Subphrenic abscess

Anatomy

The complicated arrangement of the peritoneum results in the formation of four peritoneal and three extraperitoneal spaces in which pus may collect. Three of these spaces are on either side of the body, and one is approximately in the midline (Figs 56.8 and 56.9).

Left superior (anterior) intraperitoneal (‘left subphrenic’) is hounded above by the diaphragm, and behind by the left triangular ligament and the left lobe of the liver, the gastrohepatic omentum and anterior surface of the stomach. To the right is the falciform ligament and to the left the spleen, gastrosplenic omentum and diaphragm. The common cause of an abscess here is an operation on the stomach, the tail of the pancreas, the spleen or the splenic flexure of the colon.

Left inferior (posterior) intraperitoneal (‘left subhepatic’) is another name for the ‘lesser’ sac. The commonest cause of infection here is complicated acute pancreatitis. In practice a perforated gastric ulcer rarely causes a collection here because the potential space is obliterated by adhesions.

Right superior (anterior) intraperitoneal (‘right subphrenic’) lies between the right lobe of the liver and the diaphragm. It is limited posteriorly by the anterior layer of the coronary and the right triangular ligaments, and to the left by the falciform ligament. Common causes here are perforating cholecystitis, a perforated duodenal ulcer, a duodenal cap ‘blow out’ following gastrectomy and appendicitis.

Right inferior (posterior) intraperitoneal (‘right subhepatic’) lies transversely beneath the right lobe of the liver in Rutherford Morison’s pouch. It is bounded on the right by the right lobe of the liver and the diaphragm. To the left is situated the foramen of Winslow and below this lies the duodenum. In front are the liver and the gall bladder, and behind, the upper part of the right kidney and diaphragm. The space is bounded above by the liver, and below by the transverse colon and hepatic flexure. It is the deepest space of the four and the commonest site of a subphrenic abscess which usually arises from appendicitis, cholecystitis, a perforated duodenal ulcer or following upper abdominal surgery.

Extraperitoneal. There are three of these:

right and left extra peritoneal which are terms given to perinephric abscesses (Chapter 64);

midline extraperitoneal which is another name for the ‘bare’ area of the liver which may develop an abscess in amoebic hepatitis (the commonest cause) or a pyogenic liver abscess (Chapter 52).

Clinical features

The symptoms and signs of subphrenic infection are frequently nonspecific, and it is well to remember the aphorism, ‘pus somewhere, pus nowhere else, pus under diaphragm’.

Symptoms

A common history is that when some infective focus in the abdominal cavity has been dealt with, the condition of the patient improves temporarily, but after an interval of a few days or weeks, symptoms of toxaemia reappear. The condi­tion of the patient steadily, and often rapidly, deteriorates. Sweating, wasting and anorexia are present. There is some­times epigastric fullness and pain, or pain in the shoulder on the affected side, owing to irritation of sensory fibres in the phrenic nerve, referred along the descending branches of the cervical plexus. Persistent hiccup may be a presenting symptom.

Signs

A swinging pyrexia is usually present, unless antibiotics or drugs (steroids) have interfered. If the abscess is anterior, abdominal examination will reveal some tenderness, rigidity or even a palpable swelling. Sometimes the liver is displaced downwards, but more often it is fixed by adhesions. Examination of the chest is important, and in the majority of cases collapse of the lung or evidence of basal effusion or empyema is to be found.

Investigations

A number of these may be helpful as follows. Blood count usually shows a leucocytosis.

A plain radiograph sometimes demonstrates the presence of gas or a pleural effusion. On screening, the diaphragm is often seen to be elevated (so-called ‘tented’ diaphragm) and its movements impaired.

Ultrasound or CT scanning is the investigation of choice and permits early detection of subphrenic collections (Fig. 56.10).

Radiolabelled white cell scanning may occasionally prove helpful when other imaging techniques have failed.

Differential diagnosis. Pyelonephritis, amoebic abscess, pulmonary collapse and pleural empyema give rise to most of the diagnostic difficulties.

Treatment

The clinical course of suspected cases is watched, and blood and imaging investigations are made at suitable intervals. If suppuration seems probable, intervention is indicated. If skilled help is available it is possible to insert a percutaneous drainage tube under ultrasound or CT control. The same tube can be used to instil antibiotic solutions or irrigate the abscess cavity. To pass an aspirating needle at the bedside through the pleura and diaphragm invites potentially catastrophic spread of the infection into the pleural cavity.

If an operative approach is necessary and a swelling can be detected in the subcostal region or in the loin, an incision is made over the site of maximum tenderness, or over any area where oedema or redness is discovered. The parietes usually form part of the abscess wall so that contamination of the general penitoneal cavity is unlikely.

If no swelling is apparent, the subphrenic spaces should be explored either by an anterior subcostal approach or from behind after removal of the outer part of the 12th rib according to the position of abscess on imaging. With the posterior approach the pleura must not be opened and after the fibres of the diaphragm have been separated a finger is inserted beneath the diaphragm so as to explore the adjacent area. The aim with all techniques of drainage is to avoid dissemination of pus into the penitoneal or pleural cavities.

When the cavity is reached, all of the fibrinous loculi must be broken down with the finger and one or two drains or drainage tubes must be fully inserted. These drains are withdrawn gradually during the next 10 days and the closure of the cavity is checked by sinograms or scanning. The appropriate antibiotics are also given.