Renal pathology

Roughly how many nephrons are in each healthy adult kidney?

~800,000 to 1.5 million nephrons.

What are the main parts of the nephron?

Proximal convoluted tubule, Loop of Henle, Distal convoluted tubule.

What does the proximal convoluted tubule (PCT) reabsorb?

Glucose (100%), amino acids (100%), bicarbonate (80–90%), Na⁺ (65–70%), water (65–70%).

What does the PCT secrete/eliminate?

Secretes H⁺ and ammonia, eliminates drugs/water/H⁺ ions; retains plasma proteins and blood cells.

Loop of Henle: which limb is water-permeable and which is impermeable?

Descending limb = water-permeable; ascending limb = impermeable to water.

What does the thick ascending limb reabsorb (key transporter)?

Reabsorbs Na⁺, K⁺, 2Cl⁻ (NKCC) about 20–30%.

Distal convoluted tubule (DCT): key early vs late features?

Early DCT: reabsorbs Na⁺/Cl⁻ and is impermeable to water.

Late DCT: reabsorbs Na⁺ (under ADH), HCO₃⁻; secretes H⁺, NH₄⁺, K⁺ and wastes/drugs.

Normal blood urea range?

7–21 mg/dl.

Normal creatinine range?

0.6–1.2 mg/dl.

What does raised creatinine usually indicate?

Reduced glomerular filtration.

What is proteinuria and why is it important?

Albumin in urine; most common sign of renal disease.

Normal GFR and CKD cutoffs?

Normal 90–120 mL/min/1.73m².
<60 for ≥3 months = CKD; <5 = kidney failure.

Define prerenal failure (cause pattern).

Sudden drop in renal perfusion (shock, fluid loss, cardiac failure, anaphylaxis, sepsis).

Define intrarenal failure.

Direct kidney damage (inflammation, toxins/drugs, infection, tumour, reduced blood supply).

Define postrenal failure.

Obstruction of urine flow (enlarged prostate, stones, bladder tumour, injury).

What is azotemia?

Elevated nitrogen-containing waste in blood (e.g., urea, creatinine).

What is uremia?

Azotemia with systemic symptoms due to accumulation of waste products.

Define polyuria.

Persistent large increase in urine output; can be due to excess water intake, glycosuria, or defective concentration ability.

Define oliguria.

<300 mL urine/day; causes include hypotension, obstruction, renal failure.

Define haematuria.

RBCs in urine; can indicate stones or urinary tract tumour.

What is dysuria?

Pain/burning/discomfort with urination; causes include stones and UTIs.

What is renal colic?

Severe sudden pain from stones in kidney/renal pelvis/ureter due to ureter dilation/spasm.

What is oedema?

Abnormal fluid accumulation beneath skin or in body cavities.

Major factors that contribute to oedema?

↑ hydrostatic pressure, ↓ oncotic pressure, ↑ vessel permeability (inflammation), lymphatic obstruction.

Key manifestations of nephritic syndrome?

Haematuria, variable proteinuria, impaired renal function, hypertension, oedema.

Pathology basis of nephritic syndrome?

Endothelial damage + inflammation of glomerulus.

Classic acute nephritis triad (e.g., post-strep GN)?

Haematuria + oliguria + hypertension.

. Key manifestations of nephrotic syndrome?

Massive proteinuria (>4 g/day), hypoalbuminemia (<3 g/100 mL), generalised oedema, hyperlipidemia; often insidious onset.

Pathology basis of nephrotic syndrome?

Podocyte foot process effacement; basement membrane damage (e.g., diabetes).

. Two key pathology mechanisms in glomerular disease?

Cellular proliferation (podocytes/endothelium/parietal epithelium/mesangial) and immune complex deposition (subepithelial, subendothelial, mesangial).

What does “focal” vs “diffuse” mean in glomerular disease?

Focal = only some glomeruli affected; Diffuse = most/all glomeruli affected.

What does “segmental” mean?

Only part of an individual glomerulus is affected (vs global).

Most common cause of nephrotic syndrome in children + prognosis?

Minimal change disease; excellent prognosis.

What is focal segmental glomerulosclerosis (FSGS)?

Scarring: focal (some glomeruli) + segmental (part of glomerulus); major cause of adult renal failure.

FSGS proportion in nephrotic syndrome?

~20% in children and 40% in adults.

Key pathology feature of membranous glomerulonephritis (MGN)?

: Immune complexes deposited on basement membrane (subepithelial) with 5–10× thickening; often adults 40–60; poor steroid response.

In adults, which nephrotic condition has a highly variable prognosis and is immune-complex mediated?

Membranous nephropathy (MGN).