Sandbox: Bronchiolitis DD

Bronchiolitis should be differentiated with other diseases that cause cough and dysnea.

Diseases	Symptoms			Signs				Diagosis
	Fever	Cough	Chest pain	Wheezes	Crackles	Edema	Tachycardia	Lab tests	Imaging
Bronchiolitis	+/-	Dry	-	+	+	-	+/-	No specific lab findings Viral tests like ELISA and immunoassays may be done in case of RSV infection. Pulmonary function test is performed to exclude other lung diseases.	Ct scan shows Intense bronchiolar mural inflammation of cellular bronchiolitis results in centrilobular nodules that are usually associated with the tree-in-bud pattern and bronchial wall thickening
Asthma	-	Dry/Productive	-	+	-	+ Pulmonary edema	-	Lab tests are not specific for asthma but they are performed to exclude other diseases. Serum examination shows elevated level of esoinophils due to allergy.	CT scan shows dilated bronchi, bronchial wall thickening and air trapping.
COPD	+	Productive	-	+	+	+	+	Spirometry: FEV1/FVC < 70% Atrial blood gases: hypoxemia and hypercapnia Sputum culture	EKG may show P pulmonale, right ventricular hypertrophy and low QRS. CT scan is more sensitive in diagnosing COPD than X ray.
Bacterial pneumonia	+	Productive	+	+	+	-	+/-	Diagnosis depends mainly on the presentation and physical examination. Laboratory tests: arterial blood gases may show hypoxia and acidosis. Sputum culture.	X ray is performed to detect pleural effusion and inflitrates within the lungs. CT scan shows consolidation and ground glass appearance.
Pulmonary embolism	+/-	Bloody	+	+	+	+	+	D-dimer level test is performed to rule out other diseases like DVT. Routine blood tests are non specific. Hypercoagulability tests are performed in patients with unprovoked venous thrombosis at an early age (< 40 years) and family history of VTE syndromes. Arterial blood gases show the following: Hypoxemia Hypocapnia Respiratory alkalosis Increased alveolar-arterial gradient	CT pulmonary angiography is the gold standard imaging to diagnose the pulmonary embolism. It shows the following: Acute:Centrally located thrombus or occluding the vessel. Chronic:Eccentric changes in the vessel wall, recanalization in the thrombous and arterial web. EKG is not specific or sensitive in PE diagnosis but it may show T wave inversion, P pulmonale and sinus tachycardia. Chest X ray is performed to exclude other differentials.
Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia	-	Dry	-	+	-	-	-	Pulmonary function test shows obstructive lung disease	CT scan shows multiple nodules , ground glass appearance and bronchiectasis.
Tuberculosis	+	Bloody	+	-	-	+	-	Sputum culture: three successive positive culture for M. tuberculosis confirms the diagnosis. The presence of acid fast bacilli in sputum smear indicates to high extent tuberculosis.	Chest X ray is an important diagnostic imaging procedure in TB diagnosis. It shows the following: Parenchymal infilration Hilar adnopathy Nodules pleural effusion CT scan shows the following: Micronodules Cavitation Consolidation Interlobular septal thickening EKG may have abnormalities in case pleural effussion associated with TB.
Interstitial pneumonitis (Hamman - Rich syndrome)	+	Productive	-	-	+	-	-	Arterial blood gases: hypoxemia and PaO2/FiO2 less than 200 mmHg which indicates acute respiratory distress syndrome. Other lab tests are non specific and usually used to exclude other diseases.	Chest X ray shows bilateral airway opacification. CT scan shows ground glass appearance. Bronchoscopy may be performed to exclude other causes like alveolar hemorrhage and lymphoma. Lung biopsy is a last step in diagnosis of acute interstitial pnemonitis in order to confirm the disease and exclude other causes of ARDS.
Foreign body aspiration	+	Bloody	+	+	-	-	-	Lab tests are not specific. They are performed to evaluate the ventilation function.	Chest X ray shows hyperinflation, mediastinal shift and atelectasis.
Pertussis	+	Dry		-	-	-	-	Nasopharyngeal swab for PCR testing. Sputum culture Serology to detect pertussis toxin.	No remarkable imaging findings.
Congestive heart failure	-	Dry/Productive	+ while walking	-	-	+	+	Routine lab tests in order to know the cause of the heart failure: Renal function tests including urinalysis and electrolytes assessment Complete blood count Thyroid studies specially in patients who are being treated with concomitant therapy with an agent such as amiodarone. Biomarkers: Natriuretic Peptides: BNP or NT-proBNP Biomarkers of myocardial Injury: Cardiac Troponin T or I Carbohydrate Antigen 125	EKG can be performed to detect the underlaying cause. Chest x ray shows cardiomegaly. Echocardiography is used to determine the stroke volume and to assess the heart failure.

Differential diagnosis of bronchiolitis: Asthma, COPD, sarcoidosis, pneumonia, heart failure, DIPNECH, foreign body inhalation, pulmonary embolism and GERD (in case it is associated with asthma).