

32. Proteinuria and Amyloidosis

An important cause not listed originally is:

Amyloidosis.

Amyloid deposition in the glomeruli can cause:

Heavy proteinuria

and

Nephrotic syndrome.

This is particularly important in:

AL amyloidosis

and

AA amyloidosis.

33. Proteinuria and SLE

Systemic lupus erythematosus can cause:

Lupus nephritis.

Proteinuria may occur in several lupus nephritis classes.

A particularly strong nephrotic association is:

Class V membranous lupus nephritis.

34. Measuring Proteinuria

Modern assessment usually uses a spot urine:

Albumin:creatinine ratio – ACR

for albuminuria.

A:

Protein:creatinine ratio – PCR

may be useful when total protein is more relevant.

35. ACR Categories

Albuminuria is commonly classified as:

A1 – normal to mildly increased.

A2 – moderately increased.

A3 – severely increased.

Interpretation should always be combined with:

eGFR

and

clinical context.

36. Confirm Persistent Proteinuria

A single positive urine result does not necessarily indicate chronic kidney disease.

Proteinuria may be transient because of:

Fever.

Exercise.

UTI.

Acute illness.

Therefore persistent proteinuria usually requires:

Repeat testing.

37. First-Morning Urine

A:

First-morning urine sample

is useful because it reduces the effects of:

Posture.

Exercise.

Daytime activity.

It is especially useful when considering:

Orthostatic proteinuria.

38. Proteinuria with Haematuria

The combination:

Proteinuria + haematuria

raises concern for:

Glomerular disease.

This is particularly important when associated with:

Dysmorphic RBCs.

RBC casts.

Reduced renal function.

Hypertension.

39. Proteinuria with Oedema

Heavy urinary protein loss causes:

Hypoalbuminaemia.

This lowers plasma oncotic pressure and contributes to:

Generalised oedema.

Therefore:

HEAVY PROTEINURIA + HYPOALBUMINAEMIA + OEDEMA → THINK NEPHROTIC SYNDROME.

40. Proteinuria with Diabetes

In diabetes, persistent albuminuria may indicate:

Diabetic kidney disease.

However, consider another diagnosis if there is:

Rapid renal deterioration.

Active urine sediment.

Marked haematuria.

Abrupt heavy proteinuria.

41. Proteinuria with Myeloma Features

Think of myeloma when proteinuria occurs with:

Anaemia.

Bone pain.

Hypercalcaemia.

Renal dysfunction.

Monoclonal protein abnormalities.

42. Infection Causes – Note Form

Fever:

Transient proteinuria.

Usually resolves when illness settles.

UTI:

Usually mild post-renal proteinuria.

Often accompanied by pyuria and bacteriuria.

Chronic pyelonephritis:

Usually low-grade proteinuria from tubulointerstitial scarring.

Renal TB:

Can cause proteinuria, but sterile pyuria is more characteristic.

43. Glomerular Causes – Note Form

Diabetes:

Major cause of persistent albuminuria.

May progress to nephrotic-range proteinuria.

Hypertension:

Usually low-to-moderate proteinuria.

Very heavy proteinuria suggests another glomerular disorder.

Pre-eclampsia:

Proteinuria due to glomerular endotheliosis.

Acute and chronic GN:

Proteinuria often with haematuria and RBC casts.

Nephrotic syndrome:

Heavy proteinuria with hypoalbuminaemia and oedema.

44. Neoplastic Causes – Note Form

Renal tract tumour:

Can cause proteinuria through bleeding or local tissue injury.

Haematuria is more characteristic.

Multiple myeloma:

Overflow proteinuria due to monoclonal free light chains.

45. Tubular Causes – Note Form

Acute tubular injury:

Impaired reabsorption of low-molecular-weight proteins.

Usually mild-to-moderate proteinuria.

Acute interstitial nephritis:

Mild-to-moderate proteinuria.

Often with sterile pyuria and WBC casts.

46. Important Additions

Other important causes include:

Orthostatic proteinuria.

Exercise-induced transient proteinuria.

Amyloidosis.

Lupus nephritis.

Minimal change disease.

FSGS.

Membranous nephropathy.

Rhabdomyolysis-related myoglobinuria.

47. Important Corrections to the Original Notes

Nephrotic syndrome is not itself a single disease.

It is a:

CLINICAL SYNDROME CAUSED BY UNDERLYING GLOMERULAR DISORDERS.

Hypertension generally causes:

LOW-TO-MODERATE PROTEINURIA.

Marked nephrotic-range proteinuria should prompt consideration of:

ANOTHER GLOMERULAR DISEASE.

Renal tract tumours more classically cause:

HAEMATURIA

than heavy proteinuria.

Renal TB is more classically associated with:

STERILE PYURIA.

ATN/ATI and interstitial nephritis usually cause:

TUBULAR, GENERALLY NON-NEPHROTIC PROTEINURIA.

Key Clinical Pattern

Think of proteinuria by mechanism:

GLOMERULAR → ALBUMIN LEAK.

Examples:

DIABETES + GN + NEPHROTIC DISEASE + PRE-ECLAMPSIA.

TUBULAR → FAILURE TO REABSORB SMALL PROTEINS.

Examples:

ATI/ATN + INTERSTITIAL NEPHRITIS.

OVERFLOW → TOO MUCH SMALL PROTEIN IN THE BLOOD.

Classic example:

MYELOMA LIGHT CHAINS.

POST-RENAL → PROTEIN ENTERS URINE FROM THE URINARY TRACT.

Examples:

UTI + TUMOUR + BLEEDING.

And remember:

HEAVY PROTEINURIA + OEDEMA + HYPOALBUMINAEMIA → NEPHROTIC SYNDROME.

PROTEINURIA + HAEMATURIA + RBC CASTS → THINK GLOMERULONEPHRITIS.

Medicine – Causes of Acute Kidney Injury

Acute kidney injury (AKI) is the modern term that has largely replaced acute renal failure (ARF). It refers to an abrupt reduction in kidney function, usually detected by a rise in serum creatinine and/or a fall in urine output.

The causes are classically divided into:

Pre-renal AKI – reduced renal perfusion.

Intrinsic renal AKI – structural injury within the kidney.

Post-renal AKI – obstruction to urine flow.

Historically, more than 90% of cases were said to result from pre-renal causes or acute tubular necrosis, but this should be regarded as older teaching rather than a fixed modern percentage because the distribution varies with the patient population and clinical setting.

1. Pre-Renal AKI

Pre-renal AKI occurs when the kidneys receive insufficient blood flow but the renal parenchyma is initially structurally intact.

The kidney responds appropriately to poor perfusion by retaining:

Sodium.

Water.

This produces:

Low-volume, concentrated urine.

If renal perfusion is restored early, renal function can recover rapidly.

2. Hypovolaemia

A major cause of pre-renal AKI is:

Reduced circulating volume.

Causes include:

Vomiting.

Diarrhoea.

Haemorrhage.

Burns.

Poor fluid intake.

Excessive fluid losses.

These reduce renal perfusion and therefore lower:

GFR.

3. Haemorrhage

Major blood loss reduces:

Effective circulating volume.

Examples include:

Gastrointestinal bleeding.

Trauma.

Surgical bleeding.

Obstetric haemorrhage.

If severe or prolonged, pre-renal hypoperfusion can progress to:

Acute tubular injury.

4. Sepsis

Sepsis is an important cause of AKI.

It may cause:

Systemic vasodilatation.

Relative hypovolaemia.

Abnormal renal microcirculation.

Inflammatory tubular injury.

Therefore septic AKI may contain both:

Pre-renal and intrinsic renal components.

5. Heart Failure

Severe cardiac failure can reduce:

Effective renal blood flow.

Even when the patient is fluid overloaded, renal perfusion may still be poor.

This can produce:

Cardiorenal AKI.

6. Cirrhosis

Advanced cirrhosis causes marked:

Splanchnic vasodilatation.

This reduces effective arterial circulating volume and renal perfusion.

Severe cases may develop:

Hepatorenal syndrome.

7. ACE Inhibitors and ARBs

The original notes correctly include:

ACE inhibitors.

ACE inhibitors and ARBs dilate the:

Efferent arteriole.

This reduces intraglomerular pressure.

They can precipitate AKI particularly when renal filtration is dependent on angiotensin II, for example in:

Severe volume depletion.

Bilateral renal artery stenosis.

Stenosis of a solitary functioning kidney.

8. NSAIDs and Renal Perfusion

NSAIDs can also contribute to haemodynamic AKI.

They inhibit prostaglandin synthesis, causing:

Afferent arteriolar vasoconstriction.

Therefore:

NSAID → reduced renal blood flow → reduced GFR.

The risk is greater in:

Volume depletion.

Heart failure.

CKD.

Older patients.

9. Intrinsic Renal AKI

Intrinsic renal AKI occurs when there is structural injury involving:

Tubules.

Glomeruli.

Interstitial tissue.

Renal blood vessels.

The most common intrinsic cause is:

Acute tubular injury, traditionally called acute tubular necrosis – ATN.

10. Acute Tubular Necrosis / Acute Tubular Injury

ATN is commonly caused by:

Ischaemia

or

Nephrotoxicity.

The modern term:

Acute tubular injury – ATI

is often more accurate because widespread true tubular necrosis is not always present.

11. Ischaemic ATN

Ischaemic ATN may occur after:

Hypovolaemia.

Severe haemorrhage.

Shock.

Sepsis.

Cardiovascular collapse.

Major surgery.

The typical progression is:

Hypoperfusion → pre-renal AKI → prolonged ischaemia → tubular injury.

12. Nephrotoxic ATN

Nephrotoxins can directly damage renal tubular epithelial cells.

Examples include:

Aminoglycosides.

Some chemotherapy drugs.

Radiographic contrast in susceptible patients.

Myoglobin from rhabdomyolysis.

Haemoglobin from severe intravascular haemolysis.

Various toxins.

13. Multifactorial ATN

The original notes correctly state that ATN is often:

Multifactorial.

A critically ill patient may simultaneously have:

Sepsis.

Hypotension.

Volume depletion.

Nephrotoxic drug exposure.

Therefore more than one mechanism may contribute to AKI.

14. Renal Vascular Causes

Renal vascular disease may cause AKI through obstruction or injury to:

Large vessels

or

Small renal vessels.

15. Renal Artery Thrombosis or Embolism

Acute occlusion of a renal artery may cause:

Renal infarction.

Possible features include:

Sudden flank pain.

Haematuria.

Raised LDH.

AKI is particularly likely when the lesion is:

Bilateral

or affects a:

Solitary functioning kidney.

16. Renal Artery Stenosis

Chronic renal artery stenosis more commonly causes:

Hypertension

than sudden AKI.

However, severe bilateral stenosis can cause AKI, particularly after:

ACE inhibitor or ARB treatment.

17. Hypertensive Emergency

The older term:

Accelerated hypertension

is now often replaced by:

Hypertensive emergency.

Severe hypertension can cause:

Endothelial injury.

Fibrinoid necrosis.

Hyperplastic arteriolosclerosis.

Renal ischaemia.

This may lead to:

AKI.

18. Scleroderma Renal Crisis

Systemic sclerosis can cause:

Scleroderma renal crisis.

Typical features include:

Abrupt severe hypertension.

Rapidly rising creatinine.

Microangiopathic haemolytic anaemia.

Treatment requires prompt:

ACE inhibitor therapy, usually with captopril initially.

19. Pre-Eclampsia

Pre-eclampsia can cause renal dysfunction through:

Endothelial injury

and

Glomerular endotheliosis.

Features include:

Hypertension.

Proteinuria.

Reduced renal function.

Severe disease may be associated with:

HELLP syndrome.

20. Glomerulonephritis

Glomerulonephritis can cause:

Nephritic AKI.

Typical urinary findings include:

Haematuria.

Proteinuria.

Dysmorphic RBCs.

RBC casts.

Patients may also develop:

Hypertension.

Oedema.

Reduced GFR.

21. IgA Nephropathy

IgA nephropathy may cause acute deterioration in renal function, particularly in severe disease.

The classic clinical pattern is:

Visible haematuria occurring during or shortly after an upper respiratory infection.

This is called:

Synpharyngitic haematuria.

22. Mesangiocapillary GN

The older term:

Mesangiocapillary GN

corresponds broadly to:

Membranoproliferative glomerulonephritis – MPGN.

Modern classification separates:

Immune-complex-mediated disease

from

Complement-mediated disease such as C3 glomerulopathy.

23. Post-Infectious Glomerulonephritis

Post-infectious GN may follow:

Streptococcal infection.

Typical features include:

Cola-coloured urine.

Haematuria.

Oedema.

Hypertension.

AKI.

Low C3.

24. Infective Endocarditis

Infective endocarditis can cause:

Immune-complex glomerulonephritis.

Possible findings include:

Fever.

Heart murmur.

Haematuria.

Proteinuria.

Low complement.

AKI.

25. Other Infection-Related GN

Persistent infections such as:

Deep abscesses

may occasionally produce:

Immune-complex glomerular injury.

These are less common but remain recognised causes.

26. Acute Interstitial Nephritis

Acute interstitial nephritis affects:

Renal interstitium and tubules.

The most common cause is:

Drug-induced immune injury.

27. Drugs Causing AIN

Important examples include:

Penicillins and other beta-lactam antibiotics.

Rifampicin.

Sulfonamides.

NSAIDs.

Proton-pump inhibitors.

Thiazide diuretics.

Furosemide.

28. Clinical Features of AIN

AIN may produce:

AKI.

Sterile pyuria.

WBC casts.

Mild proteinuria.

Microscopic haematuria.

Some patients develop:

Fever.

Rash.

Eosinophilia.

However, the classic triad is present in only a minority.

29. Pyelonephritis

Severe pyelonephritis can cause AKI, especially when there is:

Sepsis.

Bilateral disease.

Obstruction.

Pre-existing renal impairment.

Uncomplicated unilateral pyelonephritis usually does not cause severe renal failure.

30. Legionella Infection

Legionella can be associated with AKI through:

Sepsis.

Rhabdomyolysis.

Tubulointerstitial injury.

Therefore its renal effects may be multifactorial.

31. Epstein–Barr Virus

EBV can rarely cause:

Tubulointerstitial nephritis.

This is much less common than drug-induced AIN.

32. Leptospirosis

Leptospirosis may cause:

Tubulointerstitial renal injury

and severe systemic disease.

Possible associated findings include:

Jaundice.

Thrombocytopenia.

AKI.

Severe leptospirosis is sometimes termed:

Weil disease.

33. Vasculitic and Rapidly Progressive Renal Disease

Systemic vasculitides can cause:

Necrotising glomerulonephritis

and rapidly progressive AKI.

These conditions usually require urgent:

ANCA testing.

Other immunological investigations.

Kidney biopsy.

34. Anti-GBM Disease

The older notes place:

Goodpasture syndrome

under vasculitis.

Strictly, anti-GBM disease is not a classic systemic vasculitis.

It causes:

Rapidly progressive crescentic GN

and may also cause:

Pulmonary alveolar haemorrhage.

Typical renal biopsy immunofluorescence shows:

Linear IgG along the GBM.

35. Granulomatosis with Polyangiitis

The old term:

Wegener’s granulomatosis

is now:

Granulomatosis with polyangiitis – GPA.

Features may include:

ENT disease.

Pulmonary nodules or haemorrhage.

Rapidly progressive GN.

It is commonly associated with:

PR3-ANCA.

36. Microscopic Polyangiitis

Microscopic polyangiitis – MPA commonly causes:

Pauci-immune necrotising glomerulonephritis.

It may also produce:

Pulmonary haemorrhage.

It is often associated with:

MPO-ANCA.

37. Eosinophilic Granulomatosis with Polyangiitis

The old term:

Churg–Strauss syndrome

is now:

Eosinophilic granulomatosis with polyangiitis – EGPA.

Typical features include:

Asthma.

Eosinophilia.

Systemic vasculitis.

Renal involvement can occur.

38. IgA Vasculitis

The old term:

Henoch–Schönlein purpura

is now:

IgA vasculitis.

Typical features include:

Palpable purpura.

Arthralgia.

Abdominal pain.

Renal involvement resembling IgA nephropathy.

39. Cryoglobulinaemia

Cryoglobulinaemic disease may cause:

Immune-complex glomerulonephritis.

Possible findings include:

Purpura.

Neuropathy.

Haematuria.

Proteinuria.

Low complement, especially C4.

40. Haematological Causes

Important haematological causes of AKI include:

Multiple myeloma.

Haemolytic uraemic syndrome.

Other thrombotic microangiopathies.

41. Multiple Myeloma

The classic mechanism of AKI in myeloma is:

Light-chain cast nephropathy.

Filtered monoclonal light chains form casts within tubules and produce:

Tubular obstruction and direct toxicity.

42. Other Mechanisms in Myeloma

Myeloma may also cause kidney injury through:

Hypercalcaemia.

Dehydration.

AL amyloidosis.

Monoclonal immunoglobulin deposition disease.

Infection.

43. Haemolytic Uraemic Syndrome

HUS is a:

Thrombotic microangiopathy.

The classic triad is:

Microangiopathic haemolytic anaemia.

Thrombocytopenia.

AKI.

44. Thrombotic Microangiopathy

A patient with:

AKI + thrombocytopenia + haemolytic anaemia + schistocytes

should raise suspicion for:

TMA.

This includes:

HUS.

TTP.

Complement-mediated TMA.

45. Rhabdomyolysis

Rhabdomyolysis causes:

Massive skeletal muscle breakdown.

This releases:

Myoglobin.

Myoglobin can cause:

Pigment-associated acute tubular injury.

Typical clues include:

Markedly raised CK.

Dark urine.

Hyperkalaemia.

46. Hepatorenal Syndrome

The original notes place hepatorenal syndrome among intrinsic renal causes, but it is better understood as:

Functional renal failure caused by severe circulatory disturbance in advanced liver disease.

The kidney may initially be structurally normal.

Therefore it is more closely related to:

Pre-renal physiology.

47. Systemic Lupus Erythematosus

SLE may cause AKI through:

Lupus nephritis.

Severe proliferative lupus nephritis can cause:

Haematuria.

Proteinuria.

RBC casts.

Rapidly declining GFR.

Typical immunological clues include:

Raised anti-dsDNA.

Low C3 and C4.

48. Acute Pancreatitis

Severe pancreatitis may cause AKI through:

Hypovolaemia.

Third-space fluid losses.

Systemic inflammation.

Sepsis.

Shock.

Therefore the renal injury is often:

Pre-renal initially, followed by tubular injury if severe or prolonged.

49. Hypercalcaemia

Severe hypercalcaemia can cause AKI through:

Renal vasoconstriction.

Nephrogenic diabetes insipidus.

Volume depletion.

Tubular injury.

Therefore:

HYPERCALCAEMIA → POLYURIA + DEHYDRATION + REDUCED RENAL PERFUSION → AKI.

50. Acute Urate Nephropathy

Large quantities of uric acid can precipitate within renal tubules.

This causes:

Tubular obstruction

and

AKI.

The classic setting is:

Tumour lysis syndrome.

51. Tumour Lysis Syndrome

Tumour lysis syndrome produces:

Hyperuricaemia.

Hyperkalaemia.

Hyperphosphataemia.

Hypocalcaemia.

These abnormalities can cause severe:

AKI and cardiac arrhythmias.

52. Post-Renal AKI

Post-renal AKI occurs when:

Urinary outflow is obstructed.

For significant AKI to develop, obstruction usually needs to be:

Bilateral

or involve a:

Solitary functioning kidney.

53. Renal and Ureteric Stones

Renal stones can cause post-renal AKI when there is:

Bilateral ureteric obstruction

or obstruction of a:

Single functioning kidney.

A unilateral stone in a patient with two normal kidneys usually does not cause major AKI.

54. Benign Prostatic Enlargement

In older men, an important cause is:

Benign prostatic enlargement.

This may cause:

Bladder outlet obstruction.

Urinary retention.

Hydronephrosis.

Post-renal AKI.

55. Malignant Obstruction

Malignancy may obstruct the urinary tract.

Examples include:

Prostate cancer.

Bladder cancer.

Pelvic malignancies.

Retroperitoneal tumours.

These may produce:

Bilateral ureteric obstruction.

56. Retroperitoneal Fibrosis

Retroperitoneal fibrosis may surround and compress:

Both ureters.

This can lead to:

Hydronephrosis

and

Post-renal AKI.

57. Papillary Necrosis

Papillary necrosis is primarily an:

Intrinsic renal papillary lesion.

However, sloughed papillae can obstruct the ureter and cause:

Post-renal obstruction.

Therefore it may contribute to post-renal AKI in selected cases.

58. Causes of Papillary Necrosis

Classic associations include:

Diabetes mellitus.

Analgesic nephropathy.

Sickle-cell disease or trait.

Severe pyelonephritis.

Detached papillae may then:

Obstruct urine flow.

59. Other Post-Renal Causes

Important additional causes include:

Neurogenic bladder.

Urethral stricture.

Blood clots.

Bladder tumours.

Pelvic masses.

60. Pre-Renal Causes – Note Form

Hypovolaemia:

Vomiting.

Diarrhoea.

Haemorrhage.

Burns.

Poor fluid intake.

Reduced effective circulating volume:

Heart failure.

Cirrhosis.

Sepsis.

Drug-related haemodynamic AKI:

ACE inhibitors.

ARBs.

NSAIDs.

61. Intrinsic Renal Causes – Note Form

Acute tubular injury:

Prolonged hypoperfusion.

Haemorrhage.

Shock.

Sepsis.

Nephrotoxins.

Rhabdomyolysis.

Vascular:

Renal artery thrombosis or embolism.

Severe bilateral renal artery stenosis.

Hypertensive emergency.

Scleroderma renal crisis.

Pre-eclampsia.

Thrombotic microangiopathy.

Glomerular:

IgA nephropathy.

MPGN pattern.

Post-infectious GN.

Endocarditis-associated GN.

Lupus nephritis.

ANCA-associated GN.

Anti-GBM disease.

Cryoglobulinaemic GN.

Interstitial:

Drug-induced AIN.

Severe pyelonephritis.

Leptospirosis.

Rare viral-associated interstitial nephritis.

Haematological:

Myeloma.

HUS and other TMA.

Other intrinsic or mixed causes:

Rhabdomyolysis.

Hypercalcaemia.

Urate nephropathy.

Severe pancreatitis-related AKI.

62. Post-Renal Causes – Note Form

Stones:

Bilateral ureteric stones.

Stone in a solitary functioning kidney.

Prostatic obstruction:

Benign prostatic enlargement.

Prostate cancer.

Malignant obstruction:

Bladder cancer.

Pelvic malignancy.

Retroperitoneal tumour.

Other obstruction:

Retroperitoneal fibrosis.

Neurogenic bladder.

Urethral stricture.

Blood clot.

Sloughed renal papilla.

63. Important Corrections to the Original Notes

ARF should generally be replaced with:

AKI – ACUTE KIDNEY INJURY.

The statement:

“More than 90% are pre-renal or ATN”

is best regarded as:

Historical teaching rather than a universal modern figure.

Goodpasture syndrome is better classified as:

ANTI-GBM DISEASE

rather than a conventional systemic vasculitis.

Wegener’s granulomatosis is now:

GRANULOMATOSIS WITH POLYANGIITIS – GPA.

Churg–Strauss syndrome is now:

EOSINOPHILIC GRANULOMATOSIS WITH POLYANGIITIS – EGPA.

Henoch–Schönlein purpura is now:

IgA VASCULITIS.

Hepatorenal syndrome is primarily a:

FUNCTIONAL HAEMODYNAMIC RENAL FAILURE

rather than intrinsic tubular damage.

Pancreatitis usually causes AKI through:

HYPOVOLAEMIA + SYSTEMIC INFLAMMATION + SHOCK.

Papillary necrosis is an intrinsic renal lesion, but:

SLOUGHED PAPILLAE MAY SECONDARILY CAUSE POST-RENAL OBSTRUCTION.

64. Practical Diagnostic Approach

When AKI is detected, first ask:

Is the kidney underperfused?

If yes:

Think pre-renal.

Then ask:

Is there urinary obstruction?

Check for:

Urinary retention.

Hydronephrosis.

Prostatic disease.

Stones.

If yes:

Think post-renal.

If neither clearly explains the AKI, investigate:

Intrinsic renal disease.

Important clues include:

RBC casts → glomerulonephritis.

WBC casts → AIN or pyelonephritis.

Muddy brown casts → acute tubular injury.

Heavy proteinuria → glomerular disease.

Anaemia + thrombocytopenia + schistocytes → TMA.

High CK → rhabdomyolysis.

Key Clinical Pattern

Remember:

PRE-RENAL = PERFUSION PROBLEM.

Examples:

HYPOVOLAEMIA + SEPSIS + HEART FAILURE + CIRRHOSIS + HAEMODYNAMIC DRUG EFFECTS.

INTRINSIC RENAL = KIDNEY TISSUE DAMAGE.

Examples:

ATN/ATI + GN + AIN + VASCULAR DISEASE + MYELOMA + TMA + RHABDOMYOLYSIS.

POST-RENAL = OBSTRUCTION.

Examples:

PROSTATE + STONES + MALIGNANCY + RETROPERITONEAL FIBROSIS + NEUROGENIC BLADDER.

The simplest examination framework is:

LOW PERFUSION → PRE-RENAL.

ACTIVE URINE SEDIMENT → INTRINSIC RENAL.

ANURIA / RETENTION / HYDRONEPHROSIS → POST-RENAL.