How accurate are us for blood clot? Came back negative. Said I have sciatica, does the cause soreness behind the knee and calf to? Thanks

Accurate. Us dopplers and venous duplex scans are accurate to diagnose vascular issues, including blood clots and dvt's, etc. Assuming you had some sort of other x-ray that diagnosed a sciatic nerve impingement issue, that condition can certainly cause your symptoms as the sciatic nerve innervates those areas. Best wishes.
Pretty accurate. Ultrasound is usually very accurate in diagnosing a deep vein thrombosis, sciatica can certainly cause pain that radiates down the leg and into the calf.
Symptom Vs Cause. Sciatica is the symptom of leg pain caused by a disc herniation or narrowing where the nerve exits the spine. A disc herniation is a outpouching of the disc from its normal place into the spinal canal or on the nerve and can be a source of pain in the back or down the leg or even the groin area. The nerve then goes to the muscle which can then hurt, spasm or feel sore or irritated.