Past exam of the medicine course of the University of Oxford / 1865 / Second examination / Diseases of women and children, and surgery / 5

How would you perform the operation of tapping the abdomen and the thorax, and in what pathological states may it be expedient to resort to it?

Tapping must follow identification of the fluid-containing cavity: abdominal paracentesis for ascites, thoracentesis for a pleural effusion. An enlarged abdomen or a dull area of chest is not, by itself, a sufficient indication for blind puncture. The object may be relief of pressure or obtaining fluid for diagnosis; neither necessarily removes the underlying cause.

Abdomen: states in which tapping is useful. Tense or troublesome ascites can interfere with breathing, eating and comfort, particularly when it persists despite treatment of its cause. Causes include cirrhosis with portal hypertension, heart failure, malignant peritoneal disease and some inflammatory or infective conditions. New or unexplained ascites can also require diagnostic sampling. General swelling without a drainable peritoneal collection is a different problem. An ovarian cyst, a gravid uterus, a distended urinary bladder and gaseous distension must not be mistaken for free ascites. ^{[ref] [ref]}

Abdomen: operative account. The characteristic historical apparatus is a sharp trocar within a hollow cannula. The patient is supported, the presence and distribution of fluid established, and the urinary bladder emptied to keep it away from the lower abdominal puncture route. Traditional descriptions use an appropriate abdominal site, often in the midline below the umbilicus; a landmark is not sufficient if an enlarged organ, a vessel or adherent intestine is in the way. Once the instrument has entered fluid, withdrawal of the trocar leaves the cannula as the drainage channel. The patient and the flow are observed, and the opening is dressed after removal. This describes the operation's principle, not a universally safe blind puncture point.

Modern performance uses sterile preparation, appropriate local anaesthesia, a selected fluid pocket and a catheter system rather than assuming that every distended abdomen can be tapped in the same place. Ultrasound helps identify a safe pocket and avoid organs and vessels. Samples may be sent for cell counts, protein and albumin measurements, culture or cytology according to the clinical question. Therapeutic drainage requires reassessment because haemorrhage, intestinal injury, leakage, infection and circulatory or renal disturbance can occur. In cirrhotic large-volume drainage, albumin replacement has a specific modern role; it is not an 1865 routine to be projected backwards. ^[ref]

Thorax: states in which tapping is useful. A large pleural effusion producing respiratory difficulty can be relieved, and an unexplained effusion can be sampled to identify its cause. Serous fluid, blood and pus have different implications: pleural effusion associated with heart failure, malignant disease or inflammation is not identical to empyema. A purulent collection may require continuing drainage and treatment of the infection, not merely one palliative aspiration. Contemporary experience already included tapping in hydrothorax; an 1864 report with subsequent anatomical examination illustrates how removal of fluid could coexist with serious underlying disease. ^[ref]

Thorax: operative account. The supported position exposes a suitable part of the chest; the operator first distinguishes fluid from consolidated lung and identifies its upper extent and the diaphragm. An appropriate intercostal route enters the fluid above a rib, avoiding the principal vessels and nerve running along its lower border. The drainage apparatus should permit controlled outflow without freely introducing air. The position of the lung, diaphragm, liver and spleen makes an arbitrarily low puncture unsafe. Historic trocar-and-cannula entry and modern small catheter aspiration share the need to enter the collection without injuring these structures.

Current guidance requires thoracic ultrasound for aspiration of a pleural effusion, a suitable needle or catheter, and slow controlled drainage. Chest tightness, pain, persistent cough or increasing breathlessness are reasons to stop and reassess, not simply to continue until no more fluid runs. Complications include pneumothorax, haemorrhage, injury to an abdominal organ, infection and re-expansion pulmonary oedema. These precautions belong to current practice; they must not be represented as technology available in 1865. ^[ref]