65. Benign and malignant nephrosclerosis and diffuse cortical necrosis. Urolithiasis and obstructive uropathy.

Nephrosclerosis?

More precisely: arterio-nephro-sclerosis

= Thickening and sclerosis of the arterial/arteriolar walls in the kidney

- Related to HYPERTENSION

Can lead to CKD

Two types of nephrosclerosis?

- Benign nephrosclerosis

- Malignant nephrosclerosis

Benign nephrosclerosis?

Occurs when there is chronic hypertension

- Hyaline thickening of the walls of small arteries & arterioles w/ narrowing of lumen => hyaline arteriolosclerosis

Kidney morphology of benign nephrosclerosis?

Surface of kidney:

- Granular and leathery

Kidneys are atrophic

Tubules show ischemic atrophy -> due to less perfusion from the narrowed arteries

There is interstitial fibrosis

Who can have severe kidney damage from nephrosclerosis alone?

- African Americans -> are genetically susceptible

In these patients, the benign nephrosclerosis may progress into chronic renal failure

All patients will show some degree of functional impairment, such as slightly decreased GFR

Malignant nephrosclerosis?

Occurs when there is malignant hypertension > 200/120 mmHg

- The high pressure damages the walls of small arteries & arterioles

- Increases their permeability => fibrin, causing fibrinoid necrosis of the vessels

If left untreated, acute kidney failure occurs

Hyperplastic arteriolosclerosis?

Occurs in malignant nephrosclerosis

- Proliferative factors in the plasma enters the vessel wall & causes hyperplasia of the tunica intima

Progression of malignant nephrosclerosis - what happens?

- Renal perfusion decreases -> RAAS activation

= Further increases BP

Microthrombi appears in the glomeruli

= Necrotizing glomerulitis will occur

Diffuse cortical necrosis?

Rare cause of acute renal failure due to ischemic necrosis of the renal cortex

Necrosis is sharply limited to the renal cortex

- Typically occurs in neonates, pregnancy or postpartum women due to sepsis or complications

What can the ischemia be caused by in diffuse cortical necrosis?

- Vascular spasm

- Microvascular injury

- DIC

Urolithiasis?

Formation of stones at any level of the urinary collecting system

- Most commonly arise in the kidney

- They are quite common

- There is a familial tendency to this

4 major types of urolithiasis?

- Calcium oxalate stone (80%)

- Struvite stone (10%)

- Uric acid stone (6%)

- Cysteine stone (1%)

Why does stone occurs?

When urine is supersaturated with the component of the stone

In some cases other factors will contribute to stone formation, like abnormal pH

Calcium stones?

When urine is supersaturated with calcium

Causes:

- Hypercalcemia

- Absorptive hypercalciuria (Calcium is absorbed from the gut in excessive amounts)

- Renal hypercalciuria (defect in renal calcium reabsorption)

Struvite stones?

(Magnesium ammonium phosphate)

- Occur in people with alkaline urine -> a result of UTIs

Especially by bacteria that produce urease (Staph.)

- Struvite stones can make a cast of the renal pelvis -> staghorn calculi

Uric acid stones?

Occur in people with acidic urine & increased excretion of uric acid

- Latter can be idiopathic or in combination with gout

OR diseases that cause rapid cell turnover - leukemia

Cysteine stones?

Occur in patients with genetic defects in renal transport of cysteine

- Acidic urine increases the risk for this

Symptoms of kidney stone?

Small stones may dislodge from renal pelvis, and enter the ureter -> colicky pain

Gross hematuria

Ulceration -> by dislodged stones

• Predispose to bacterial infection

• Obstruct outflow of urine

Obstructive uropathy?

Aka. urinary tract obstruction

- A mechanical- or functional block to the outflow of urine

Obstruction may be partial or complete, unilateral or bilateral

Can occur anywhere in the urinary tracy

Causes of obstructive uropathy - inside kidney?

- Nephrolithiasis

- Urothelial carcinoma

Causes of obstructive uropathy - ureter?

- Nephrolithiasis - in young adults

- Ureter stricture - fibrosis after surgery

- Urothelial carcinoma

- Pregnancy

- Extraluminal neoplasm - from other surrounding structures

Causes of obstructive uropathy - bladder?

- Urothelial carcinoma

- Neurogenic bladder - spinal cord injury w/ paralysis of the bladder

Causes of obstructive uropathy - urethra?

- Prostatic enlargement (BPH or cancer) - elderly

- Congenital abnormality of the urethral valves - most common in children

Obstruction at or below level of the ureter?

Increases the pressure backwards up into the renal pelvis -> dilation of all parts along the way

- Hydroureter: dilation of ureter

- Pyelectasis: dilation of the renal pelvis

- Hydronephrosis

Hydronephrosis?

Dilation of the renal pelvis and calyces w/ accompanying atrophy of the renal parenchyma

The increased pressure will compress renal vasculature -> ischemic atrophy

How long time does it take from obstructive uropathy to hydronephrosis?

(Before irreversible damage occurs*)

• 3 weeks of complete obstruction

• 3 months of incomplete obstruction

Therefore: early diagnosis is important

What does hydronephrosis quickly progress to?

-Anuria and renal failure (if bilateral or if the unobstructed kidney is already damaged)

- It predispose to pyelonephritis -> can progress into urosepsis