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Emergency Management of Massive Pulmonary Embolism

Autopsy Image: Massive PE

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1. Definition and Classification

• Systolic BP < 90 mmHg sustained for ≥15 minutes not attributable to dysrhythmia or other cause
• A drop in baseline SBP of >40 mmHg
• Requirement for vasopressors
• Profound bradycardia (<40 bpm)

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2. Pathophysiology of Hemodynamic Collapse

1. Acute RV dilation - the RV distends toward the interventricular septum ("D-sign")
2. Septal bowing - this reduces LV filling volume and cardiac output
3. Myocardial ischemia - RV wall tension compresses coronary perfusion; septal tension on the AV node may produce agonal rhythms
4. PEA arrest - the most common cardiac arrest rhythm in PE (>20 depolarizations/min without palpable pulses)

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3. Immediate Resuscitation Priorities

A. Airway and Oxygenation

• Supplemental oxygen targeting SpO₂ >90% to prevent hypoxic pulmonary vasoconstriction (which worsens acute pulmonary hypertension)
• Avoid intubation whenever possible - positive-pressure ventilation increases intrathoracic pressure, reduces preload, and can precipitate complete hemodynamic collapse in severe PE
• When intubation is unavoidable, optimize hemodynamics with vasopressors before induction

B. Hemodynamic Resuscitation

• Cautious fluid resuscitation: small boluses (250-500 mL) may improve cardiac output, but aggressive fluid loading worsens RV distension and further compresses the LV - use with restraint
• Vasopressors: norepinephrine is the first-line vasopressor for hemodynamic support
• Dobutamine: useful adjunct for RV support, but may worsen hypotension unless co-administered with norepinephrine

C. Anticoagulation

• Initiate IV unfractionated heparin (UFH) immediately in all suspected massive PE - UFH is preferred when thrombolysis or surgical intervention is being considered (short half-life allows rapid reversal)
• Do not delay anticoagulation while awaiting imaging in hemodynamically unstable patients with high clinical suspicion

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4. Definitive Treatment: Reperfusion

Management Flowchart

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4a. Systemic Thrombolysis (First-Line for Massive PE)

Absolute Contraindications to Thrombolysis:

1. GI bleeding within the previous 30 days
2. Active hemorrhage (intraperitoneal, retroperitoneal, pulmonary, uterine, bladder, nasal)
3. Recent intracranial surgery or head trauma
4. Intracranial neoplasm or brain metastasis
5. History of hemorrhagic stroke
6. Aortic dissection
7. Liver failure (INR >1.7)
8. Surgery requiring opening of the chest, peritoneum, skull, or spinal canal within the previous 14 days
9. Subacute bacterial endocarditis under treatment
10. Pregnancy
11. Large pericardial effusion

Relative Contraindications:

• Age >75 years; dementia
• Surgery 30-60 days prior; any prior stroke
• Symptoms suggesting TIA in past 30 days
• Any prior GI bleeding; concurrent thienopyridine use (e.g., clopidogrel)
• INR >1.7 from warfarin; metastatic cancer
• Recent fracture, head strike, hematuria, dental extraction, or orthopedic surgery

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4b. Catheter-Directed Thrombolysis (CDT)

• Relative contraindications to systemic thrombolysis
• Intermediate-high risk PE requiring advanced intervention
• Failed systemic thrombolysis

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4c. Surgical Embolectomy

• Massive PE with absolute contraindications to thrombolysis
• Failed thrombolysis with persistent hemodynamic compromise
• Presence of intracardiac thrombus or patent foramen ovale (PFO) with paradoxical embolism risk

• Placing an IVC filter before surgery in stable patients reduces operative mortality
• Prior thrombolytic administration does not absolutely preclude surgery - patients can undergo sternotomy after thrombolytics and survive without fatal hemorrhage, but this decision rests with the cardiothoracic surgeon

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4d. Percutaneous Mechanical Thrombectomy (Aspiration/Fragmentation)

• Aspiration thrombectomy (e.g., FlowTriever, Indigo system)
• Ultrasound-assisted CDT

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4e. Extracorporeal Membrane Oxygenation (ECMO)

• A bridge to definitive therapy (CDT, surgical embolectomy, or catheter thrombectomy)
• A rescue strategy for refractory hemodynamic instability despite all other interventions

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5. Pulmonary Embolism Response Teams (PERT)

• ~60% of PERT activations originate in the ED
• PERTs facilitate access to advanced therapies (CDT, surgery, ECMO) and reduce disposition times
• Current guidelines recommend PERT activation for all intermediate-high and high-risk PE patients
• Activate PERT early - do not wait for hemodynamic deterioration to call for help

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6. IVC Filters

• Confirmed PE with an absolute contraindication to anticoagulation (e.g., recent cerebral hemorrhage, large cerebral infarction, brain metastases)
• Central PE in a patient unlikely to survive embolization of a proximal (iliofemoral) mobile DVT

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7. Cardiac Arrest Management in PE

• PEA is the most common arrest rhythm
• If PE is suspected as the cause of PEA, give empirical thrombolysis (alteplase 50 mg IV bolus)
• Continue CPR for at least 60-90 minutes after thrombolytic administration before considering cessation - thrombolytics take time to work
• If available, ECPR/VA-ECMO should be deployed during or after resuscitation

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8. Summary of Priorities

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Recent Evidence Updates (2023-2026)

• ACR Appropriateness Criteria 2025 (PMID 41193046) and 2025 ESVM Guidelines (PMID 40587333) both support catheter-directed interventions as valid alternatives to systemic thrombolysis in high-risk PE, particularly when bleeding risk is elevated.
• A 2025 meta-analysis (Choksi et al., PMID 39365670) found that aspiration thrombectomy and ultrasound-accelerated thrombolysis had comparable safety and efficacy - supporting the role of catheter-based strategies alongside traditional thrombolysis.
• The trend in 2024-2026 guidelines is toward earlier PERT activation and more individualized decisions using catheter-based therapy, rather than defaulting to systemic thrombolysis for all massive PE patients.

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Interpretation of General Urinalysis in Renal Pathology

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PART 1 — MACROSCOPIC ASSESSMENT

1a. Urine Color

1b. Urine Odor

• Ammonia: bacterial infection (urease-producing organisms)
• Fruity/sweet: ketonuria (DKA, starvation)
• Mousy: phenylketonuria
• Maple syrup: maple syrup urine disease
• Fishy: hypermethioninemia; trimethylaminuria

1c. Turbidity/Clarity

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PART 2 — DIPSTICK (CHEMICAL) ANALYSIS

2a. Specific Gravity (SG) and Osmolality

• Normal SG: 1.003-1.030
• SG of 1.001-1.003 = isosthenuria (inability to concentrate) - seen in chronic kidney disease (CKD), diabetes insipidus
• SG 1.008-1.010 = isosthenuric range (equal to plasma osmolality ~280 mOsmol/kg)
• High SG (>1.020): dehydration, prerenal azotemia, SIADH, glucosuria (glucose adds to weight but not ionic strength, causing discrepancy between dipstick and refractometry)
• Fixed SG of 1.010: loss of tubular concentrating and diluting ability; hallmark of end-stage renal disease

Osmolality is the gold standard for concentration. Urine SG rises ~0.001 per 35-40 mOsmol/kg increase in osmolality. SG ≤1.003 by refractometry always indicates maximally dilute urine (≤100 mOsmol/kg).

2b. Urine pH

• Normal range: 4.5 to 7.8
• Alkaline urine (>7.0): infection with urease-producing organisms (Proteus mirabilis, Ureaplasma), renal tubular acidosis type I (distal), metabolic alkalosis
• Acidic urine (<5.5): metabolic acidosis, uric acid crystals/stones
• Persistently alkaline despite systemic acidosis: distal RTA (inability to acidify urine below pH 5.5)

2c. Protein

• Normal: <150 mg/day of total protein; <30 mg/day of albumin
• Dipstick detects: primarily albumin; threshold ~200-300 mg/L (trace = 15-30 mg/dL)
• Dipstick can be falsely positive with: concentrated urine, alkaline pH, hematuria, antiseptic contamination
• Dipstick can be falsely negative for: low-molecular-weight (LMW) proteins (light chains in myeloma, β2-microglobulin in tubular disease)

Albuminuria is now a KDIGO criterion for CKD staging and is a stronger predictor of progression to ESKD and cardiovascular mortality than eGFR alone.

2d. Glucose (Glucosuria)

• Normally absent (glucose is fully reabsorbed by SGLT2 in the proximal tubule)
• With normal blood glucose (euglycemic glucosuria): proximal tubule defect - Fanconi syndrome, SGLT2 inhibitor therapy, hereditary renal glucosuria
• With hyperglycemia: exceeds tubular threshold (~180 mg/dL) - diabetes mellitus
• Clinical pearl: glucosuria in the absence of hyperglycemia is a key finding of Fanconi syndrome (tubular dysfunction)

2e. Blood / Hemoglobin

• Positive dipstick + RBCs on microscopy = true hematuria
• Positive dipstick + no RBCs = hemoglobinuria or myoglobinuria
• False positives: myoglobin, oxidizing agents, bacterial peroxidase, povidone-iodine
• False negatives: high vitamin C concentration

2f. Leukocyte Esterase and Nitrites

• Leukocyte esterase (+): pyuria (>5 WBC/hpf); indicates infection, AIN, or glomerulonephritis
• Nitrites (+): nitrate-reducing bacteria (Gram-negatives); specific for bacterial UTI but not sensitive
• Sterile pyuria (positive leukocyte esterase, negative nitrites, negative culture): tuberculosis, AIN, interstitial nephritis, papillary necrosis, contamination

2g. Ketones

2h. Bilirubin and Urobilinogen

• Bilirubin (+): conjugated hyperbilirubinemia; hepatocellular disease or obstructive jaundice
• Urobilinogen (elevated): hepatocellular disease, hemolytic anemia

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PART 3 — URINE MICROSCOPY (SEDIMENT EXAMINATION)

Key principle: Casts are the only formed elements of urine that originate exclusively in the kidney.

3a. Red Blood Cells (Erythrocytes)

• Indicate non-glomerular bleeding: urological source (tumor, stones, cystitis, trauma, prostatitis)
• RBCs may appear crenated in hypertonic urine or as "ghost cells" in dilute urine

• Indicate glomerular origin (passage through damaged GBM causes deformation)
• Acanthocytes (G1 cells): doughnut shape with membrane blebs; most specific for glomerular hematuria
• Generally >10-80% dysmorphic RBCs (threshold varies by institution) = glomerular source
• RBC casts + dysmorphic RBCs = pathognomonic of glomerulonephritis

• Persistent microscopic hematuria (≥3 RBCs/hpf on ≥2 samples) warrants investigation
• Associated with 19.5× increased hazard for ESKD in long-term follow-up studies
• Warfarin-induced nephropathy: over-anticoagulation → glomerular RBC cast formation → tubular obstruction → AKI

3b. White Blood Cells (Leukocytes)

3c. Renal Tubular Epithelial Cells (RTECs)

• RTECs + granular casts + epithelial casts = acute tubular necrosis (ATN) - the hallmark triad
• RTECs are rarely seen in prerenal AKI (where hyaline casts predominate)
• Scoring systems based on RTEC/granular cast counts predict AKI progression, dialysis need, and death
• Decoy cells: RTECs infected with BK polyomavirus, showing characteristic ground-glass nuclei (see figure below) - important in renal transplant recipients

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PART 4 — URINARY CASTS

• Low tubular flow (stasis)
• Acidic pH
• High ionic concentration
• Increased protein load

Cast Types and Clinical Significance:

Red cell casts are ALWAYS pathologic and indicate significant glomerular pathology. (Brenner & Rector's The Kidney)

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PART 5 — CRYSTALS

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PART 6 — URINE SEDIMENT PROFILES IN SPECIFIC RENAL DISEASES

"Telescoped Sediment"

• Lupus nephritis (Class IV/V)
• IgA nephropathy with nephrotic features
• Membranoproliferative GN
• Rapidly progressive GN

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PART 7 — SUMMARY: KEY CLINICAL INTERPRETIVE PRINCIPLES

1. RBC casts - always abnormal; point to glomerular disease (GN, vasculitis, lupus)
2. Dysmorphic RBCs - glomerular bleeding; when >10-80% of RBCs are dysmorphic, suspect GN
3. RTECs + granular casts - ATN; score correlates with dialysis need and mortality
4. Leukocyte casts - AIN or pyelonephritis; sterile pyuria suggests AIN or TB
5. Fatty casts + lipiduria - nephrotic syndrome; look for Maltese cross under polarized light
6. Broad/waxy casts - advanced CKD; dialysis-level nephron loss; poor prognosis
7. High proteinuria (>3.5 g/day) + normal sediment - minimal change disease or membranous nephropathy
8. Isosthenuria (SG fixed at 1.010) - loss of tubular concentrating ability; ESKD or severe CKD
9. Glucosuria with normo-glycemia - proximal tubular dysfunction (Fanconi syndrome)
10. Cystine crystals - pathognomonic for cystinuria
11. Uric acid crystals in quantity + AKI - tumor lysis syndrome / acute urate nephropathy
12. Decoy cells in transplant recipient - BK polyomavirus nephropathy; screen with viral PCR

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"Cardiogenic Hypertension" vs. Pulmonary Hypertension

Important Clarification First

Blood Pressure (BP) = Cardiac Output (CO) × Systemic Vascular Resistance (SVR)

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Part 1: What "Cardiogenic Hypertension" Actually Means

Mechanism A: High Cardiac Output (the "Cardiogenic" / High-Output Mechanism)

"Essential hypertension developing in young adults may be initiated by an increase in cardiac output, associated with signs of overactivity of the sympathetic nervous system; the blood pressure (BP) is labile, and the heart rate is increased. Later, the BP increases further because of a rise in SVR, with return to a normal cardiac output."

"Younger individuals may present with hypertension associated with an elevated cardiac output (high-output hypertension). High-output hypertension results from volume and sodium retention by the kidney, leading to increased stroke volume and, often, with cardiac stimulation by adrenergic hyperactivity. Systemic vascular resistance is generally not increased at such earlier stages."

Mechanism B: High Systemic Vascular Resistance (the more common mechanism)

• Renal mechanisms (RAAS activation, salt retention)
• Structural vascular remodeling
• Endothelial dysfunction
• Autonomic dysregulation

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Why Is "Cardiogenic Hypertension" Not a Standard Term?

1. High-output hypertension is the preferred, more precise term
2. "Cardiogenic" usually refers to something caused by cardiac failure (e.g., cardiogenic shock = low output), so calling hypertension "cardiogenic" is terminologically confusing and potentially misleading
3. The cardiac output mechanism is just one part of how secondary hypertension is classified - the standard classification is by etiology (renovascular, endocrine, primary, etc.), not by hemodynamic mechanism

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Part 2: Pulmonary Hypertension - Definition and Classification

Hemodynamic Definition (Updated 2022 ESC/ERS Guidelines)

WHO Classification of Pulmonary Hypertension (5 Groups)

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Part 3: Key Differences - Cardiogenic (High-Output) Hypertension vs. Pulmonary Hypertension

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Part 4: The Important Overlap - Group 2 PH (Post-Capillary PH)

• In this setting, both systemic hypertension AND pulmonary hypertension may coexist - the systemic hypertension (often from elevated SVR in HFpEF) may be the original insult, and the pulmonary hypertension is a downstream consequence of left heart dysfunction
• This is the most common cause of PH encountered in clinical practice
• Distinction from Group 1 PAH is critical because:
  • Group 1 PAH requires pulmonary vasodilators
  • Group 2 PH requires treatment of the underlying left heart disease - giving pulmonary vasodilators in Group 2 can be harmful (by reducing preload, worsening LV filling)

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Summary

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Nephrogenic (Renal) Hypertension

Definition

1. Renovascular hypertension (RVH) - caused by reduced perfusion to the kidney due to renal artery disease
2. Renal parenchymal hypertension - caused by intrinsic kidney disease (CKD, glomerulonephritis, polycystic kidneys, etc.)

"Renovascular hypertension is defined as a syndrome of elevated blood pressure produced by any condition that leads to reduced perfusion of the kidneys."

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The Kidney's Central Role in Blood Pressure Regulation

1. Pressure-Natriuresis

2. The Renin-Angiotensin-Aldosterone System (RAAS)

Angiotensinogen → Angiotensin I → Angiotensin II (via ACE)
                                       ↓
                        Vasoconstriction + Aldosterone release
                                       ↓
                        Na⁺/H₂O retention → ↑ blood volume → ↑ BP

"Salt sensitivity is almost twice as frequent in patients with hypertension and is particularly common among CKD, Black persons, and the elderly... The kidney has a unique role in BP regulation. Kidney salt and water retention sufficient to increase ECF volume, blood volume, and mean circulatory filling pressure enhances venous return, cardiac output, and BP."

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Part 1: Renovascular Hypertension (RVH)

Pathogenesis - The Goldblatt Model

1. Activates the RAAS (renin → Ang II → vasoconstriction + aldosterone)
2. Activates the sympathetic nervous system
3. Impairs nitric oxide generation (loss of vasodilation)
4. Promotes endothelin release
5. Causes hypertensive microvascular injury to the kidney

"Bilateral critical renal artery stenosis is a volume-dependent form of hypertension that, unlike unilateral renal artery stenosis, can cause azotemia."

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Causes of Renovascular Hypertension

Two Main Etiologies:

• Affects middle-aged to older patients, more commonly men
• Typically involves the proximal renal artery near the ostia
• Associated with diffuse atherosclerosis (CAD, PVD, cerebrovascular disease)
• Risk factors: hypertension, diabetes, smoking, dyslipidemia, CKD
• Can be unilateral or bilateral
• Bilateral critical stenosis → flash pulmonary edema, recurrent heart failure, ischemic nephropathy

• Affects younger patients (mean onset of hypertension 44.8 years; mean diagnosis age 53.3 years)
• ~80-90% of cases occur in women
• Involves the mid and distal renal artery
• Non-inflammatory, non-atherosclerotic structural dysplasia of the arterial wall
• Associated with genetic polymorphism in PHACTR1 locus (endothelin 1 regulation)
• Risk factors: cigarette smoking, hormonal influences
• Systemic: can also affect carotid, vertebral, mesenteric arteries
• May be asymptomatic; prevalence in kidney donors: 3.8-6.6%
• Classical angiographic sign: "string of beads" (alternating stenoses and aneurysms of the mid-renal artery)

"String of Beads" - CT Angiogram Image

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Other Causes of RVH (Comprehensive Clinical Nephrology, 7e):

• Renal artery aneurysm, embolism, infarction
• Traumatic arterial occlusion
• Arteriovenous fistula
• Renal artery dissection or thrombosis
• Aortic dissection compromising renal ostium
• Page kidney (subcapsular hematoma compressing the kidney)
• Takayasu arteritis (granulomatous aortitis affecting young women)
• Neurofibromatosis
• Pheochromocytoma compressing renal artery

• Bilateral arterial stenosis or dissection
• Coarctation of the aorta
• Vasculitis involving renal arteries
• Congenital vascular anomalies

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Clinical Features - When to Suspect RVH

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Diagnosis

• Peak systolic velocity (PSV) >200-220 cm/sec and renal-aortic ratio >3.0-3.5 = >60% stenosis
• Resistive index >0.80 = intrinsic small-vessel renal disease (poor response to intervention)
• Limitations: operator-dependent, difficult in obese patients, misses accessory vessels

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Treatment

• ACEi/ARBs - target RAAS, most pathophysiologically rational; preferred in unilateral RAS with intact contralateral kidney
• Caution with ACEi/ARBs in bilateral RAS or stenosis to solitary kidney - can cause acute prerenal AKI by abolishing the Ang II-driven efferent arteriolar tone that maintains GFR
• Calcium channel blockers - effective, safe alternative
• Diuretics - useful in volume-dependent (bilateral) RVH

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Part 2: Renal Parenchymal Hypertension

Mechanisms:

Causes:

• Chronic kidney disease (CKD) of any etiology
• Glomerulonephritis (acute and chronic)
• Diabetic nephropathy
• Polycystic kidney disease (PKD)
• Reflux nephropathy / chronic pyelonephritis
• Obstructive uropathy
• Renovascular disease (overlap with RVH above)
• Renal transplant dysfunction

The CKD-Hypertension Vicious Cycle:

CKD → impaired Na⁺ excretion + RAAS activation
         ↓
     Hypertension
         ↓
 Glomerular hyperfiltration + hypertensive injury to residual nephrons
         ↓
   Further nephron loss → worsening CKD

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Part 3: Summary Comparison Table

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Key Clinical Pearls

1. Renovascular hypertension is the most common surgically correctable form of hypertension - identifying FMD in a young woman can be curative with PTA
2. ACEi/ARBs can precipitate acute kidney injury in bilateral renal artery stenosis - a rise in creatinine >30% after starting these agents warrants investigation for RAS
3. Flash pulmonary edema in a hypertensive patient without obvious cardiac cause should trigger evaluation for bilateral renal artery stenosis
4. Resistant hypertension (uncontrolled on 3+ agents) is a strong indication to screen for renovascular disease
5. Pressure natriuresis is the fundamental link between kidney disease and hypertension - when damaged kidneys cannot respond to rising BP with natriuresis, a new equilibrium is set at a higher BP
6. Salt restriction and diuretics are especially effective in renal parenchymal hypertension because of the volume-dependent component

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