Renal Vasculature and Related Conditions

Vascular Diseases of the Kidney

• Ischemic renal disease shows a significant reduction in the glomerular filtration rate.
• This is due to significant renovascular occlusive disease affecting the entire functioning renal parenchyma.
• Larger arteries may experience diseases like atherosclerosis, thrombosis, and thromboembolism.
• Hypertension and thromboembolism affect smaller arteries and arterioles more.
• Renal arteries are considered end-organ type, lacking effective collateral circulation.
• Sudden arterial occlusion often results in infarction.
• Renal ischemia from main renal artery stenosis or intrarenal artery narrowing activates the renin-angiotensin-aldosterone system.
• This activation leads to an increase in blood pressure.

Essential Hypertension

• Essential hypertension is the most common cause of systemic hypertension
• It is divided into mild to moderate (benign) and severe (malignant) forms

Essential Hypertension Risks

• Benign form increases the risk of cerebrovascular accidents, coronary artery disease, myocardial infarction, and renal disease.
• Malignant form typically presents with pressure exceeding 190/120.
• It's defined by associated clinical conditions such as papilledema, congestive heart failure, stroke, encephalopathy, and renal insufficiency.

Benign Hypertension Indicators

• Kidneys are normal or moderately reduced in size and weight;
• Kidneys develop a granular capsule, the cortex thins;
• Ischemic nephropathy changes may be present.
• Arteries have intimal fibroplasia and reduplication of the internal elastic. lamina.
• Homogeneous eosinophilic material replaces the media of arterioles, characterizing hyaline arteriolosclerosis.

Malignant Hypertension Indicators

• Cortical surface petechial hemorrhages are typically present.
• Ischemic nephropathy changes are possible
• Expect arterial intimal fibroplasia
• Look for fibrinoid necrosis of arterioles with or without necrotizing arteriolitis.
• Interlobular and larger arterioles may express hyperplastic arteriolitis (onion-skin lesion).

Renal Artery Stenosis Facts

• Renal Artery Stenosis is a significant cause of secondary hypertension.
• Atherosclerosis is the most common cause of large renal artery occlusion, predominately in older men affecting mostly the proximal renal arteries.
• Bilateral disease is present in up to 60% of renal artery stenosis cases.
• In 50% of cases, renal Artery Stenosis originates from the aorta.
• Less common causes of occlusion: thromboembolic disease, thrombosis of main renal arteries, vasculitis, and fibromuscular dysplasia.

Fibromuscular Dysplasia

• Fibromuscular Dysplasia occurs more commonly in young women.
• It causes usually concentric narrowing of the artery.
• Alternating constrictions and aneurysmal dilatations may be present.
• Medial fibroplasia is the most common variant.
• It is most often bilateral and seldom causes total occlusion.

Clinical Course

• Consequences of occlusion depends on size and of vessels involved
• Rate of closure,
• The presence or absence of collateral circulation and/or occlusion being unilateral or bilateral.
• Gradual narrowing results in ischemic nephropathy.
• Ischemic disease tends to progress fairly rapidly, with approximately half of patients showing progression within two years.
• Sudden occlusion commonly results in infarction

Renal Artery Stenosis Treatment

• Early detection may allow reversal with angioplasty or bypass graft.
• In long-standing unilateral stenosis, correction may not relieve hypertension.

Thrombotic Microangiopathies

• Hemolytic uremic syndrome (HUS) and Thrombotic thrombocytopenic purpura (TTP) are closely related.
• Both share virtually identical renal pathology, making them difficult to distinguish.
• Characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure.
• Disease is related to endothelial Injury and subsequent activation of the coagulation system.

Hemolytic Uremic Syndrome Forms

• Classic form occurs mainly in young children and is associated with prodromal diarrhea.
• Classic form cases associate with infection from verotoxin-producing strains of E. coli (especially 0157:H7, recently 0104.H4).
• Non-diarrhea-associated disease classifies as sporadic or familial.
• Pregnancy, SLE, HIV, and drugs can be associated with the sporadic form.
• The familial form is linked to mutations in complement regulatory protein factor H.

Thrombotic Thrombocytopenic Purpura

• Disease occurs most commonly in women during the fourth and fifth decades.
• Neurologic symptoms (seizures, aphasia, altered consciousness) present in most patients.
• Severe renal damage is uncommon.
• Disease has been linked to abnormalities of metalloprotease ADAMTS-13, which breaks down large Von Willebrand factor multimers.
• ADAMTS-13 absence results in excess VWF multimers, which are prothrombotic and promote platelet activation.

Thrombotic Microangiopathies Course

• Plasma exchange is the single most important treatment in TTP and HUS.
• Renal damage resolves spontaneously in over 90% of classic HUS cases.
• The survival rate for patients with TTP is up to 80%.

Cholesterol Emboli

• Kidneys are the most common organs involved by cholesterol embolization.
• Occur usually occur in older arteriosclerosis patients of the thoracic or upper abdominal aorta.
• Onset occurs one to several weeks after angiography, cardiovascular surgery, or another precipitating event.
• Emboli impacts smaller arteries and arterioles.
• Renal manifestations include increased serum BUN and creatinine.
• Renal involvement's severity is variable; if progression occurs, it can result in severe renal failure that needs dialysis.

Renal Cortical Necrosis

• Uncommon cause of renal failure occurring in severe circulatory failure.
• The condition is frequently bilateral.
• Is most common from obstetric complications such as placental abruption or eclampsia.
• Acute renal failure is the common clinical finding.
• The histologic appearance resembles those of renal infarction.
• A significant number of patients survive with hemodialysis but are left with considerable residual renal insufficiency.

Renal Infarction Causes

• Typically related to embolism, usually from the left side of the heart.
• Many renal infarcts are clinically silent.
• The severity of disease depends on vessel size and the amount of infarcted renal tissue.