18  Atypical-Site Thrombosis

Key Points
  • MVT: abd pain out of proportion; CT/MRI gold standard; treat all w/ anticoagulation → improves portal recanalization.
  • CVT/CST: 1–2/100,000; 3× women (OCP, pregnancy); MRI/MRV required; anticoagulate despite intracranial event.
  • RVT: flank pain + hematuria; ~25% bilateral; nephrotic syndrome 20–30%; anticoagulation may not restore renal function.
  • Gonadal VT: postpartum >malignancy; CT (not MRI) most reliable; anticoagulate 2–3 mo.
  • Retinal VT: CRVO 1/250–1000 age >40; DM, HTN, smoking; no good evidence for anticoagulation.
  • Arterial TE <50y no atherosclerosis: r/o thrombophilia, PFO, dissection, vasculitis.

18.1 Mesenteric Vein Thrombosis

Pathophysiology & Presentation - SMV/IMV obstruction → intestinal ischemia, may extend to portal vein - Acute: abd pain > exam, N/V/D - Subacute: asymptomatic, incidental on imaging

Risk Factors - Pancreatitis, pancreatic CA - IBD - Prior PVT, JAK2 V617F, FLT3-ITD, familial thrombophilia

Diagnosis & Management - Imaging: CT w/ IV + venous phase (gold standard); MRI/MRV alternative - Anticoagulation: Mandatory—↓ recurrence & ischemia risk, ↑ portal vein recanalization - Parenteral (LMWH/UFH) → VKA or DOAC - Rivaroxaban, edoxaban, dabigatran safe in cirrhosis (Child-Pugh A/B) - Screen cirrhosis & portal HTN before starting - Duration: 2–6 mo min (longer if persistent triggers) - Alternatives: TIPS, thrombectomy if refractory

18.2 Splenic Vein Thrombosis

  • Rare, isolated form
  • Assoc w/ pancreatitis (12%), pancreatic CA
  • Often asymptomatic, incidental discovery
  • Frequently post-splenectomy (physiologic adaptation)
  • No consensus on anticoagulation (observation reasonable)

18.3 Cerebral Vein & Cerebral Sinus Thrombosis

Epidemiology & Pathophysiology - Thrombosis of cerebral veins & dural sinuses - 1–2/100,000 population; 3× women (due to OCP, pregnancy, postpartum) - Risk factors: - Thrombophilia (inherited/acquired) - OCP, pregnancy, postpartum - Head/neck surgery, transsphenoidal procedures - Recent SARS-CoV-2 (↑ mortality) - VITT (adenovirus vaccines; appears 5–30d post-vaccination) - Meds: corticosteroids, L-asparaginase, thalidomide, tranexamic acid

Diagnosis & Management - Imaging: MRI/MRV w/ contrast (gold standard) - Anticoagulation: Standard, even w/ intracranial hemorrhage - Exceptions: uncontrolled HTN, recent ICH, severe thrombocytopenia - Minimize plt transfusions (risk paradoxical clot) - Duration: Per persistent risk factors, thrombophilia workup

18.4 Renal Vein Thrombosis

Clinical Presentation & Diagnosis - Acute: flank pain, hematuria - Chronic: flank pain, ↑ Cr, ↑ LDH - Assoc w/ nephrotic syndrome (20–30%), rare spontaneous - ~25% bilateral (suggests intrinsic renal vascular disease) - Imaging: Duplex ultrasound or CT w/ venous phase (preferred)

Pathophysiology - Thrombosis often begins in renal microvasculature, extends to large vessels - Right ovarian vein most common (longer length, compression from aortocaval nodes) - RAS & renal artery compression should be r/o’d

Management - Anticoagulation: Parenteral → VKA or DOAC - Caveat: Large vessel clearance may NOT restore renal function - Duration: 2–6 mo minimum (per triggers & persistency)

18.5 Gonadal Vein Thrombosis

Pathophysiology & Risk Factors - OVT (ovaries) vs SVT (testes/spermatic cord) - Postpartum > malignancy, hormonal therapy, IBD, trauma - Postpartum triggers: C-section, forceps delivery, uterine infection, abd surgery - Complications: septic thrombophlebitis, abscess, PE, hemorrhagic infarction, DIC

Diagnosis - Contrast CT (gold standard); MRI unreliable & may miss early disease - CT w/o contrast often non-diagnostic - High clinical suspicion essential

Management - Anticoagulation: Parenteral → VKA or DOAC - Duration: 2–3 mo (per severity & triggers) - IVC filter: Consider if recurrent/threatening renal failure - Thrombolysis: For acute disease ± bilateral w/ renal failure risk

18.6 Retinal Vein Thrombosis

Types - CRVO (central): prevalence 1/250–1000 age >40; 2nd leading retinal vascular cause of vision loss (after DM) - BRVO (branch) & HRVO (hemiretinal) - Retinal artery runs w/ vein at optic disc → arterial risk factors apply

Risk Factors - DM, HTN, hyperlipidemia - Smoking (esp. young) - Presentation: sudden painless vision loss, scotoma, gray vision

Management - Ophthalmology diagnosis - No high-quality evidence for anticoagulation or antiplatelet therapy - Hypercoagulability workup: FHx, age <50, no strong atherosclerotic risk

18.7 Arterial Thromboembolism

Overview - Mostly atherosclerotic domain (not hematology focus) - Young (<50y) unexplained TE requires r/o non-atherosclerotic etiologies

Evaluation: Young (<50y) Unexplained Arterial TE - Atherosclerotic: Risk factors, prior CAD/CVA, imaging findings - Cardiac: PFO, A-fib, endocarditis, prosthetic valve - Vascular: Dissection, fibromuscular dysplasia, external compression, vasculitis - Systemic: Malignancy, myeloproliferative d/o (JAK2, MPL, CALR), antiphospholipid Ab, HIT, COVID-19/vaccination, heparin-induced thrombocytopenia

Thrombophilia Workup - Indicated: FHx, age <50, no strong atherosclerotic risk - Protein C/S/AT deficiency r/o’d - Anticoagulation benefit in young arterial TE: Unproven vs antiplatelet monotherapy

Clinical Pearls
  • MVT: Treat ALL acute/subacute w/ anticoagulation—↑ portal recanalization, ↓ ischemia regardless of bleeding.
  • CVT/CST: High suspicion women age 15–45 w/ headache + OCP/pregnancy; MRI/MRV w/ contrast mandatory; anticoagulate even w/ ICH.
  • RVT: ~25% bilateral → intrinsic renal vascular pathology; anticoagulation alone may not restore function.
  • OVT: Postpartum most common; contrast-enhanced CT required (MRI misses disease).
  • Arterial TE <50y: Always r/o PFO, dissection, vasculitis, malignancy before assuming atherosclerosis.