COPD and PE combines this with features of COPD exacerbation. Clinical for thromboembolism. Review of diagnostic laboratory and history, physical exam, and laboratory data provide the imaging studies as described above suggests an algorithm impetus for pursuing PE diagnosis. In the absence of typi- that incorporates appropriate pretest probability, laboratory cal symptoms such as productive cough, fever, or decreased studies such as D-dimer with emphasis on Doppler ultra- breath sounds diffusely, obtaining laboratory and diagnos- sonography and CT angiography over perfusion scanning. tic studies such as D-dimer, B – type natriuretic peptide, Diagnosis of PE in COPD exacerbation is diminished by troponin, and arterial blood gas may be helpful in deﬁning clinical difﬁculty, but incorporating thromboembolism into other underlying pathologies. Similarly, a nonresponse to the differential may mean improved outcomes in COPD aggressive COPD treatment with beta agonists, antibiotics, patients presenting with dyspnea and occult emboli. and steroids in patients with typical presentations supports evaluation for other causes of dyspnea. Suspicion for PE in the setting of atypical COPD exacer- bation can be divided into low, intermediate, or high pretest probabilities. Obtaining appropriate imaging beginning with assessment of serum creatinine is recommended as a ﬁrst step. Where creatinine is less than 1.5 mg/dl and suspicion is intermediate or high, direct evaluation by spiral CT or angiog- raphy is the preferred conﬁrmatory test. If there is low pretest probability, direct evaluation by spiral CT or angiography may not be appropriate, particularly if acute or chronic kidney disease precludes possibly nephrotoxic dye load. In this set- ting, lower extremity Doppler ultrasound and V/Q scanning may be helpful in establishing or ruling out diagnosis without risk of kidney injury. A low pre – test probability with a low D-dimer effectively rules out thromboembolism. Following the algorithm, high or intermediate pre – test probability and negative perfusion scanning or lower extremity Dopplers still warrants spiral CT or angiography. Often times, particularly in the setting of severe or advanced clinical picture, it may be necessary to forgo the possibility of false negative tests to obtain more deﬁnitive diagnostic imaging, so that treatment may be started in a timely fashion. Protecting the kidneys as much as possible from contrast nephropathy with standard pharmacological regimens is recommended. Again, there is little general data evaluating the preva- lence of PE in lone COPD with typical infectious features, making screening for PE on initial presentation unsupported. 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