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History of SOB
Diagnosis:Ankylosing spondylitis- bell shaped chest, fusion of costotransverse and costovertebral joints. Parallel linear densities in the upper mediastinum represent thoracic syndesmophytes. Occurs late in the course of disease, restrictive pulmonary function with a high residual functional capacity and vital capacity unlike progressive idiopathic scoliosis. "Fibrobullous" upper lobe disease is rarer occuring in approx 1% of cases after a 15-20year period.
Confirmatory imaging of the pelvis demonstrates symmetric fusion of the sacro-iliac joints.

Two different cases- two diagnoses please
Pulmonary oedema with loculated pleural fluid collections including loculations in the left major fissure.Similar appearances with soft tissue opacity in the right major fissure- however, the right hemithorax is contracted with lobular pleural thickening (see right paratracheal region). Differential diagnosis now becomes in order of likelihood: mesothelioma, metastatic adenocarcinoma, thymoma with drop mets and lymphoma. Pertinent additional findings are therfore the presence of pleural plaques (seen in 50% of mesothelioma), a mastectomy or obvious gastric mass. Right posterior rib defect is secondary to operative biopsy- confirmed metastatic adenocarcinoma of the parotid. Mesothelioma should be first choice. 

History of malaise.
Loss of clarity of the supraaortic contours with increased density and lobularity.Normal concave border of left subclavian vessels is replaced by convex border. CT confirms presence of prevascular and superior mediastinal nodes - lymphoma.

History of Haemoptysis
Two nodules are demonstrated (right and left mid-lung) with a further left retrocardiac nodule (see right highlight). Pertinent negatives include the absence of calcification and cavitation (fat being unreliably detectable on plain CXRs). General pertinent negatives are the absence of effusions, nodal enlargement or a suggested primary (e.g. mastectomy in a female). At this point the differential is enormous including:
Neoplasms (benign and malignant)
Infectious (including TB and fungal)
Non-infectious inflammatory (e.g. rheumatoid, Wegeners)
Other rarities (vascular, traumatic, etc.)

What is the best next investigation?

Not CT. Cheaper and more sensible first is prior films.
2 years earlier (see left and below).Highlights of two of the nodules demonstrate stability
By definition we are now looking at benign entities. All malignant neoplasms are essentially out as are active infectious aetiologies. We are left with a much shorter differential of hamartomas, granulomas, some fungal diseases, rheumatoid nodules, and rarities.
Now what are the stable rarities to consider?
AVMs, posttraumatic splenosis, amyloid, lipoid pneumonia.

The presence of large feeding vessels to these lesions gives us the correct diagnosis of AVMs.
AVMs are probably multiple in approximately 50% of cases, more frequently in association with Osler-Weber-Rendu syndrome, with which 90% of all pulmonary AVMs are associated. Often asymptomatic other presentations include dyspnea, paradoxical embolisation, bruits, clubbing and polycythaemia. Haemoptysis/Haemothorax are relatively rare. In infants and children in particular the left to right shunt may cause cyanosis particularly in the erect position. This phenomenon, orthodeoxia, is related to the basilar predominance of these lesions and increased physiologic flow to the lower lobes on erect repositioning. This partially explains variability in size of these lesions when repositioning or with Valsalva (smaller).

AVMs may slowly grow with age. Very rarely they will contain pathognomonic phleboliths. 

Diagnosis Please
Pinpoint high density nodules are present in the lung bases and right upper lobe peripherally. The differential for pinpoint nodules is short because normal soft tissues of this density are not sufficiently radioopaque to cause appreciable discrete nodules. Remember that granulomas, varicella etc are bigger than pinpoint. So consider:

High atomic number pneumoconiosis (e.g.stannosis (tin) or baritosis (barium) or silicosis- look for upper lobe predominance and dense septal lines)
Post lymphangiogram (not done now)
Haemosiderosis (primary: children, secondary: look for mitral valve disease)
Alveolar microlithiasis (nodules usually a little bigger, often perivascular and may be outlined by black band of pericardium or pleural edges) and
Heterotopic pulmonary calcification (hyperparathyroidism)- for which this appearance is characteristic.

On CT these nodules are subpleural and anterior. Bone isotope imaging may how diffuse pulmonary and gastric uptake even in the absence of plain film findings.

Porcelain gallbladder in same patient and calcified mesenteric nodes – postulated related to hyperparathyroidism in this patient. More characteristically an abdominal film may demonstrate nephrocalcinosis. 

The patient has bullous emphysema. In addition, a tubular density is present in the medial right lower lung. Diagnostic considerations should include a vascular malformation, a bronchocoele and in this particular location a congenital venolobar syndrome (scimitar vein). The latter is effectively excluded by the absence of right pulmonary hypoplasia, normal levocardia and a normal left hemidiaphragm. At the left base a sequestration may have multilobulated appearances. Finally do not forget a lung primary may appear lobulated - so play it safe and include it until CT confirms a genuinely tubular lesion.CT demonstrates a dilated fluid filled bronchus with peripheral branching. Appearances confirm a bronchocoele. CT may demonstrate a proximal slow growing lesion such as a carcinoid or foreign body. If the appearances are in the left upper lobe bronchial atresia becomes a realistic proposition. If there is central marked bronchiectasis consider ABPA. Even in the absence of proximal endobronchial abnormality on CT, bronchoscopic exclusion of proximal abnormality is required.

History: Cough
Multiple nodules are identified. Several of these appear very well defined with a crescent of well defined air surrounding them. This should alert to the possibility of the nodules being subcutaneous or cutaneous. Careful inspection will then reveal several nodules extend outside the borders of the lungs. Only one diagnosis fits here- neurofibromatosis. For a perfect analysis take it a step further and comment on the spine (scoliosis, posterior scalloping, posterior mediastinal lesions), the ribs (superior or inferior rib notching or both (ribbon ribs)), the aorta (long segment coarctation), lungs (cystic change). All absent in this case.

If there is only one or two nodules consider nipple densities, sebaceous cysts, warts etc.