07.1 Haematuria, nephrotic and nephritic syndromes

Study Notes

Haematuria is the presence of red blood cells (RBCs) in the urine, often indicating renal or urogenital issues.
Microhaematuria is when at least 3 RBCs are present per high-power field, only visible under a microscope. It's common in glomerular diseases like IgA nephropathy.
Macrohaematuria is blood visible to the naked eye in the urine. Differentiate from pseudohaematuria via microscopy.
Pseudohaematuria is discoloured urine without RBCs, caused by things like foods (e.g., beetroot), drugs (e.g., rifampicin), or conditions like myoglobinuria or haemoglobinuria.

Define and classify haematuria, differentiating true from pseudohaematuria, and identifying sources (e.g., glomerular vs. non-glomerular).
Define and classify proteinuria, including glomerular, tubular, and overflow proteinuria.
Differentiate between nephrotic and nephritic syndromes, focusing on clinical presentation, pathophysiology, and diagnostic implications.

Proteinuria: Elevated protein levels in urine, a key sign of kidney disease.
Glomerular Proteinuria: Damage to the glomerular barrier leads to excessive albumin leakage.
Tubular Proteinuria: Tubular dysfunction results in failure to reabsorb small proteins.
Overflow Proteinuria: Excess low-molecular-weight proteins overwhelm tubular reabsorption.
Functional Proteinuria: Benign, temporary proteinuria due to factors like fever or exercise.
Nephrotic Syndrome: Marked by significant proteinuria (over 3.5g/day), hypoalbuminemia, edema, and hyperlipidemia. Indicates glomerular filtration barrier damage.
Nephritic Syndrome: Characterised by haematuria, reduced glomerular filtration rate (GFR), and non-nephrotic proteinuria.

Haematuria Mechanisms:
- Glomerular origin: Blood leaks from damaged glomeruli, often indicated by dark urine and dysmorphic RBCs; a proteinuria of over 500mg/day frequently accompanies it.
- Non-glomerular origin: Blood originates outside the glomeruli (e.g., urinary tract infection, stones). Often does not show dysmorphic RBCs, and proteinuria is usually under 500mg/day.
Nephrotic Syndrome Pathophysiology:
- Hypoalbuminemia and Oedema:
  - Underfilling mechanism: Low albumin results in lower oncotic pressure, shifting fluid to extracellular spaces and causing edema.
  - Overfilling mechanism: Sodium retention and RAAS (Renin-Angiotensin-Aldosterone System) activation lead to enhanced water retention and oedema formation.
Nephritic Syndrome Pathophysiology:
- Inflammation in the glomeruli leads to increased capillary permeability and a reduced GFR, marked by oliguria, dysmorphic red blood cells (RBCs), and RBC casts.
- RAAS activation contributes to volume expansion and hypertension.

Case Study: A male patient (45) presents with dark urine, facial swelling, and high blood pressure suggesting potential nephritic syndrome.
Diagnostic Approach: Dipstick urinalysis, microscopic examination (to identify RBC morphology), urine protein/creatinine ratio, and other tests (e.g., kidney function tests, urine culture) assess proteinuria.

ACE Inhibitors/ARBs: Reduce proteinuria, manage hypertension, and protect kidneys. Particularly in nephrotic and nephritic syndromes with concurrent hypertension.

Haematuria: Differentiate pseudohaematuria (non-RBC causes) from glomerular (e.g., IgA nephropathy, thin basement membrane disease, glomerulonephritis) and non-glomerular sources.
Proteinuria: Characterise as overflow, tubular, or glomerular. Note protein levels and any specific symptoms.

Urine dipstick: Initial assessment of haematuria and proteinuria; needs microscopy and examination.
Microscopic Urinalysis: Identifies RBC morphology (dysmorphic vs isomorphic) and presence of casts.
Urine Protein/Creatinine Ratio (PCR): Quantifies proteinuria from a spot urine sample.
Urine culture: Checks for urinary tract infections.

Dysmorphic RBCs and RBC casts strongly suggest a glomerular origin for haematuria.
Nephrotic syndrome is characterized by heavy proteinuria, hypoalbuminemia, and hyperlipidaemia; it requires treatment focused on managing these factors.
Nephritic syndrome presents with haematuria, hypertension, and moderate proteinuria, requiring early blood pressure control and immunosuppression if autoimmune.