vascular injuries to the kidneys-lecture 2013
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Vascular Injuries to the Kidneys-lecture 2013TRANSCRIPT
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Vascular Injuries to the Kidneys
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•Kidney filtering organ rich in blood supply
•Vascular injury could be…•Microvascular •Macrovascular
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Macrovascular
• Renal Artery Stenosis• Atheroembolic renal
disease• Thromboembolic renal
disease• Renal Vein Thrombosis
Microvascular
•Malignant HTN• Hypertensive Nephrosclerosis• Thrombotic microangiopathy• Hemolytic-Uremic Syndrome (HUS)/
Thrombotic Thrombocytopenic Purpura (TTP)• Transplantation-Associated
Thrombotic Microangiopathy (Ta-Tma)• HIV-Related Tma• Radiation Nephropathy• Scleroderma (Progressive Systemic
Sclerosis)• Antiphospholipid Syndrome (Aps)• HELLP Syndrome• Sickle Cell Nephropathy
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Macrovascularo Large-vessel renal artery occlusive disease can result
from o extrinsic compression of the vessel
o fibromuscular dysplasiaso atherosclerotic disease (most common)
o Any disorder that reduces perfusion pressure to the kidney can activate mechanisms to restore renal pressures at the expense of developing systemic
hypertension. o restoration of perfusion pressures can reverse these
pathways
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• Renal artery stenosis • considered specifically treatable "secondary" cause of HTN
• Atherosclerotic renal artery stenosis (ARAS)• common (6.8% of a community-based sample >65 yo)• prevalence increases w/ age & w/ other vascular conditions • coronary artery disease (18–23%) &/or • peripheral aortic/lower extremity disease ( >30%)
• untreated, it progresses in 50% of cases over a 5-year period (sometimes to total occlusion) • Intensive treatment of arterial BP & statin therapy slow these
rates & improve clinical outcomes
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• Critical levels of stenosis lead to reduced perfusion pressure…• activates renin-angiotensin system• reduces sodium excretion• activates sympathetic adrenergic pathways
• Renovascular HTN treated w/ agents that block the renin-angiotensin system & other drugs that modify these pressor pathways• also treated w/ renal blood flow restoration by endovascular or
surgical revascularization
•most patients require continued antihypertensive therapy revascularization alone rarely lowers BP to normal
HTN
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• ARAS & systemic HTN: affect both poststenotic & contralateral kidneys reducing overall GFR in ARAS
• Ischemic nephropathy: when kidney function is threatened by large vessel disease
• Unlike FMD, ARAS develops in pts w/ other risk factors for atherosclerosis & commonly superimposed upon preexisting small vessel dse in the kidney d/t HTN, aging, & DM
• Nearly 85% of pts considered for renal revascularization have stage 3–5 CKD w/ GFR <60 mL/min per 1.73 m2. • The presence of ARAS is a strong predictor of morbidity- and
mortality-related cardiovascular events, independent of whether renal revascularization is undertaken.
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• Diagnostic approaches to RAS depend on the specific issues to be addressed.
• Noninvasive characterization of the renal vasculature may be achieved by several techniques (Table 286-1).
• Activation of renin-angiotensin system is a key step in developing renovascular HTN, but it is transient.
• Renal artery velocities by Doppler UTZ >200 cm/s predict hemodynamically important lesions (> 60% vessel lumen occlusion)
• Renal resistive index has predictive value regarding the viability of the kidney operator- & institution- dependent
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•Captopril-enhanced renography has a strong negative predictive value when entirely normal.
•Magnetic resonance angiography (MRA): less often used •gadolinium contrast associated w/ nephrogenic
systemic fibrosis
•Contrast-enhanced CT w/ vascular reconstruction: excellent vascular images & functional assessment (small risk of contrast toxicity)
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• FMD pts are younger females w/ otherwise normal vessels & long life expectancy• TX: respond well to percutaneous renal artery angioplasty
• For ARAS: If BP is controlled to goal levels & kidney function remains stable medical therapy w/ follow-up for disease progression is equally effective
•Medical therapy includes:• blockade of renin-angiotensin system, attainment of goal BPs,
cessation of tobacco, statins, & ASA
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•Techniques of renal revascularization are improving.
•Major complications (9%) • renal artery dissection, capsular perforation,
hemorrhage, & occasional atheroembolic disease
•Renal blood flow usually restored by endovascular stenting
• recovery of renal function is limited to 25% of cases, no change in 50%, some deterioration in others
•When HTN is refractory to effective therapy, revascularization offers real benefits.
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Atheroembolic Renal Disease•Arise as a result of cholesterol crystals breaking free of
atherosclerotic vascular plaque & lodging in downstream microvessels
•Most events follow angiographic procedures (coronary vessels)• incidence has been increasing w/ more vascular
procedures & longer life spans • suspected in >3% of ESRD, elderly & likely
underdiagnosed• common in males, w/ history of DM, HTN, & ischemic
cardiac disease• strongly associated w/ aortic aneurysmal disease &
renal artery stenosis
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•asso w/ precipitating events: angiography, vascular surgery, anticoagulation w/ heparin, thrombolytic therapy, or trauma
•Clinical manifestations develop b/n 1 & 14 days after an inciting event• fever, abdominal pain, & weight loss <1/2 of pts• cutaneous manifestations: livedo reticularis & localized
toe gangrene are more common •worsening HTN & deteriorating kidney function are
common •progressive renal failure can occur & require dialysis
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• Laboratory findings…• rising creatinine, eosinophilia (60–80%), elevated
sedimentation rate, & hypocomplementemia (15%)
•Definitive diagnosis: kidney biopsy •microvessel occlusion w/ cholesterol crystals that
leave a "cleft" in the vessel•Diagnosis of exclusion
•Treatment…No effective therapy is available. Withdrawal of anticoagulation is recommended. Statin therapy may improve outcome.
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Thromboembolic Renal Disease• can lead to declining renal function & HTN•difficult to diagnose & often overlooked (esp in elderly)
•Causes: local vessel abnormalities (local dissection, trauma, or
inflammatory vasculitis) hypercoagulability conditions (rare)distant embolic events (from left atrium in patients w/
AF or fat emboli from traumatized tissue --- large bone fractures)
Cardiac sources (vegetations from subacute bacterial endocarditis)
venous circulation if RL shunting occurs (through a patent foramen ovale)
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• Acute arterial thrombosis• flank pain, fever, leukocytosis, nausea, & vomiting
• If kidney infarction results LDH rise to extreme levels
• both kidneys affected decline in renal function w/ a drop in urine output • single kidney involved minor renal function changes
• HTN related to sudden release of renin from ischemic tissue can develop rapidly, so long as some viable tissue in the "peri-infarct" border zone remains.
• Diagnosis of renal infarction may be established by vascular imaging with MR, CT angiography, or arteriography
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•Options for interventions of newly detected arterial occlusion:• surgical reconstruction, anticoagulation, thrombolytic
therapy, endovascular procedures, & supportive care (antihypertensive therapy)
•Depends upon the patient's overall condition, precipitating factors, magnitude of renal tissue & function at risk, & likelihood of recurrent events in the future
•Depending upon the precipitating event, surgical or thrombolytic therapies can sometimes restore kidney viability.
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Malignant HTN• rapidly progressive BP elevations w/ target organ injury
(retinal hemorrhages, encephalopathy, & declining kidney function)
• If untreated, pts w/ target organ injury (papilledema & declining kidney function) mortality rates >50% over 6–12 months "malignant"
•Pathology: “fibroid necrosis” & “onionskin” lesion
•most common in patients w/ treated hypertension that neglect to take meds, or who use vasospastic drugs (cocaine)
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• Labs: rising serum creatinine, occ’lly hematuria & proteinuria, evidence of hemolysis (anemia, schistocytes, reticulocytosis) & changes associated w/ kidney failure
•African-American males are more likely affected•Genetic polymorphisms (MYH9) predispose to subtle
focal sclerosing glomerular disease
•Antihypertensive therapy: mainstay of Tx•effective BP reduction manifestations of vascular
injury including microangiopathic hemolysis & renal dysfunction can improve over time
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Hypertensive Nephrosclerosis•Term used for a large portion of pts reaching ESRD w/o a
specific etiologic diagnosis
•Pathology: afferent arteriolar thickening w/ deposition of homogeneous eosinophilic material (hyaline arteriolosclerosis) asso w/ narrowing of vascular lumina
•Clinical manifestations: retinal vessel changes asso w/ HTN (arteriolar narrowing, crossing changes), LVH & elevated BP
•Antihypertensive therapy does NOT alter the course of kidney dysfunction
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Thrombotic Microangiopathy (TMA)• refers to injured endothelial cells that are thickened,
swollen, or detached mainly from arterioles & capillaries
•partial or complete occlusion by platelet & hyaline thrombi integral to the histopathology
•histologic result of microangiopathic hemolytic anemia (MAHA) consumes platelets & RBCs, characterized by thrombocytopenia and schistocytes
•Kidneys characterized by swelling of the endocapillary cells (endotheliosis), fibrin thrombi, platelet plugs, arterial intimal fibrosis, & membranoproliferative changes
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Hemolytic-Uremic Syndrome (HUS)•4 variants
•D+ HUS•most common variant •associated w/ bacterial gastroenteritis•affects young children (<5 years)•>80% are preceded w/in a week by diarrhea (bloody)•GI symptoms: abdominal pain, cramping, & vomiting•Fever is ABSENT. •Neurologic symptoms are common (lethargy,
encephalopathy, seizures, even cerebral infarction) •pathogenic agent: shiga toxin/verotoxin (E.coli &
Shigella dysenteriae)
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•STEC strain 0157:H7: most common shiga-toxigenic E. coli in US & Europe• shiga toxin enters the circulation binds to PMNs &
preferentially localizes in the kidney damages endothelial cells results in platelet aggregation initiates microangiopathic process
Streptococcus pneumoniae•another bacterium associated w/ HUS•produces neuraminidase cleaves N-acetyl neuraminic
acid moieties that cover the Thomsen-Friedenreich antigen on platelets & endothelial cells•Exposure of this normally cryptic antigen to preformed
IgM results in severe MAHA.
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Atypical HUS (aHUS) • caused by congenital complement dysregulation• low C3 levels (characteristic of alternative pathway activation) •most common cause: deficiency of factor H• Factor H competes with factor B prevent formation of C3b,Bb &
acts as cofactor for factor I degrades C3b
Deficient for CHFR protein and factor H autoantibody–positive (DEAP) HUS • autoantibody is formed against factor H• deletion of 84-kb fragment of chromosome encoding for CFHR1 &
CFHR3• autoantibody blocks binding of factor H to C3b & surface-bound C3
convertase
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Thrombotic Thrombocytopenic Purpura (TTP) • pentad (hemolytic anemia, thrombocytopenia, neurologic
symptoms, fever, & renal failure)• Classic TTP is differentiated from HUS by neurologic involvement. • absence or marked decreased activity in ADAMTS13 specific for
vWF (not universally present)• Even complete absence of ADAMTS13 alone does not produce
TTP. • initiated by additional trigger (infection, surgery, pancreatitis, or
pregnancy) •median age: 40 years• Higher frequency among blacks (incidence >9x higher)•Women: 3x incidence • Untreated TTP mortality rate >90%
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Acquired or Idiopathic TTP•Classic form•usually follows an infection, malignancy, or intense
inflammatory reaction (pancreatitis)•occurs w/ ADAMTS13 deficiency or its activity • result of an autoantibody(IgG or IgM) increase
clearance of ADAMTS13 or inhibit its activity
Upshaw-Schulman •hereditary form w/ congenital deficiency of ADAMTS13 • characterized by MAHA & thrombocytopenia• can start in the 1st weeks of life
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Drug-induced TTP/TMA• complication of chemotherapeutic agents, immunosuppressive
agents, antiplatelet agents, & quinine • 2 mechanisms are responsible for drug-induced TMA• Endothelial damage dose-dependent
chemotherapeutic agents (mitomycin C, gemcitabine, etc.) & immunosuppressive agents (cyclosporine, tacrolimus, sirolimus)
• Induction of autoantibodies• Ticlopidine Suppress ADAMTS13 activity form autoantibody • Quinine autoantibodies against granulocytes, lymphocytes,
endothelial cells & platelet glycoprotein IbB/IX or IIb/IIIa complexes• Common in women
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Treatment…•Autoantibody-mediated TTP & DEAP HUS: plasma exchange or
plasmapheresis (remove autoantibodies & replaces ADAMTS13) • Congenital TTP: Plasma infusion• Plasma exchange if larger volumes of plasma are needed
• TTP due to drug-induced autoantibodies responds well to plasma exchange (drugs that cause endothelial damage may not)•D+ HUS: supportive measures (Plasma exchange is not
effective)• aHUS: plasma infusion/exchange may be beneficial•Neuraminidase-associated HUS: Antibiotics & washed RBCs. • Plasma & WB should be avoided contain IgM w/c would
exacerbate the MAHA
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Transplantation-Associated Thrombotic Microangiopathy (Ta-Tma)• develop after hematopoietic stem cell transplantation (HSCT)
8.2% • Etiologic factors :conditioning regimens, immunosuppression,
infections, & graft-versus-host disease• Other risk factors: female sex, age, & HLA-mismatched donor grafts• occurs w/in first 100 days after HSCT• high mortality rate (75% in 3 months)• Plasma exchange is beneficial in <50% • Calciuria inhibitors should be discontinued & substitute w/
daclizumab [antibody to IL-2receptor] • Rituximab & defibrotide may be helpful
• . Table 286-3 lists definitions of TA-TMA currently used for clinical trials. A firm diagnosis may be difficult because thrombocytopenia, anemia, and renal insufficiency are common in the posttransplant period.
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HIV-Related Tma
•seen in advanced AIDS & low CD4 count•Occasionally the 1st manifestation of HIV infection•(+) MAHA thrombocytopenia & renal failure are suggestive •Renal biopsy is required to establish the diagnosis •median platelet count: 77,000/L (10,000 to 160,000/L) •CMV coinfection may be a risk factor
•Tx: Plasma exchange + antiviral therapy
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Radiation Nephropathy
•kidney 1 of the most radiosensitive organs• injury can result w/ as little as 4–5 Gy exposure •characterized by renal insufficiency, proteinuria & HTN•usually presenting >6 months after radiation
•Renal biopsy classic TMA in the kidney w/ damage to glomerular, tubular, & vascular cells
•Tx: No specific therapy is available
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Scleroderma (Progressive Systemic Sclerosis)• affects the kidney 52% of subjects on follow-up [19%=
scleroderma renal crisis (SRC)]
• SRC • occurs in diffuse systemic sclerosis (12% vs. 2% in limited systemic
sclerosis)•most severe manifestation• characterized by accelerated HTN, rapid decline in renal function,
nephrotic proteinuria, & hematuria • Retinopathy & encephalopathy may accompany HTN• Salt & water retention w/ microvascular injury can lead to
pulmonary edema. • Other manifestations: myocarditis, pericarditis & arrhythmias
poor prognosis.
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• Renal lesion in SRC: arcuate artery intimal & medial proliferation w/ luminal narrowing onionskinning Histologically indistinguishable from malignant HTN Fibrinoid necrosis & thrombosis: common
•Mortality rate: 30% at 3 years• 2/3 w/ SRC require dialysis [1/2 will recover renal function
(median time = 1 year)]•Anti-U3-RNP: identify young patients at risk for SRC •Anticentromere antibody (ACA): (-) predictor of SRC• Renal biopsy recommended for atypical renal involvement
(esp. if HTN is absent)
• TX: ACE inhibition 1st-line therapy •Goal: reduce systolic BP by 20 mmHg & diastolic by 10
mmHg q24 hours until BP is normal
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Antiphospholipid Syndrome (Aps)
•vascular compartment w/in the kidney: main site of renal involvement •Arteriosclerosis in the arcuate & intralobular arteries are
common• In intralobular arteries (+) fibrous intimal hyperplasia
(intimal thickening sec. to intense myofibroblastic intimal cellular proliferation w/ extracellular matrix deposition) + onionskinning
•Renal biopsy: (+) TMA but (-) signs of MAHA & platelet consumption •TMA is especially common in catastrophic variant of APS
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•Can involve large vessels•Renal vein thrombosis can occur (suspected in pts w/
lupus anticoagulant LA + nephrotic range proteinuria) •Can progress to ESRD •Hypertension is common
•Treatment (APS):lifelong anticoagulationGlucocorticoids may be beneficial in accelerated HTNImmunosuppression & plasma exchange: helpful for
catastrophic episodes (but do not reduce recurrent thrombosis
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HELLP Syndrome•hemolysis, elevated liver enzymes, low platelets •dangerous complication of pregnancy (0.5–0.9% of all
pregnancies; 10–20% w/ severe preeclampsia)•mortality rate: b/n 7.4 & 34%•3rd trimester, 10% before week 27 & 30% postpartum•nearly 20% are not preceded by preeclampsia•Renal failure in 1/2 of patients (etiology is not well
understood)•Renal histo findings= TMA w/ endothelial cell swelling &
occlusion of capillary lumens ; (-) luminal thrombi • shares many features w/ other forms of MAHA •both aHUS & TTP flares can be triggered by pregnancy•Aps patients have a higher risk for HELLP
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Diagnosis…•A history of MAHA episodes before pregnancy is
helpful. •Reduced serum levels of ADAMTS13 (30–60%) •Some suggest LDH to AST ratio for diagnosis•Antithrombin III decreased in HELLP but not in TTP•d-dimer elevated in HELLP but not in TTP
Treatment…Glucocorticoids may decrease inflammatory markersPlasma exchange: considered if hemolysis is refractory
to glucocorticoids &/or delivery (esp if TTP is not ruled out)
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Sickle Cell Nephropathy• result from occlusion of vasa recta in the renal medulla• The low partial pressure of oxygen and high osmolarity predispose
to hemoglobin S polymerization & RBC sickling.
• Sequelae hyposthenuria, hematuria, & papillary necrosis • Kidney’s response: increase blood flow & GFR mediated by
prostaglandins• SCD pts have greater GFR reduction by NSAIDS
• (+) enlarged glomeruli• Intracapillary fragmentation and phagocytosis of sickled
erythrocytes responsible for membranoproliferative glomerulonephritis-like lesion• (+) Proteinuria (20–30%)
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•ACE inhibitors reduce proteinuria ((data lacks on prevention of renal failure)•SCD pts are more prone to acute renal failure•The cause reflects microvascular occlusion asso w/ nontraumatic rhabdomyolysis, high fever, infection, & generalized sickling
•(+) Chronic kidney disease in 12–20% •HTN is uncommon
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Renal Vein Thrombosis (RVT)•May present w/ flank pain, tenderness, hematuria, rapid
decline in renal function, & proteinuria OR it can be silent• Left renal vein is more common; 2/3 are bilateral• Etiologies divided into 3 broad categories:
endothelial damage - Homocystinuria, endovascular intervention, & surgery
venous stasis - dehydration- compression & kinking renal veins from retroperitoneal processes {retroperitoneal fibrosis & abdominal neoplasms}
hypercoagulable states - Aps, proteins C & S, antithrombin deficiency, factor V Leiden, disseminated malignancy, & OCPs
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•Diagnostic screening: Doppler ultrasound (more sensitive than UTZ alone) •CT angiography: most sensitive test (nearly 100%
sensitive)•MR angiography: more expensive & requires sedation in
pedia pts.
Treatment…•Anticoagulation & tx for the underlying cause•Endovascular thrombolysis: severe cases•Nephrectomy: life-threatening complications•Vena caval filters: prevent migration of the thrombi