32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis

ABFM Family Medicine Certification Study Guide Exam

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1 Chapter 1: Exam Structure, Blueprint & Clinical Decision-Making

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7 Chapter 7: Pediatric Health Maintenance & Surveillance

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8 Chapter 8: Behavioral Health & Safety Screening

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9 Chapter 9: Adult Preventive Screening: Cardiovascular & Metabolic

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10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

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12 Chapter 12: Sexual Health, Infectious Disease Screening & Contraception

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13 Chapter 13: Reproductive Life Planning, Lactation & Preoperative Care

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14 Chapter 14: Emergent Cardiovascular Conditions

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15 Chapter 15: Cardiac Arrhythmias, Heart Failure & Hypertensive Crises

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16 Chapter 16: Vascular & Thromboembolic Emergencies

16.1 Pulmonary Embolism & Deep Vein Thrombosis 16.2 Acute Aortic Syndromes & Peripheral Vascular Emergencies 16.3 Critical Limb Ischemia & Acute Arterial Occlusion

17 Chapter 17: Neurologic Emergencies: Stroke & Altered Consciousness

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18 Chapter 18: Neurologic Trauma & Acute Cranial Emergencies

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19 Chapter 19: Acute Abdominal, Pelvic & Gastrointestinal Emergencies

19.1 Acute Abdominal & Pelvic Pain Triage 19.2 Upper & Lower Gastrointestinal Bleeding 19.3 Acute Hepatic Failure, Cholangitis & Severe Jaundice

20 Chapter 20: Acute Pulmonary & Airway Emergencies

20.1 Acute Hypoxic Respiratory Failure & ARDS 20.2 Severe Community-Acquired Pneumonia & Empyema 20.3 Acute Severe Epistaxis & Airway Obstruction

21 Chapter 21: Acute Traumatic Injuries & Wound Care

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22 Chapter 22: Acute Orthopedic & Musculoskeletal Emergencies

22.1 Acute Ambulatory Fractures & Initial Splinting 22.2 Compartment Syndrome & Major Orthopedic Trauma 22.3 Septic Arthritis & Acute Microcrystalline Crises

23 Chapter 23: Severe Infections, Sepsis & Systemic Emergencies

23.1 Sepsis, Septic Shock & Initial Fluid Resuscitation 23.2 Necrotizing Soft Tissue Infections & Severe CNS Infections 23.3 Anaphylaxis Diagnosis, Epinephrine Dosing & Airway Protection

24 Chapter 24: Metabolic, Endocrine & Electrolyte Emergencies

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25 Chapter 25: Hematologic, Urologic & Dental Emergencies

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26 Chapter 26: Psychiatric, Behavioral & Obstetric/Gynecologic Emergencies

26.1 Suicidal Ideation, Acute Agitation & Behavioral Emergencies 26.2 Acute Physical & Sexual Assault Care 26.3 Life-Threatening Vaginal Bleeding & Ectopic Pregnancy 26.4 Environmental Heat Stroke & Severe Hypothermia

27 Chapter 27: Acute Head, Neck & Neurologic Symptoms

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28 Chapter 28: Acute Cranial Nerves, Hearing & Sensory Symptoms

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29 Chapter 29: Acute Upper Respiratory Tract Infections

29.1 Acute Viral Rhinosinusitis vs. Bacterial Rhinosinusitis 29.2 Acute Pharyngitis: Group A Streptococcus & Centor Criteria 29.3 Acute Otitis Media, Otitis Externa & Serous Effusion

30 Chapter 30: Acute Lower Respiratory Infections & Cough

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31 Chapter 31: Allergic, Nasal & Non-Infectious Pulmonary Conditions

31.1 Allergic Rhinitis & Acute Non-Anaphylactic Allergic Reactions 31.2 Acute Dyspnea in Ambulatory Care 31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

32 Chapter 32: Acute Chest, Cardiac & Vascular Symptoms

32.1 Palpitations Evaluation & Arrhythmia Triage in Primary Care 32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis 32.3 Ambulatory Hypotension & Orthostasis Evaluation

33 Chapter 33: Acute Upper Gastrointestinal Conditions

33.1 Peptic Ulcer Disease & Gastritis 33.2 Dysphagia, Esophagitis & Acute Esophageal Disorders 33.3 Acute Nausea, Vomiting & Foodborne Illness

34 Chapter 34: Acute Lower Gastrointestinal Conditions

34.1 Acute Infectious Diarrhea & Gastroenteritis 34.2 Acute Constipation & Functional Bowel Changes 34.3 Ano-Rectal Disorders: Hemorrhoids, Fissures, Abscesses & Pruritus Ani

35 Chapter 35: Inflammatory, Functional & Malabsorptive GI Disorders

35.1 Acute Flares of Inflammatory Bowel Disease 35.2 Irritable Bowel Syndrome: Diagnosis, Subtyping & Management 35.3 Celiac Disease & Malabsorption Syndromes

36 Chapter 36: Acute Abdominal, Hepatic & Biliary Disorders

36.1 Ambulatory Abdominal & Pelvic Pain Triage 36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis 36.3 Acute Liver Injury & Viral Hepatitis

37 Chapter 37: Acute Abdominal Wall, Hernias & Dental Conditions

37.1 Abdominal Wall, Inguinal & Ventral Hernias 37.2 Acute Dental Pain, Odontogenic Abscess & Aphthous Ulcers 37.3 Acute Edema: Unilateral vs. Bilateral Diagnostic Evaluation

38 Chapter 38: Acute Infectious Dermatoses

38.1 Bacterial Skin Infections: Impetigo, Cellulitis & Cutaneous Abscesses 38.2 Fungal Skin Infections: Tinea Corporis, Cruris, Pedis & Onychomycosis 38.3 Viral Cutaneous Infections: Herpes Simplex, Zoster & Molluscum Contagiosum

39 Chapter 39: Inflammatory, Allergic & Autoimmune Dermatoses

39.1 Atopic Dermatitis, Contact Dermatitis & Eczematous Flares 39.2 Non-Infectious Rashes: Urticaria, Drug Eruptions & Erythema Multiforme 39.3 Cutaneous Malignancies & Premalignant Lesions: AK, BCC, SCC & Melanoma

40 Chapter 40: Acute Shoulder, Elbow & Upper Extremity Injuries

40.1 Rotator Cuff Pathology, Tendinopathy & Shoulder Impingement 40.2 Lateral & Medial Epicondylitis, Olecranon Bursitis & Elbow Sprains 40.3 Wrist & Hand Soft-Tissue Injuries: De Quervain, TFCC & Finger Sprains

41 Chapter 41: Acute Knee, Ankle & Lower Extremity Injuries

41.1 Meniscal Tears, Ligamentous Knee Injuries & Patellofemoral Pain 41.2 Ankle Sprains, Ottawa Ankle Rules & Achilles Tendinopathy 41.3 Plantar Fasciitis, Shin Splints & Overuse Syndromes

42 Chapter 42: Acute Ambulatory Fractures & Dislocations

42.1 Distal Radius, Scaphoid & Common Upper Extremity Fractures 42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures 42.3 Joint Dislocation Management: Nursemaid's Elbow & Shoulder Subluxation

43 Chapter 43: Acute Axial Musculoskeletal Pain & Falls

43.1 Acute Low Back Pain: Red Flags, Strain & Disc Herniation 43.2 Acute Cervical Strain, Whiplash & Axial Neck Pain 43.3 Evaluation of Falls in Ambulatory & Older Patients

44 Chapter 44: Acute Inflammatory Arthropathies & Generalized Pain

44.1 Acute Inflammatory Arthritis & Spondyloarthropathies 44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes 44.3 Acute Non-Headache Pain Management Strategies

45 Chapter 45: Acute Renal, Urinary & Genitourinary Conditions

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46 Chapter 46: Acute Male Genitourinary & Prostatic Conditions

46.1 Acute Prostatitis, Epididymitis & Orchitis 46.2 Acute Scrotal Pain: Torsion vs Appendage, BPH & Male Genital Emergencies 46.3 Acute Urinary Retention & Incontinence Evaluation

47 Chapter 47: Acute Women's Health & Early Pregnancy Care

47.1 Early Pregnancy Diagnosis, Dating & Initial Complications 47.2 Abnormal Uterine Bleeding & Acute Menstrual Disorders 47.3 Premenstrual Syndrome & Premenstrual Dysphoric Disorder

48 Chapter 48: Breast Disorders, STIs & Pediatric Elimination

48.1 Palpable Breast Mass, Mastitis & Nipple Discharge 48.2 Sexually Transmitted Infections: Diagnosis, Staging & CDC Guidelines 48.3 Pediatric Enuresis & Encopresis

49 Chapter 49: Systemic Signs, Metabolic Dysregulation & Miscellaneous Infections

49.1 Acute Fever, Sepsis Screening & FUO in Primary Care 49.2 Acute Hyperglycemia & Symptomatic Hypoglycemia 49.3 Electrolyte Abnormalities: Mild-to-Moderate Disturbances 49.4 Vector-Borne, Tick-Borne & Rickettsial Illnesses

50 Chapter 50: Chronic Cardiovascular Diseases: Hypertension & Ischemia

50.1 Essential Hypertension Management: 2025 AHA/ACC Guideline & JNC Strategies 50.2 Chronic Coronary Artery Disease & Post-MI Secondary Prevention 50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

51 Chapter 51: Chronic Vascular, Valvular & Dyslipidemic Diseases

51.1 Peripheral Arterial Disease & Claudication 51.2 Chronic Valvular Heart Disease & Murmur Evaluation 51.3 Lipid Disorders & ASCVD Risk-Based Statin Therapy

52 Chapter 52: Chronic Respiratory Diseases: Asthma & COPD

52.1 Chronic Asthma Management: GINA Stepwise SMART Therapy 52.2 Chronic Obstructive Pulmonary Disease: GOLD Recommendations 52.3 Solitary Pulmonary Nodule Evaluation & Fleischner Society Criteria

53 Chapter 53: Chronic Metabolic Diseases: Diabetes Mellitus

53.1 Type 2 Diabetes Management: ADA Pharmacotherapy Algorithms 53.2 Type 1 Diabetes: Basal-Bolus Insulin, CGMs & Diabetic Complications 53.3 Diabetic Microvascular & Macrovascular Disease Surveillance

54 Chapter 54: Obesity, Nutrition & Metabolic Bone Diseases

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55 Chapter 55: Chronic Endocrine Disorders

55.1 Primary & Subclinical Hypothyroidism, Hyperthyroidism & Nodules 55.2 Adrenal Disorders: Addison's Disease & Cushing's Syndrome 55.3 Hypercalcemia, Hyperparathyroidism & Pituitary Disorders

56 Chapter 56: Chronic Kidney Disease & Venous Disorders

56.1 Chronic Kidney Disease: KDIGO Staging & Renoprotective Therapy 56.2 Chronic Venous Insufficiency, Stasis Dermatitis & Lymphedema 56.3 Chronic Electrolyte & Acid-Base Management in CKD

57 Chapter 57: Chronic Gastrointestinal & Hepatic Diseases

57.1 Gastroesophageal Reflux Disease, Barrett's Esophagus & Dyspepsia 57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension 57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

58 Chapter 58: Colorectal Surveillance & Chronic Pancreaticobiliary Care

58.1 Post-Polypectomy Colorectal Polyp Surveillance Guidelines 58.2 Chronic Pancreatitis & Exocrine Pancreatic Insufficiency 58.3 Chronic Nausea, Gastroparesis & Functional GI Disorders

59 Chapter 59: Chronic Musculoskeletal & Rheumatologic Disorders

59.1 Osteoarthritis: Hip, Knee & Hand Management 59.2 Spinal Conditions: Spinal Stenosis, Spondylolisthesis & Compression Fractures 59.3 Chronic Myopathies & Fibromyalgia Syndrome

60 Chapter 60: Chronic Neurologic & Neurodegenerative Disorders

60.1 Dementia: Alzheimer's, Vascular & Lewy Body Disease 60.2 Parkinson's Disease & Essential Tremor 60.3 Epilepsy: Chronic Antiseizure Medications & Post-Stroke Care

61 Chapter 61: Chronic Peripheral Nerves, Pain & Sensory Disorders

61.1 Diabetic & Chronic Peripheral Neuropathies 61.2 Chronic Pain Syndromes & Chronic Daily Headaches 61.3 Chronic Tinnitus, Presbycusis & Persistent Dizziness

62 Chapter 62: Chronic Psychiatric Disorders

62.1 Major Depressive Disorder & Generalized Anxiety Disorder 62.2 Bipolar Disorder: Maintenance Pharmacotherapy & Lithium Monitoring 62.3 Adult & Pediatric Attention-Deficit/Hyperactivity Disorder

63 Chapter 63: Chronic Behavioral Health & Neurodevelopmental Conditions

63.1 Chronic Behavioral Conditions: PTSD, OCD & Somatization 63.2 Autism Spectrum Disorder & Intellectual Disabilities 63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

64 Chapter 64: Chronic Substance Use Disorders & Tobacco Cessation

64.1 Alcohol Use Disorder: Pharmacotherapy & Relapse Prevention 64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction 64.3 Longitudinal Tobacco Cessation Pharmacotherapy

65 Chapter 65: Chronic Dermatologic Conditions

65.1 Acne Vulgaris, Rosacea & Seborrheic Dermatitis 65.2 Chronic Plaque Psoriasis & Biologic Therapies 65.3 Chronic Eczema, Hidradenitis Suppurativa & Cutaneous Lupus

66 Chapter 66: Chronic Reproductive, Infectious & Geriatric Special Care

66.1 Chronic Menstrual Disorders, Infertility & Sexual Dysfunction 66.2 Menopause Management & Hormone Replacement Therapy 66.3 Chronic HIV Infection Management & Primary Care Integration 66.4 Gender-Affirming Primary Care & Hormone Therapy 66.5 Advance Care Planning, Palliative Care & End-of-Life Symptom Control

67 Chapter 67: Continuity Care: Sleep, Fatigue, Cancer, Pregnancy & the Adult Preventive Visit

67.1 Chronic Insomnia & Obstructive Sleep Apnea 67.2 Chronic Malaise, Fatigue & ME/CFS 67.3 Primary Care During Cancer Treatment & Survivorship 67.4 Routine Prenatal Care & Longitudinal Pregnancy Management 67.5 The Periodic Adult Health Examination & Medicare Annual Wellness Visit

32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis

Key Takeaways Explain This Topic AI

The Wells clinical prediction rule categorizes deep vein thrombosis (DVT) probability into 'unlikely' (<2 points) or 'likely' (≥2 points); for DVT-unlikely patients, a normal high-sensitivity D-dimer safely rules out DVT without imaging, while utilizing age-adjusted D-dimer cutoffs (age × 10 µg/L for patients >50 years) significantly improves diagnostic specificity without compromising safety.

Compression venous ultrasonography (CUS) is the imaging standard for suspected DVT; in patients with high clinical suspicion (Wells score ≥2) or elevated D-dimer but an initial negative proximal CUS, a repeat proximal ultrasound must be performed in 5 to 7 days to detect potential propagating calf-vein thrombi.

Direct oral anticoagulants (DOACs) are first-line therapy for acute DVT in eligible outpatients without severe renal impairment: apixaban is dosed at 10 mg twice daily for 7 days followed by 5 mg twice daily, and rivaroxaban is dosed at 15 mg twice daily with food for 21 days followed by 20 mg once daily, obviating the need for initial parenteral heparin bridging.

Superficial venous thrombosis (SVT) requires duplex ultrasonography to rule out concomitant deep vein thrombosis (present in 15% to 25% of cases) and to precisely measure the distance of the thrombus head from the saphenofemoral junction (SFJ) or saphenopopliteal junction (SPJ).

High-risk SVT (thrombus length ≥5 cm and located within 3 to 5 cm of the SFJ or SPJ) is treated with therapeutic anticoagulation for 3 months identical to DVT; intermediate-risk SVT (≥5 cm and >3 cm from deep junctions) is managed with prophylactic-dose fondaparinux (2.5 mg subcutaneous daily) or rivaroxaban (10 mg oral daily) for 45 days based on the CALISTO and SURPRISE trials.

Last updated: September 2026

Deep Vein Thrombosis: Pathophysiology & Clinical Assessment

Deep vein thrombosis (DVT) and pulmonary embolism (PE) collectively constitute venous thromboembolism (VTE), which affects an estimated 1 to 2 per 1,000 individuals annually in the United States. DVT occurs predominantly within the deep venous system of the lower extremities, developing when factors satisfying Virchow's Triad converge: (1) venous stasis (immobilization, prolonged travel, paralysis, heart failure), (2) endothelial vascular injury (surgery, trauma, central venous catheterization), and (3) hypercoagulability (active malignancy, pregnancy, estrogen therapy, inherited thrombophilias such as Factor V Leiden, or antiphospholipid syndrome).

Clinical Presentation & Physical Exam Nuances

Symptoms : Unilateral leg pain, dull aching or heaviness that worsens with ambulation, dependent swelling, erythema, and localized warmth.

Calf Circumference Measurement : The circumference of both calves must be measured using a flexible tape measure exactly 10 cm below the tibial tuberosity . A difference greater than 3 cm between the symptomatic and asymptomatic leg is a sensitive and validated predictor of acute DVT.

Homans Sign Pitfall : Pain in the calf upon abrupt, forced passive dorsiflexion of the foot with the knee flexed ( Homans sign ) is historically notorious. Clinical studies demonstrate that Homans sign has an unacceptably low sensitivity (~30%) and specificity (~50%), and vigorous manipulation theoretically risks mechanical dislodgement of a fragile, non-adherent thrombus into the pulmonary circulation. It should never be used to confirm or exclude DVT.

The Wells Clinical Prediction Rule for DVT

Clinical examination alone is notoriously inaccurate for diagnosing DVT (diagnostic accuracy <50%). The validated Wells Clinical Prediction Rule integrates clinical risk factors to calculate pre-test probability, guiding subsequent diagnostic testing:

• Clinical Parameter Points
• Active cancer (treatment ongoing, within previous 6 months, or palliative) +1
• Paralysis, paresis, or recent plaster cast immobilization of lower extremities +1
• Recently bedridden >3 days or major surgery within past 12 weeks requiring general or regional anesthesia +1
• Localized tenderness along the distribution of the deep venous system +1
• Entire lower extremity swollen +1
• Calf swelling >3 cm compared to the asymptomatic side (measured 10 cm below tibial tuberosity) +1
• Pitting edema confined to the symptomatic leg +1
• Collateral superficial non-varicose veins (visible superficial collateral channels) +1
• Previously documented deep vein thrombosis +1
• Alternative diagnosis at least as likely as DVT (e.g., Baker cyst rupture, cellulitis, muscle tear) -2
• Clinical Probability Stratification and Diagnostic Pathways

Two-Tier Model (Recommended in Outpatient Primary Care) :

DVT Unlikely : Total Score <2 points (pre-test probability ~5% to 6%).

DVT Likely : Total Score ≥2 points (pre-test probability ~25% to 40%).

Three-Tier Model :

Low probability: 0 points (~5% risk).

Moderate probability: 1 to 2 points (~17% risk).

High probability: ≥3 points (~53% to 75% risk). WELLS CLINICAL PREDICTION ALGORITHM FOR DVT

• Calculate Wells Clinical Score
• │
• ┌──────────────────────┴──────────────────────┐
• ▼ ▼
• DVT UNLIKELY (<2) DVT LIKELY (≥2)
• │ │
• ▼ ▼
• High-Sensitivity D-Dimer Proximal Compression US
• (Apply Age-Adjusted Cutoff) (CUS) within 24 hours
• │ │ │
• ▼ ▼ ┌───────┴───────┐
• Normal Elevated ▼ ▼
• DVT Excluded! Proceed to CUS Positive Negative
• No ultrasound Ultrasound │ │
• ▼ ▼

Treat DVT High suspicion?

• Repeat CUS in 5-7d
• D-Dimer Biomarker Strategy: Standard & Age-Adjusted Thresholds

D-dimer is a degradation product of cross-linked fibrin produced during endogenous plasmin-mediated fibrinolysis. High-sensitivity D-dimer assays (quantitative ELISA or automated turbidimetric tests) exhibit an exceptional sensitivity (>95% to 98%) and negative predictive value (>99%), making a normal result invaluable for safely ruling out VTE.

Limitations and Causes of False Positives

D-dimer has notoriously poor specificity (~40% to 50%). Circulating levels increase physiologically with advancing age and pathologically during conditions characterized by tissue inflammation or fibrin deposition: pregnancy, active malignancy, recent trauma or major surgery, infection/sepsis, liver disease, and systemic rheumatologic disorders. Therefore, D-dimer testing should NEVER be ordered in patients with a high pre-test probability (Wells ≥2) , as a negative result does not reliably exclude DVT and imaging is mandatory regardless.

The Age-Adjusted D-Dimer Strategy

In patients older than 50 years, physiologic elevations in baseline D-dimer lead to excessive false-positive results, triggering costly and unnecessary ultrasonography or CT scans. The landmark ADJUST-PE study validated the age-adjusted D-dimer strategy:

Patients ≤50 years of age : Standard cutoff is 500 µg/L (or 0.5 µg/mL fibrinogen equivalent units [FEU]).

Patients >50 years of age : Age-adjusted cutoff = Patient's Age × 10 µg/L.

Example : In a 74-year-old patient with an "unlikely" Wells score, a D-dimer result of 680 µg/L is considered negative because it is below their age-adjusted threshold (74 × 10 = 740 µg/L). DVT is safely excluded without an ultrasound.

This approach increases specificity by 20% to 30% in elderly cohorts without increasing false-negative rates (three-month thromboembolic failure rate remains <0.3%).

Compression Venous Ultrasonography (CUS) Protocols

Venous duplex ultrasonography combining B-mode imaging with color and spectral Doppler is the gold-standard modality for diagnosing DVT. The single definitive diagnostic criterion for DVT is the absence of complete luminal compressibility of the venous walls under gentle, direct ultrasound transducer pressure .

Diagnostic Protocols

Proximal Compression Ultrasonography (Proximal CUS) :

Evaluates the common femoral vein at the groin, the bifurcation of the femoral and deep femoral veins, and the popliteal vein down to its trifurcation in the popliteal fossa.

Proximal CUS is rapid and highly accurate for proximal DVT (sensitivity ~95%, specificity ~98%).

Mandatory Serial Protocol : Up to 20% to 30% of symptomatic DVTs originate in the calf veins. If proximal CUS is negative in a patient categorized as DVT likely (Wells ≥2) or with an elevated D-dimer, the clinician must repeat a proximal CUS in 5 to 7 days . This detects isolated calf-vein thrombi that propagate proximally into the popliteal vein (which occurs in ~20% of untreated calf thrombi within 1 to 2 weeks).

Whole-Leg Duplex Ultrasonography :

Evaluates both the proximal veins and the deep calf veins (posterior tibial, peroneal, and anterior tibial veins).

Advantage : A single negative whole-leg scan rules out both proximal and distal DVT, eliminating the need for a repeat 5- to 7-day ultrasound.

Controversy / Management of Isolated Distal (Calf) DVT : Isolated calf DVTs have a very low risk of fatal PE (<1% to 2%). In stable outpatients without severe symptoms or risk factors for propagation, international guidelines (CHEST) permit either: (a) therapeutic anticoagulation for 3 months, OR (b) serial duplex imaging at 1 and 2 weeks to monitor for proximal extension without immediate anticoagulation.

Outpatient Direct Oral Anticoagulant (DOAC) Pharmacotherapy

The American College of Chest Physicians (CHEST) and American Society of Hematology (ASH) guidelines unequivocally recommend direct oral anticoagulants (DOACs) over low-molecular-weight heparin (LMWH) and vitamin K antagonists (warfarin) for acute lower extremity DVT in non-pregnant outpatients without severe renal dysfunction or antiphospholipid syndrome.

First-Line DOAC Monotherapy Regimens (No Parenteral Lead-In Required)

Apixaban (Eliquis) (Direct Factor Xa Inhibitor):

Loading Dose : 10 mg PO twice daily for 7 days .

Maintenance Dose : 5 mg PO twice daily thereafter.

Clinical Advantage : Lowest gastrointestinal bleeding risk among all DOACs; approved for use without parenteral bridging.

Rivaroxaban (Xarelto) (Direct Factor Xa Inhibitor):

Loading Dose : 15 mg PO twice daily WITH FOOD for 21 days .

Maintenance Dose : 20 mg PO once daily WITH FOOD thereafter.

Clinical Pearl : Doses ≥15 mg must be taken with the largest meal of the day; taking rivaroxaban on an empty stomach reduces bioavailability by 34%, risking therapeutic failure.

Alternative Regimens Requiring Initial Parenteral Anticoagulation

Dabigatran (Pradaxa) (Direct Thrombin Inhibitor): Dosed at 150 mg PO twice daily , but REQUIRES a minimum of 5 to 10 days of initial parenteral anticoagulation (e.g., enoxaparin 1 mg/kg SC q12h) before starting oral dabigatran.

Edoxaban (Savaysa) (Direct Factor Xa Inhibitor): Dosed at 60 mg PO once daily (30 mg daily if CrCl 15-50 mL/min or weight ≤60 kg), also REQUIRES ≥5 days of initial parenteral anticoagulation .

Warfarin (Coumadin) (Vitamin K Antagonist): Target INR 2.0 to 3.0 . Requires continuous bridging with LMWH or unfractionated heparin for a minimum of 5 days AND until the INR is ≥2.0 for at least 24 consecutive hours. DOAC DOSING COMPARISON FOR ACUTE DVT

DRUG INITIAL LOADING PHASE MAINTENANCE PHASE HEPARIN BRIDGE?

• ─────────────────────────────────────────────────────────────────────────────
• Apixaban 10 mg PO BID x 7 days 5 mg PO BID NO
• Rivaroxaban 15 mg PO BID x 21 days 20 mg PO Daily (with food) NO
• Dabigatran Parenteral LMWH x ≥5-10 d 150 mg PO BID YES (≥5 days)
• Edoxaban Parenteral LMWH x ≥5-10 d 60 mg PO Daily YES (≥5 days)
• Warfarin Parenteral LMWH x ≥5 d Target INR 2.0-3.0 YES (Until INR ≥2)
• Duration of Anticoagulation

Provoked DVT by a Transient Major Risk Factor (e.g., major surgery, prolonged bed rest >3 days, major trauma): Treat for exactly 3 months , then discontinue.

Unprovoked DVT or Persistent Risk Factor (e.g., active cancer, chronic medical immobilization): Treat for a minimum of 3 to 6 months, followed by indefinite extended-phase anticoagulation provided bleeding risk is acceptable.

Superficial Venous Thrombosis (SVT / Superficial Thrombophlebitis)

Superficial venous thrombosis (SVT)—frequently referred to as superficial thrombophlebitis—is an inflammatory thrombosis of a superficial vein, most frequently the great saphenous vein (GSV, ~70% to 80%) or small saphenous vein (SSV, ~15%) .

Clinical Presentation and Diagnostic Imperative

Clinical Presentation : Erythematous, indurated, exquisitely tender, warm palpable cord tracking along the anatomic path of a superficial vein. Patients may have surrounding cutaneous edema and warmth, frequently misdiagnosed as bacterial cellulitis.

Mandatory Duplex Ultrasonography : Clinical diagnosis alone is hazardous. A complete lower extremity venous duplex ultrasound must be performed in every patient with suspected SVT because:

15% to 25% of patients with clinically isolated SVT have concomitant occult deep vein thrombosis (DVT) at the time of presentation.

The ultrasound determines the exact anatomical thrombus length and its distance from deep venous junctions (saphenofemoral junction [SFJ] in the groin or saphenopopliteal junction [SPJ] in the popliteal fossa).

Risk-Stratified Management Hierarchy for SVT (High vs. Intermediate vs. Low Risk)

Evidence-based guidelines (CHEST 2021, European Society for Vascular Surgery [ESVS]) categorize SVT into three distinct tiers based on anatomical extent and proximity to the deep venous circulation:

1. High-Risk SVT (Treated as Deep Vein Thrombosis)

Criteria : Thrombus length ≥5 cm AND extending to within 3 cm (or 3 to 5 cm) of the Saphenofemoral Junction (SFJ) or Saphenopopliteal Junction (SPJ) .

Pathophysiology : Thrombus approaching within 3 cm of the junction behaves clinically like a deep vein thrombosis, carrying an imminent risk of extending across the junctional valve into the common femoral or popliteal vein and embolizing to the lungs.

Management : Full-dose therapeutic anticoagulation for 3 months (e.g., apixaban 10 mg BID x 7 days then 5 mg BID; or rivaroxaban 15 mg BID x 21 days then 20 mg daily; or therapeutic LMWH), managed identically to acute proximal DVT.

2. Intermediate-Risk SVT (Prophylactic Anticoagulation)

Criteria : Thrombus length ≥5 cm AND located greater than 3 cm away from the SFJ and SPJ , with or without underlying risk factors (prior VTE, malignancy, oral contraceptives).

Evidence Base :

The CALISTO Trial (NEJM) : 3,002 patients with acute SVT ≥5 cm and >3 cm from junctions randomized to Fondaparinux 2.5 mg SC once daily for 45 days vs. placebo. Fondaparinux produced an 85% relative risk reduction in death, DVT, and PE (0.9% vs. 5.9%, p<0.001) without increasing major bleeding.

The SURPRISE Trial : Demonstrated that oral Rivaroxaban 10 mg PO once daily for 45 days was non-inferior to subcutaneous fondaparinux 2.5 mg daily for composite symptomatic DVT, PE, and thrombus extension.

Management : Prescribe Fondaparinux 2.5 mg SC daily for 45 days OR Rivaroxaban 10 mg PO daily for 45 days .

3. Low-Risk SVT (Conservative / Non-Pharmacologic Management)

Criteria : Thrombus length <5 cm AND remote (>3 to 5 cm) from the SFJ/SPJ, or confined to isolated tributary/varicose veins.

Management :

Symptom Relief : Warm, moist compresses applied for 20 minutes 3 to 4 times daily.

Anti-Inflammatory Analgesia : Oral nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., ibuprofen 600 mg PO TID or naproxen 500 mg PO BID for 7 to 14 days) to reduce localized pain and inflammation.

Mechanical Support : Below-knee graduated compression stockings (20 to 30 mmHg).

Ambulation : Active walking is strongly encouraged; bed rest is strictly contraindicated to prevent stasis.

Follow-up : Repeat duplex ultrasound in 7 to 10 days if symptoms progress, pain worsens, or erythema extends proximally toward the groin.

Loading diagram... Clinical Decision Algorithm for Suspected DVT and SVT