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Fig 1 Ventilation and perfusion lung scan
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Questions
1 What abnormalities can be seen andwhat is the cause?
2 What is the probable cause of her abdominal symptoms?
3 List two possible changes on her electrocardiograph.
4 How would you manage this patient?

Answers
1 While ventilation is mostly uniform there are multiple perfusion defects. The cause of this ventilation perfusion mismatch is multiple pulmonary emboli.

2 The most likely cause of her abdominal symptoms is intestinal obstruction due to an underlying right colonic lesion, most likely to be carcinoma of the caecum.

3 Electrocardiographic (ECG) abnormalities associated with pulmonary emboli include: right bundle branch block, right ventricular strain (T wave inversion in right ventricular leads), S1 Q3 T3 pattern. The commonest arrhythmia is atrial fibrillation.

4 This patient presents a difficult management problem. She had multiple pulmonary emboli on arrival, which were secondary to a deep vein thrombosis in her leg. The deep vein thrombosis was not clinically obvious, which is usually the case. Cancer of the caecum caused her subacute intestinal obstruction and anaemia. Although she had no obvious bleeding from her gastrointestinal tract, her bowel habit had changed. Caecal carcinomas often present with occult anaemia.

She requires full anticoagulation, initially with heparin then with warfarin. This is risky as she is already anaemic owing to occult bleeding. She should be transfused with four units of blood. Other investigations should include a chest x ray, ECG, liver function tests, abdominal ultrasound to check for hepatic metastases, and a barium enema. The advice of a surgeon should be sought early.

She will require a laparotomy, followed by either a palliative procedure (stoma formation) or a definitive procedure (right hemicolectomy for carcinoma of caecum). Although pulmonary emboli increase the risk of this procedure she will develop acute intestinal obstruction if left untreated. Discussion

Pulmonary emboli arise from thrombus that has formed in the veins of the pelvis or legs. There are clinical signs of deep vein thromboses in less than one third of cases. A swollen warm leg which is sometimes accompanied by cyanosis and dilated superficial veins suggests a deep veinous thrombosis. Venography confirms the diagnosis.

Deep vein thrombosis and subsequent emboli are more likely in the following situations:

1 Postoperatively, usually about 10 days after surgery.
2 Prolonged bed rest.
3 Other medical conditions, for example, heart failure, stroke, myocardial infarction.
4 Trauma, especially to the legs and pelvis.
5 Hypercoagulability states, such as neoplasia, haematological disorders.

Clinical presentations of pulmonary emboli are variable and depend on the size of the emboli. Large emboli can cause sudden dyspnoea, shock, and death. Patients with smaller emboli have variable symptoms including dyspnoea, haemoptysis, and pleurisy. On examination there may be evidence of a pleural effusion, which a chest x ray will confirm. Often the chest x ray is normal, but there may be areas of pulmonary oligemia or areas of linear collapse. Electrocardiographic changes are described above. Arterial blood gases may be normal but often the patient has a low pO2. With larger emboli the pCO2 is also low.

An isotope lung scan is a useful non- invasive investigation which helps to confirm the diagnosis. Patients with chronic lung disease have matched ventilation and perfusion defects. Multiple perfusion abnormalities with normal ventilation is indicative of emboli. When the diagnosis is established the patient should be anticoagulated with intravenous heparin for immediate effect whilst warfarin is also given. When the international normalised ratio is in the range of 2-4 heparin can be discontinued.

Anticoagulation is usually given for at least three months. Patients with recurrent deep vein thrombosis or pulmonary embolism should receive lifelong anticoagulation or for as long as the risks of anticoagulation do not outweigh the benefits.