L5 -9- Renal involvement in systemic disease

Renal Involvement in Systemic Diseases: Lecture Guide

This lecture covers how major systemic diseases impact renal function and structure, emphasizing pathophysiology, screening, and diagnostic hallmarks.

I. Metabolic & Endocrine Disorders

A. Diabetes Mellitus (Diabetic Nephropathy)

• Mechanisms of Injury:
• • Osmotic Polyuria: Glucose acts as an osmotic agent, pulling water into the urine.
  • Glomerulosclerosis: Diffuse or nodular (Kimmelstiel-Wilson) hardening of the glomeruli.
  • Recurrent Infections: Glucosuria predisposes to frequent UTIs, potentially leading to chronic pyelonephritis or papillary necrosis.
  • Type IV Renal Tubular Acidosis (RTA): Common in diabetics.
• ⭐️Important/📝MCQ: Screening & Detection:
• • Detection starts with microalbuminuria (30–300 mg/day).
  • Type 2 Diabetes: Screen at the time of initial diagnosis.
  • Type 1 Diabetes: Screen starting 5 years after the initial diagnosis.

B. Amyloidosis

• Types: Primary (AL) and Secondary (AA). AA is more common, associated with chronic inflammation (e.g., TB, RA).
• ⭐️Important: Clinical Hallmarks:
• • Causes Heavy Proteinuria/Nephrotic Syndrome.
  • Unique Feature (📝MCQ): Unlike most chronic kidney diseases where kidneys shrink, in amyloidosis, the kidney size is maintained or enlarged on ultrasound.

C. Hyperuricemia & Gout

• Acute Hyperuricemia: Often seen in Tumor Lysis Syndrome (post-chemotherapy) or Rhabdomyolysis.
• • 📝MCQ (Tumor Lysis Labs): Increased Uric Acid, Phosphate, and Potassium; Decreased Calcium (Hypocalcemia).
• Chronic Hyperuricemia: Leads to chronic tubulointerstitial nephritis, ischemia, or renal calculi.

D. Thyroid Dysfunction

• Hemodynamics: Thyroid hormones influence cardiac output and GFR. Hypothyroidism can reduce renal perfusion.
• Mechanism: Can cause interstitial nephritis (often drug-induced) or immune-mediated injury.

II. Hematological Disorders & Malignancies

A. Multiple Myeloma

• ⭐️Important: CRAB Criteria: Calcium elevation, Renal failure, Anemia, Bone lesions.
• 📝MCQ: Renal Mechanisms:
• • Cast Nephropathy: Light chains (Bence-Jones proteins) obstruct tubules, causing "Toxic ATN".
  • Secondary Amyloidosis or Hypercalcemia-induced injury.

B. Sickle Cell Disease

• Pathophysiology: Sickled RBCs cause vaso-occlusion in small renal vessels, leading to medullary ischemia and papillary necrosis.

C. Thrombotic Microangiopathy (TMA)

• Hemolytic Uremic Syndrome (HUS):
• • 📝MCQ: Classic Triad: Microangiopathic Hemolytic Anemia (MAHA), Thrombocytopenia, and Acute Kidney Injury (AKI).
  • Often follows a Shiga-toxin-producing diarrheal infection.
• Thrombotic Thrombocytopenic Purpura (TTP):
• • ⭐️Important: Classic Pentad: HUS Triad + Fever + Neurological Symptoms.

III. Pulmonary-Renal Syndromes (Vasculitis)

These conditions affect both the lungs (hemoptysis) and kidneys (hematuria).

A. ANCA-Positive Vasculitis

1. Wegener’s (GPA): Granulomatosis with Polyangiitis.
2. Churg-Strauss (EGPA): Eosinophilic GPA, associated with asthma and high eosinophils.
3. Microscopic Polyangiitis (MPA).

B. Anti-GBM Disease (Goodpasture Syndrome)

• ⭐️Important/📝MCQ: Caused by antibodies against the Glomerular Basement Membrane. Characterized by the combination of Hemoptysis and Hematuria.

IV. Rheumatological Diseases

A. Systemic Lupus Erythematosus (SLE)

• Lupus Nephritis: Can present as asymptomatic proteinuria or full-blown nephrotic/nephritic syndrome. It follows a staging system (Classes I-VI).

B. Rheumatoid Arthritis (RA)

• Mechanisms: Secondary Amyloidosis, immune-mediated GN, or drug-induced injury (NSAIDs causing interstitial nephritis).

C. Henoch-Schönlein Purpura (HSP) / IgA Vasculitis

• ⭐️Important: Classic Tetrad (📝MCQ/OSPE):
• 1. Purpura (Non-thrombocytopenic).
  2. Arthritis/Arthralgia.
  3. Abdominal Pain (GI bleeding).
  4. Hematuria.

D. Systemic Sclerosis (Scleroderma)

• ⭐️Important: Scleroderma Renal Crisis: Acute kidney injury with malignant (accelerated) hypertension.

V. Cardiovascular & Cardiorenal Syndromes

A. Hypertension

• Chronic hypertension leads to glomerulosclerosis and interstitial fibrosis.
• Malignant Hypertension: Can cause AKI and pre-eclampsia-like manifestations.

B. Cardiorenal Syndrome (Types)

• Type 1 (Acute Cardiorenal): Acute heart failure (e.g., MI) leading to AKI.
• Type 2 (Chronic Cardiorenal): Chronic heart failure leading to CKD.
• Type 3 (Acute Renocardiac): AKI (e.g., hyperkalemia) causing cardiac arrhythmia or pump failure.
• Type 4 (Chronic Renocardiac): CKD leading to cardiac hypertrophy/failure.
• Type 5 (Secondary): Systemic disease (e.g., Sepsis, Diabetes) affecting both organs.

C. Infective Endocarditis (IE)

• Renal Affection: Septic emboli causing micro-infarctions, immune-mediated GN, or drug toxicity (e.g., Aminoglycosides like Gentamicin).

VI. Hepato-Renal & Viral Infections

A. Hepatorenal Syndrome (HRS)

• Renal failure occurring in advanced liver cirrhosis with portal hypertension, where the kidney is histologically normal.

B. Viral Infections (📝MCQ)

• Hepatitis B (HBV): Primarily associated with Membranous GN and Polyarteritis Nodosa (PAN).
• Hepatitis C (HCV): Primarily associated with Membranoproliferative GN (MPGN) and Cryoglobulinemia.
• HIV: Characteristically causes Focal Segmental Glomerulosclerosis (FSGS).

C. Tuberculosis (TB)

• Can cause granulomatous disease, retroperitoneal fibrosis (obstructing ureters), or secondary amyloidosis.
• 📝MCQ: Rifampicin (anti-TB drug) causes harmless red-orange discoloration of urine.

VII. Gastrointestinal Disorders

Inflammatory Bowel Disease (IBD)

• Ulcerative Colitis: Immune-mediated GN or dehydration-induced AKI.
• Crohn's Disease: Malabsorption leads to electrolyte imbalances and calcium oxalate/uric acid stones.