Patient is an 18 year-old male with recent COVID symptoms for about 2 weeks who presented as a transfer from a small Hospital for further management of extensive DVT c/f phlegmasia cerulea dolens and early compartment syndrome. Patient started having COVID symptoms (cough, subjective fevers, muscle aches) since 9/28 (despite a negative rapid COVID test on 9/27, at that time, he received the first dose of Pfizer). Patient's mom and sister were all tested positive for COVID on the 27th. Patient had been essentially bedridden for 2-3 weeks due to his COVID symptoms. Pt. started limping and experiencing some right leg pain/soreness about a week and half ago and went to see his PCP and was given Mucinex for residual cough and Tylenol for leg pain. Three days ago, the pain migrated to the left leg and the pain was initially intermittent, then became constant 10/10 pain associated with significant swelling and "left foot turning purple and numb" which prompted the patient to go to the ED. Patient also endorses intermittent cough, dizziness, mild SOB, mild abdominal pain, dysuria and polyuria, denies any trauma or falls, chest pain, headache, fever/chils, diarrhea. Patient lives with mom, younger sister, home school, plays soccer. Vaccines are up to date.   Of note, pt. has been getting weekly and then monthly blood work at his PCP's office for a workup of his severe abdominal pain that started 4-5 months ago c/f liver & kidney disease, MRI of the abdomen was done and unremarkable. Per mom, PCP wants to have a series of labs (not sure what labs were drawn) before referring the patient bigger hospital.   At the hospital, pt. was given morphine q1h for pain, heparin bolus x2, on heparin drip 1200units/hr and mIVF. Pt. remained afebrile and hemodynamically stable, slightly tachycardia, but normotensive, no hypoxia. He has slight increase in his LFTs and a mild leukocytosis. Chest x-ray is unremarkable, EKG is nonischemic with no significant demand. Ultrasound of left lower extremity shows extensive deep venous thrombosis from groin to toe. Proximal vasculature obscured by overlying bowel gas. CTA of the chest shows bilateral basilar pulmonary emboli. Troponin was undetectable and BNP was only 25.   Hospital Course  #Cardiovascular: patient was started on heparin drip. Vascular surgery was consulted and recommended thrombectomy for his extensive DVTs in the setting of early compartment syndrome. S/P urgent Left common iliac, external iliac, femoral, and popliteal vein mechanical thrombectomy with ClotTriever system and left CFV balloon angioplasty (10/19). Due to difficulty in achieving a therapeutic anti Xa while on heparin drip, heparin drip was discontinued and patient was started on Xarelto BID PO. Hematology was consulted and they recommended baseline LFTs and chem 10 prior to starting Xarelto which came back WNL. Obtain coags including fibrinogen (normal) and D-dimer(elevated), lupus anticoagulant assay, Factor V Leiden, prothrombin gene mutation, and homocysteine levels (negative).   #Resp: Small bilateral PEs was found at OSH CTA, but pt. has been sating well and remained on RA throughout admission.   #FENGI: Pt. was made NPO with mIVF on 10/19 from the thrombectomy. Resumed regular diet afterwards  #Neuro: Pt.'s pain has been managed with morphine q2h PRN and Tylenol q6h PRN. Please avoid NSAIDs. Patient discharged with only Tylenol prn for pain.  #Hem: Hematology team was consulted and they recommended labs to rule out hypercoagulability (anti thrombin gene mutation, lupus anticoagulant assay, homocysteine, and factor V Leiden). LFTs and chem10 were checked before starting rivaroxaban and it was WNL. He should f/u with pedi heme/onc on 11/8.  #ID: rapid COVID 3 weeks ago negative. We discussed with ID the role of antibody testing to help differentiate if clot may be related to COVID versus possible vaccine-related complication. COVID nucleocapsid and PF4 antibody testing sent(pending). Patient should hold off on getting the booster. Patient worked with PT while inpatient. He is safe to go home but will need PT at home.