Emergency Medicine Forum

A 37 y/o male presents for a prescription refill.  He was in the ED last week for vague leg pain, was given Vicoden for pain, and now returns for a refill of his pain medication as his leg is still hurting him.  He denies any trauma, and notes the leg began to bother him about 10 days ago, and hasn’t improved.  The pain is described all over, not worse in any one place, better with Vicoden, worse when he stands for too long.   When he was in the ED, he had an x-ray and an ultrasound done.  He doesn’t have any insurance, so he has not made a follow-up appointment.

PMH:  Struck by a car 8 years ago and subsequent femur fracture with open repair. 
Social history:  Recovered alcoholic, lives in basement of friend’s home, unemployed. Non-smoker
ROS:  No fevers, chest pain, shortness of breath, abdominal pain, vomiting, bowel or bladder problems, rashes.  
PE:  Appears older than stated age. Rest of exam unremarkable except R. leg.
R.leg:  Scar present lateral thigh, +1 pretibial pitting edema.  Entire R. leg swollen compared to left (although patient notes leg is always swollen some after accident, he thinks the swelling is worse). 
Pulses normal, normal capillary refill, R. calf 3 cm greater compared to L.leg.
Normal motor and sensory exam, no point boney tenderness.  On palpation, diffuse tenderness to entire leg (not localized to venous system).  ROM of leg normal.  No significant swelling or edema noted on left leg.
Review of last ED visit:  X-ray: no acute abnormality, hardware in femur unchanged.
Ultrasound of leg: No DVT.

Questions:

1. What is his Wells score?

The Wells score is a prospectively validated clinical prediction rule which estimates the pre-test probability of a DVT.  It involves both historical  (for example, history of active cancer (treatment within 6 months)) and physical exam findings.  (1,2) Although its impossible for me to remember all the components of the Wells score, a quick internet search brings up an online calculator.  In this patient, his score is 3, which puts him at high risk for a DVT. 

There are numerous risk factors for DVT, with the most important being a history of a previous DVT. (3)  Age is also an independent risk factor, with a 30-fold increase in incidence from age 30 to 80 yrs. Venous stasis is also important, with DVT found in 53% of stroke patients paralyzed limbs, compared to only 7% on the non-affected side. (3) Finally, malignancy is found in up to 30% of DVT patients. (3)

2. Does he need a repeat ultrasound?

Unfortunately, there is no simple correct answer to this question. But, there are several strategies available to help answer this question. 

I personally would repeat the ultrasound, as the patient is in a high risk category, and is still symptomatic. 

Another option at the initial visit for this patient considered high risk by Wells criteria, would have been to do both ultrasound and d-dimer, as suggested by the Institute for Clinical Systems Improvement Guidelines. (4) If both were negative, no further workup necessary. If D-dimer is positive, then repeat follow-up ultrasound or venography.

One cost effectiveness study (5) found the following algorithm most helpful: Discharge patients with low or intermediate Wells score and negative D-dimer, and ultrasound those with high score or positive D-dimer, and repeat scanning for those with positive D-dimer and high Wells score but negative initial scan.

 
3. What is the difference between heparin and a Low-Molecular-Weight Heparin (LMWH) like Enoxaparin?

Both heparin and LMWH bind to antithrombin III, activating it. The activated antithrombin III then inactivates thrombin and factor Xa (which normally promote blood clotting). LMWH is obtained from heparin, but is much smaller.  LMWH is only 1000-10,000 daltons, compared to heparin which is 5000-30000 daltons. (6) With LMWH there is less risk of heparin induced thrombocytopenia, or heparin induced osteoporosis. (6)
Outcome:

Patient had repeat ultrasound performed, and the result was positive. He was admitted to the hospital for anticoagulation as he was not considered a reliable candidate for outpatient initiation of anticoagulation.

References:

1. Wells PS, Anderson DR, Bormanis J, Guy F, Mitchell M, Gray L, et al. Value of Assessment of Pretest Probability of Deep-Vein Thrombosis in Clinical Management. Lancet 1997;350:1796. Abstract accessed at: http://www.ncbi.nlm.nih.gov/pubmed/9428249
2. Well’s Criteria for DVT by MD Calculator, accessed at: http://www.mdcalc.com/wells-criteria-for-dvt
3. Kaushal P, Rowe VL  Deep Venous Thrombosis.  MEdscape, Jan21, 2011.  Accessed at: http://emedicine.medscape.com/article/462390-overview
4. Ramzi DW, Leeper KV.  DVT and Pulmionary   Embolism:  Part 1.  Diagnosis.  Am Fam Physician 2004 Jun15;69(12):2829-36.  Entire manuscript accessed at: http://www.aafp.org/afp/2004/0615/p2829.html
5. Goodacre S, Sampson F, Stevenson M, Wailoo A, Sutton A, Thomas S, Locker T, Ryan A.  Measurement of the Clinical and Cost-Effectiveness of Non-Invasive Diagnostic Testing Strategies for Deep Vein Thrombosis.  HealthTech Assessment 2006;Vol10;15.  Entire manuscript available at: http://www.hta.ac.uk/execsumm/summ1015.htm
6. Rydberg EJ, Westfalll JM, Nicholas RA.  Low-Molecular-Weight Heparin in Preventing and Treating DVT.  AM Fam Physicina, 1999 Mar 15;59(6):1607-12.  Accessed at: http://www.aafp.org/afp/990315ap/1607.html