Biomedical subjects
Publications and source records attributed to O F Hennessy.
Intrathoracic extramedullary haematopoiesis occurring as a complication of osteopetrosis is uncommon. The combination of classic plain film and CT findings should suggest the diagnosis, which can be non-invasively confirmed with bone marrow scintigraphy.
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OBJECTIVE: Positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG), a glucose analogue, as a metabolic tumour marker, has been proposed for the non-invasive staging of oncological disease. Tumours demonstrate increased glycolytic activity and thereby, FDG PET can differentiate benign from malignant lesions. To determine its role in the mediastinal staging of patients with suspected non-small cell lung cancer, a prospective study of FDG PET and computed tomography (CT) compared to surgery and pathology was performed. The analysis group consists of 50 patients, 37 men and 13 women, mean age 64 years (range, 41-78 years). METHODS: A nuclear physician, blind to the clinical and CT data, graded the FDG PET studies qualitatively on a five-point scale, based on the intensity of glucose uptake, for the presence of mediastinal nodal tumour involvement. Scores of four or greater were considered positive for tumour. An experienced radiologist interpreted the patients' CT scans blind to the other data. The CT criterion for tumour involvement was a nodal long axis diameter of 10 mm or greater. All patients underwent either thoracotomy or mediastinoscopy to obtain surgical specimens. The PET, CT, surgery and pathology were mapped according to the American Thoracic Society nodal classification resulting in 201 nodal stations evaluated. The imaging studies were analysed for N2 or N3 tumour involvement compared to histology or dissection of nodal stations. RESULTS: All patients had proven non-small cell lung carcinoma. PET excluded tumour in 175 of 181 nodal stations (specificity 97%) compared to 162 of 181 (specificity 90%) by CT. PET correctly identified 16 of 20 (sensitivity 80%) nodal stations with tumour compared to 13 of 20 by CT (sensitivity 65%). Overall, PET correctly staged 191 of 201 nodal stations (accuracy 95%) compared to 175 of 201 by CT (accuracy 87%). By the McNemar test, PET was significantly more specific than CT in excluding nodal tumour involvement (X2 = 5.5, P < 0.05). CONCLUSIONS: FDG PET is more specific than computed tomography in the non-invasive mediastinal staging of non-small cell lung cancer and has an important clinical role in the pre-operative staging of lung cancer patients.
Non-traumatic extradural spinal haematoma is an uncommon condition that is usually associated with a poor outcome. It may present acutely with signs and symptoms of major neurological dysfunction secondary to cord compression, or subacutely over a number of days or weeks with fluctuating symptoms. The exact aetiology of this condition is incompletely understood, but it is believed that the blood is venous in origin, as distinct from the arterial origin of intracranial extradural haematomas. Causes of non-traumatic extradural spinal haematoma include anticoagulation, vasculitis such as systemic lupus erythematosus (SLE), and spinal arteriovenous malformations. Conditions that may mimic an acute spinal haematoma include extradural abscess and extradural metastatic infiltration. It is important to make a diagnosis of extradural compression because surgery may offer the best hope in restoring neurological function in these patients. Imaging modalities used for the investigation of extradural haematomas include myelography, CT myelography (CTM) and MRI with or without gadolinium enhancement. The MR appearances of acute extradural abscess and extradural tumour can mimic an extradural haematoma. In subacute haematoma, owing to the magnetic properties of blood degradation products, MR is more specific in diagnosing and ageing of the haematoma.
Magnetic resonance cholangiopancreatography (MRCP) is a rapidly evolving non-invasive imaging modality that produces images of the pancreatic duct and biliary tree without the need for intravenous or oral contrast. The images are equivalent to those from endoscopic retrograde cholangiopancreatography (ERCP), but the non-invasive acquisition avoids the morbidity and mortality associated with diagnostic ERCP. Magnetic resonance cholangiopancreatography is indicated in patients who require only a diagnostic ERCP, who fail an ERCP or who are unable to undergo ERCP due to altered post-surgical anatomy. Other evolving indications include triaging of patients with obstructive jaundice into percutaneous or endoscopic management drainage pathways depending on the site, length and nature of the duct obstruction, thereby potentially decreasing the number of failed or unsuccessful ERCP. Pre-operative identification of anomalous biliary anatomy and choledocholithiasis prior to laparoscopic cholecystectomy promise to modify the pre-operative and operative management of the patient in order to minimize the risk of duct injury and unnecessary intra-operative dissection and cholangiography. The advantages of the technique include its non-invasiveness, the absence of contrast administration, its relative operator independence and the ability to evaluate both sides of an obstructed duct, thereby accurately evaluating stricture morphology and length. The disadvantages of MRCP compared to ERCP include its lack of an immediate therapeutic solution to duct obstruction, procedural cost, unit availability and the inability to evaluate patients with pacemakers or ferromagnetic implants.
Producing images similar to those acquired by the invasive procedures of endoscopic retrograde cholangiopancreatography (ERCP) or percutaneous transhepatic cholangiography, magnetic resonance cholangiopancreatography (MRCP) is indicated in patients who are unable to undergo ERCP or have had previously unsuccessful ERCP. It is used increasingly in non-invasive evaluation of the pancreaticobiliary tree in cases where the need for intervention during ERCP is expected to be low. MRCP may help in identifying anomalous biliary anatomy or choledocholithiasis before laparoscopic cholecystectomy, and in deciding between percutaneous or endoscopic treatment for patients with obstructive jaundice to decrease the rate of failed ERCP procedures.
The use of intravenous analgesia and anxiolytics in interventional radiology improves the patient's tolerance of potentially painful and prolonged procedures and allows the radiologist better control of the course of the procedure being undertaken. Monitoring of the patient's oxygen saturation, pulse rate, respiration, blood pressure and cardiac rhythm during a procedure is essential. Fentanyl and midazolam is a combination that is effective and convenient to use because both agents are relatively short acting, have little cardiovascular depression and are easily reversible (with naloxone and flumazenil). They are a better alternative to pethidine and diazepam because they can be more tightly titrated and controlled and are safer and more suitable for use in outpatients. Monitoring for respiratory depression is important and special care must be taken in the elderly and patients with hepatic, renal or chronic airways disease. General anaesthesia may be unavoidable in patients who are unstable, unco-operative or who have raised intracranial pressure.
A 20 year old leukaemic patient with neutropaenia secondary to chemotherapy, who developed overwhelming sepsis, myonecrosis, vascular occlusion and necrotizing enterocolitis due to Clostridium septicum infection is described. Plain abdominal radiographs and a computed tomography scan of the abdomen and pelvis showed gas in the retroperitoneal soft tissues. Clostridium septicum septicaemia has a recognized association with malignancy and neutropaenia and has a high mortality if not diagnosed and treated early. Computed tomography scanning of the abdomen, pelvis and head is advised in any patient with a positive C. septicum blood culture.
The features of hepatic congestion on computed tomography, ultrasound and nuclear medicine sulphur colloid scans have been reviewed. Hepatic congestion may not be appreciated clinically, especially in the elderly, but the features described should be sufficiently characteristic to establish the diagnosis. The CT appearance may be confused with neoplastic infiltration, so that recognition of the condition may avoid further unnecessary investigations.
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The use of a series of giant steel coils is described for the therapeutic embolization of a post-traumatic arteriovenous fistula between the superior mesenteric artery and the portal vein.
Obstruction of a transplanted kidney may occur during pregnancy and necessitate early cesarean section, with considerable risk to the immature fetus. We report a case where percutaneous catheter nephrostomy relieved the obstruction and allowed the pregnancy to progress until the fetus was mature.
Complications of central venous catheterisation are not uncommon, although, fortunately, the majority are not serious. Five patients suffering major complications are reported and a brief review of the literature presented.
Percutaneous nephrostomy (PCN) was performed 70 times in 46 patients. In the majority of cases the procedure was carried out as an emergency to relieve urinary obstruction. 20 of the patients had subsequent elective surgery, in others PCN allowed time for other forms of treatment to become effective. The technique carries a low mortality and morbidity, can be performed using either fluoroscopic or ultrasound imaging and should be available in all radiology departments.
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